2013年08月, The 15-th Asian Chemical Congress Singapore, ”Asian Raising Star”　　　　　　　　　　　　　　　

2011年09月, Centre de Mecanique Ondulatoire, QSCP Promising Scientist Award　　　　　　　　　　　　　　　
長谷川 淳也

2009年, 分子科学会奨励賞　　　　　　　　　　　　　　　
日本国

A DFT Mechanistic Study on the Aza-Aldol Reaction of Boron Aza-Enolates: Relative Stability of Six-Membered Transition State and Its Relevance to the Coordination Mode of the Leaving Group
Sho Miyakawa, Ray Miyazaki, Tomoya Miura, Jun-ya Hasegawa
The Journal of Organic Chemistry, 2024年10月04日, ［査読有り］
研究論文（学術雑誌）

Exploring Catalytic Intermediates in Pd-Catalyzed Aerobic Oxidative Amination of 1,3-Dienes: Multiple Metal Interactions of the Palladium Nanoclusters
Kazuki Tabaru, Tetsuaki Fujihara, Kazuyuki Torii, Takeyuki Suzuki, Yuan Jing, Takashi Toyao, Zen Maeno, Ken-ichi Shimizu, Takeshi Watanabe, Hiromitsu Sogawa, Fumio Sanda, Jun-ya Hasegawa, Yasushi Obora
Journal of the American Chemical Society, 2024年08月21日
研究論文（学術雑誌）

Mitigating the Poisoning Effect of Formate during CO₂ Hydrogenation to Methanol over Co-Containing Dual-Atom Oxide Catalysts
Nazmul Hasan MD Dostagir, Carlo Robert Tomuschat, Kai Oshiro, Min Gao, Jun-ya Hasegawa, Atsushi Fukuoka, Abhijit Shrotri
JACS Au, American Chemical Society (ACS), 2024年02月02日, ［査読有り］
研究論文（学術雑誌）

Characterization of changes in the electronic structure of platinum sub-nanoclusters supported on graphene induced by oxygen adsorption
Hinoki Hirase, Kenji Iida, Jun-ya Hasegawa
Physical Chemistry Chemical Physics, 26, 27, 18530, 18537, Royal Society of Chemistry (RSC), 2024年, ［査読有り］, ［最終著者, 責任著者］
英語, 研究論文（学術雑誌）, The characteristics of changes in the electronic structure of a platinum sub-nanocluster caused by oxygen adsorption is elucidated by analyzing the integrated local density of states.

A Multiconfigurational Wave Function Theoretical Study on Electronic Structure and Magnetic Susceptibility of Dilanthanide Single Molecule Magnet
Yue Chen, Ray Miyazaki, Shigeyoshi Sakaki, Jun-ya Hasegawa
The Journal of Physical Chemistry A, 128, 1, 81, 88, American Chemical Society (ACS), 2023年12月19日, ［査読有り］, ［最終著者, 責任著者］
研究論文（学術雑誌）

DFT insight into metals and ligands substitution effects on reactivity of phenoxy-imine catalysts for ethylene polymerization
Pavee Apilardmongkol, Manussada Ratanasak, Jun-ya Hasegawa, Vudhichai Parasuk
Journal of Molecular Graphics and Modelling, 125, 108586, 108586, Elsevier BV, 2023年12月, ［査読有り］, ［責任著者］
研究論文（学術雑誌）

Theoretical Investigation of the Alkali Metal Poisoning Tolerance Mechanism of CeO2-Containing Fe and H2SO4 Additives
Kai Oshiro, Min Gao, Lupeng Han, Dengsong Zhang, Jun-ya Hasegawa
The Journal of Physical Chemistry C, 2023年09月28日, ［査読有り］, ［最終著者, 責任著者］
研究論文（学術雑誌）

Crystal-in-Amorphous Vanadate Catalysts for Universal Poison-Resistant Elimination of Nitric Oxide
Jiang Deng, Sixiang Cai, Min Gao, Jun-ya Hasegawa, Heyan Yao, Yongjie Shen, Zhiping Si, Jiayu Song, Dengsong Zhang
ACS Catalysis, 13, 18, 12363, 12373, American Chemical Society (ACS), 2023年09月06日, ［査読有り］
研究論文（学術雑誌）

Dynamic Behavior of Intermediate Adsorbates to Control Activity and Product Selectivity in Heterogeneous Catalysis: Methanol Decomposition on Pt/TiO2(110)
Can Liu, Bang Lu, Hiroko Ariga-Miwa, Shohei Ogura, Takahiro Ozawa, Katsuyuki Fukutani, Min Gao, Jun-ya Hasegawa, Ken-ichi Shimizu, Kiyotaka Asakura, Satoru Takakusagi
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 145, 36, 19953, 19960, AMER CHEMICAL SOC, 2023年08月, ［査読有り］
英語, 研究論文（学術雑誌）, Dynamic behavior of intermediate adsorbates, such as diffusion, spillover, and reverse spillover, has a strong influence on the catalytic performance in oxide-supported metal catalysts. However, it is challenging to elucidate how the intermediate adsorbates move on the catalyst surface and find active sites to give the corresponding products. In this study, the effect of the dynamic behavior of methoxy intermediate on methanol decomposition on a Pt/TiO2(110) surface has been clarified by combination of scanning tunneling microscopy (STM), temperature-programmed desorption (TPD), and density functional theory (DFT) calculations. The methoxy intermediates were formed by the dissociative adsorption of methanol molecules on Pt nanoparticles at room temperature followed by spillover to the TiO2(110) support surface. TPD results showed that the methoxy intermediates were thermally decomposed at >350 K on the Pt sites to produce CO (dehydrogenation) and CH4 (C-O bond scission). A decrease of the Pt nanoparticle density lowered the activity for the decomposition reaction and increased the selectivity toward CH4, which indicates that the reaction is controlled by diffusion and reverse spillover of the methoxy intermediates. Time-lapse STM imaging and DFT calculations revealed that the methoxy intermediates migrate on the five-fold coordinated Ti (Ti-5c) sites along the [001] or [1 (1) over bar 0] direction with the aid of hydrogen adatoms bonded to the bridging oxygens (O-br) and can move over the entire surface to seek and find active Pt sites. This work offers an in-depth understanding of the important role of intermediate adsorbate migration in the control of the catalytic performance in oxide-supported metal catalysts.

Highly Enantioselective Radical Cation [2 + 2] and [4 + 2] Cycloadditions by Chiral Iron(III) Photoredox Catalysis
Shuhei Ohmura, Kei Katagiri, Haruna Kato, Takahiro Horibe, Sho Miyakawa, Jun-ya Hasegawa, Kazuaki Ishihara
Journal of the American Chemical Society, 145, 28, 15054, 15060, American Chemical Society (ACS), 2023年07月05日, ［査読有り］
研究論文（学術雑誌）

Optimization of General Molecular Properties in the Equilibrium Geometry Using Quantum Alchemy: An Inverse Molecular Design Approach
Takafumi Shiraogawa, Jun-ya Hasegawa
The Journal of Physical Chemistry A, 2023年05月18日, ［査読有り］, ［最終著者］
研究論文（学術雑誌）

Paddle‐Wheel Dirhodium Complexes Bearing Bulky Carboxylate Ligands: Synthesis and Catalysis in Carbene Insertion Reactions
Kotaro Yamashita, Kota Sato, Yutaka Tanji, Jun‐ya Hasegawa, Tetsuaki Fujihara
Chemistry – An Asian Journal, 18, 11, Wiley, 2023年04月25日, ［査読有り］
研究論文（学術雑誌）, Abstract

Dirhodium complexes bearing bulky carboxylate ligands are synthesized and characterized. The steric bulk of carboxylate ligands could affect the reaction selectivity in Rh‐catalyzed intramolecular reactions: Rh catalysts with bulky carboxylate ligands provided five‐membered ring products preferentially via the insertion into a carbon–hydrogen bond. Meanwhile, six‐membered ring products were obtained using conventional Rh catalysts via the insertion of a carbon‐carbon double bond.

First-principles study on unidirectional proton transfer on anatase TiO2 (101) surface induced by external electric fields
Takahiro Chiba, Kenji Iida, Shinya Furukawa, Jun-ya Hasegawa
PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 25, 13, 9454, 9460, ROYAL SOC CHEMISTRY, 2023年03月, ［査読有り］, ［最終著者］
英語, 研究論文（学術雑誌）, The electric field (EF) effect on hydrogen or proton transfer (PT) via hydroxyl groups on an anatase TiO2 (101) surface is examined using first-principles density functional theory and the modern theory of polarization. This study focuses on unidirectional surface PT caused by external EFs at various orientations toward the surface. The preferred PT pathway can change depending on the magnitude and direction of the EF. Detailed analysis reveals that the variation in the energy profile with the EF is significantly different from that determined by the classical electric work of an EF carrying a point charge. The EF effect on the energy profile of the PT is governed by the rearrangement of the chemical bond network at the interface between the water molecules and the surface.

Dimethyl carbonate synthesis from CO₂ and methanol over CeO₂: elucidating the surface intermediates and oxygen vacancy-assisted reaction mechanism
Dragos Stoian, Toshiyuki Sugiyama, Atul Bansode, Francisco Medina, Wouter van Beek, Jun-ya Hasegawa, Akira Nakayama, Atsushi Urakawa
Chemical Science, 14, 47, 13908, 13914, Royal Society of Chemistry (RSC), 2023年, ［査読有り］
研究論文（学術雑誌）, Oxygen vacancy-assisted reaction mechanisms and key surface intermediates were uncovered by operando spectroscopic and DFT-based molecular dynamics simulations in direct dimethyl carbonate (DMC) synthesis from CO₂ and methanol over CeO₂ catalyst.

Unravelling the Anomalous Coking Resistance over Boron Nitride-Supported Ni Catalysts for Dry Reforming of Methane
Min Gao, Jiang Deng, Min Gao, Jun-ya Hasegawa, Xiaoyu Zhang, Aiyong Wang, Aling Chen, Dengsong Zhang
CCS Chemistry, 1, 14, Chinese Chemical Society, 2022年11月30日, ［査読有り］
英語, 研究論文（学術雑誌）

Substrate-Assisted Reductive Elimination Determining the Catalytic Cycle: A Theoretical Study on the Ni-Catalyzed 2,3-Disubstituted Benzofuran Synthesis via C–O Bond Activation
Ray Miyazaki, Kenji Iida, Shohei Ohno, Tsuyoshi Matsuzaki, Takeyuki Suzuki, Mitsuhiro Arisawa, Jun-ya Hasegawa
Organometallics, 41, 23, 3581, 3588, American Chemical Society (ACS), 2022年11月21日, ［査読有り］, ［最終著者, 責任著者］
研究論文（学術雑誌）

Asymmetric Dehydrative Cyclization of Allyl Alcohol to Cyclic Ether Using Chiral Brønsted Acid/CpRu(II) Hybrid Catalysts: A DFT Study of the Origin of Enantioselectivity
Manussada Ratanasak, Shinji Tanaka, Masato Kitamura, Jun-ya Hasegawa
The Journal of Organic Chemistry, 87, 19, 13062, 13072, American Chemical Society (ACS), 2022年10月07日, ［査読有り］, ［最終著者, 責任著者］, ［国際誌］
英語, 研究論文（学術雑誌）

Metastable structure of photoexcited WO₃ determined by the pump-probe extended X-ray absorption fine structure spectroscopy and constrained thorough search analysis
Daiki Kido, Yohei Uemura, Yuki Wakisaka, Akihiro Koide, Hiromitsu Uehara, Yasuhiro Niwa, Shunsuke Nozawa, Kohei Ichiyanagi, Ryo Fukaya, Shin-ichi Adachi, Tokushi Sato, Harry Jenkins, Toshihiko Yokoyama, Satoru Takakusagi, Jun-ya Hasegawa, Kiyotaka Asakura
Chemistry Letters, 51, 11, 1083, 1086, The Chemical Society of Japan, 2022年09月27日, ［査読有り］, ［国際共著］, ［国内誌］
英語, 研究論文（学術雑誌）, The local structure of WO3 photocatalyst in the photoexcited
metastable state created 150 ps after laser irradiation have been
determined by pump-probe L3-edge EXAFS and constrained
thorough search analysis. A highly distorted octahedral local
structure was found where one of the shortest W-O bonds was
further shortened to 1.66 ¡ while the other five bonds were
rather elongated even though theoretical calculations predicted
the reverse change. We discuss this contradiction and propose a
possible structure for the metastable state.

Iron/Photosensitizer Hybrid System Enables the Synthesis of Polyaryl-Substituted Azafluoranthenes
Yoshimi Kato, Tatsuhiko Yoshino, Min Gao, Jun-ya Hasegawa, Masahiro Kojima, Shigeki Matsunaga
Journal of the American Chemical Society, American Chemical Society (ACS), 2022年09月27日, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）

Mechanism of BPh ₃ ‐Catalyzed N‐Methylation of Amines with CO ₂ and Phenylsilane: Cooperative Activation of Hydrosilane
Manussada Ratanasak, Takumi Murata, Taishin Adachi, Jun‐ya Hasegawa, Tadashi Ema
Chemistry – A European Journal, Wiley, 2022年09月20日, ［査読有り］, ［責任著者］, ［国際誌］
英語, 研究論文（学術雑誌）

Exploration of Chemical Space for Designing Functional Molecules Accounting for Geometric Stability
Takafumi Shiraogawa, Jun-ya Hasegawa
The Journal of Physical Chemistry Letters, 13, 36, 8620, 8627, American Chemical Society (ACS), 2022年09月15日, ［査読有り］, ［最終著者］, ［国際誌］
英語, 研究論文（学術雑誌）

MD studies of methanol confined in the metal-organic framework MOF MIL-88B-Cl
Siwarut Siwaipram, Philippe A. Bopp, Panyapat Ponchai, Jean-Christophe Soetens, Jun-ya Hasegawa, Rochus Schmid, Sareeya Bureekaew
Journal of Molecular Liquids, 359, 119252, 119252, Elsevier BV, 2022年08月, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）

Reaction Mechanism of Deoxydehydration by Ceria-Supported Monomeric Rhenium Catalysts: A Computational Study
Ryu Hosaka, Daiki Asada, Ji Cao, Masazumi Tamura, Yoshinao Nakagawa, Keiichi Tomishige, Jun-ya Hasegawa, Akira Nakayama
The Journal of Physical Chemistry C, 126, 28, 11566, 11573, American Chemical Society (ACS), 2022年07月21日, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）

Carbon(sp ² )‐carbon(sp ³ ) Bond‐forming Cross‐coupling Reactions Using Sulfur‐Modified Au‐Supported Nickel Nanoparticle Catalyst
Ryousuke Ohta, Yasunori Shio, Toshiki Akiyama, Makito Yamada, Shuhei Shimoda, Kazuo Harada, Makoto Sako, Jun‐ya Hasegawa, Mitsuhiro Arisawa
Asian Journal of Organic Chemistry, Wiley, 2022年07月13日, ［査読有り］
英語, 研究論文（学術雑誌）

Revisiting Activity Tuning Using Lattice Strain: CO Decomposition in Terrace Ru(0001) and Stepped Ru(1015) Surfaces
Danjo De Chavez, Jun-ya Hasegawa
The Journal of Physical Chemistry C, 126, 22, 9324, 9333, American Chemical Society (ACS), 2022年06月09日, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）

Unraveling the promotional effects of NiCo catalysts over defective boron nitride nanosheets in dry reforming of methane
Sanchai Kuboon, Jiang Deng, Min Gao, Kajornsak Faungnawakij, Jun-ya Hasegawa, Xiaoyu Zhang, Liyi Shi, Dengsong Zhang
Catalysis Today, Elsevier BV, 2022年05月, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）

Exploring the Reaction Mechanism of Heterobimetallic Nickel-Alkali Catalysts for Ethylene Polymerization: Secondary-Metal-Ligand Cooperative Catalysis
Pavee Apilardmongkol, Manussada Ratanasak, Jun-ya Hasegawa, Vudhichai Parasuk
ChemCatChem, 2022年04月, ［査読有り］, ［責任著者］

Doubly linked chiral phenanthrene oligomers for homogeneously π-extended helicenes with large effective conjugation length
Yusuke Nakakuki, Takashi Hirose, Hikaru Sotome, Min Gao, Daiki Shimizu, Ruiji Li, Jun-ya Hasegawa, Hiroshi Miyasaka, Kenji Matsuda
Nature Communications, 13, 1, 1, 10, Springer Science and Business Media LLC, 2022年04月, ［査読有り］
研究論文（学術雑誌）, Abstract

Helically twisted conductive nanocarbon materials are applicable to optoelectronic and electromagnetic molecular devices working on the nanometer scale. Herein, we report the synthesis of per-peri-perbenzo[5]- and [9]helicenes in addition to previously reported π-extended [7]helicene. The homogeneously π-extended helicenes can be regarded as helically fused oligo-phenanthrenes. The HOMO−LUMO gap decreased significantly from 2.14 to 1.15 eV with increasing helical length, suggesting the large effective conjugation length (ECL) of the π-extended helical framework. The large ECL of π-extended helicenes is attributed to the large orbital interactions between the phenanthrene subunits at the 9- and 10-positions, which form a polyene-like electronic structure. Based on the experimental results and DFT calculations, the ultrafast decay dynamics on the sub-picosecond timescale were attributed to the low-lying conical intersection.

Deoxygenative CO2 conversions with triphenylborane and phenylsilane in the presence of secondary amines or nitrogen-containing aromatics
Takumi Murata, Mahoko Hiyoshi, Shinsuke Maekawa, Yuta Saiki, Manussad Ratanasak, Jun-ya Hasegawa, Tadashi Ema
Green Chemistry, 24, 2385, 2390, 2022年02月, ［査読有り］
英語, 研究論文（学術雑誌）

C–H Bond Activation Mechanism by a Pd(II)–(μ-O)–Au(0) Structure Unique to Heterogeneous Catalysts
Daisuke Takei, Takafumi Yatabe, Tomohiro Yabe, Ray Miyazaki, Jun-ya Hasegawa, Kazuya Yamaguchi
JACS Au, American Chemical Society (ACS), 2022年01月14日, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）

Photoinduced Copper-Catalyzed Asymmetric Acylation of Allylic Phosphates with Acylsilanes
Yusuke Ueda, Yusuke Masuda, Tomohiro Iwai, Keisuke Imaeda, Hiroki Takeuchi, Kosei Ueno, Min Gao, Jun-ya Hasegawa, Masaya Sawamura
Journal of the American Chemical Society, 144, 5, 2218, 2224, American Chemical Society (ACS), 2022年01月06日, ［査読有り］, ［責任著者］
英語, 研究論文（学術雑誌）

Bulky magnesium(II) and sodium(I) bisphenoxide catalysts for chemoselective transesterification of methyl (meth)acrylates
Xue Zhao, Manussada Ratanasak, Kazumasa Kon, Jun-ya Hasegawa, Kazuaki Ishihara
Chemical Science, Royal Society of Chemistry (RSC), 2022年
研究論文（学術雑誌）, Given the industrial importance of (meth)acrylate esters, various groups have devoted considerable effort to investigating their chemoselective transesterification. In 2021, we developed magnesium(II) and sodium(I) complexes derived from 2,6-di-tert-butyl-p-cresol (BHT-H)...

OpenMechanochem: A Python module for mechanochemical simulations
D. P. De Chavez, J. Hasegawa
SoftwareX, 16, 100879, 2021年12月, ［査読有り］, ［責任著者］
英語, 研究論文（学術雑誌）, 30608236

A boron-transfer mechanism mediating the thermally induced revival of frustrated carbene–borane pairs from their shelf-stable adducts
Yoichi Hoshimoto, Mahiro Sakuraba, Takuya Kinoshita, Masaki Ohbo, Manussada Ratanasak, Jun-ya Hasegawa, Sensuke Ogoshi
Communications Chemistry, 4, 1, Springer Science and Business Media LLC, 2021年12月, ［査読有り］, ［責任著者］
研究論文（学術雑誌）, Chemists have designed strategies that trigger the conformational isomerization of molecules in response to external stimuli, which can be further applied to regulate the complexation between Lewis acids and bases. We have recently developed a system in which frustrated carbene–borane pairs are revived from shelf-stable but external-stimuli-responsive carbene–borane adducts comprised of N-phosphine-oxide-substituted imidazolylidenes (PoxIms) and triarylboranes. Herein, we report the detailed mechanism on this revival process. A thermally induced borane-transfer process from the carbene carbon atom to the N-phosphinoyl oxygen atom initiates the transformation of the carbene–borane adduct. Subsequent conformational isomerization via the rotation of the N-phosphinoyl group in PoxIm moieties eventually leads to the revival of frustrated carbene–borane pairs that can cleave H₂. We believe that this work illustrates an essential role of dynamic conformational isomerization in the regulation of the reactivity of external-stimuli-responsive Lewis acid-base adducts that contain multifunctional substituents.

Co Single Atoms in ZrO2 with Inherent Oxygen Vacancies for Selective Hydrogenation of CO2 to CO
Nazmul Hasan MD Dostagir, Rattanawalee Rattanawan, Min Gao, Jin Ota, Jun-ya Hasegawa, Kiyotaka Asakura, Atsushi Fukouka, Abhijit Shrotri
ACS Catalysis, 11, 15, 9450, 9461, American Chemical Society (ACS), 2021年08月06日, ［査読有り］
研究論文（学術雑誌）

Ionic Liquid-Stabilized Single-Atom Rh Catalyst Against Leaching
Shipeng Ding, Max J. Hülsey, Hua An, Qian He, Hiroyuki Asakura, Min Gao, Jun-ya Hasegawa, Tsunehiro Tanaka, Ning Yan
CCS Chemistry, 1814, 1822, Chinese Chemical Society, 2021年06月24日, ［査読有り］
研究論文（学術雑誌）

A Triad Fluorenone Derivative Bearing Two Imidazole Groups That Switches between Three States by Base and Acid Stimuli
Yuting Wang, Nabin Maity, Liming Zhao, Maximilian Krämer, Jun-ya Hasegawa, Yukatsu Shichibu, Katsuaki Konishi, Xiaoyuan Wang, Zhiyi Song, Masayoshi Bando, Tamaki Nakano
Chemistry Letters, 50, 7, 1363, 1367, The Chemical Society of Japan, 2021年04月15日, ［査読有り］
研究論文（学術雑誌）

Mechanism of the Asymmetric Dehydrative Allylative Cyclization of Alcohols to Cyclic Ethers Catalyzed by a CpRu Complex of the Chiral Picolinic Acid-Type Ligand, Cl-Naph-PyCOOH: Is a π-Allyl Intermediate Present?
Yusuke Suzuki, Shoutaro Iwase, Manussada Ratanasak, Jun-ya Hasegawa, Shinji Tanaka, Masato Kitamura
Bulletin of the Chemical Society of Japan, 94, 2, 440, 450, The Chemical Society of Japan, 2021年02月15日, ［査読有り］
研究論文（学術雑誌）

Tuning Transition Electric and Magnetic Dipole Moments: [7]Helicenes Showing Intense Circularly Polarized Luminescence
Hiromu Kubo, Takashi Hirose, Takuya Nakashima, Tsuyoshi Kawai, Jun-ya Hasegawa, Kenji Matsuda
The Journal of Physical Chemistry Letters, 12, 1, 686, 695, American Chemical Society (ACS), 2021年01月14日, ［査読有り］
研究論文（学術雑誌）

On the Electronic Structure Origin of Mechanochemically Induced Selectivity in Acid-Catalyzed Chitin Hydrolysis
Danjo De Chavez, Hirokazu Kobayashi, Atsushi Fukuoka, Jun-ya Hasegawa
The Journal of Physical Chemistry A, 125, 1, 187, 197, American Chemical Society (ACS), 2021年01月14日, ［査読有り］, ［最終著者, 責任著者］
研究論文（学術雑誌）

Impact of tensile and compressive forces on the hydrolysis of cellulose and chitin
Hirokazu Kobayashi, Yusuke Suzuki, Takuya Sagawa, Kyoichi Kuroki, Jun-ya Hasegawa, Atsushi Fukuoka
Physical Chemistry Chemical Physics, 23, 30, 15908, 15916, Royal Society of Chemistry (RSC), 2021年, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）,

Compressive forces produced by ball-milling can activate glycosidic bonds of polysaccharides towards mechanocatalytic hydrolysis.

Design and prediction of high potent ansa-zirconocene catalyst for olefin polymerizations: combined DFT calculations and QSPR approach
Manussada Ratanasak, Jun-ya Hasegawa, Vudhichai Parasuk
New Journal of Chemistry, 45, 18, 8248, 8257, Royal Society of Chemistry (RSC), 2021年, ［査読有り］
研究論文（学術雑誌）,

Density functional calculations were carried out to predict activities, regio- and stereoselectivity, and to design new ansa-zirconocene catalysts for olefin polymerizations.

Mechanistic study of C–H bond activation by O2 on negatively charged Au clusters: α,β-dehydrogenation of 1-methyl-4-piperidone by supported Au catalysts
Ray Miyazaki, Xiongjie Jin, Daichi Yoshii, Takafumi Yatabe, Tomohiro Yabe, Noritaka Mizuno, Kazuya Yamaguchi, Jun-ya Hasegawa
Catalysis Science & Technology, 11, 10, 3333, 3346, Royal Society of Chemistry (RSC), 2021年, ［査読有り］, ［最終著者, 責任著者］
研究論文（学術雑誌）,

Aerobic C–H activation by Au/OMS-2 catalyst is driven by charge transfer from OMS-2 to adsorbed O₂via Au cluster.

Chemoselective Transesterification of Methyl (Meth)acrylates Catalyzed by Sodium(I) or Magnesium(II) Aryloxides
Jie Qi Ng, Hiro Arima, Takuya Mochizuki, Kohei Toh, Kai Matsui, Manussada Ratanasak, Jun-Ya Hasegawa, Manabu Hatano, Kazuaki Ishihara
ACS Catalysis, 11, 1, 199, 207, American Chemical Society (ACS), 2021年01月01日, ［査読有り］, ［責任著者］
研究論文（学術雑誌）

Catalytic Mechanism of Liquid-Metal Indium for Direct Dehydrogenative Conversion of Methane to Higher Hydrocarbons
Yuta Nishikawa, Yuhki Ohtsuka, Hitoshi Ogihara, Rattanawalee Rattanawan, Min Gao, Akira Nakayama, Jun-ya Hasegawa, Ichiro Yamanaka
ACS Omega, 5, 43, 28158, 28167, American Chemical Society (ACS), 2020年11月03日, ［査読有り］
研究論文（学術雑誌）

Spin-inversion mechanisms inO(2)binding to a model heme compound: A perspective from nonadiabatic wave packet calculations
Kohei Saito, Yuya Watabe, Takaaki Miyazaki, Toshiyuki Takayanagi, Jun-ya Hasegawa
JOURNAL OF COMPUTATIONAL CHEMISTRY, 41, 29, 2527, 2537, WILEY, 2020年11月, ［査読有り］, ［最終著者］
英語, 研究論文（学術雑誌）, Spin-inversion dynamics in O(2)binding to a model heme complex, which consisted of Fe(II)-porphyrin and imidazole, were studied using nonadiabatic wave packet dynamics calculations. We considered three active nuclear degrees of freedom in the dynamics, including the motions along the Fe-O distance, Fe-O-O angle, and Fe out-of-plane distance. Spin-free potential energy surfaces for the singlet, triplet, quintet, and septet states were developed using density functional theory calculations, and spin-orbit coupling elements were obtained from CASSCF-level electronic structure calculations. The spin-inversion mainly occurred between the singlet state and one of the triplet states due to large spin-orbit couplings and the contributions of other states were extremely small. The present quantum dynamics calculations suggested that the narrow crossing region model plays a dominant role in the O(2)binding dynamics. In addition, the one-dimensional Landau-Zener model underestimated the nonadiabatic transition probability.

Mechanistic Study on Deoxydehydration and Hydrogenation of Methyl Glycosides to Dideoxy Sugars over a ReOx–Pd/CeO2 Catalyst
Ji Cao, Masazumi Tamura, Ryu Hosaka, Akira Nakayama, Jun-ya Hasegawa, Yoshinao Nakagawa, Keiichi Tomishige
ACS Catalysis, 10, 20, 12040, 12051, American Chemical Society (ACS), 2020年10月16日, ［査読有り］
英語, 研究論文（学術雑誌）, We found that nonprotected methyl glycosides with cis-vicinal OH groups could be converted to the corresponding methyl dideoxy glycosides by deoxydehydration and consecutive hydrogenation (DODH + HG) over a ReOx-Pd/CeO2 catalyst with gaseous H-2. In the study, the reactivity of the methyl glycosides in DODH was clearly lower than that of simple cyclic vicinal diols, such as cis-1,2-cyclohexanediol and cis-1,2-cyclo-pentanediol, and the reactivity of the methyl glycosides was also different. Herein, we investigated the reactivity difference based on kinetic studies and density-functional theory (DFT) calculations. The kinetic studies suggest that the reactivity difference between the methyl glycosides and the simple diols is derived from the OH group of methyl glycosides except the cis-vicinal diols, and that the reactivity difference among the methyl glycosides will be associated with the configuration of the substituents adjacent to the cis-vicinal diols, while the reaction mechanism of DODH is suggested to be basically similar judging from almost the same reaction orders with respect to the substrate concentration and H-2 pressure in all substrates. The adsorption and transition states of methyl alpha-L-rhamnopyranoside and methyl alpha-L-fucopyranoside, which have a large reactivity difference (methyl alpha-L-rhamnopyranoside >> methyl alpha-L-fucopyranoside), were estimated by DFT calculations with ReOx/CeO2 as the active site of the ReOx-Pd/CeO2 catalyst, showing that the main difference is the activation energy in DODH of these substrates (65 kJ mol(-1) for methyl alpha-Lrhamnopyranoside and 77 kJ mol(-1) for methyl alpha-L-fucopyranoside), which was also supported by the results of Arrhenius plots (63 and 73 kJ mol(-1) for methyl alpha-L-rhamnopyranoside and methyl alpha-L-fucopyranoside, respectively). The activation energy was influenced by the torsional angle of the substituents adjacent to the cis-vicinal OH groups, which is derived from the interaction of the OH group adjacent to the cis-vicinal OH groups and the surface hydroxy groups on CeO2.

Extending nudged elastic band method to reaction pathways involving multiple spin states
Liming Zhao, K-jiro Watanabe, Naoki Nakatani, Akira Nakayama, Xin Xu, Jun-ya Hasegawa
The Journal of Chemical Physics, 153, 13, 134114, 134114, AIP Publishing, 2020年10月07日, ［査読有り］, ［責任著者］, ［国際誌］
英語, 研究論文（学術雑誌）, There are diverse reactions including spin-state crossing, especially the reactions catalyzed by transition metal compounds. To figure out the mechanisms of such reactions, the discussion of minimum energy intersystem crossing (MEISC) points cannot be avoided. These points may be the bottleneck of the reaction or inversely accelerate the reactions by providing a better pathway. It is of great importance to reveal their role in the reactions by computationally locating the position of the MEISC points together with the reaction pathway. However, providing a proper initial guess for the structure of the MEISC point is not as easy as that of the transition state. In this work, we extended the nudged elastic band (NEB) method for multiple spin systems, which is named the multiple spin-state NEB method, and it is successfully applied to find the MEISC points while optimizing the reaction pathway. For more precisely locating the MEISC point, a revised approach was adopted. Meanwhile, our examples also suggest that special attention should be paid to the criterion to define an image optimized as the MEISC point.

Self-Assembled Multilayer Iron(0) Nanoparticle Catalyst for Ligand-Free Carbon-Carbon/Carbon-Nitrogen Bond-Forming Reactions
Toshiki Akiyama, Yuki Wada, Makito Yamada, Yasunori Shio, Tetsuo Honma, Shuhei Shimoda, Kazuki Tsuruta, Yusuke Tamenori, Hitoshi Haneoka, Takeyuki Suzuki, Kazuo Harada, Hayato Tsurugi, Kazushi Mashima, Jun-ya Hasegawa, Yoshihiro Sato, Mitsuhiro Arisawa
ORGANIC LETTERS, 22, 18, 7244, 7249, AMER CHEMICAL SOC, 2020年09月, ［査読有り］
英語, 研究論文（学術雑誌）, Self-assembled multilayer iron(0) nanoparticles (NPs, 6-10 nm), namely, sulfur-modified Au-supported Fe(0) [SAFe(0)], were developed for ligand-free one-pot carbon-carbon/carbon-nitrogen bond-forming reactions. SAFe(0) was successfully prepared using a well-established metal-nanoparticle catalyst preparative protocol by simultaneous in situ metal NP and nanospace organization (PSSO) with 1,4-bis(trimethylsilyl)-1,4-dihydropyrazine (Si-DHP) as a strong reducing agent. SAFe(0) was easy to handle in air and could be recycled with a low iron-leaching rate in reaction cycles.

Zeolite-supported ultra-small nickel as catalyst for selective oxidation of methane to syngas
Shuhei Yasuda, Ryota Osuga, Yusuke Kunitake, Kazuya Kato, Atsushi Fukuoka, Hirokazu Kobayashi, Min Gao, Jun-ya Hasegawa, Ryo Manabe, Hisashi Shima, Susumu Tsutsuminai, Toshiyuki Yokoi
COMMUNICATIONS CHEMISTRY, 3, 1, NATURE RESEARCH, 2020年09月, ［査読有り］
英語, 研究論文（学術雑誌）, Catalytic oxidation of methane to syngas is an important process, but efficient and stable catalyts remain in demand. Here dispersion of nickel on zeolites yields nickel oxide nanoparticles as small as 1.6 nm which act as selective and efficient catalysts for conversion of methane to syngas.The development of simple catalysts with high performance in the selective oxidation of methane to syngas at low temperature has attracted much attention. Here we report a nickel-based solid catalyst for the oxidation of methane, synthesised by a facile impregnation method. Highly dispersed ultra-small NiO particles of 1.6 nm in size are successfully formed on the MOR-type zeolite. The zeolite-supported nickel catalyst gives continuously 97-98% methane conversion, 91-92% of CO yield with a H-2/CO ratio of 2.0, and high durability without serious carbon deposition onto the catalyst at 973 K. DFT calculations demonstrate the effect of NiO particle size on the C-H dissociation process of CH4. A decrease in the NiO particle size enhances the production of oxygen originating from the NiO nanoparticles, which contributes to the oxidation of methane under a reductive environment, effectively producing syngas.

Delocalization Effect Promoted the Indoor Air Purification via Directly Unlocking the Ring-Opening Pathway of Toluene
Wenqiang Qu, Penglu Wang, Min Gao, Jun-ya Hasegawa, Zhi Shen, Qing Wang, Ruomei Li, Dengsong Zhang
ENVIRONMENTAL SCIENCE & TECHNOLOGY, 54, 15, 9693, 9701, AMER CHEMICAL SOC, 2020年08月, ［査読有り］
英語, 研究論文（学術雑誌）, The ring-opening process was generally considered as the rate-determining step for aromatic volatile organic compound photocatalytic degradation. A sophisticated and intensive degradation pathway is critical to the poor removal efficiency and low mineralization. In the present contribution, we successfully tailored and identified the ring-opening pathway of toluene elimination by electron delocalization in a borocarbonitride photocatalyst. By means of modulation of the dopant coordination configuration and electron geometry in the catalyst, the lone electrons of carbon transform into delocalized counterparts, sequentially elevating the interaction between the toluene molecules and photocatalyst. The aromatic ring of toluene can be attacked directly in the effect of electron delocalization without engendering additional intermediate species, significantly facilitating the removal and mineralization of toluene. This unprecedented route-control strategy alters the aromatic-ring-based reaction behavior from toluene to CO2 and paves a way to purify the refractory pollutants from the top design.

Aluminum porphyrins with quaternary ammonium halides as catalysts for copolymerization of cyclohexene oxide and CO2: metal-ligand cooperative catalysis
Jingyuan Deng, Manussada Ratanasak, Yuma Sako, Hideki Tokuda, Chihiro Maeda, Jun-ya Hasegawa, Kyoko Nozaki, Tadashi Ema
CHEMICAL SCIENCE, 11, 22, 5669, 5675, ROYAL SOC CHEMISTRY, 2020年06月, ［査読有り］, ［責任著者］
英語, 研究論文（学術雑誌）, Bifunctional Al-III porphyrins with quaternary ammonium halides, 2-Cl and 2-Br, worked as excellent catalysts for the copolymerization of cyclohexene oxide (CHO) and CO2 at 120 degrees C. Turnover frequency (TOF) and turnover number (TON) reached 10 000 h(-1) and 55 000, respectively, and poly(cyclohexene carbonate) (PCHC) with molecular weight of up to 281 000 was obtained with a catalyst loading of 0.001 mol%. In contrast, bifunctional Mg-II and Zn-II counterparts, 3-Cl and 4-Cl, as well as a binary catalyst system, 1-Cl with bis(triphenylphosphine)iminium chloride (PPNCl), showed poor catalytic performances. Kinetic studies revealed that the reaction rate was first-order in [CHO] and [2-Br] and zero-order in [CO2], and the activation parameters were determined: Delta H double dagger = 12.4 kcal mol(-1), Delta S double dagger = -26.1 cal mol(-1) K-1, and Delta G double dagger = 21.6 kcal mol(-1) at 80 degrees C. Comparative DFT calculations on two model catalysts, Al-III complex 2' and Mg-II complex 3', allowed us to extract key factors in the catalytic behavior of the bifunctional Al-III catalyst. The high polymerization activity and carbonate-linkage selectivity originate from the cooperative actions of the metal center and the quaternary ammonium cation, both of which facilitate the epoxide-ring opening by the carbonate anion to form the carbonate linkage in the key transition state such as TS3b (Delta H double dagger = 13.3 kcal mol(-1), Delta S double dagger = -3.1 cal mol(-1) K-1, and Delta G double dagger = 14.4 kcal mol(-1) at 80 degrees C).

Synthesis of silyl formates, formamides, and aldehydes via solvent-free organocatalytic hydrosilylation of CO2
Takumi Murata, Mahoko Hiyoshi, Manussada Ratanasak, Jun-ya Hasegawa, Tadashi Ema
CHEMICAL COMMUNICATIONS, 56, 43, 5783, 5786, ROYAL SOC CHEMISTRY, 2020年05月, ［査読有り］, ［責任著者］
英語, 研究論文（学術雑誌）, Carbon dioxide (CO2) was used as a C1 source to prepare silyl formates, formamides, and aldehydes. Tetrabutylammonium acetate (TBAA) catalyzed the solvent-free N-formylation of amines with CO2 and hydrosilane to give formamides including Weinreb formamide, Me(MeO)NCHO, which was successively converted into aldehydes by one-pot reactions with Grignard reagents.

A detailed analysis of the spin-crossover reaction of H⁠2S binding to heme and the six-coordinated FeP(Im)-HS⁠− porphyrin complex
B.D. Ostojić, P. Schwerdtfeger, A. Nakayama, J. Hasegawa, D.S. Đorđević
J. Inorg. Biochem., 206, 111049, 111049, Elsevier BV, 2020年05月, ［査読有り］
英語, 研究論文（学術雑誌）

Roles of Salicylate Donors in Enhancement of Productivity and Isotacticity of Ziegler-Natta Catalyzed Propylene Polymerization
Manussada Ratanasak, Jun-ya Hasegawa, Vudhichai Parasuk
POLYMERS, 12, 4, MDPI, 2020年04月, ［査読有り］
英語, 研究論文（学術雑誌）, Roles of internal salicylate donors (SID) in enhancing activity and stereoselectivity of Ziegler-Natta catalyzed propylene (PP) polymerization were examined using DFT calculations. Five salicylate donors were studied. The chelate mode is the preferred adsorption mode. The linear relationship (R-2 = 0.96) between calculated adsorption energies (E-ads) of five SIDs and the experimental PP activities was observed. Thus, the SID with the strongest adsorption energy will provide the highest activity in agreement with our previous studies. Compared with diisobutyl phthalate (DIBP), which is the industrial electron donor, SID has stronger E-ads. The insertion step, which involves the pi-complex formation (E-pi) and the insertion activation or intrinsic activation energy (E-a) for PP polymerization was also examined. The relation between ln(activity) and apparent activation energy (E-a(app)), which is E-pi + E-a for the primary(1,2)-re insertion with R-2 = 0.99, was observed. The salicylate donor also has a lower E-a(app) than that of DIBP. This explains the better catalytic performance of SID. Our results also demonstrated that the size and the type of hydrocarbon substituents play a key role in controlling stereoselectivity and activity. In addition, we found a good relationship between E-ads and both intrinsic (E-a) and apparent (E-a(app)) activation energies of five salicylate donors with R-2 of 0.90 and 0.97, respectively.

Spin‐inversion mechanisms in O2 binding to a model heme complex revisited by density function theory calculations
K. Saito, Y. Watabe, T. Fujihara, T. Takayanagi, J. Hasegawa
J. Comput. Chem., 41, 11, 1130, 1138, WILEY, 2020年04月, ［査読有り］, ［最終著者］
英語, 研究論文（学術雑誌）, Spin-inversion mechanisms in O-2 binding to a model heme complex, consisting of Fe(II)-porphyrin and imidazole, were investigated using density-functional theory calculations. First, we applied the recently proposed mixed-spin Hamiltonian method to locate spin-inversion structures between different total spin multiplicities. Nine spin-inversion structures were successfully optimized for the singlet-triplet, singlet-quintet, triplet-quintet, and quintet-septet spin-inversion processes. We found that the singlet-triplet spin-inversion points are located around the potential energy surface region at short Fe-O distances, whereas the singlet-quintet and quintet-septet spin-inversion points are located at longer Fe-O distances. This suggests that both narrow and broad crossing models play roles in O-2 binding to the Fe-porphyrin complex. To further understand spin-inversion mechanisms, we performed on-the-fly Born-Oppenheimer molecular dynamics calculations. The reaction coordinates, which are correlated to the spin-inversion dynamics between different spin multiplicities, are also discussed.

Methyl‐Selective α‐Oxygenation of Tertiary Amines to Formamides by Employing Copper/Moderately Hindered Nitroxyl Radical (DMN‐AZADO or 1‐Me‐AZADO)
S. Nakai, T. Yatabe, K. Suzuki, Y. Sasano, Y. Iwabuchi, J. Hasegawa, N. Mizuno, K. Yamaguchi
Angew. Chem. Int. Ed., 58, 46, 16651, 16659, WILEY-V C H VERLAG GMBH, 2019年12月, ［査読有り］
英語, 研究論文（学術雑誌）, Methyl-selective alpha-oxygenation of tertiary amines is a highly attractive approach for synthesizing formamides while preserving the amine substrate skeletons. Therefore, the development of efficient catalysts that can advance regioselective alpha-oxygenation at the N-methyl positions using molecular oxygen (O-2) as the terminal oxidant is an important subject. In this study, we successfully developed a highly regioselective and efficient aerobic methyl-selective alpha-oxygenation of tertiary amines by employing a Cu/nitroxyl radical catalyst system. The use of moderately hindered nitroxyl radicals, such as 1,5-dimethyl-9-azanoradamantane N-oxyl (DMN-AZADO) and 1-methyl-2-azaadamanane N-oxyl (1-Me-AZADO), was very important to promote the oxygenation effectively mainly because these N-oxyls have longer life-times than less hindered N-oxyls. Various types of tertiary N-methylamines were selectively converted to the corresponding formamides. A plausible reaction mechanism is also discussed on the basis of experimental evidence, together with DFT calculations. The high regioselectivity of this catalyst system stems from steric restriction of the amine-N-oxyl interactions.

L-Cysteine-Modified Acacia Gum as a Multifunctional Binder for Lithium-Sulfur Batteries
Qi Qi, Yaqian Deng, Sichen Gu, Min Gao, Jun-ya Hasegawa, Guangmin Zhou, Xiaohui Lv, Wei Lv, Quan-Hong Yang
ACS APPLIED MATERIALS & INTERFACES, 11, 51, 47956, 47962, AMER CHEMICAL SOC, 2019年12月, ［査読有り］
英語, 研究論文（学術雑誌）, A binder plays an important role in stabilizing the electrode structure and improving the cyclic stability of batteries. However, the traditional binders are no longer satisfactory in lithium-sulfur (Li-S) batteries because of their failure in accommodating the large volume changes of sulfur and trapping soluble intermediate polysulfides, thus causing severe capacity decay. In this work, we prepared a multifunctional binder for Li-S batteries by merely modifying the acacia gum (AG), a low-cost biomass polymer, with L-cysteine under mild conditions. Owing to the introduced amino and carboxyl branches by the L-cysteine, the modified AG shows enhanced polysulfide trapping ability and can effectively restrain the shuttling of polysulfides. In addition, the introduction of branches can help form a cross-linked 3D network with better mechanical strength and flexibility for adhering sulfur and accommodating the volume changes of cathode materials. As a result, compared with the normally used polyvinylidene fluoride binder and the unmodified AG binder, the L-cysteine-modified AG binder effectively enhanced the rate capability and cycling stability of the Li-S batteries directly using sulfur as the cathode, showing a promising way to prompt the practical use of Li-S batteries.

Electrostatic Stabilization of Single-Atom Catalysts by Ionic Liquids
Shipeng Ding, Yalin Guo, Max J. Hulsey, Bin Zhang, Hiroyuki Asakura, Lingmei Liu, Yu Han, Min Gao, Jun-ya Hasegawa, Botao Qiao, Tao Zhang, Ning Yan
CHEM, 5, 12, 3207, 3219, CELL PRESS, 2019年12月, ［査読有り］
英語, 研究論文（学術雑誌）, In single-atom catalysts (SACs), the isolated metal atoms on solid support are often charged. Taking advantage of this common feature, we establish ionic liquid-stabilized single-atom catalysts (ILSSACs) employing electrostatic interaction as a general stabilization strategy. While Pt nanoparticles were formed on hydroxyapatite after reaction when unprotected, Pt remained atomically dispersed on ionic liquid-stabilized samples. Density functional theory calculations reveal that the activation energy for the transformation of two isolated Pt atoms to a Pt dimer increases remarkably from 0.11 to 0.72 eV with the protection of [Bmim][BF4]. The presence of ILs also tunes the electronic state of Pt-1, inducing an order-of-magnitude hydrogenation activity increase. The simple stabilization strategy is easily extended to SACs comprising various metal atom-support combinations. For instance, ILs significantly improved the stability and selectivity of a Pd-1 catalyst for the hydrogenation of acetylene, thus outperforming unprotected SACs.

Ni-catalyzed cycloisomerization between 3-phenoxy acrylic acid derivatives and alkynes via intramolecular cleavage and formation of C–O bond, to give 2,3-disubstituted benzofurans
S. Ohno, J. Qiu, R. Miyazaki, H. Aoyama, K. Murai, J. Hasegawa, M. Arisawa
Org. Lett., 21, 20, 8400, 8403, AMER CHEMICAL SOC, 2019年10月, ［査読有り］
英語, 研究論文（学術雑誌）, Reactions based on transition-metal-catalyzed C-O bond cleavage have attracted much attention as a new synthetic method. Until now, several intermolecular reactions via C-O bond cleavage of aryl ethers, alkenyl ethers, esters, and others have been reported. Here we report an unprecedented C-O bond cleavage of 3-phenoxy acrylic acid derivatives, followed by intramolecular C-O bond formation with alkynes. This reaction gave 2,3-disubstituted benzofurans having useful functional groups-silyl substituents and acrylic acid derivatives-at the 2- and 3-positions, respectively. This report also described theoretical (DFT) insights into the mechanism.

Theoretical Study on the C-H Activation of Methane by Liquid Metal Indium: Catalytic Activity of Small Indium Clusters
Yuhki Ohtsuka, Yuta Nishikawa, Hitoshi Ogihara, Ichiro Yamanaka, Manussada Ratanasak, Akira Nakayama, Jun-ya Hasegawa
JOURNAL OF PHYSICAL CHEMISTRY A, 123, 41, 8907, 8912, AMER CHEMICAL SOC, 2019年10月, ［査読有り］, ［責任著者］
英語, 研究論文（学術雑誌）, The mechanism of C-H activation of methane by liquid indium, which is the first step of the dehydrogenative conversion of methane to higher hydrocarbons, was investigated using density functional theory calculations. In the first-principle molecular dynamics trajectory at the experimental temperature (1200 K), low-coordinated indium atoms continuously appear on the disordered liquid surface. The C-H cleavage is endothermic on clean surfaces, while the low-coordinated indium atoms reduce the endothermicity significantly. In small indium clusters, which are models of low-coordinated atoms on a surface, the calculated activation energy is much smaller than that on the clean surface. The energy level of the methane C-H sigma* orbital is reduced by the interaction with the indium 5p sigma orbitals. In-2 shows the lowest activation energy and exothermicity in the C-H bond cleavage.

Selective Catalytic Reduction of NOx with NH3 by Using Novel Catalysts: State of the Art and Future Prospects
Lupeng Han, Sixiang Cai, Min Gao, Jun-ya Hasegawa, Penglu Wang, Jianping Zhang, Liyi Shi, Dengsong Zhang
CHEMICAL REVIEWS, 119, 19, 10916, 10976, AMER CHEMICAL SOC, 2019年10月, ［査読有り］
英語, Selective catalytic reduction with NH3(NH3-SCR) is the most efficient technology to reduce the emission of nitrogen oxides (NOx) from coal-fired industries, diesel engines, etc. Although V2O5-WO3(MoO3)/TiO2 and CHA structured zeolite catalysts have been utilized in commercial applications, the increasing requirements for broad working temperature window, strong SO2 /alkali/heavy metal-resistance, and high hydrothermal stability have stimulated the development of new-type NH3-SCR catalysts. This review summarizes the latest SCR reaction mechanisms and emerging poison-resistant mechanisms in the beginning and subsequently gives a comprehensive overview of newly developed SCR catalysts, including metal oxide catalysts ranging from VOx, MnOx, CeO2, and Fe2O3 to CuO based catalysts; acidic compound catalysts containing vanadate, phosphate and sulfate catalysts; ion exchanged zeolite catalysts such as Fe, Cu, Mn, etc. exchanged zeolite catalysts; monolith catalysts including extruded, washcoated, and metal-mesh/foam-based monolith catalysts. The challenges and opportunities for each type of catalysts are proposed while the effective strategies are summarized for enhancing the acidity/redox circle and poison-resistance through modification, creating novel nanostructures, exposing specific crystalline planes, constructing protective/sacrificial sites, etc. Some suggestions are given about future research directions that efforts should be made in. Hopefully, this review can bridge the gap between newly developed catalysts and practical requirements to realize their commercial applications in the near future.

Adsorption mediated tandem acid catalyzed cellulose hydrolysis by ortho-substituted benzoic acids
Danjo P. De Chavez, Min Gao, Hirokazu Kobayashi, Atsushi Fukuoka, Jun-ya Hasegawa
MOLECULAR CATALYSIS, 475, 110459, ELSEVIER, 2019年10月, ［査読有り］, ［最終著者, 責任著者］
英語, 研究論文（学術雑誌）, Carboxylic acid and phenol moiety containing carbon materials are proven to catalyze cellulose hydrolysis. Experiments utilizing benzoic acid and substituted derivatives as model catalysts revealed that vicinal oxygenated group containing catalysts showed significantly higher activities regardless of acidity. However, the increase in catalytic activity was not well understood. Using density functional theory, the mechanism of catalysis was elucidated. Calculated binding energy followed the experimental turnover number suggesting that the formation and the stability of the adduct complex is imperative to catalysis. In addition to this, protonated system effectively modeled the experimental activation energy implying that a hydronium participates in the reaction. These calculations indicated that during the life time of the adduct complex, a dissolved proton assists in the overall catalytic mechanism.

Selective Synthesis of Primary Anilines from NH3 and Cyclohexanones by Utilizing Preferential Adsorption of Styrene on the Pd Nanoparticle Surface
Yu Koizumi, Xiongjie Jin, Takafumi Yatabe, Ray Miyazaki, Jun-ya Hasegawa, Kyoko Nozaki, Noritaka Mizuno, Kazuya Yamaguchi
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 58, 32, 10893, 10897, WILEY-V C H VERLAG GMBH, 2019年08月, ［査読有り］
英語, 研究論文（学術雑誌）, Dehydrogenative aromatization is one of the attractive alternative methods for directly synthesizing primary anilines from NH3 and cyclohexanones. However, the selective synthesis of primary anilines is quite difficult because the desired primary aniline products and the cyclohexanone substrates readily undergo condensation affording the corresponding imines (i.e., N-cyclohexylidene-anilines), followed by hydrogenation to produce N-cyclohexylanilines as the major products. In this study, primary anilines were selectively synthesized in the presence of supported Pd nanoparticle catalysts (e.g., Pd/HAP, HAP=hydroxyapatite, Ca-10(PO4)(6)(OH)(2)) by utilizing competitive adsorption unique to heterogeneous catalysis; in other words, when styrene was used as a hydrogen acceptor, which preferentially adsorbs on the Pd nanoparticle surface in the presence of N-cyclohexylidene-anilines, various structurally diverse primary anilines were selectively synthesized from readily accessible NH3 and cyclohexanones. The Pd/HAP catalyst was reused several times though its catalytic performance gradually declined.

Theoretical Study on the Rhodium-Catalyzed Hydrosilylation of C=C and C=O Double Bonds with Tertiary Silane
Liming Zhao, Naoki Nakatani, Yusuke Sunada, Hideo Nagashima, Jun-ya Hasegawa
JOURNAL OF ORGANIC CHEMISTRY, 84, 13, 8552, 8561, AMER CHEMICAL SOC, 2019年07月, ［査読有り］, ［最終著者, 責任著者］
英語, 研究論文（学術雑誌）, Reaction mechanisms of hydrosilylation of ketone and alkene with tertiary silane using the Wilkinson-type catalyst were theoretically investigated on the basis of density functional calculations using omega B97XD functional. Previously proposed three mechanisms, the Chalk-Harrod (CH) mechanism, the modified Chalk-Harrod (mCH) mechanism, and the outer-sphere mechanism were examined. Besides, we also found two mechanisms, the alternative CH (aCH) mechanism and the double hydride (DH) mechanism. In the aCH mechanism, a four-coordinate rhodium hydride complex formed through the elimination of R3Si-Cl is a catalytically active species. In the DH mechanism, the active species is a six-coordinate complex with two Rh-H bonds. For the C=O double bond hydrosilylation, the rate-determining steps of the aCH and DH mechanisms are both acetone insertion into the Rh-H bond, and the order of the activation barrier is DH < aCH approximate to CH < mCH. For the C=C double bond hydrosilylation, except for the mCH pathway whose rate-determining step is the hydrosilane addition reaction, the rate-determining steps of the CH, aCH, and DH pathways are Si-C reductive elimination reactions. The order of the energy barrier is DH approximate to mCH < aCH approximate to CH. In the outer-sphere mechanism, no stable intermediate or transition state was found. Consequently, we concluded that the DH mechanism is adopted as the mechanism for the Rh-catalyzed hydrosilylation of the carbonyl group while the mCH or DH mechanism is adopted as the mechanism for alkenes under conditions where their active intermediates are formed. The present result revises a hypothesis that the hydrosilylation of the carbonyl group is in general accomplished by the mCH mechanism. The active species in the DH mechanism has one more extra Rh-H bond compared to that of the other pathways, and its interaction with a silyl group, trans-influence, and small steric effect are the origin of the highly efficient catalytic activity, which was not reported before.

Experimental and theoretical study of multinuclear indium-oxo clusters in CHA zeolite for CH4 activation at room temperature
Zen Maeno, Shunsaku Yasumura, Chong Liu, Takashi Toyao, Kenichi Kon, Akira Nakayama, Jun-ya Hasegawa, Ken-ichi Shimizu
PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 21, 25, 13415, 13427, ROYAL SOC CHEMISTRY, 2019年07月, ［査読有り］
英語, 研究論文（学術雑誌）, We have carried out an experimental and theoretical study of CHA-zeolite supported indium (In)-oxo clusters that promote CH4 activation at room temperature. X-ray absorption fine structure (XAFS) measurements indicate the formation of multinuclear In-oxo clusters by the O-2 activation of the In(I)-exchanged CHA zeolite prepared through reductive solid-state ion exchange (RSSIE). The structure of the In-oxo clusters and their locations were investigated in detail using ab initio thermodynamic analysis. The redox properties of the In species during RSSIE and the formation of the In-oxo clusters were also studied by temperature programmed reaction and in situ XAFS measurements. The reaction of CH4 on the O-2-activated In-CHA zeolite was monitored using IR spectroscopy where adsorbed formic acid was generated at room temperature. The adsorption and C-H activation of CH4 on our plausible model of the In-oxo clusters were theoretically investigated using density functional theory calculations. We found that CH4 is likely to adsorb and react more easily on dinuclear In-oxo ions than on monomeric In-oxo ions and that the C-H bond cleavage reaction occurs via a heterolytic pathway rather than a homolytic pathway. This study reveals the potential of multinuclear In-oxo clusters as active sites for the transformation of CH4 to oxygenates under mild reaction conditions.

SO2-Tolerant Selective Catalytic Reduction of NOx over Meso-TiO2@Fe2O3@Al2O3 Metal-Based Monolith Catalysts
Lupeng Han, Min Gao, Jun-ya Hasegawa, Shuangxi Li, Yongjie Shen, Hongrui Li, Liyi Shi, Dengsong Zhang
ENVIRONMENTAL SCIENCE & TECHNOLOGY, 53, 11, 6462, 6473, AMER CHEMICAL SOC, 2019年06月, ［査読有り］
英語, 研究論文（学術雑誌）, It is an intractable issue to improve the low-temperature SO2-tolerant selective catalytic reduction (SCR) of NOx with NH3 because deposited sulfates are difficult to decompose below 300 degrees C. Herein, we established a low-temperature self-prevention mechanism of mesoporous-TiO2@Fe2O3 core-shell composites against sulfate deposition using experiments and density functional theory. The mesoporous TiO2-shell effectively restrained the deposition of FeSO4 and NH4HSO4 because of weak SO2 adsorption and promoted NH4HSO4 decomposition on the mesoporous-TiO2. The electron transfer at the Fe2O3 (core)-TiO2 (shell) interface accelerated the redox cycle, launching the "Fast SCR" reaction, which broadened the low-temperature window. Engineered from the nano- to macro-scale, we achieved one-pot self-installation of mesoporous-TiO2@Fe2O3 composites on the self-tailored AlOOH@Al-mesh monoliths. After the thermal treatment, the mesoporous-TiO2@Fe2O3@Al2O3 monolith catalyst delivered a broad window of 220-420 degrees C with NO conversion above 90% and had superior SO2 tolerance at 260 degrees C. The effective heat removal of Al-mesh monolithcatalysts restrained NH3 oxidation to NO and N2O while suppressing the decomposition of NH4NO3 to N2O, and this led to much better high-temperature activity and N-2 selectivity. This work supplies a new point for the development of low-temperature SO2-tolerant monolithic SCR catalysts with high N-2 selectivity, which is of great significance for both academic interests and practical applications.

DFT Mechanistic Study on the Complete Oxidation of Ethylene by the Silica-Supported Pt Catalyst: C═C Activation via the Ethylene Dioxide Intermediate
R. Miyazaki, N. Nakatani, S. V. Levchenko, T. Yokoya, K. Nakajima, K. Hara, A. Fukuoka, J. Hasegawa
J. Phys. Chem. C, 123, 20, 12706, 12715, AMER CHEMICAL SOC, 2019年05月, ［査読有り］, ［最終著者, 責任著者］
英語, 研究論文（学術雑誌）, Low-temperature complete oxidation of ethylene by the mesoporous silica-supported Pt catalyst is a forefront technology for food preservation. Public implementations of the Pt catalyst have already begun, and spectroscopy analyses on the catalytic mechanism have been reported. In this study, density functional theory calculations were conducted to clarify the potential energy profile and electronic mechanism of the catalytic reaction. Based on the experimental findings, a reaction pathway was proposed for ethylene oxidation up to CO2 formation via the HCHO intermediate. Among several possibilities, a reaction pathway via ethylene dioxide species is energetically plausible for the C-C bond cleavage to generate HCHO. Particular focus was given to the electronic effect of the silica support in the ethylene dioxide route. The reservoir effect, in which the siloxide groups take electrons from the Pt moiety, reduces the activation energy of the C-C bond cleavage step by taking electrons from sigma(C-C) orbital.

Catalysis of liquid-metal indium for direct dehydrogenative conversion of methane into higher hydrocarbons　　　　　　　　　　　　　　　
Yuta Nishikawa, Ayumi Nakaya, Hitoshi Ogihara, Yuki Ohtsuka, Akira Nakayama, Jun-ya Hasegawa, Shoji Iguchi, Ichiro Yamanaka
12th Natural Gas Conversion Symposium 2019, 263, 266, AIChE, 2019年
英語, 研究論文（国際会議プロシーディングス）, Dehydrogenative conversion of methane (DCM) is an attractive reaction. We already reported that liquid-metal indium supported on silica (In/Si02) was an effective catalyst for DCM. Characterization studies and kinetic studies indicated that liquid-metal indium catalyzed cleavage of a C-H bond of methane and coupling methane to ethane selectively. In addition, conversion of ethane and temperature-programmed reaction in ethane (TPR-C2H6) suggested that indium did not activate both a C-H bond and a C-C bond of ethane. Indium has the unique catalysis to activate only a C-H bond of methane, therefore, selectivity to hydrocarbons was still high despite high temperature.

Constraint structure optimization to a specific minimum using ionization energy
Iori Harada, Akira Nakayama, Jun-ya Hasegawa
JOURNAL OF COMPUTATIONAL CHEMISTRY, 40, 2, 507, 514, WILEY, 2019年01月, ［査読有り］, ［最終著者, 責任著者］
英語, 研究論文（学術雑誌）, A structure optimization method with ionization energy constraint is developed to explore structures with specific ionization energy. The Levine-Coe-Martinez penalty function (J Phys Chem B 2008, 112, 405) was adopted, and the penalty function includes a predefined core-ionization energy and inner-shell ionization energy. For an S(N)2 reaction, isomerization of a platinum complex, a proton transfer reaction, and carbon monoxide adsorption on a palladium cluster, the present method was tested, and the targeted energy minima were obtained as designated by the input ionization energy. The shape of the objective function, the parameters in the penalty function, and structural changes during the optimization process were discussed. An automated parameter setting and possible problems are discussed for future direction. (c) 2018 Wiley Periodicals, Inc.

First-Order Interacting Space Approach to Excited-State Molecular Interaction: Solvatochromic Shift of p-Coumaric Acid and Retinal Schiff Base
Kazuma Yanai, Kazuya Ishimura, Akira Nakayama, Jun-ya Hasegawa
JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 14, 7, 3643, 3655, AMER CHEMICAL SOC, 2018年07月, ［査読有り］, ［最終著者, 責任著者］
英語, 研究論文（学術雑誌）, A triple-layer QM/sQM/MM method was developed for accurately describing the excited-state molecular interactions between chromophore and the molecular environment (Hasegawa, J.; Yanai, K.; Ishimura, K. ChemPhysChem 2015, 16, 305). A first-order-interaction space (FOIS) was defined for the interactions between QM and secondary QM (sQM) regions. Moreover, configuration interaction singles (CIS) and its second-order perturbation theory (PT2) calculations were performed within this space. In this study, numerical implementation of this FOISPT2 method significantly reduced the computing time, which realized application to solvatochromic systems, p-coumaric acid in neutral (p-CA) and anionic forms in aqueous solution, retinal Schiff base in methanol (MeOH) solution, and bacteriorhodopsin (bR). The results were consistent with the experimentally observed absorption spectra of the applied systems. The QM/sQM/MM result for the opsin shift was in better agreement to the experimental result than that of the ordinary QM/MM. A decomposition analysis was performed for the excited-state molecular interactions. Among the electronic interactions, charge-transfer (CT) effect, excitonic interaction, and dispersion interaction showed significant large contributions, while the electronic polarization effect presented only minor contribution. Furthermore, the result was analyzed to determine the contributions from each environmental molecule and was interpreted based on the distance of the molecules from the pi system in the chromophores.

CuCl/TMEDA/nor-AZADO-catalyzed aerobic oxidative acylation of amides with alcohols to produce imides
Kengo Kataoka, Keiju Wachi, Xiongjie Jin, Kosuke Suzuki, Yusuke Sasano, Yoshiharu Iwabuchi, Jun-ya Hasegawa, Noritaka Mizuno, Kazuya Yamaguchi
CHEMICAL SCIENCE, 9, 21, 4756, 4768, ROYAL SOC CHEMISTRY, 2018年06月, ［査読有り］
英語, 研究論文（学術雑誌）, Although aerobic oxidative acylation of amides with alcohols would be a good complement to classical synthetic methods for imides (e.g., acylation of amides with activated forms of carboxylic acids), to date, there have been no reports on oxidative acylation to produce imides. In this study, we successfully developed, for the first time, an efficient method for the synthesis of imides through aerobic oxidativeacylation of amides with alcohols by employing a CuCl/TMEDA/nor-AZADO catalyst system (TMEDA = teramethylethylendiamine; nor-AZADO = 9-azanoradamantane N-oxyl). The proposed acylation proceeds through the following sequential reactions: aerobic oxidation of alcohols to aldehydes, nucleophilic addition of amides to the aldehydes to form hemiamidal intermediates, and aerobic oxidation of the hemiamidal intermediates to give the corresponding imides. This catalytic system utilizes O-2 as the terminal oxidant and produces water as the sole by-product. An important point for realizing this efficient acylation system is the utilization of a TMEDA ligand, which, to the best of our knowledge, has not been employed in previously reported Cu/ligand/N-oxyl systems. Based on experimental evidence, we consider that plausible roles of TMEDA involve the promotion of both hemiamidal oxidation and regeneration of an active Cu-II-OH species from a Cu-I species. Here promotion of hemiamidal oxidation is particularly important. Employing the proposed system, various types of structurally diverse imides could be synthesized from various combinations of alcohols and amides, and gram-scale acylation was also successful. In addition, the proposed system was further applicable to the synthesis of -ketocarbonyl compounds (i.e., -ketoimides, -ketoamides, and -ketoesters) from 1,2-diols and nucleophiles (i.e., amides, amines, and alcohols).

Quaternary Alkyl Ammonium Salt-Catalyzed Transformation of Glycidol to Glycidyl Esters by Transesterification of Methyl Esters
Shinji Tanaka, Takuya Nakashima, Toshie Maeda, Manussada Ratanasak, Jun-ya Hasegawa, Yoshihiro Kon, Masanori Tamura, Kazuhiko Sato
ACS CATALYSIS, 8, 2, 1097, 1103, AMER CHEMICAL SOC, 2018年02月, ［査読有り］
英語, 研究論文（学術雑誌）, Catalytic transformation of glycidol while maintaining its epoxide moiety intact is challenging because the terminal epoxide that interacts with the hydroxyl group via a hydrogen bond is labile for the ring-opening reaction. We found that a quaternary alkyl ammonium salt catalyzes the selective transformation of glycidol to glycidyl esters by transesterification of methyl esters. The developed method can be applied to the synthesis of multiglycidyl esters, which are valuable epoxy resin monomers. Mechanistic studies revealed the formation of a binding complex of glycidol and quaternary alkyl ammonium salt in a nonpolar solvent and the generation of the alkoxide anion as a catalyst through the ring-opening reaction of the epoxide. Computational studies of the reaction mechanism indicated that the alkoxide anion derived from glycidol tends to abstract the proton of another glycidol rather than work as a nucleophile, initiating the catalytic transesterification. Payne rearrangement of the deprotonated glycidol, which produces a destabilized base that promotes nonselective reactions, is energetically unfavorable due to the double hydrogen bond between the anion and diol. The minimal interaction between the quaternary alkyl ammonium cation and the epoxide moiety inhibited the random ring-opening pathway leading to polymerization.

Transition States of Spin-State Crossing Reactions from Organometallics to Biomolecular Excited States　　　　　　　　　　　　　　　
N. Nakatani, A. Nakayama, J. Hasegawa
Frontiers of Quantum Chemistry, 289, 314, 2018年, ［査読有り］, ［招待有り］, ［最終著者, 責任著者］
英語

Recyclable and efficient polyurethane-Ir catalysts for direct borylation of aromatic compounds
Akihiro Kimura, Haruka Hayama, Jun-ya Hasegawa, Hassan Nageh, Yue Wang, Naofumi Naga, Mayumi Nishida, Tamaki Nakano
POLYMER CHEMISTRY, 8, 47, 7406, 7415, ROYAL SOC CHEMISTRY, 2017年12月, ［査読有り］
英語, 研究論文（学術雑誌）, Four polyurethanes comprising 2,2'-bipyridyl moieties incorporated in the main chain were synthesized as a novel polymer ligand for the Ir(I)-catalyzed direct borylation of aromatic compounds. The polyurethanes were insoluble in common organic solvents and soluble in dimethylsulfoxide. The borylation reaction of benzene catalyzed by Ir(I) in the presence of the polymer prepared from 4,4'-bis(hydroxylmethyl)-2,2'-bipyridyl and 1,6-diisocyanatohexane led to the catalytic activities comparable to that in the presence of 2,2'-bipyridyl, while the polymers prepared by the reactions of 4,4'-bis(hydroxylmethyl)-2,2'-bipyridyl with 1,4-diisocyanatobenzene, 1,4-diisocyanato-3-methylbenzene, and bis(4-isocyanatophenyl)methane possesed lower catalytic activities. The high activity observed using the 1,6-diisocyanatohexane-based polyurethane catalyst could have a connection to the fact that this polymer has the highest tendency to form the inter-chain hydrogen bond. The borylation reaction systems with the polymers were biphasic, where the top and bottom layers contained the product and the polymer-based catalysts, respectively. Due to the phase separation, the product isolation and catalyst recycle were readily performed through a simple decantation. The catalyst prepared from 1,6-diisocyanatohexane-based polyurethane was able to be recycled at least five times without a significant decrease in activity. Further, the regio-selectivity in borylation of toluene, anisole, and trifluoromethybenzene was studied using the polyurethane ligands as well as the corresponding small-molecular ligands.

Catalytic Cyclopropanation by Myoglobin Reconstituted with Iron Porphycene: Acceleration of Catalysis due to Rapid Formation of the Carbene Species
Koji Ohora, Hiroyuki Meichin, Liming Zhao, Matthew W. Wolf, Akira Nakayama, Jun-ya Hasegawa, Nicolai Lehnert, Takashi Hayashi
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 139, 48, 17265, 17268, AMER CHEMICAL SOC, 2017年12月, ［査読有り］, ［責任著者］
英語, 研究論文（学術雑誌）, Myoglobin reconstituted with iron porphycene catalyzes the cyclopropanation of styrene with ethyl diazoacetate. Compared to native myoglobin, the reconstituted protein significantly accelerates the catalytic reaction and the k(cat)/K-m value is 26-fold enhanced. Mechanistic studies indicate that the reaction of the reconstituted protein with ethyl diazoacetate is 615-fold faster than that of native myoglobin. The metallocarbene species reacts with styrene with the apparent second-order kinetic constant of 28 mM(-1) s(-1) at 25 degrees C. Complementary theoretical studies support efficient carbene formation by the reconstituted protein that results from the strong ligand field of the porphycene and fewer intersystem crossing steps relative to the native protein. From these findings, the substitution of the cofactor with an appropriate metal complex serves as an effective way to generate a new biocatalyst.

Photo-induced beta-elimination of 9-fluorenylmethanol leading to dibenzofulvene
Hassan Nageh, Liming Zhao, Akira Nakayama, Jun-ya Hasegawa, Yue Wang, Tamaki Nakano
CHEMICAL COMMUNICATIONS, 53, 60, 8431, 8434, ROYAL SOC CHEMISTRY, 2017年08月, ［査読有り］
英語, 研究論文（学術雑誌）, An effective photo-induced beta-elimination of an alcohol leading to a vinyl compound is introduced for the first time. 9-Fluorenylmethanol was irradiated in a solution using a Xe lamp and was efficiently converted to dibenzofulvene (DBF) (9-methylenefluorene) in the absence of base which is necessary in the corresponding ground-state reaction.

Formation of a New, Strongly Basic Nitrogen Anion by Metal Oxide Modification
Masazumi Tamura, Ryota Kishi, Akira Nakayama, Yoshinao Nakagawa, Jun-ya Hasegawa, Keiichi Tomishige
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 139, 34, 11857, 11867, AMER CHEMICAL SOC, 2017年08月, ［査読有り］
英語, 研究論文（学術雑誌）, Development of new hybrid materials having unique and unprecedented catalytic properties is a challenge for chemists, and heterogeneous-homogeneous hybrid catalysts have attracted much attention because of the preferable and exceptional properties that are highly expected to result from combination of the components. Base catalysts are widely used in organic synthesis as key materials, and a new class of base catalysts has made a large impact from academic and industrial-viewpoints. Here, a principle for creating a new strong base by hybridization of homogeneous and heterogeneous components is presented. It is based on the modification of organic compounds with metal oxides by using the acid-base property of metal oxides. Based on kinetic and DFT studies, combination of CeO2 and 2-cyanopyridine drastically enhanced the basicity of 2-cyanopyridine by a factor of about 10(9) (similar to 9 by pK(a) (in CH3CN)), and the pK(a) was estimated to be similar to 21, which locates it in the superbase category. 2-Cyanopyridine and CeO2 formed a unique adsorption complex-via two interaction modes: (i) coordinative interaction between the Ce atom of CeO2 and the N atom of the pyridine ring in 2-cyanopyridine, and (ii) covalent interaction between the surface O atom of CeO2 and the C atom of the CN group in 2-cyanopyridine by addition of the lattice oxygen of CeO2 to the CN group of 2-cyanopyridine. These interactions established a new, strongly basic site of N- over the CeO2 surface.

Hidden radical reactivity of the [FeO](2+) group in the H-abstraction from methane: DFT and CASPT2 supported mechanism by the example of model iron (hydro)oxide species
V. Kovalskii, A. Shubin, Y. Chen, D. Ovchinnikov, S. Ph. Ruzankin, J. Hasegawa, I. Zilberberg, V. N. Parmon
CHEMICAL PHYSICS LETTERS, 679, 193, 199, ELSEVIER SCIENCE BV, 2017年07月, ［査読有り］
英語, 研究論文（学術雑誌）, Reactivity of the [FeO](2+) group in the abstraction of hydrogen from methane is determined by metastable oxyl state Fe-III-O-center dot causing the negative spin polarization of the methyl moiety as was shown by quantum-chemical means with the use of model iron hydroxide species FeO(OH)(2), Fe2O(OH)(5), and Fe4O5(OH)(3) as an example. The energy of the gap between the ground-state ferryl configuration Fe-IV=O and the oxyl state correlates with the energy barrier of the H-abstraction from methane. (C) 2017 Elsevier B.V. All rights reserved.

Selective Dehydration of Mannitol to Isomannide over H beta Zeolite
Haruka Yokoyama, Hirokazu Kobayashi, Jun-ya Hasegawa, Atsushi Fukuoka
ACS CATALYSIS, 7, 7, 4828, 4834, AMER CHEMICAL SOC, 2017年07月, ［査読有り］
英語, 研究論文（学術雑誌）, Isomannide is a potential feedstock for the production of super engineering plastics. A prospective route to obtain isomannide is dehydration of mannitol derived from lignocellulosic biomass, but homogeneous acid catalysts reported in the literature produce a large amount of 2,5-sorbitan as a byproduct in the dehydration reaction. In this work, we initially studied the mechanism of proton-induced dehydration of mannitol by density functional theory calculations, which suggested that local steric hindrance around acid sites designed at the angstrom level can tune the selectivity toward isomannide formation. Based on this prediction, we found that the precisely defined microporous confinement offered by H beta provides improved selectivity and high catalytic activity for the production of isomannide, where 1,4-dehydration is favored by 20 kJ mol(-1) of activation energy. The optimization of the Si/Al ratio of H beta to balance the acid amount and hydrophobicity improved the catalytic activity and achieved 63% yield of isomannide, far exceeding the best result reported previously (35% yield).

Selected configuration interaction method using sampled first-order corrections to wave functions
Yuhki Ohtsuka, Jun-ya Hasegawa
JOURNAL OF CHEMICAL PHYSICS, 147, 3, 34102, AMER INST PHYSICS, 2017年07月, ［査読有り］
英語, 研究論文（学術雑誌）, A new selected configuration interaction (CI) method was proposed for the potential energy surfaces of quasi-degenerate and excited states. Slater determinants are generated by sampling the first-order corrections to the target-state wave functions using the quantum Monte Carlo method in determinant space. As in the Monte Carlo (MC) CI method, the wave function is improved at each iteration by generating new determinants and applying a pruning step. Compared to the random generation in the MCCI calculations, the number of iterations before convergence is significantly reduced. Regarding the potential energy curves of the ground and excited states of C-2, the non-parallelity errors were sufficiently small, thus indicating the method's applicability to the calculations of potential energy surfaces. Published by AIP Publishing.

A coordination strategy to realize a sextuply-bonded complex
Yue Chen, Jun-ya Hasegawa, Kazuya Yamaguchi, Shigeyoshi Sakaki
PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 19, 23, 14947, 14954, ROYAL SOC CHEMISTRY, 2017年06月, ［査読有り］
英語, 研究論文（学術雑誌）, The synthesis of higher-order multiple bonds is a great challenge in chemistry. However, no stable compound with a sextuple bond has been reported, except for Mo-2 in an inert matrix at low temperatures. Herein, we propose a strategy to construct a sextuple bond in a dinuclear transition metal complex based on complete active space second-order perturbation theory (CASPT2) and density functional theory calculations. When the dinuclear core M-2 (M = W, Mo, and Re+) is capped by two neutral electron-donating ligands at both M-M ends, a sextuple bond can be realized. The proposed ligands stabilize the M-2 core by the coordination, conserve the six bonding orbitals in the occupied space, and suppress the weight of the delta-delta(star) excited electronic configuration. Calculated large formation energies of these complexes indicate the large possibility of the synthesis. Electronic structures and sextuply bonding interactions were analyzed in detail.

Electronic Polarization Effect of the Water Environment in Charge-Separated Donor-Acceptor Systems: An Effective Fragment Potential Model Study
Kazuma Yanai, Kazuya Ishimura, Akira Nakayama, Michael W. Schmidt, Mark S. Gordon, Jun-ya Hasegawa
JOURNAL OF PHYSICAL CHEMISTRY A, 120, 51, 10273, 10280, AMER CHEMICAL SOC, 2016年12月, ［査読有り］
英語, 研究論文（学術雑誌）, The electronic polarization (POL) of the surrounding environment plays a crucial role in the energetics of charge-separated systems. Here, the mechanism of POL in charge-separated systems is studied using a combined quantum mechanical and effective fragment potential (QM/EFP) method. In particular, the POL effect caused by charge separation (CS) is investigated at the atomic level by decomposition into the POL at each polarizability point. The relevance of the electric field generated by the CS is analyzed in detail. The model systems investigated are Na+-Cl- and guanine thymine solvated in water. The dominant part of the POL arises from solvent molecules close to the donor (D) and acceptor (A) units. At short D-A distances, the electric field shows both positive and negative interferences. The former case enhances the POL energy. At longer distances, the interference is weakened, and the local electric field determines the POL energy.

Theoretical Study on Highly Active Bifunctional Metalloporphyrin Catalysts for the Coupling Reaction of Epoxides with Carbon Dioxide
Jun-ya Hasegawa, Ray Miyazaki, Chihiro Maeda, Tadashi Ema
CHEMICAL RECORD, 16, 5, 2260, 2267, WILEY-V C H VERLAG GMBH, 2016年10月, ［査読有り］
英語, 研究論文（学術雑誌）, Highly active bifunctional metalloporphyrin catalysts were developed for the coupling reaction of epoxides with CO2 to produce cyclic carbonates. The bifunctional catalysts have both quaternary ammonium halide groups and a metal center. To elucidate the roles of these catalytic groups, DFT calculations were performed. Control reactions using tetrabutylammonium halide as a catalyst were also investigated for comparison. In the present article, the results of our computational studies are overviewed. The computational results are consistent with the experimental data and are useful for elucidating the structure-activity relationship. The key features responsible for the high catalytic activity of the bifunctional catalysts are as follows: 1) the cooperative action of the halide anion (nucleophile) and the metal center (Lewis acid); 2) the near-attack conformation, leading to the efficient opening of the epoxide ring in the rate-determining step; and 3) the conformational change of the quaternary ammonium cation to stabilize various anionic species generated during catalysis, in addition to the robustness (thermostability) of the catalysts.

Spin-Blocking Effect in CO and H-2 Binding Reactions to Molybdenocene and Tungstenocene: A Theoretical Study on the Reaction Mechanism via the Minimum Energy Intersystem Crossing Point
K-jiro Watanabe, Naoki Nakatani, Akira Nakayama, Masahiro Higashi, Jun-ya Hasegawa
INORGANIC CHEMISTRY, 55, 16, 8082, 8090, AMER CHEMICAL SOC, 2016年08月, ［査読有り］
英語, 研究論文（学術雑誌）, Potential energy profiles and electronic structural interpretation of the CO and H-2 binding reactions to molybdenocene and tungstenocene complexes [MCp2] (M = Mo and W, Cp = cycropentadienyl) were studied using density functional theory calculations and ab initio multiconfigurational electronic structure calculations. Experimentally observed slow H-2 binding was reasonably explained in terms of the spin-blocking effect. Electronic structural analysis at the minimum-energy intersystem crossing point (MEISCP) revealed that the singly occupied molecular orbital's pi-bonding/sigma-antibonding character in the M-CO/H-2 moiety determines the energy levels of the MEISCP. Analysis of the reaction coordinate showed that the singlet-triplet gap significantly depends on the Cp-M-Cp angle. Therefore, not only the metal ligand distance but also the Cp-M-Cp angle is an important reaction coordinate to reach the MEISCP, the transition state of H-2 binding. The role of spin orbit coupling is also discussed.

Bifunctional Porphyrin Catalysts for the Synthesis of Cyclic Carbonates from Epoxides and CO2: Structural Optimization and Mechanistic Study (vol 136, pg 15270, 2014)
Tadashi Ema, Yuki Miyazaki, Junta Shimonishi, Chihiro Maeda, Jun-ya Hasegawa
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 28, 8982, 8982, AMER CHEMICAL SOC, 2016年07月, ［査読有り］
英語

A DFT and multi-configurational perturbation theory study on O-2 binding to a model heme compound via the spin-change barrier
Y. Kitagawa, Y. Chen, N. Nakatani, A. Nakayama, J. Hasegawa
PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18, 27, 18137, 18144, ROYAL SOC CHEMISTRY, 2016年07月, ［査読有り］
英語, 研究論文（学術雑誌）, Dioxygen binding to a model heme compound via intersystem crossing (ISC) was investigated with a multi-state multi-configurational self-consistent field method with second-order perturbation theory (MS-CASPT2) and density functional theory (DFT) calculations. In elongated Fe-O distances, the energy levels of the S-0 and T-1 states are separated, which decreases the probability of intersystem crossing in these structures. At the DFT(B97D) level of calculation, the Fe-O distances of the S-0 and T-1 states were 1.91 and 2.92 angstrom, respectively. The minimum energy intersystem crossing point (MEISCP) was located as a transition state at a Fe-O distance of 2.17 angstrom with an energy barrier of 1.0 kcal mol(-1) from the T-1 minimum. The result was verified with MS-CASPT2 calculations including the spin-orbit interaction which also showed the intersystem crossing point at a Fe-O distance of 2.05 angstrom. An energy decomposition analysis on the reaction coordinate showed the important contribution of the ring-shrinking mode of the porphyrin ring, indicating that the reaction coordinates which control the relative energy level of the spin-states play a key role in intersystem crossing.

Highly Active and Robust Metalloporphyrin Catalysts for the Synthesis of Cyclic Carbonates from a Broad Range of Epoxides and Carbon Dioxide
Chihiro Maeda, Junta Shimonishi, Ray Miyazaki, Jun-ya Hasegawa, Tadashi Ema
CHEMISTRY-A EUROPEAN JOURNAL, 22, 19, 6556, 6563, WILEY-V C H VERLAG GMBH, 2016年05月, ［査読有り］
英語, 研究論文（学術雑誌）, Bifunctional metalloporphyrins with quaternary ammonium bromides (nucleophiles) at the meta, para, or ortho positions of meso-phenyl groups were synthesized as catalysts for the formation of cyclic carbonates from epoxides and carbon dioxide under solvent-free conditions. The meta-substituted catalysts exhibited high catalytic performance, whereas the para- and ortho-substituted catalysts showed moderate and low activity, respectively. DFT calculations revealed the origin of the advantage of the meta-substituted catalyst, which could use the flexible quaternary ammonium cation at the meta position to stabilize various anionic species generated during catalysis. A zinc(II) porphyrin with eight nucleophiles at the meta positions showed very high catalytic activity (turnover number (TON)=240000 at 120 degrees C, turnover frequency (TOF)=31500h(-1) at 170 degrees C) at an initial CO2 pressure of 1.7MPa; catalyzed the reaction even at atmospheric CO2 pressure (balloon) at ambient temperature (20 degrees C); and was applicable to a broad range of substrates, including terminal and internal epoxides.

Facile Synthesis of 1,4-Bis(diaryl)-1,3-butadiynes Bearing Two Amino Moieties by Electrochemical Reaction-Site Switching, and Their Solvatochromic Fluorescence
Natsuyo Kamimoto, Nariaki Nakamura, Akina Tsutsumi, Hiroki Mandai, Koichi Mitsudo, Atsushi Wakamiya, Yasujiro Murata, Jun-ya Hasegawa, Seiji Suga
ASIAN JOURNAL OF ORGANIC CHEMISTRY, 5, 3, 373, 379, WILEY-V C H VERLAG GMBH, 2016年03月, ［査読有り］
英語, 研究論文（学術雑誌）, Bis(diaryl)-1,3-butadiynes bearing two amino moieties were easily synthesized by a sequential coupling reaction by using an electrochemical method. This sequential reaction consists of electrochemical oxidative homocoupling and Suzuki-Miyaura coupling. The fluorescence of the obtained bis(diaryl)-1,3-butadiynes is solvatochromic despite their symmetric linear structure and lack of a strong acceptor moiety.

Gold nanoparticles on OMS-2 for heterogeneously catalyzed aerobic oxidative α, β-dehydrogenation of b-heteroatom-substituted ketones
長谷川 淳也
Chem. Comm., 52, 99, 14314, 14317, ROYAL SOC CHEMISTRY, 2016年, ［査読有り］
英語, 研究論文（学術雑誌）, In the presence of Au nanoparticles supported on manganese oxide OMS-2 (Au/OMS-2), various kinds of beta-heteroatom-substituted alpha, beta-unsaturated ketones (heteroatom = N, O, S) can be synthesized through alpha, beta-dehydrogenation of the corresponding saturated ketones using O-2 (in air) as the oxidant. The catalysis of Au/OMS-2 is truly heterogeneous, and the catalyst can be reused.

Electronic spectra of azaindole and its excited state mixing: A symmetry-adapted cluster configuration interaction study
Sundaram Arulmozhiraja, Michelle L. Coote, Jun-ya Hasegawa
JOURNAL OF CHEMICAL PHYSICS, 143, 20, AMER INST PHYSICS, 2015年11月, ［査読有り］
英語, 研究論文（学術雑誌）, Electronic structures of azaindole were studied using symmetry-adapted cluster configuration interaction theory utilizing Dunning's cc-pVTZ basis set augmented with appropriate Rydberg spd functions on carbon and nitrogen atoms. The results obtained in the present study show good agreement with the available experimental values. Importantly, and contrary to previous theoretical studies, the excitation energy calculated for the important n-pi* state agrees well with the experimental value. A recent study by Pratt and co-workers concluded that significant mixing of pi-pi* and n-pi* states leads to major change in the magnitude and direction of the dipole moment of the upper state vibrational level in the 0,0 + 280 cm(-1) band in the S-1 <- S-0 transition when compared to that of the zero-point level of the S-1 state. The present study, however, shows that all the four lowest lying excited states, (1)Lb pi-pi*, La-1 pi-pi*, n-pi*, and pi-sigma*, cross each other in one way or another, and hence, significant state mixing between them is likely. The upper state vibrational level in the 0,0 + 280 cm(-1) band in the S-1 <- S-0 transition benefits from this four-state mixing and this can explain the change in magnitude and direction of the dipole moment of the S1 excited vibrational level. This multistate mixing, and especially the involvement of pi-sigma* state in mixing, could also provide a route for hydrogen atom detachment reactions. The electronic spectra of benzimidazole, a closely related system, were also investigated in the present study. (C) 2015 AIP Publishing LLC.

Synergy of Vicinal Oxygenated Groups of Catalysts for Hydrolysis of Cellulosic Molecules
Hirokazu Kobayashi, Mizuho Yabushita, Jun-ya Hasegawa, Atsushi Fukuoka
JOURNAL OF PHYSICAL CHEMISTRY C, 119, 36, 20993, 20999, AMER CHEMICAL SOC, 2015年09月, ［査読有り］
英語, 研究論文（学術雑誌）, Carbon materials bearing carboxylic acids and phenolic groups efficiently catalyze the hydrolysis of cellulose. In this work, we demonstrate that salicylic acid and phthalic acid show higher activity than other substituted benzoic acids as models of catalytic sites on carbons in the hydrolysis of cellobiose and cellulose. Notably, their turnover frequencies are larger than those of o-chlorobenzoic acid and o-trifluoromethylbenzoic acid, despite their lower acid strength. The high catalytic performance of salicylic acid and phthalic acid is not attributed to a reduction of activation energy but to an increase in the frequency factor. Nuclear magnetic resonance and density functional theory studies indicate that one oxygenated group forms a hydrogen bond with a hydroxyl group in cellobiose, which boosts the probability of attack of the neighboring carboxylic acid on the glycosidic bond. The computation also predicts a hydrolysis mechanism including an S(N)1 reaction with anomeric inversion, which reasonably accounts for the experimental results in the conversion of cellobiose.

Computational Investigation into Photoswitching Efficiency of Diarylethene Derivatives: An Insight Based on the Decay Constant of Electron Tunneling
Shohei Nishizawa, Jun-ya Hasegawa, Kenji Matsuda
JOURNAL OF PHYSICAL CHEMISTRY C, 119, 34, 20169, 20178, AMER CHEMICAL SOC, 2015年08月, ［査読有り］
英語, 研究論文（学術雑誌）, The switching efficiency (SE) of the intramolecular exchange interaction J between the open- and the closed-ring isomers of diarylethenes (DAEs) was investigated using DFT calculations of DAE biradicals with different core structures: DAEs with 3-thienyl, thiophene-S,S-dioxide-3-yl, 2-thienyl, or thiophene-S,S-dioxide-2-y1 rings. The SE of DAB with a 3-thienyl ring is calculated to be around 400-fold, which is the largest among the four calculated DAEs. The decay constant beta of the exchange interaction J for the DAB molecular wires was evaluated by calculating J for biradicals with different lengths of wires. For the wires of the closed-ring isomers of DAB with 3-thienyl- and thiophene-S,S-dioxide-3-yl rings, which are supposed to take a quinoid structure, allyl nitronyl nitroxide radical was successfully employed. The calculated beta values showed a significant difference between the open- and the closedring isomers, and this difference of beta is considered to be the origin of photoswitching of J. The difference of beta upon isomerization, Delta beta, is in good agreement with SE, and the largest Delta beta was obtained for the DAB with a 3-thienyl ring. We can understand the switching of J as the switching of electron tunneling efficiency beta between the open- and the closed-ring isomers.

meso-Dibenzoporphycene has a Large Bathochromic Shift and a Porphycene Framework with an Unusual cis Tautomeric Form
Koji Oohora, Ayumu Ogawa, Tamaki Fukuda, Akira Onoda, Jun-ya Hasegawa, Takashi Hayashi
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 54, 21, 6227, 6230, WILEY-V C H VERLAG GMBH, 2015年05月, ［査読有り］
英語, 研究論文（学術雑誌）, meso-Monobenzoporphycene (mMBPc) and meso-dibenzoporphycene (mDBPc), in which one or two benzene moieties are fused at ethylene-bridged positions (meso-positions) of porphycene, were prepared in an effort to further delocalize the -electrons within the porphycene molecule. mMBPc and mDBPc were fully characterized by mass spectrometry, H-1 and (CNMR)-C-13 spectroscopy, and X-ray crystallography. The longest-wavelength Q-bands of mMBPc and mDBPc are red-shifted by 92nm and 418nm, respectively, compared to that of the unsubstituted porphycene (Pc). Electrochemical measurements indicate that the HOMO is destabilized and the LUMO is stabilized by the fused benzene moieties at the mesopositions. Furthermore, both XPS and theoretical studies support the presence of a cis tautomeric form in the ground state of mDBPc, despite the fact that essentially all known porphycene derivatives adopt the trans tautomeric form.

Theoretical Investigation on the Decaying Behavior of Exchange Interaction in Quinoid and Aromatic Molecular Wires
Shohei Nishizawa, Jun-ya Hasegawa, Kenji Matsuda
JOURNAL OF PHYSICAL CHEMISTRY C, 119, 9, 5117, 5121, AMER CHEMICAL SOC, 2015年03月, ［査読有り］
英語, 研究論文（学術雑誌）, The difference in the decaying behavior of the exchange interaction between quinoid and aromatic molecular wires was investigated by means of density functional theory calculations. The biradical quinoid structure was realized when the molecular wire consists of thiophene-S,S-dioxide and allyl nitronyl nitroxide radical. While the calculated decay constant (beta) for oligothiophene was 0.23 angstrom(-1), the obtained beta value for the quinoid structure of oligothiophene-S,S-dioxide was 0.09 angstrom(-1); this finding suggested that the quinoid molecular wire had a smaller beta value than the aromatic wire. It was also found that beta decreases upon oxidation of the sulfur atom in the oligothiophene due to an increase in its olefinic nature. The quinoid molecular wire made of thiophene-S,S-dioxide can be thus considered as a suitable system for the charge and spin transport in molecular electronics and spintronics.

Quantum Mechanical Molecular Interactions for Calculating the Excitation Energy in Molecular Environments: A First-Order Interacting Space Approach
Jun-ya Hasegawa, Kazuma Yanai, Kazuya Ishimura
CHEMPHYSCHEM, 16, 2, 305, 311, WILEY-V C H VERLAG GMBH, 2015年02月, ［査読有り］
英語, 研究論文（学術雑誌）, Intermolecular interactions regulate the molecular properties in proteins and solutions such as solvatochromic systems. Some of the interactions have to be described at an electronic-structure level. In this study, a commutator for calculating the excitation energy is used for deriving a first-order interacting space (FOIS) to describe the environmental response to solute excitation. The FOIS wave function for a solute-in-solvent cluster is solved by second-order perturbation theory. The contributions to the excitation energy are decomposed into each interaction and for each solvent.

Energy dissipative photoprotective mechanism of carotenoid spheroidene from the photoreaction center of purple bacteria Rhodobacter sphaeroides
Sundaram Arulmozhiraja, Naoki Nakatani, Akira Nakayama, Jun-ya Hasegawa
PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 17, 36, 23468, 23480, ROYAL SOC CHEMISTRY, 2015年, ［査読有り］
英語, 研究論文（学術雑誌）, Carotenoid spheroidene (SPO) functions for photoprotection in the photosynthetic reaction centers (RCs) and effectively dissipates its triplet excitation energy. Sensitized cis-to-trans isomerization was proposed as a possible mechanism for a singlet-triplet energy crossing for the 15,15'-cis-SPO; however, it has been questioned recently. To understand the dissipative photoprotective mechanism of this important SPO and to overcome the existing controversies on this issue, we carried out a theoretical investigation using density functional theory on the possible triplet energy relaxation mechanism through the cis-to-trans isomerization. Together with the earlier experimental observations, the possible mechanism was discussed for the triplet energy relaxation of the 15,15'-cis-SPO. The result shows that complete cis-to-trans isomerization is not necessary. Twisting the C15-C15' bond leads to singlet-triplet energy crossing at phi(14,15,15',14') = 77 degrees with an energy 32.5 kJ mol(-1) (7.7 kcal mol(-1)) higher than that of the T-1 15,15'-cis minimum. Further exploration of the minimum-energy intersystem crossing (MEISC) point shows that triplet relaxation could occur at a less distorted structure (phi = 58.4 degrees) with the energy height of 26.5 KJ mol(-1) (6.3 kcal mol(-1)). Another important reaction coordinate to reach the MEISC point is the bond-length alternation. The model truncation effect, solvent effect, and spin-orbit coupling were also investigated. The singlet-triplet crossing was also investigated for the 13,14-cis stereoisomer and locked-13,14-cis-SPO. We also discussed the origin of the natural selection of the cis over trans isomer in the RC.

Quaternary ammonium hydroxide as a metal-free and halogen-free catalyst for the synthesis of cyclic carbonates from epoxides and carbon dioxide
Tadashi Ema, Kazuki Fukuhara, Takashi Sakai, Masaki Ohbo, Fu-Quan Bai, Jun-ya Hasegawa
CATALYSIS SCIENCE & TECHNOLOGY, 5, 4, 2314, 2321, ROYAL SOC CHEMISTRY, 2015年, ［査読有り］
英語, 研究論文（学術雑誌）, Tetrabutylammonium hydroxide (TBAH) and other quaternary ammonium hydroxides catalyzed the cycloaddition of CO2 to epoxides under solvent-free conditions to give cyclic carbonates. When TBAH was exposed to CO2, TBAH was converted into tetrabutylammonium bicarbonate (TBABC), which was a catalytically active species. A D-labeled epoxide and an optically active epoxide were used to study the reaction mechanism, which invoked three plausible pathways. Among them, path A seemed to be predominant; the bicarbonate ion of TBABC attacks the less hindered C atom of the epoxide to generate a ring-opened alkoxide intermediate, which adds to CO2 to give a carbonate ion, and the subsequent cyclization yields a cyclic carbonate. Density functional theory (DFT) calculations successfully delineated the potential energy profile for each reaction pathway, among which path A was the lowest-energy pathway in accordance with the experimental results. The tetrabutylammonium (TBA) cation carries the positive charges on the H atoms, but not on the central N atom, and the positively charged H atoms close to the central N atom form an anion-binding site capable of stabilizing various anionic transition states and intermediates.

Platinum-catalyzed reduction of amides with hydrosilanes bearing dual Si-H groups: a theoretical study of the reaction mechanism
Naoki Nakatani, Jun-ya Hasegawa, Yusuke Sunada, Hideo Nagashima
DALTON TRANSACTIONS, 44, 44, 19344, 19356, ROYAL SOC CHEMISTRY, 2015年, ［査読有り］
英語, 研究論文（学術雑誌）, A platinum-catalyzed amide reduction through hydrosilylation with 1,2-bis(dimethylsilyl) benzene (BDSB) was investigated on a theoretical basis. While the platinum-catalyzed hydrosilylation of alkenes is well known, that of carbonyl groups rarely occurs. The only exception involves the use of bifunctional hydrosilanes having dual, closely located Si-H groups, which accelerate the hydrosilylation of carbonyl groups, leading to successful reduction of amides to amines under mild conditions. In the present study, we determined through density functional theory calculations that the platinum-catalyzed hydrosilylation of the C=O bond proceeds via a Pt(IV)-disilyl-dihydride intermediate with an associated activation energy of 29.6 kcal mol(-1). Although it was believed that the hydrosilylation of carbonyl groups does not occur via the classical Chalk-Harrod cycle, the computational results support a mechanism involving the insertion of the amide CvO bond into a Pt-H bond. This insertion readily occurs because a Pt-H bond in the Pt(IV)-disilyl-dihydride intermediate is highly activated due to the strong s-donating interaction of the silyl groups. The modified Chalk-Harrod mechanism that occurs preferentially in rhodium-catalyzed hydrosilylation as well as the ionic outer sphere mechanism associated with iridium-catalyzed amide reduction were both safely ruled out as mechanisms for this platinum-catalyzed amide reduction, because of the unexpectedly large activation barrier (>40 kcal mol(-1)) for the Si-O bond formation.

Bifunctional Porphyrin Catalysts for the Synthesis of Cyclic Carbonates from Epoxides and CO2: Structural Optimization and Mechanistic Study
Tadashi Ema, Yuki Miyazaki, Junta Shimonishi, Chihiro Maeda, Jun-ya Hasegawa
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136, 43, 15270, 15279, AMER CHEMICAL SOC, 2014年10月, ［査読有り］
英語, 研究論文（学術雑誌）, We prepared bifunctional Mg-II porphyrin catalysts 1 for the solvent-free synthesis of cyclic carbonates from epoxides and CO2. The activities of 1d, 1h, and 1i, which have Br, Cl, and I counteranions, respectively, increased in the order 1i < 1h < 1d. Catalysts 1d and 1jm, which bear four tetraalkylammonium bromide groups with different alkyl chain lengths, showed comparable but slightly different activities. Based on the excellent catalyst 1d, we synthesized MgII porphyrin 1o with eight tetraalkylammonium bromide groups, which showed even higher catalytic activity (turnover number, 138,000; turnover frequency, 19,000 h(-1)). The catalytic mechanism was studied by using 1d. The yields were nearly constant at initial CO2 pressures in the 16 MPa range, suggesting that CO2 was not involved in the rate-determining step in this pressure range. No reaction proceeded in supercritical CO2, probably because the epoxide (into which the catalyst dissolved) dissolved in and was diluted by the supercritical CO2. Experiments with O-18-labeled CO2 and D-labeled epoxide suggested that the catalytic cycle involved initial nucleophilic attack of Br on the less hindered side of the epoxide to generate an oxyanion, which underwent CO2 insertion to afford a CO2 adduct; subsequent intramolecular ring closure formed the cyclic carbonate and regenerated the catalyst. Density functional theory calculations gave results consistent with the experimental results, revealing that the quaternary ammonium cation underwent conformational changes that stabilized various anionic species generated during the catalytic cycle. The high activity of 1d and 1o was due to the cooperative action of the Mg-II and Br and a conformational change (induced-fit) of the quaternary ammonium cation.

Versatile and Sustainable Synthesis of Cyclic Imides from Dicarboxylic Acids and Amines by Nb2O5 as a Base-Tolerant Heterogeneous Lewis Acid Catalyst
Md. Ayub Ali, S. M. A. Hakim Siddiki, Kenichi Kon, Junya Hasegawa, Ken-ichi Shimizu
CHEMISTRY-A EUROPEAN JOURNAL, 20, 44, 14256, 14260, WILEY-V C H VERLAG GMBH, 2014年10月, ［査読有り］
英語, 研究論文（学術雑誌）, Catalytic condensation of dicarboxylics acid and amines without excess amount of activating reagents is the most atom-efficient but unprecedented synthetic method of cyclic imides. Here we present the first general catalytic method, proceeding selectively and efficiently in the presence of a commercial Nb2O5 as a reusable and base-tolerant heterogeneous Lewis acid catalyst. The method is effective for the direct synthesis of pharmaceutically or industrially important cyclic imides, such as phensuximide, N-hydroxyphthalimide (NHPI), and unsubstituted cyclic imides from dicarboxylic acid or anhydrides with amines, hydroxylamine, or ammonia.

Excited States of a Significantly Ruffled Porphyrin: Computational Study on Structure-Induced Rapid Decay Mechanism via Intersystem Crossing
Fu-Quan Bai, Naoki Nakatani, Akira Nakayama, Jun-ya Hasegawa
JOURNAL OF PHYSICAL CHEMISTRY A, 118, 23, 4184, 4194, AMER CHEMICAL SOC, 2014年06月, ［査読有り］
英語, 研究論文（学術雑誌）, The compound meso-tetra-tert-butylporphyrin (H2T(t-Bu)P) is a significantly ruffled porphyrin and known as a good quencher. Compared with planar porphyrins, H2T(t-Bu)P showed bathochromic shift and rapid radiationless decay of the (1)(pi, pi*) excited state. Density functional theory, approximated coupled-cluster theory, and complete active space self-consistent field method level calculations were performed for the potential energy surface (PES) of the low-lying singlet and triplet states of H2T(t-Bu)P. The origin of the bathochromic shift in the absorption and fluorescence spectra was attributed to both steric distortions of the ring and electronic effects of the substituents. The nonradiative deactivation process of H2T(t-Bu)P via intersystem crossing (ISC) is proposed as (S-1 --> T-2 --> T-1 --> S-0). Along a nonplanar distortion angle, the PESs of the S-1 and T-2 states are very close to each other, which suggests that many channels exist for ISC. For the T-1 --> S-0 transition, minimum energy ISC points were located, and spin-orbit coupling (SOC) was evaluated. The present results indicate that the ISC can also occur at the T-1/S-0 intersection, in addition to the vibrational SOC promoted by specific normal modes.

Entropically Favored Adsorption of Cellulosic Molecules onto Carbon Materials through Hydrophobic Functionalities
Mizuho Yabushita, Hirokazu Kobayashi, Jun-ya Hasegawa, Kenji Hara, Atsushi Fukuoka
CHEMSUSCHEM, 7, 5, 1443, 1450, WILEY-V C H VERLAG GMBH, 2014年05月, ［査読有り］
英語, 研究論文（学術雑誌）, Carbon-based materials have attracted interest as high-performance catalysts for the aqueous-phase conversion of cellulose. The adsorption of -glucans plays a crucial role in the catalytic performance of carbons, although the primary driving force and details of the adsorption process remain unclear. This study demonstrates that adsorption occurs at hydrophobic sites on the carbon surface and that hydrophilic groups are not involved. Analysis of adsorption temperature dependence also reveals that the entropy change associated with adsorption is positive. Our results indicate that adsorption occurs by entropically driven hydrophobic interactions in addition to CH- hydrogen bonding. These same CH- hydrogen bonds are also confirmed by DFT calculations. The adsorption of -glucans on carbons is significantly stronger than the affinity between -glucans. The adsorption equilibrium constants of -glucans on carbons increase exponentially with increasing degrees of polymerization, which supports the theory of strong interactions between the carbon and the long -glucans found in cellulose.

Theoretical Investigation of the Dependence of Exchange Interaction on Dihedral Angle between Two Aromatic Rings in a Wire Unit
Shohei Nishizawa, Jun-ya Hasegawa, Kenji Matsuda
CHEMISTRY LETTERS, 43, 4, 530, 532, CHEMICAL SOC JAPAN, 2014年04月, ［査読有り］
英語, 研究論文（学術雑誌）, The dependence of intramolecular exchange interaction on dihedral angle between two aromatic rings in a wire unit was investigated by using broken-symmetry UDFT (BS-UDFT) calculation. Biphenyl rings and 2,2'-bithiophene rings were used for molecular rods and nitronyl nitroxide and verdazyl were chosen as organic radical species. The exchange interaction was proportional to cos(2)theta where theta is the dihedral angle between two aromatic rings. This result shows good agreement with the dependence of conductance on dihedral angle between two phenyl rings. Our calculation strongly suggests the similarity of molecular conductance and intramolecular exchange interaction and reinforced the existence of an electron-tunneling mechanism underlying two physical properties.

Excited states and molecular interactions in photofunctional proteins
Jun-ya Hasegawa
ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 247, AMER CHEMICAL SOC, 2014年03月, ［査読有り］
英語

An Investigation on CD Inversion at Visible Region Caused by a Tilt of π-Conjugated Substituent: Theoretical and Experimental Approaches by Using Asymmetric Framework of Diarylethene Annulated Isomer
Takashi Hirose, Yuki Inoue, Jun-ya Hasegawa, Kenji Higashiguchi, Kenji Matsuda
J. Phys. Chem. A, 118, 6, 1084, 1093, AMER CHEMICAL SOC, 2014年02月, ［査読有り］
英語, 研究論文（学術雑誌）, A substituent effect of asymmetric diarylethene annulated isomer on their chiroptical properties was investigated by means of theoretical and experimental approaches. The absolute configuration of the annulated isomer was determined by X-ray structural analysis and DFT calculation. The TD-DFT calculation successfully reproduced not only the sign but also the shape and magnitude of experimental CD spectrum by considering the Boltzmann-weighted average of four atrop-isomers. A fragment decomposition (FD) analysis of rotatory strength clearly revealed a noteworthy effect; the tilting motion concomitant with the rotating motion of the substituent affects the sign and magnitude of CD signals. It was found that even when the absolute structure of the chiral core moiety does not change, the slight motion of the substituent can trigger the inversion of the CD signal.

Theoretical Investigation of the β Value of the π-Conjugated Molecular Wires by Evaluating Exchange Interaction between Organic Radicals
Shohei Nishizawa, Jun-ya Hasegawa, Kenji Matsuda
J. Phys. Chem. C, 117, 49, 26280, 26286, AMER CHEMICAL SOC, 2013年12月, ［査読有り］
英語, 研究論文（学術雑誌）, The decay constant beta of pi-conjugated molecular wire corresponds to the efficiency of electron tunneling through the molecule. We have calculated beta values of intramolecular magnetic exchange interactions by density functional theory for organic bis(nitronyl nitroxide)s that have several molecular wire units, namely, oligo-p-phenylene (OPP), oligophenylene ethynylene (OPE), oligophenylene vinylene (OPV), oligophenylene imine (OPI), bicyclo[1.1.1]pentane oligomer (BCP), beta,meso,beta-triply fused porphyrin oligomer (TFP), and meso,meso-linked porphyrin oligomer (MLP). For OPP, OPE, OPV, OPI, BCP, TFP, and MLP, beta was calculated to be 0.41, 0.25, 0.22, 0.32, 0.77, 0.03, and 0.65 angstrom(-1), respectively. The obtained beta values are in good agreement with the experimental value of the molecular tunneling conductance, suggesting similarity of the mechanism between exchange interaction and molecular conductance. This method can be used to estimate the efficiency of electron tunneling through the molecular wire.

Fragment-based configuration interaction wave function to calculate environmental effect on excited states in proteins and solutions
Jun-ya Hasegawa
CHEMICAL PHYSICS LETTERS, 571, 77, 81, ELSEVIER SCIENCE BV, 2013年05月, ［査読有り］
英語, 研究論文（学術雑誌）, Solvatochromic effect in proteins and solutions was described by a configuration interaction singles (CIS) wave function with fragment-localized molecular orbitals. Coarse-grained analysis indicated that the CI wave function can be described by local excitations and charge-transfer (CT) excitations between the chromophore and the environment. We developed an atomic-orbital direct runcated CIS code and applied the excited states of retinal chromophore in bacteriorhodopsin and MeOH environments, and those of s-trans-acrolein in water. Number of excitation operators was significantly reduced by eliminating the CT excitations between the environmental fragments. The truncated CIS wave functions reproduced the original excitation energies very well. (C) 2013 Elsevier B.V. All rights reserved.

Excitation energy transfer in GFP-X-CFP model peptides (X = amino acids): Direct Versus through-bridge energy transfers
Tsutomu Kawatsu, Jun-ya Hasegawa
INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 113, 4, 563, 568, WILEY-BLACKWELL, 2013年02月, ［査読有り］
英語, 研究論文（学術雑誌）, The excitation energy transfer (EET) between a fluorescent resonance energy transfer (FRET) pair, cyan fluorescent protein chromophore (CFPc)/ green fluorescent protein chromophore (GFPc), is used for measuring molecular proximity in experimental studies. In this article, the role of the bridging protein media has been investigated using the quantum chemical calculations for the EET electronic coupling. We adopted a model peptide connecting GFPc and CFPc, a GFPc-X-CFPc model, and examined the X (amino acids) dependence. The major part of the EET coupling element arises from the direct interaction between GFPc and CFPc via the Forster mechanism. The magnitude of the through-X interactions vary for the type of residues. The contribution of the X was, however, at most 10% of the total value. Together with the contributions from through-peptide and charge-transfer types, X gives minor modifications to the total coupling via the super-exchange mechanism. (C) 2012 Wiley Periodicals, Inc. DOI: 10.1002/qua.24027

Theoretical Investigation of the β Value of the Phenylene and Phenylene Ethynylene Units by Evaluating Exchange Interaction between Organic Radicals
S. Nishizawa, J.-y. Hasegawa, K. Matsuda
Chem. Phys. Lett., 555, 187, 190, ELSEVIER, 2013年01月, ［査読有り］
英語, 研究論文（学術雑誌）, The nature of pi-conjugated wire is characterized by the decay constant beta of electron tunneling. To evaluate the decay constant, intramolecular magnetic exchange interaction was calculated by density functional theory for organic biradicals: nitronyl nitroxide and verdazyl were chosen for the radical substituent and oligophenylene and oligo(phenylene ethynylene) were chosen for the wire. For phenylene and phenylene ethynylene units, beta was calculated to be 0.42 angstrom(-1) and 0.24 angstrom(-1), respectively, and the beta value was independent of radical species. The obtained beta values are in good agreement with the experimental value of the molecular tunneling conductance. (C) 2012 Elsevier B. V. All rights reserved.

Sequentially Coupled Hole-Electron Transfer Pathways for Bridge-Mediated Triplet Excitation Energy Transfer
Tsutomu Kawatsu, Jun-ya Hasegawa
JOURNAL OF PHYSICAL CHEMISTRY C, 116, 44, 23252, 23256, AMER CHEMICAL SOC, 2012年11月, ［査読有り］
英語, 研究論文（学術雑誌）, The donor acceptor electronic coupling for a bridge-mediated triplet excitation energy transfer (EET) was analyzed to determine the tunneling pathway using intergroup tunneling configuration fluxes. In the singlet EET, the electronic coupling is primarily composed of direct coupling between the donor and acceptor with a secondary contribution from bridge-mediated single-step through-exciton pathways. In contrast, the triplet EET is dominated by superexchange interactions due to the Forster-type interaction becoming forbidden. The triplet EET tunneling pathways are characterized as a sequentially coupled hole and electron transfer (CHET) for both direct and bridge-mediated EETs. This is the first report concerning the difference between the triplet and singlet EETs of the electronic mechanism of bridge-mediated superexchange mechanisms.

A Configuration Interaction Picture for a Molecular Environment Using Localized Molecular Orbitals: The Excited States of Retinal Proteins
Jun-ya Hasegawa, Kazuhiro J. Fujimoto, Tsutomu Kawatsu
JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 8, 11, 4452, 4461, AMER CHEMICAL SOC, 2012年11月, ［査読有り］
英語, 研究論文（学術雑誌）, Electronic excitations of chromophores in proteins and solutions are associated with the electronic response of the molecular environment. The underlying interactions are important origins of solvatochromism. We performed large-scale configuration interaction singles (CIS) calculations (up to 1000 atoms) for retinal chromophores in proteins and methanol solution, in which one electron processes (polarization and charge transfer effects of the environment) are included The present approach also improved the electrostatic potential, as compared to that described by a molecular Mechanics (MM) force field The CIS results were combined with the symmetry adapted cluster (SAC)-CI result using our own N-layer integrated molecular orbital molecular mechanics (ONIOM) method. As compared to the MM description, the CIS reduces the calculated excitation energy by 0.1-0.3 eV and also improves the relative. excitation energies. among,retinal proteins..;We: applied our localized molecular orbital (LMO) transformation scheme to analyze the CI Wave functions The result clarified the contributions Of the amino acids. In bacteriorhodopsin, Tyr185 contributes intermolecular CT excitations. The radial distribution of amino acids' contributions to the CI wave function was also analyzed. The results of the analysis are useful not only for understanding the molecular interactions and the role of amino acids in color tuning, but also for providing insight into the structure of the excited state wave function for the molecular environment An excitation energy decomposition analysis also supported the results of the excited-state wave functions.

Singlet Excitation Energy Transfer Mediated by Local Exciton Bridges
Tsutomu Kawatsu, Kenji Matsuda, Jun-ya Hasegawa
JOURNAL OF PHYSICAL CHEMISTRY C, 116, 26, 13865, 13876, AMER CHEMICAL SOC, 2012年07月, ［査読有り］
英語, 研究論文（学術雑誌）, Singlet excitation energy transfer (EET) generally occurs via a Forster mechanism and originates from direct electronic coupling between the donor (D) and acceptor (A). However, indirect EET (the so-called superexchange mechanism) can be crucial in some situations. In this study, we have explored the contributions of various linker types, linker lengths, and tunneling energies in D-linker-A molecular systems using quantum chemical methods [Kawatsu et al. J. Phys. Chem. A 2011, 115, 10814], obtaining conditions in which the super-exchange term emerges. To analyze the results in terms of physical parameters, a model Hamiltonian was developed and found to yield results qualitatively consistent with those from the quantum chemical calculations. In a model compound, the superexchange term can be up to 4 times larger than the direct (Forster) term when the energy of the excited state at a linker unit is close to the tunneling energy and when the interactions between these excited states are strong. The ratio of the indirect term to the direct term is greatest at a certain D-A distance because the number of multistep terms increases and the sizes of multistep indirect terms decay exponentially. Single-step indirect terms, which exhibit a polynomial decay, dominate the indirect term for larger D-A distances. The decay behavior with the distance is very different from that of the McConnell type donor-bridge-acceptor superexchange mechanism proposed for the charge transfer (CT). The result of pathway analysis showed that the exciton states mediate EET. The coupling between the local excited states is driven by the pseudo-Coulombic interaction, even in the superexchange terms.

Kinetic investigation on carbamate formation from the reaction of carbon dioxide with amino acids in homogeneous aqueous solution
Yuki Yamamoto, Jun-ya Hasegawa, Yoshikatsu Ito
JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, 25, 3, 239, 247, WILEY, 2012年03月, ［査読有り］
英語, 研究論文（学術雑誌）, The kinetics of carbamate formation from the reaction of carbon dioxide with a-amino acids in D2O was first investigated by means of nuclear magnetic resonance spectroscopy. Potassium carbonate was used as the CO2 source. For each amino acid, the maximum carbamate yield, the apparent rate constant for the carbamate formation k(app), and the rate constants for the formation k(1) and the breakdown k(-1) of the carbamate were estimated. Plots of log k(1) or log k(-1) versus pK(a) of amino acids indicated that the formation rate k(1) increased with the basicity (pK(a)) of amino acid, while the decomposition rate k(-1) decreased. A Bronsted beta value of 0.39 was obtained from the former plot, being in good agreement with the previously reported ones (0.26-0.43). The observed negative pK(a) dependence of log k(-1) (Bronsted alpha = 0.34) is reasonable, because the carbamate decomposition is acid-catalyzed and the steady-state concentration of H+ should be higher for weaker basic amines. The charge (sigma) and the lone-pair energy (E-N) at the nitrogen atom of the amino group were calculated. Although log k(1) correlated with s and E-N, log k(-1) was unrelated with both of these parameters. Considering that the carbamate formation (k(1)) is not only base-catalyzed but should also be promoted by the nucleophilicity of the amino nitrogen, its correlation with sigma and E-N in addition to pK(a) is rational. The irrelevance of log k(-1) to s and E-N is not surprising, because sigma and E-N are not a direct measure of [H+] of the solution. Copyright (C) 2011 John Wiley & Sons, Ltd.

Chronological Change from Face-On to Edge-On Ordering of Zinc-Tetraphenylporphyrin at the Phenyloctane-Highly Oriented Pyrolytic Graphite Interface
Takeshi Sakano, Jun-ya Hasegawa, Kenji Higashiguchi, Kenji Matsuda
CHEMISTRY-AN ASIAN JOURNAL, 7, 2, 394, 399, WILEY-V C H VERLAG GMBH, 2012年02月, ［査読有り］
英語, 研究論文（学術雑誌）, The self-assembled structure of alkoxy- and N-alkylcarbamoyl-substituted zinctetraphenylporphyrin at the liquidhighly oriented pyrolytic graphite (HOPG) interface was observed by using scanning tunneling microscopy. The alkoxy porphyrin showed a phase transition from face-on to edge-on ordering. The phase transition requires the close-packed structure of alkoxy porphyrin. The chronological change of the ordering was traced to show the existence of several types of Ostwald ripening including two-step phase transition from small edge-on to face-on and then further to edge-on orderings. On the other hand, the N-alkylcarbamoyl porphyrin showed persistent edge-on ordering, and the ordering was analyzed by the Moire pattern. Although the edge-on ordering is observed only in the nonpolar solvent, the orderings have potential applications in the charge and energy transfer.

SAC-CI Methodology Applied to Molecular Spectroscopy and Photo-Biology
J. Hasegawa, T. Miyahara, H. Nakashima, H. Nakatsuji
THEORY AND APPLICATIONS IN COMPUTATIONAL CHEMISTRY: THE FIRST DECADE OF THE SECOND MILLENNIUM, 1456, 101, 108, AMER INST PHYSICS, 2012年, ［査読有り］
英語, 研究論文（国際会議プロシーディングス）, The SAC-CI method was applied to the spectroscopy of radical cations and anions of various organic molecules. It was also applied to photo-biology, in particular, to elucidate the bio-molecular color-tuning mechanism of human visions and to the circular dichroism spectroscopy that is used to understand the helical structures of DNA and RNA.

Color tuning in human cone visual pigments: the role of the protein environment
J. Hasegawa, K. Fujimoto, H. Nakatsuji
Progress in Theoretical Chemistry and Physics, 26, 489, 502, 2012年, ［査読有り］

Message to Molecular Scientists from the late Professor B. Roos
B. O. Roos, R. Lindh, J. Hasegawa, M. Atsumi
Mol. Sci., 6, 1, A0046, Japan Society for Molecular Science, 2012年
英語, 研究論文（学術雑誌）

Color Tuning in Photofunctional Proteins
Jun-ya Hasegawa, Kazuhiro J. Fujimoto, Hiroshi Nakatsuji
CHEMPHYSCHEM, 12, 17, 3106, 3115, WILEY-V C H VERLAG GMBH, 2011年12月, ［査読有り］
英語, Depending on protein environment, a single photofunctional chromophore shows a wide variation of photoabsorption/emission energies. This photobiological phenomenon, known as color tuning, is observed in human visual cone pigments, firefly luciferase, and red fluorescent protein. We investigate the origin of color tuning by quantum chemical calculations on the excited states: symmetry-adapted cluster-configuration interaction (SAC-CI) method for excited states and a combined quantum mechanical (QM)/molecular mechanical (MM) method for protein environments. This Minireview summarizes our theoretical studies on the above three systems and explains a common feature of their color-tuning mechanisms. It also discuss the possibility of artificial color tuning toward a rational design of photoabsorption/emission properties.

Theoretical study of the excited states of the photosynthetic reaction center in photosystem II: Electronic structure, interactions, and their origin
Yuya Kitagawa, Kenji Matsuda, Jun-ya Hasegawa
BIOPHYSICAL CHEMISTRY, 159, 2-3, 227, 236, ELSEVIER SCIENCE BV, 2011年12月, ［査読有り］
英語, 研究論文（学術雑誌）, The excited states of the chlorophyll 6-mer in the photosystem II (PSII) reaction center (RC) were investigated theoretically using ab initio quantum chemical calculations, and the results are compared with those of the bacterial reaction center (bRC). A significant difference in the peak at the lowest energy in the absorption spectra arises from the structural asymmetry of the special pair (SP). The origin can be traced back to the structural difference in the CD helix. The low-lying excited states are characterized as a linear combination of the excited states of the chlorophyll monomers, which verifies the applicability of exciton theory. Analysis of the molecular interactions clearly explains the cause of the constructive/destructive interferences in the state transition moment. The protein electrostatic potential (ESP) decreases the energy of the charge-transfer (Chl(D1) -> Pheo(D1)) state. The ESP also localizes the HOMO distribution to the Pm moiety and increases the ionization potential. (C) 2011 Elsevier B.V. All rights reserved.

Theoretical study of the excited states and the redox potentials of unusually distorted β-trifluoromethylporphycene
J. Hasegawa, K. Matsuda
Theoret. Chem. Acc, 130, 2-3, 175, 185, SPRINGER, 2011年10月, ［査読有り］
英語, 研究論文（学術雑誌）, Quantum chemical calculations were performed to analyze the excited states and the redox potentials of a recently synthesised fluorine-containing porphycene, 2,7,12,17-tetraethyl-3,6,13,16-tetrakis(trifluoromethyl) porphycene. The reduction and oxidation potentials of the porphycenes measured by cyclic voltammetry were semiquantitatively reproduced using density-functional theory (DFT) and polarizable continuum model calculations, in which solvent effect and basis-sets extension effect were indispensable. Symmetry-adapted cluster configuration interaction and time-dependent (TD) DFT calculations were performed to analyze the visible region of the absorption spectra, and the results were in good agreement with the experimental data. The results of the calculations showed that both structural distortion and electronic effects cause specifically large stabilization of the LUMO level and become the origin of the particularly large positive-side shift of the reduction potential and the red-shift in the Q band absorption.

Bridge-Mediated Excitation Energy Transfer Pathways through Protein Media: a Slater Determinant-Based Electronic Coupling Calculation Combined with Localized Molecular Orbitals
Tsutomu Kawatsu, Kenji Matsuda, Jun-ya Hasegawa
JOURNAL OF PHYSICAL CHEMISTRY A, 115, 39, 10814, 10822, AMER CHEMICAL SOC, 2011年10月, ［査読有り］
英語, 研究論文（学術雑誌）, A computational method for calculating electronic coupling and pathway of electron transfer (ET) has been extended to that for excitation energy transfer (EET). A molecular orbital (MO)-based description has been generalized to one based on Slater determinants. This approach reduces the approximations used for the Green's function method from the perturbation of chemical-bond interactions to the perturbation of the configuration interactions. It is, therefore, reasonable to apply this method to EET, which involves the transfer of an electron hole pair. To represent EET donor, acceptor, and bridge states, we adopted recently developed localized molecular orbitals (LMOs) for constructing locally excited determinants. The LMO approach provides a chemically meaningful interpretation of how each local excitation on the bridge contributes to the total electronic coupling of the EET. We applied the method to six model peptides and calculated their electronic couplings as well as the direct and through-peptide terms. Although the through-peptide term is usually negligibly small compared with the direct term, it can dominate the EET reaction in appropriate situations. The direct term dominates in long-range interactions because the indirect term decays in shorter distances.

Chemical-intuition based LMO transformation simplifies excited-state wave functions of peptides
Jun-ya Hasegawa, Tsutomu Kawatsu, Kazuo Toyota, Kenji Matsuda
CHEMICAL PHYSICS LETTERS, 508, 1-3, 171, 176, ELSEVIER SCIENCE BV, 2011年05月, ［査読有り］
英語, 研究論文（学術雑誌）, A molecular-orbital (MO) localization scheme for peptide molecules has been proposed. Combining the minimum orbital deformation (MOD) and population localization methods, the present scheme produces MOs localized within predefined fragment regions. Because the transformed MOs become similar to externally-introduced reference MOs, we can introduce MO representations commonly used in chemistry. Calculated Lowdin populations and overlap integrals showed that the extent of localization was satisfactory. The transformed MOs were applied to the configuration interaction singles (CIS) calculations. The results clearly showed that the chemically-intuitive MO localization simplified not only one-electron orbitals, but also the structure of the excited-state wave functions. (C) 2011 Elsevier B.V. All rights reserved.

Theoretical Investigation on the Origin of the CD Signal Reversal for the Closed-ring Isomer of Diarylethene with Peripherical pi-Conjugated Substituents
Takashi Hirose, Jun-ya Hasegawa, Kenji Matsuda
CHEMISTRY LETTERS, 39, 5, 516, 517, CHEMICAL SOC JAPAN, 2010年05月, ［査読有り］
英語, 研究論文（学術雑誌）, Theoretical investigation was performed on the CD signal of the closed-ring isomer of diarylethene with an extended pi-conjugated substituent. The result showed that the different contribution of the substituent to the transition electronic and magnetic dipole moments induces CD signal reversal. The obtained finding can be applied to general dyes with a chiral core and extended pi-conjugated substituents.

Theoretical Investigation on the Origin of the CD Signal Reversal for the Closed-ring Isomer of Diarylethene with Peripherical pi-Conjugated Substituents
Takashi Hirose, Jun-ya Hasegawa, Kenji Matsuda
CHEMISTRY LETTERS, 39, 5, 516, 517, CHEMICAL SOC JAPAN, 2010年05月, ［査読有り］
英語, 研究論文（学術雑誌）, Theoretical investigation was performed on the CD signal of the closed-ring isomer of diarylethene with an extended pi-conjugated substituent. The result showed that the different contribution of the substituent to the transition electronic and magnetic dipole moments induces CD signal reversal. The obtained finding can be applied to general dyes with a chiral core and extended pi-conjugated substituents.

Excited States of Fluorescent Proteins, mKO and DsRed: Chromophore-Protein Electrostatic Interaction Behind the Color Variations
Jun-ya Hasegawa, Takehiko Ise, Kazuhiro J. Fujimoto, Akihiro Kikuchi, Eiko Fukumura, Atsushi Miyawaki, Yoshitsugu Shiro
JOURNAL OF PHYSICAL CHEMISTRY B, 114, 8, 2971, 2979, AMER CHEMICAL SOC, 2010年03月, ［査読有り］
英語, 研究論文（学術雑誌）, The emitting states of green fluorescent protein (GFP), monomeric Kusabira orange (mKO), and Discosoma red (DsRed) were studied using QM/MM and SAC-CI methods. By comparing the electronic structures among the green-, orange-, and red-emitting states as well as their electrostatic and quantum mechanical interactions within the protein cavity, the basic mechanisms for determining emission colors have been clarified. We found that the orange and red emissions of mKO and DsRed, respectively, result from cancellation between two effects, the pi skeleton extension (red shift) and protein electrostatic potential (blue shift). The extension of the pi skeleton enhances the intramolecular charge-transfer character of the transition, which makes the fluorescence energy more sensitive to the protein's electrostatic potential. On the basis of this mechanism, we predicted amino acid mutations that Could red shift the emission energy of DsRed. A novel single amino acid mutation, which was examined computationally, reduced the DsRed emission energy from 2.14 (579 tint) to 1.95 eV (636 nm), which is approaching near-infrared fluorescence.

Generalizing the bra state in the symmetry-adapted cluster singles and doubles method and the second-order perturbation correction
Jun-ya Hasegawa, Akihiro Obata, Kenji Matsuda
CHEMICAL PHYSICS LETTERS, 486, 1-3, 84, 88, ELSEVIER SCIENCE BV, 2010年02月, ［査読有り］
英語, 研究論文（学術雑誌）, We present a procedure to overcome the quasi-degeneracy problem in the CCSD and SACSD methods. A multi-configuration bra state in the SACSD equations (MRbra-SACSD equation) together with a second-order perturbation correction gives quantitatively correct potential curves for bond dissociations. The benchmark results for HF, F-2, and H2O show that the perturbative triple correction reduces the deviations from Full-Cl energies to within 3 mHartree (1.9 kcal/mol). Within the benchmark calculations, the results of the present method are comparable with the recent post-CCSD corrections, the CR-CCSD(T) and CCSD(2)(T) methods, and are slightly less accurate than the CR-CC(2,3) method. (C) 2010 Elsevier B. V. All rights reserved.

Theoretical study of the opsin shift of deprotonated retinal schiff base in the M state of bacteriorhodopsin
Kazuhiro J. Fujimoto, Kota Asai, Jun-ya Hasegawa
PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 12, 40, 13107, 13116, ROYAL SOC CHEMISTRY, 2010年, ［査読有り］
英語, 研究論文（学術雑誌）, The origin of the opsin shift, which deprotonated Schiff base (DPSB) shows in the M state of the bacteriorhodopsin (bR) photocycle, was theoretically investigated for the first time using a combined quantum mechanical and molecular mechanical (QM/MM) method. From the QM(SAC-CI)/MM(AMBER99) results, the chromophore conformational effect was found to be the main factor, whereas the Coulombic interaction with the protein environment gave a non-negligible contribution. The present result revised the conclusion drawn by previous studies and provided a new interpretation of the opsin shift mechanism of DPSB. To test the computational models for taking into account the electronic polarization and charge redistribution effects of the surrounding environment, the size of the QM region was expanded up to 5-7 angstrom from DPSB, which decreased the excitation energies in solution and in protein by 0.08-0.13 eV and 0.21-0.26 eV, respectively. We also found that the rCAM-B3LYP functional significantly improves the B3LYP results when calculating the potential energy curve for the C-6-C-7 twisting.

Circular Dichroism and Absorption Spectroscopy for Three-Membered Ring Compounds Using Symmetry-Adapted Cluster-Configuration Interaction (SAC-CI) Method
Tomoo Miyahara, Jun-ya Hasegawa, Hiroshi Nakatsuji
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, 82, 10, 1215, 1226, CHEMICAL SOC JAPAN, 2009年10月, ［査読有り］
英語, 研究論文（学術雑誌）, The singlet excited states of oxirane and thiirane derivatives, ethylene oxide, (R)-methyloxirane, (2S,3S)-dimethyloxirane, ethylene sulfide, (R)-methylthiirane, and (2S,3S)-dimethylthiirane, were calculated employing the symmetry-adapted cluster (SAC)/SAC-configuration interaction (CI) method. The rotatory strengths of the CD spectra were calculated in the velocity form, which is gauge-origin independent. Both the ultraviolet (UV) spectra and the circular dichroism (CD) spectra obtained with the SAC-Cl method were in good agreement with the experimental spectra. In oxirane derivatives, the low-lying excited states were composed of excitations from n and sigma orbitals to s, p, and d Rydberg orbitals. The excitation from the sigma orbital was especially important in (2S,3S)-dimethyloxirane because of the steric effect of the methyl substitutions. However, in thiirane derivatives, the excitations to the low-lying excited states were only from the n orbital.

Color Tuning Mechanism of Human Red, Green, and Blue Cone Pigments: SAC-CI Theoretical Study
Kazuhiro Fujimoto, Jun-ya Hasegawa, Hiroshi Nakatsuji
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, 82, 9, 1140, 1148, CHEMICAL SOC JAPAN, 2009年09月, ［査読有り］
英語, 研究論文（学術雑誌）, Human red (HR), green (HG), and blue (HB) cone pigments are responsible for human color vision, and their photoabsorption wavelengths spread uniquely over the three primary colors. These pigments, however, include only one common chromophore, retinal. Here, we report physical basis of the color tuning in human vision on the basis of SAC-CI calculations for excited states of the cone pigments. The dominant origin of the red-green-blue distinction lies in differences in electrostatic interactions between retinal and its surrounding proteins. Structural distortion effect of the retinal chromophore is important in human blue pigment. Detailed analysis on individual roles of amino acids; within these proteins has clarified elaborate mechanisms of the color tuning, in accordance with previous mutagenesis experiments. Furthermore, the color tuning is regulated by amino acids at specific positions in the proteins, suggesting some genetic origins for the color tuning.

A Multicore QM/MM Approach for the Geometry Optimization of Chromophore Aggregate in Protein
Yasuomi Kiyota, Jun-Ya Hasegawa, Kazuhiro Fujimoto, Ben Swerts, Hiroshi Nakatsuji
JOURNAL OF COMPUTATIONAL CHEMISTRY, 30, 8, 1351, 1359, WILEY, 2009年06月, ［査読有り］
英語, 研究論文（学術雑誌）, In this article, we present the multicore (mc) QM/MM method, a QM/MM method that can optimize the structure of chromophore aggregate in protein. A QM region is composed of the sum of the QM subregions that are small enough to apply practical electronic structure calculations. QM/MM energy gradient calculations are performed for each QM subregion. Several benchmark examinations were carried out to figure out availabilities and limitations. In the interregion distances of more than 3.5-4.0 angstrom, the mcQM/MM energy gradient is very close to that obtained by the ordinary QM/MM method in which all the QM subregions were treated together as a single QM region. In van der Waals complex, the error exponentially drops with the distance, while the error decreases slowly in a hydrogen bonding complex. On the other hand, the optimized structures were reproduced with reasonable accuracy in both cases. The computational efficiency is the best advantage in the mc QM/MM approach, especially when the QM region is significantly large and the QM method used is computationally demanding. With this approach, we could optimize the structures of a bacterial photosynthetic reaction center protein in the ground and excited states, which consists of more than 14,000 atoms. (C) 2008 Wiley Periodicals, Inc. J Comput Chem 30: 1351-1359, 2009

Charge-Polarized Coordination Space for H-2 Adsorption
Jun-ya Hasegawa, Masakazu Higuchi, Yuh Hijikata, Susumu Kitagawa
CHEMISTRY OF MATERIALS, 21, 9, 1829, 1833, AMER CHEMICAL SOC, 2009年05月, ［査読有り］
英語, 研究論文（学術雑誌）, We investigated the concept "charge-polarized coordination spaces" in porous coordination polymers to increase the adsorption of H-2. Ab initio calculations were performed to investigate the H-2-adsorption capabilities of organic ligands. The adsorption energy of a pyrazine-carboxylate ligand (2.4 kcal/mol), relevant to a coordination polymer with a pillared layer structure, was found to be larger than that obtained by van der Waals interactions alone. An ab initio energy decomposition analysis showed that the stabilization arose mainly from the electronic polarization of H2. We therefore propose a concept of "charge-polarized spaces" to promote polarization. Under the dipolar electric field created by ideal charge-polarized spaces, the adsorption energy markedly increased to 5-8 kcal/cool, which is in the ideal energy range for H-2 adsorption in storage materials. Charge-neutral ligands can also provide electrostatically polarized spaces. Although the binding energy decreases to around 2 kcal/mol, the H-2 polarization effect still increases the adsorption energy. The charge-polarized and electrostatically polarized spaces are therefore an important direction for molecular design of H-2 storage materials.

Artificial color tuning of firefly luminescence: Theoretical mutation by tuning electrostatic interactions between protein and luciferin
Naoki Nakatani, Jun-ya Hasegawa, Hiroshi Nakatsuji
CHEMICAL PHYSICS LETTERS, 469, 1-3, 191, 194, ELSEVIER SCIENCE BV, 2009年02月, ［査読有り］
英語, 研究論文（学術雑誌）, Electrostatic interactions between firefly oxyluciferin and the surrounding proteins were analyzed, and the amino acids important for controlling emission energy were identified. We propose Arg223Ala, Glu344Ala, and Asp422Ala mutations in firefly oxyluciferase of Photinus pyralis, which artificially change the luminescence color by tuning the electrostatic effect from the luciferase proteins. In the theoretical mutation simulation, the emission energy of the triple mutant was estimated to be 2.05 eV ( 602 nm, reddish-orange), which is 0.18 eV lower than that of the wild type ( 2.23 eV, 557 nm, yellow-green). For calculating the emission energies, we used the symmetry-adapted cluster-configuration interaction (SAC-CI) method. (C) 2008 Elsevier B. V. All rights reserved.

A New Synthesis of (+)-Negamycin and Its Derivatives as a Potential Therapeutic Agent for Duchenne Muscular Dystrophy Treatment
Yoshio Hayashi, Shigenobu Nishiguchi, Magne O. Sydnes, Thomas Regnier, Jun-ya Hasegawa, Takahiro Katoh, Tetsuya Kajimoto, Manabu Node, Yoshiaki Kiso
PEPTIDES FOR YOUTH, 611, 137, 138, SPRINGER, 2009年, ［査読有り］
英語, 研究論文（学術雑誌）

Photocyclization of 2,4,6-triethylbenzophenones in the solid state
Yoshikatsu Ito, Hiroki Takahashi, Jun-ya Hasegawa, Nicholas J. Turro
TETRAHEDRON, 65, 3, 677, 689, PERGAMON-ELSEVIER SCIENCE LTD, 2009年01月, ［査読有り］
英語, 研究論文（学術雑誌）, Photocyclization of 2,4,6-triethylbenzophenones (TEBPs) into (E)- or (Z)-benzocyclobutenols ((E)- or (Z)-CBs) is E-selective in solution. By contrast, upon solid-state photolysis, TEBP-3,4-diCl and especially TEBP-4-t-Bu gave (Z)-CB relative to (E)-CB with a Much higher proportion than that in solution. For TEBP-4-t-Bu, the most major product in the solid state is an indanol derivative (Inol) (E/Z/Inol=1:3.9:10.3 at 9% conversion). On the basis of the X-ray crystallographic analysis, Inol and (Z)-CB are both topochemical products. Notably, the relative proportion of (E)-CB increased with increased conversion, namely with increased disruption of the crystal lattice. The DFT calculation of highly hindered 2,6-diisopropylbenzophenone (DIBP) was also conducted. These results in conjunction with the previous results on 2,4,6-triisopropylbenzophenones (TIBPs) indicate that CB is formed either via trans-enol followed by its conrotatory ring-closure (paths a and d) or through direct cyclization of biradical (BR) (path b) as shown in Scheme 1. Normally the former route is faster. However, in the crystalline state or in the case of sterically hindered phenyl ketones, path b tends to be adopted. (c) 2008 Elsevier Ltd. All rights reserved.

Origin of color tuning in human red, green, and blue cone pigments: SAC-CI and QM/MM study
Kazuhiro Fujimoto, Jun-Ya Hasegawa, Hiroshi Nakatsuji
CHEMICAL PHYSICS LETTERS, 462, 4-6, 318, 320, ELSEVIER SCIENCE BV, 2008年09月, ［査読有り］
英語, 研究論文（学術雑誌）, Human color vision is controlled by the red, green, and blue cone pigments. Their photo-absorption wavelengths spread uniquely over the three primary colors, although these pigments include common chromophore, retinal. In this study, molecular mechanism of color tuning in the cone pigments was clarified. The protein effect represented by the electrostatic potential is primarily important for the spectral tuning among the pigments. The structural distortion effect of the retinal chromophore is important in the human blue pigment. The result of the analysis indicates that amino acids at specific positions in the opsins regulate the color tuning. (C) 2008 Elsevier B.V. All rights reserved.

Excited states of GFP chromophore and active site studied by the SAC-CI method: Effect of protein-environment and mutations
Jun-Ya Hasegawa, Kazuhiro Fujimoto, Ben Swerts, Tomoo Miyahara, Hiroshi Nakatsuji
JOURNAL OF COMPUTATIONAL CHEMISTRY, 28, 15, 2443, 2452, JOHN WILEY & SONS INC, 2007年11月, ［査読有り］
英語, 研究論文（学術雑誌）, Excited states of fluorescent proteins were studied using symmetry-adapted cluster-configuration interaction (SAC-CI) method. Protein-environmental effect on the excitation and fluorescence energies was investigated. In green fluorescent protein (GFP), the overall protein-environmental effect on the first excitation energy is not significant. However, glutamine (Glu) 94 and arginine (Arg96) have the red-shift contribution as reported in a previous study (Laino et al., Chem Phys 2004, 298, 17). The excited states of GFP active site (GFP-W22-Ser205-Glu222Ser65) were also calculated. Such large-scale SAC-CI calculations were performed with an improved code containing a new algorithm for the perturbation selection. The SAC-CI results indicate that a charge-transfer state locates at 4.19 eV, which could be related to the channel of the photochemistry as indicated in a previous experimental study. We also studied the excitation and fluorescence energies of blue fluorescent protein, cyan fluorescent protein, and Y66F. The SAC-CI results are very close to the experimental ones. The protonation state of blue fluorescent protein was determined. Conformation of cyan fluorescent protein indicated by the present calculation agrees to the experimentally observed structure. (c) 2007 Wiley Periodicals, Inc.

Red light in chemiluminescence and yellow-green light in bioluminescence: Color-tuning mechanism of firefly, Photinus pyralis, studied by the symmetry-adapted cluster-configuration interaction method
Naoki Nakatani, Jun-ya Hasegawa, Hiroshi Nakatsuji
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 129, 28, 8756, 8765, AMER CHEMICAL SOC, 2007年07月, ［査読有り］
英語, 研究論文（学術雑誌）, The yellow-green luminescence from firefly luciferase has long been understood to be the emission from enol-oxyluciferin. However, a recent experiment showed that an oxyluciferin constrained to the keto form produced a yellow-green emission in luciferase (Branchini, B. R.; Murtiashaw, M. H.; Magyar, R. A.; Portier, N. C.; Ruggiero, M. C.; Stroh, J. G. J. Am. Chem. Soc, 124, 2112-2113). The present quantum mechanical/molecular mechanical and symmetry-adapted cluster-configuration interaction (SAC-CI) theoretical study supports the keto-form to be the yellow-green bioluminescence state in luciferase. We give the theoretically optimized structure of the excited state of oxyluciferin within luciferase, which gives luminescence calculated by the SAC-CI method that is close to the experimental value. Coulombic interactions with neighboring residues, in particular Arg218 and the phosphate group of AMP, play important roles in the color-tuning mechanism. Transformation to the enol form is energetically unfavorable in the luciferase environment. The twisted intramolecular charge-transfer (TICT) state is meta stable and would be easily relaxed to the co-planer structure. Further analyses were performed to verify the spectral-tuning mechanism based on the protonation state and the resonance structure of oxyluciferin.

SAC-CI theoretical study on the excited states of lumiflavin: Structure, excitation spectrum, and solvation effect
Jun-ya Hasegawa, Sareeya Bureekaew, Hiroshi Nakatsuji
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY, 189, 2-3, 205, 210, ELSEVIER SCIENCE SA, 2007年06月, ［査読有り］
英語, 研究論文（学術雑誌）, The excited states of a flavin-related compound, lumiflavin, were studied by the symmetry-adapted cluster (SAC)-configuration interaction (CI) method. The absorption peaks observed in the experimental spectrum were theoretically assigned. Transition energy of some low-lying n-pi* states were obtained. The energy minimum structures of the first singlet and triplet excited states were calculated by the SAC-Cl method. The structural changes upon excitation were at most 0.05 angstrom. The solvation effect on the absorption energy in aqueous solution was investigated using polarizable continuum model (PCM) and by including water molecules into the computational model. The solvatochromic shift of the second peak (3(1) A' state) originates from both microscopic (hydrogen bonding) and macroscopic (electronic polarization of solvent) solvation effects. (c) 2007 Elsevier B.V. All rights reserved.

Theoretical studies on the color-tuning mechanism in retinal proteins
Kazuhiro Fujimoto, Shigehiko Hayashi, Jun-ya Hasegawa, Hiroshi Nakatsuji
JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 3, 2, 605, 618, AMER CHEMICAL SOC, 2007年03月, ［査読有り］
英語, 研究論文（学術雑誌）, The excited states of the three retinal proteins, bovine rhodopsin (Rh), bacteriorhodopsin (bR), and sensory rhodopsin II (sRII) were studied using the symmetry-adapted cluster-configuration interaction (SAC-CI) and combined quantum mechanical and molecular mechanical (QM/MM) methods. The computed absorption energies are in good agreement with the experimental ones for all three proteins. The spectral tuning mechanism was analyzed in terms of three contributions: molecular structures of the chromophore in the binding pockets, electrostatic (ES) interaction of the chromophore with the surrounding protein environment, and quantum-mechanical effect between the chromophore and the counterion group. This analysis provided an insight into the mechanism of the large blue-shifts in the absorption peak position of Rh and sRII from that of bR. Protein ES effect is primarily important both in Rh and in sRII, and the structure effect is secondary important in Rh. The quantum-mechanical interaction between the chromophore and the counterion is very important for quantitative reproduction of the excitation energy. These results indicate that the present approach is useful for studying the absorption spectra and the mechanism of the color tuning in the retinal proteins.

Excited and ionized states of ozone studied by the MEG (multi-exponentially generated)/EX (excited)-MEG method
Yuhki Ohtsuka, Jun-ya Hasegawa, Hiroshi Nakatsuji
CHEMICAL PHYSICS, 332, 2-3, 262, 270, ELSEVIER SCIENCE BV, 2007年02月, ［査読有り］
英語, 研究論文（学術雑誌）, The MEG (multi-exponentially generated)/EX (excited)-MEG method, which is a multi-reference version of the SAC (symmetry-adapted cluster)/SAC-Cl (configuration interaction) method, has been applied to the valence excited and ionized states of ozone that has a quasi-degenerate bi-radical nature in its ground state. The MEG/EX-MEG result shows a remarkable improvement over the single-reference SAC/SAC-CI general-R one in both the correlation energy and the ionization potential. The present results were compared with the previous theoretical and experimental data. The theoretical ionization spectrum reproduced the experimental spectrum observed from outer- to inner-valence regions (similar to 28 eV). This is the first report that gives a theoretical interpretation up to a high-energy region. (c) 2006 Elsevier B.V. All rights reserved.

2P304 バクテリオロドプシンの光サイクルにおけるレチナール分子のカラー・チューニング : SAC-CI法による研究(生体膜・人工膜(輸送),ポスター発表,第45回日本生物物理学会年会)
浅井 康太, 藤本 和宏, 長谷川 淳也, 中辻 博
生物物理, 47, S189, 一般社団法人 日本生物物理学会, 2007年
英語

2P318 光合成反応中心における光誘起電子移動に関する理論的研究 : 複数のQM領域を持つQM/MM構造最適化(光生物(光合成),ポスター発表,第45回日本生物物理学会年会)
清田 泰臣, 藤本 和宏, 長谷川 淳也, 中辻 博
生物物理, 47, S192, 一般社団法人 日本生物物理学会, 2007年
英語

On the color-tuning mechanism of Human-Blue visual pigment: SAC-CI and QM/MM study
Kazuhiro Fujimoto, Jun-ya Hasegawa, Shigehiko Hayashi, Hiroshi Nakatsuji
CHEMICAL PHYSICS LETTERS, 432, 1-3, 252, 256, ELSEVIER SCIENCE BV, 2006年12月, ［査読有り］
英語, 研究論文（学術雑誌）, Color-tuning mechanism of Human-Blue pigment, visual color-receptor in the cone cells of the eye, has been investigated. Based on a previous Homology-modeling structure and experimental evidences, a working model was constructed, and the structure has been optimized by QM(B3LYP)/MM(AMBER) method. SAC-CI calculation was performed to obtain photo-absorption energy. The calculated absorption energy reasonably agrees with the experiment. A decomposition analysis was performed and compared with the case of Bovine rhodopsin. The electrostatic effect from the opsin is primarily important for the color-tuning. The electronic interaction (quantum effect) of the counter-residue is indispensable for quantitative calculation of the absorption energy. (c) 2006 Elsevier B.V. All rights reserved.

On the Yellow-Green Bioluminescence in North American Firefly: SAC-CI Study
NAKATANI Naoki, HASEGAWA Jun‐ya, NAKATSUJI Hiroshi
生物物理, 46, Supplement 2, S394, 一般社団法人 日本生物物理学会, 2006年10月01日
英語

On the O-2 binding of Fe-porphyrin, Fe-porphycene, and Fe-corrphycene complexes
Hiroyuki Nakashima, Jun-Ya Hasegawa, Hiroshi Nakatsuji
JOURNAL OF COMPUTATIONAL CHEMISTRY, 27, 12, 1363, 1372, WILEY, 2006年09月, ［査読有り］
英語, 研究論文（学術雑誌）, Based on our previous study for the O-2 binding of the Fe-Por complex, this study investigates the O-2 binding mechanism in the Fe-porphyrin isomers, Fe-porphycene (FePc), and Fe-corrphycene (FeCor) complexes. By calculating the potential energy surface of the O-2 binding, the present study explains the reason for the dramatic increase of O-2 affinities observed in the FePc complex. In the case of FeCor-O-2, the O-2 binding process includes the intersystem crossing from a triplet to singlet state, as in the FePor-O-2 complex. However, FePC-O-2 uses only a singlet surface. This is because the ground state of the FePc complex in the deoxy state is a triplet state, while those of FePor and FeCor are a quintet state. Such difference originates from character of the SOMO. We estimated an equilibrium constant for the O-2 binding that reasonably reproduced the trend observed in the experiments. (c) 2006 Wiley Periodicals, Inc.

Electronic circular dichroism spectrum of uridine studied by the SAC-CI method
Sareeya Bureekaew, Jun-ya Hasegawa, Hiroshi Nakatsuji
CHEMICAL PHYSICS LETTERS, 425, 4-6, 367, 371, ELSEVIER SCIENCE BV, 2006年07月, ［査読有り］
英語, 研究論文（学術雑誌）, Symmetry-adapted cluster-configuration interaction (SAC-CI) method was applied to calculate electronic CD spectrum of a nucleoside, uridine. Based on the theoretical CD and absorption spectra, the observed peaks in the experimental spectra were assigned. The excited states of uracil, the base part of uridine, were also calculated for comparison. The origin of CD rotational strength for the low-lying pi-pi* and n-pi* excited states was analyzed. Rotational strength of the pi-pi* transition depends on the magnitude of the electric and magnetic transition dipole moments, while that of the n-pi* originates from the angle between the two transition moments. (c) 2006 Elsevier B.V. All rights reserved.

On the reversible O-2 binding of the Fe-porphyrin complex
H Nakashima, JY Hasegawa, H Nakatsuji
JOURNAL OF COMPUTATIONAL CHEMISTRY, 27, 4, 426, 433, JOHN WILEY & SONS INC, 2006年03月, ［査読有り］
英語, 研究論文（学術雑誌）, Electronic mechanism of the reversible O-2 binding by heme was studied by using Density Functional Theory calculations. The ground state of oxyheme was calculated to be open singlet state [Fe(S = 1/2) + O-2(S = 1/2)]. The potential energy surface for singlet state is associative, while that for triplet state is dissociative. Because the ground state of the O-2 + deoxyheme system is triplet in the dissociation limit [Fe(S = 2) + O-2(S = 1)], the O-2 binding process requires relativistic spin-orbit interaction to accomplish the intersystem crossing from triplet to singlet states. Owing to the singlet-triplet crossing, the activation energies for both O-2 binding and dissociation become moderate, and hence reversible. We also found that the deviation of the Fe atom from the porphyrin plane is also important reaction coordinate for 02 binding. The potential surface is associative/dissociative when the Fe atom locates in-plane/out-of-plane. (c) 2006 Wiley Periodicals, Inc.

Generalization of the projection space improves the SAC-SD (symmetry-adapted cluster-singles and doubles) method in bond-breaking systems
JY Hasegawa, H Nakatsuji
CHEMISTRY LETTERS, 34, 10, 1356, 1357, CHEMICAL SOC JAPAN, 2005年10月, ［査読有り］
英語, 研究論文（学術雑誌）, The equation for nonvariational SAC-SD method has been generalized to have multireference projection space. The results show significant improvements in the description of the potential curves especially in the bond-breaking region.

Mechanism of color tuning in retinal protein: SAC-CI and QM/MM study
K Fujimoto, JY Hasegawa, S Hayashi, S Kato, H Nakatsuji
CHEMICAL PHYSICS LETTERS, 414, 1-3, 239, 242, ELSEVIER SCIENCE BV, 2005年10月, ［査読有り］
英語, 研究論文（学術雑誌）, The SAC-CI and QM/MM methods were applied to calculations of the absorption peaks of the five retinal proteins, bovine rhodopsin (Rh), bacteriorhodopsin (bR) in BR, K, and KL states, and sensory rhodopsin II (sRII). The results nicely agree with the experimental excitation energies and provided an insight into the mechanism of the large blue shifts in Rh and sRII from BR: geometric distortion in Rh and protein electrostatic effect in sRII. These results indicate that the present approach is useful for studying the excitation spectra and the mechanism of the color tuning in the retinal proteins. (c) 2005 Elsevier B.V. All rights reserved.

Mechanism of color tuning in retinal protein: SAC-CI and QM/MM study
K Fujimoto, JY Hasegawa, S Hayashi, S Kato, H Nakatsuji
CHEMICAL PHYSICS LETTERS, 414, 1-3, 239, 242, ELSEVIER SCIENCE BV, 2005年10月
英語, 研究論文（学術雑誌）, The SAC-CI and QM/MM methods were applied to calculations of the absorption peaks of the five retinal proteins, bovine rhodopsin (Rh), bacteriorhodopsin (bR) in BR, K, and KL states, and sensory rhodopsin II (sRII). The results nicely agree with the experimental excitation energies and provided an insight into the mechanism of the large blue shifts in Rh and sRII from BR: geometric distortion in Rh and protein electrostatic effect in sRII. These results indicate that the present approach is useful for studying the excitation spectra and the mechanism of the color tuning in the retinal proteins. (c) 2005 Elsevier B.V. All rights reserved.

Excited states and electron-transfer mechanism in the photosynthetic reaction center of Rhodobactor sphaeroides: SAC-CI theoretical study
JY Hasegawa, H Nakatsuji
CHEMISTRY LETTERS, 34, 9, 1242, 1243, CHEMICAL SOC JAPAN, 2005年09月, ［査読有り］
英語, 研究論文（学術雑誌）, The SAC-CI calculations clarify the natures of the excited states and the electron-transfer (ET) processes in the photosynthetic reaction center (PSRC) of Rhodobactor (Rb.) sphaeroides. The absorption spectrum was assigned with the averaged error of 0. 11 eV. The electronic factors calculated from the SAC-Cl wave functions clarified the mechanism of the unidirectionality of the ET in Rb. sphaeroides. It is controlled by the ET step from bacteriochlorophyll (B) to bacteriopheophytin (H), not from the special pair (P) to B as in the Rhodopseudomonas (Rps.) viridis reported previously: the electronic factor of the A-branch ET is 20 times larger than that of the B-branch. An analysis clarified that the unidirectionality originates from the inter-chromophore distances, and further that the hyperconjugations of the methyl groups with the pi electrons of the chromophores have primary contributions to the electronic factor.

Structure of phytochromobilin in the P-r and P-fr forms: SAC-CI theoretical study
J Hasegawa, M Isshiki, K Fujimoto, H Nakatsuji
CHEMICAL PHYSICS LETTERS, 410, 1-3, 90, 93, ELSEVIER SCIENCE BV, 2005年07月, ［査読有り］
英語, 研究論文（学術雑誌）, Phytochrome, an important photoreceptor in green plants, contains a cofactor, phytochromobilin, which shows photo-isomerization to respond as a sensor of light. The SAC-CI method was applied to the absorption spectra of several structural isomers of phytochromobilin and successfully identified the structure of the key isomers, P-r and P-fr forms which have long been discussed. The P-r and P-fr forms of the phytochromobilin are identified to be ZZZasa and ZZEass isomers, respectively, in their protonated forms. The results also indicated that the structures of the lumi-R and meta-R-a forms, the intermediates during the photochemical cycle, would be ZZEasa isomers. (c) 2005 Elsevier B.V. All rights reserved.

Excited states of porphyrin isomers and porphycene derivatives: A SAC-CI study
JY Hasegawa, K Takata, T Miyahara, S Neya, MJ Frisch, H Nakatsuji
JOURNAL OF PHYSICAL CHEMISTRY A, 109, 14, 3187, 3200, AMER CHEMICAL SOC, 2005年04月, ［査読有り］
英語, 研究論文（学術雑誌）, Excited states of free-base porphyrin isomers, porphycene (Pc), corrphycene (Cor), and hemiporphycene (hPc), were studied by the Symmetry-Adapted Cluster (SAC)/SAC-Configuration Interaction (CI) method. The absorption peaks of the porphyrin isomers were assigned on the basis of the SAC-Cl spectra. The X, Y, X', and Y' bands of the porphyrin isomers, which have weak intensities, are identified. The differences in the Q-band absorptions among the isomers were clearly explained by the four-orbital model. In Cor and hPc, the wave function of the B-band corresponds to the mixture of the four-orbital excitations and the optically forbidden excitation of free-base porphin (P), due to the molecular symmetry lowering in the isomers. The B-band character is described by the five-orbital model in Pc and the six-orbital model in Cor and hPc. Two tetrazaporphycenes and two ring-extended (dibenzo) porphycenes were designed, and the Q-band transition moment was successfully controlled. These examples show that the control of the four-orbital energy levels is the guiding principle for pigment design in porphyrin compounds.

SAC-CI method applied to molecular spectroscopy
M. Ehara, J. Hasegawa, H. Nakatsuji
Theory and Applications of Computational Chemistry, 1099-1141, 1099, 1141, Elsevier, 2005年, ［査読有り］
英語, 論文集(書籍)内論文, This chapter describes the SAC-CI (Symmetry-Adapted Cluster- Configuration Interaction) method applied to molecular spectroscopy. The SAC-CI method was proposed in 1978 as an accurate electronic-structure theory for the ground, excited, ionized, electron-attached, and high-spin states of atoms and molecules. Since then, it has been successfully applied to various chemistries including more than 150 molecules and established to be a useful method for studying chemistry and physics involving various electronic states. The topics covered in the chapter are electronic excitation spectra, ionization spectra, collision-induced absorption processes, photochemical reactions, inner-shell ionizations, equilibrium geometries of excited states, and ESR hyperfine splitting constants of radicals. The applied systems are organic and inorganic compounds, vander Waals complexes, transition metal complexes, phthalocyanines, and the bacterial photosynthetic reaction center. These results show the reliability and applicability of the SAC-CI method for studying molecular spectroscopy. © 2005 Elsevier B.V. All rights reserved.

Aza-substitution effect on the Q-band excitations of freebase porphin, chlorin, and bacteriochlorin: SAC-Cl theoretical study
JY Hasegawa, T Kimura, H Nakatsuji
JOURNAL OF PORPHYRINS AND PHTHALOCYANINES, 9, 5, 305, 315, WORLD SCI PUBL CO INC, 2005年, ［査読有り］
英語, 研究論文（学術雑誌）, Electronic structure of the excited states and absorption spectra of free-base azaporphins, azachlorin, and azabacteriochlorin were systematically investigated by SAC-CI calculations. Aza-substitution at the meso position affects the orbital energy of the next-HOMO, and the transition dipole moment enlarges as the number of the substitution increases. Some of the aza-substitutions dramatically affect the direction of the transition dipole, due to reduction of the molecular symmetry, which was studied in detail by a decomposition analysis of the transition dipole moment. Tetraza-substitution in chlorin and bacteriochlorin increases the oscillator strength more than that of tetrazaporphin. The mechanism underlying these changes originates mainly from the relaxation of near-degeneracy in the main configurations. These findings would be useful for the application to the molecular design of the excited states. Copyright (C) 2005 Society of Porphyrins & Phthalocyanines.

Aza-substitution effect on the Q-band excitations of freebase porphin, chlorin, and bacteriochlorin: SAC-Cl theoretical study
JY Hasegawa, T Kimura, H Nakatsuji
JOURNAL OF PORPHYRINS AND PHTHALOCYANINES, 9, 5, 305, 315, WORLD SCI PUBL CO INC, 2005年
英語, 研究論文（学術雑誌）, Electronic structure of the excited states and absorption spectra of free-base azaporphins, azachlorin, and azabacteriochlorin were systematically investigated by SAC-CI calculations. Aza-substitution at the meso position affects the orbital energy of the next-HOMO, and the transition dipole moment enlarges as the number of the substitution increases. Some of the aza-substitutions dramatically affect the direction of the transition dipole, due to reduction of the molecular symmetry, which was studied in detail by a decomposition analysis of the transition dipole moment. Tetraza-substitution in chlorin and bacteriochlorin increases the oscillator strength more than that of tetrazaporphin. The mechanism underlying these changes originates mainly from the relaxation of near-degeneracy in the main configurations. These findings would be useful for the application to the molecular design of the excited states. Copyright (C) 2005 Society of Porphyrins & Phthalocyanines.

1P265 SAC-CI法によるレチナールタンパク質オプシン依存性の理論的研究(光生物 A) 視覚)
藤本 和宏, 長谷川 淳也, 林 重彦, 中辻 博
生物物理, 44, S96, 一般社団法人 日本生物物理学会, 2004年
日本語

Electronic excitations of the green fluorescent protein chromophore in its protonation states: SAC/SAC-CI study
AK Das, JY Hasegawa, T Miyahara, M Ehara, H Nakatsuji
JOURNAL OF COMPUTATIONAL CHEMISTRY, 24, 12, 1421, 1431, WILEY-BLACKWELL, 2003年09月, ［査読有り］
英語, 研究論文（学術雑誌）, Two ground-state protonation forms causing different absorption peaks of the green fluorescent protein chromophore were investigated by the quantum mechanical SAC/SAC-CI method with regard to the excitation energy, fluorescence energy, and ground-state stability. The environmental effect was taken into account by a continuum spherical cavity model. The first excited state, HOMO-LUMO excitation, has the largest transition moment and thus is thought to be the source of the absorption. The neutral and anionic forms were assigned to the protonation states for the experimental A- and B-forms, respectively. The present results support the previous experimental observations. (C) 2003 Wiley Periodicals, Inc.

Energetics of the electron transfer from bacteriopheophytin to ubiquinone in the photosynthetic reaction center of Rhodopseudomonas viridis: Theoretical study
JY Hasegawa, M Ishida, H Nakatsuji, ZY Lu, HY Liu, WT Yang
JOURNAL OF PHYSICAL CHEMISTRY B, 107, 3, 838, 847, AMER CHEMICAL SOC, 2003年01月, ［査読有り］
英語, 研究論文（学術雑誌）, The energetics of electron transfer in the photosynthetic reaction center of Rhodopseudomonas viridis was studied using the density functional theory (DFT). By examining the basis set-dependence and the accuracy of the DFT for calculating adiabatic electron affinity, single-point calculations with 6-31+G(d) basis sets, at the geometry optimized with 6-31G(d) basis sets, were found to be almost independent of the basis set. In gas-phase calculations, bacteriopheophytin (H) had the greatest electron affinity among the three chromophores: H, menaquinone (MQ), and ubiquinone (UQ). However, the order of the electron affinity was reversed to be UQ > MQ > H by including residues that interacted with the chromophores through hydrogen bonding. Based on the QM/MM optimized geometries, cluster models for the binding sites were constructed. The computed reaction energy was comparable to values obtained experimentally. The reaction energy can be decomposed into a vertical electron affinity term and a relaxation energy term using a driving force analysis. The most important term was the vertical electron affinity of the chromophores. Based on optimization, there was little structural reorganization. The present results indicate that, with regard to the energetics of electron transfer, local interactions between the chromophores and proteins play a decisive role by tuning the electron affinity of the chromophores, whereas the effects of distant residues are of secondary importance.

Ground and excited states of linked and fused zinc porphyrin dimers: Symmetry adapted cluster (SAC)―configuration interaction (CI) study
T. Miyahara, H. Nakatsuji, J. Hasegawa, A. Osuka, N. Aratani, A. Tsuda
J. Chem. Phys., 117, 24, 11196, 11207, AMER INST PHYSICS, 2002年12月, ［査読有り］
英語, 研究論文（学術雑誌）, The symmetry adapted cluster (SAC)/SAC-configuration interaction method was applied to calculate the ground and excited states of zinc porphyrin monomers (without and with phenyl groups, ZnP and ZnPPh, respectively) and meso-meso linked (Zn2PMM) and doubly fused (Zn2PDF) zinc porphyrin dimers. Various features of the absorption spectra are studied, clarified, and assigned theoretically. The calculated electronic spectrum of ZnPPh, in comparison with that of ZnP, showed that the phenyl groups affect the spectrum in both the peak positions and intensities. In the dimers, Zn2PMM and Zn2PDF, the interactions of the monomer's four-orbitals result in an eight-orbital model of the dimers, which plays an important role in the interpretation of the excited states observed in the spectra. In Zn2PMM, the interaction is smaller and each peak in the split Soret (BI and BII) bands consists of two peaks, in contrast to the prediction based on Kasha's exciton rule. In Zn2PDF, the interaction between the two monomer units is so strong that the small highest occupied molecular orbital-lowest unoccupied molecular orbital gap causes the red-shifted Q (1.16 eV) and BI (2.13 eV) bands. In addition, the excitations out of the eight orbitals appear in the low-energy region of the spectrum, which is very different from the case of the monomer. A comprehensive and pictorial analysis is given for the excited states of the dimers in comparison with those of the monomer. (C) 2002 American Institute of Physics.

Density functional study on geometry and electronic structure of nitrile hydratase active site model
W Nowak, Y Ohtsuka, J Hasegawa, H Nakatsuji
INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 90, 3, 1174, 1187, JOHN WILEY & SONS INC, 2002年11月, ［査読有り］
英語, 研究論文（学術雑誌）, Nitrile Hydratase (R. Sp. 771, NHase, EC. 4.2.1.84, CAS registration no. 82391-37-5), the enzyme that plays an important role in the industrial production of acrylamide, is studied theoretically in this article. For the first time the electronic structure of the active site of nitrosylated form with a proper oxidation state of the cysteine ligands is calculated using the density functional theory (DFT) method with the Becke, Lee, Yang, and Paar (B3LYP)6-31G* functional. The optimized geometries of six and five coordinated complexes are different, showing that the photodissociation of NO triggers a substantial relaxation of the NHase active site. The major structural change is a shift of the position of iron with respect to the four equatorial ligands, which resembles a heme doming observed in myoglobins. Calculated charge distribution supports the role of Fe as a possible Lewis acid in catalytic cycle. We found that the cysteine-sulfinic residue (Cys112) is very strongly polarized in NHase. Sulfur atom S, Cys112 is predicted to be the most positively charged center. This result gives independent support to a very recent finding of the critical role of an oxidation in the position Cys112 for preserving catalytic activity of the enzyme (Endo, L; Nojiri, M.; Tsujimura, M.; Nakasako, M.; Nagashima, S.; Yohda, M.; Odaka, M. J Inorgan Biochem 2001, 83, 247). (C) 2002 Wiley Periodicals, Inc.

Ground state structure of CuO2: a CASPT2 study
JY Hasegawa, K Pierloot, BO Roos
CHEMICAL PHYSICS LETTERS, 335, 5-6, 503, 509, ELSEVIER SCIENCE BV, 2001年03月, ［査読有り］
英語, 研究論文（学術雑誌）, The ground state structure of CuO2, which has been discussed extensively in the literature, has been determined using a multiconfigurational SCF method and second-order perturbation theory. In the gas phase, it has been found to have a side-on C-2v structure. However, when introducing effects of a surrounding matrix, the ground state changes to an end-on C-s structure, with an energy 1.2 kcal/mol lower than the side-on structure. Computed harmonic frequencies are in agreement with experiment. MRSDCI calculations have also been performed and they confirm the results obtained at the second-order perturbation theory level. Previous density functional theory studies have failed to predict a correct ground state structure. (C) 2001 Elsevier Science B.V. All rights reserved.

Excited states and electron transfer in the photosynthetic reaction center of Bacteria　　　　　　　　　　　　　　　
H. Nakatsuji, J. Hasegawa, K. Ohkawa
Protein, Nucleic acid and Enzyme, 45, 4, 587, 594, 2000年, ［査読有り］

Radical cations of perinaphthocyclopropanes. Conditions for the observation of 1.3-perinaphthadiyl radical cations
T. Bally, Z. Zhu, J. Wirtz, M. Fuelscher, J. Hasegawa
J. Chem. Soc. , Perkin Trans., 11, 2311, 2318, 2000年, ［査読有り］

Radical cations of perinaphthocyclopropanes. Conditions for the observation of 1,3-perinaphthadiyl radical cations
T Bally, ZD Zhu, J Wirz, M Fulscher, JY Hasegawa
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2, 2,2311-2138, 11, 2311, 2318, ROYAL SOC CHEMISTRY, 2000年
英語, 研究論文（学術雑誌）, gamma -Irradiation of 7,7a-dihydro-6bH-cycloprop[a]acenaphthylene (1) and its 7,7-dimethyl derivative (2) in haloalkane glasses at 77 K yields persistent parent radical cations of these compounds. On visible irradiation, 1(.+) is transformed into the radical cation of phenalene, 3(.+), which was also generated independently from neutral 3. The transformation 1(.+)--> 3(.+) presumably proceeds by opening of the central cyclopropane bond and subsequent H-shift in the resulting perinaphthadiyl radical cation which is, however, not observed. Surprisingly, the dimethyl derivative, 2(.+), is also transformed into a phenalene radical cation by visible photolysis. In this case the mechanism is probably a different one, involving a distonic diyl cation obtained by cleavage of a lateral cyclopropane bond. In contrast to the above, the ring opening of the dicyclopropa[a,g]pyracyclene 4 radical cation proceeds stepwise, and the perinaphthadiyl cation intermediate can be observed. A second photochemical ring opening yields the radical cation of 2,7-dihydro-2,2,7,7-tetramethylpyrene that was generated independently from the neutral precursor.
The electronic absorption spectra of all observed radical cations are discussed in conjunction with the corresponding photoelectron spectra (where available) and with quantum chemical calculations.

SAC-CI general-R study of the ionization spectrum of HCl
M Ehara, P Tomasello, J Hasegawa, H Nakatsuji
THEORETICAL CHEMISTRY ACCOUNTS, 102, 1-6, 161, 164, SPRINGER VERLAG, 1999年06月, ［査読有り］
英語, 研究論文（学術雑誌）, The valence ionization spectrum of HCl is studied by symmetry-adapted-cluster configuration-interaction general-R and SD-R methods. The general-R method describes well the peak positions and intensities of seven satellite lines observed below the double ionization threshold. The twinning shake-up states due to the (4 sigma)(-1) state and the Rydberg states of HCl+ are correctly reproduced.

Excited states of the photosynthetic reaction center of Rhodopseudomonas viridis: SAC-CI study
J Hasegawa, K Ohkawa, H Nakatsuji
JOURNAL OF PHYSICAL CHEMISTRY B, 102, 50, 10410, 10419, AMER CHEMICAL SOC, 1998年12月, ［査読有り］
英語, 研究論文（学術雑誌）, The excitation spectrum of the photosynthetic reaction center (PSRC) of Rhodopseudomonas (Rps.) viridis is assigned by using the SAC(symmetry adapted cluster)-CI(configuration interaction) method. All the chromophores included in the PSRC, bacteriochlorophyll b dimer (special pair, P), bacteriochlorophyll b in L- and M-branches (B-L and B-M), bacteriopheophytin b in L- and M-branches (H-L and H-M), menaquinone (MQ), ubiquinone (UQ), and four different hemes, c-552, c-554, c-556, and c-559 in c-type cytochrome subunit, were calculated within the environment of proteins, waters, and the other chromophores which were dealt with by the point-charge electrostatic model. We have assigned successfully all the peaks in the experimental spectrum in the energy range from 1.2 to 2.5 eV. The assignment was done by comparing the SAC-CI theoretical spectrum with the experimental one in excitation energy, oscillator strength, linear dichroism data (angle of transition moment), and other experimental information available. Almost all the peaks were red shifted due to the effect of proteins. The present assignment of the spectrum would give a basis for future photoexperimental studies of the PSRC.

Mechanism and unidirectionality of the electron transfer in the photosynthetic reaction center of Rhodopseudomonas viridis: SAC-CI theoretical study
J Hasegawa, H Nakatsuji
JOURNAL OF PHYSICAL CHEMISTRY B, 102, 50, 10420, 10430, AMER CHEMICAL SOC, 1998年12月, ［査読有り］
英語, 研究論文（学術雑誌）, The electronic mechanism and the origin of the unidirectionality of the electron transfer from photoexcited special pair to bacteriopheophytin in the photosynthetic reaction center (PSRC) of Rhodopseudomonas (Rps) viridis are studied theoretically by using the SAC(symmetry adapted cluster)-CI (configuration interaction) method. The effects of the surrounding proteins are considered by using the point charge model. The L-branch selectivity of the electron transfer is explained by the asymmetry of the transfer integral, an electronic factor, which originates from a small structural asymmetry of the PSRC: the L-side chromophores are locally closer than the M-side ones, though the average separations are almost the same. The smallness of the charge recombination rate is attributed to the difference in the electron localization between the LUMO and HOMO of special pair. Protein effects on the unidirectionality are quite small as far as the electrostatic model is valid, though the proteins keep the three-dimensional arrangement of the chromophores in the PSRC. A mutation experiment for realizing M-side selectivity is suggested.

Excited states and electron transfer mechanism in the photosynthetic reaction center of Rhodopseudomonas viridis: SAC-CI study
H Nakatsuji, J Hasegawa, K Ohkawa
CHEMICAL PHYSICS LETTERS, 296, 5-6, 499, 504, ELSEVIER SCIENCE BV, 1998年11月, ［査読有り］
英語, 研究論文（学術雑誌）, The symmetry adapted cluster (SAC)-configuration interaction (CI) method has been utilized to assign the excited states in absorption and linear dichroism spectra and to clarify the mechanism of the unidirectionality in the electron transfer of the photosynthetic reaction center of Rhodopseudomonas viridis. We have calculated the ground, excited, ionized, and electron-attached states of all the chromophores in the reaction center. The protein effects were included with the use of the point-charge model. (C) 1998 Elsevier Science B.V. All rights reserved.

Theoretical study on the ionized states of ethylene by the SAC-CI (general-R) method
J. Hasegawa, M. Ehara, H. Nakatsuji
Chemical Physics, 230, 1, 23, 30, Elsevier, 1998年04月15日, ［査読有り］
英語, 研究論文（学術雑誌）, The SAC (symmetry adapted cluster)/SAC-CI (configuration interaction) general-R method is successfully applied to the photoelectron spectrum of ethylene. The theoretical spectrum satisfactorily reproduces the outer- and inner-valence regions of the spectrum. The exponential generation (EG) algorithm followed by perturbation selection (PS) is shown to be useful in the generation of small and yet effective higher-excitation operators for the SAC-CI general-R method. The peak at 23.7 eV is assigned to the 'twinning' ionized states, the 2 2Ag and 3 2Ag states, and the peak at 27.4 eV is attributed to the 6 2Ag and 7 2Ag states. In the energy region around 31 eV, some ionized states are suggested to locate with small intensities. The 1 2B2g state obtains its intensity by the initial state configuration interaction.

The outer valence ionization energies of thiazyl cyanide
P Tomasello, J Hasegawa, H Nakatsuji
EUROPHYSICS LETTERS, 41, 6, 611, 616, E D P SCIENCES, 1998年03月, ［査読有り］
英語, 研究論文（学術雑誌）, We present a theoretical ab initio investigation of the low-energy valence Photo Electron (PE) spectrum of NSCN, a novel thiazyl compound recently synthetized, by using many-body post-SCF electronic structure methods. To account for correlation and relaxation effects neglected within the Koopmanns' theorem approximation, we used the SAC/SAC-C.I. theory in calculating the lon;est ionization energies. Correlation effects are quite important to reliably understand the recorded PE intensity of NSCN. We are able to propose a different assignment of the entire outer valence PE spectrum of NSCN which seems more consistent and in better agreement with the experiment. We also discuss similarities and differences in the ionization energies of NSCN and closely related molecules (cyanogen and thiazyl halides).

SAC-CI study on the excited and ionized states of free-base porphin: Rydberg excited states and effect of polarization and Rydberg functions
Y Tokita, J Hasegawa, H Nakatsuji
JOURNAL OF PHYSICAL CHEMISTRY A, 102, 10, 1843, 1849, AMER CHEMICAL SOC, 1998年03月, ［査読有り］
英語, 研究論文（学術雑誌）, The ground, excited, and ionized states of free-base porphin (FBP) are reinvestigated by the SAC (symmetry adapted cluster)/SAC-CI (configuration interaction) method. In particular, the Rydberg excited states, the valence-Rydberg mixing, and the effect of polarization d-functions are studied. The lowest Rydberg excited state would exist at around 5.5 eV with a weak intensity, but the valence-Rydberg mixing is small. The effects of both the Rydberg and polarization d-functions are relatively small for the excitation energies of the main peaks, whereas the polarization d-functions affect considerably the ionization spectrum.

Theoretical study of the excited states of chlorin, bacteriochlorin, pheophytin a and chlorophyll a by the SAC/SAC-CI method
J Hasegawa, Y Ozeki, K Ohkawa, M Hada, H Nakatsuji
JOURNAL OF PHYSICAL CHEMISTRY B, 102, 7, 1320, 1326, AMER CHEMICAL SOC, 1998年02月, ［査読有り］
英語, 研究論文（学術雑誌）, Excited states of free base chlorin (FBC), free base Bacteriochlorin (FBBC), pheophytin a (Pheo a), and chlorophyll a (Chlo a), which are derivatives of free base porphine (FBP), were calculated by the SAC (symmetry adapted cluster)/SAC-CI (configuration interaction) method. The results reproduced well the experimentally determined excitation energies. The reduction of the outer double bonds in the porphine ring in the order of FBP, FBC, and FBBC causes a breakdown of the symmetry and a narrowing of the HOMO-LUMO gap, which result in a red shift of the Q(x) band and an increase of its intensity. In the change from Pheo a to Chlo a, the Mg coordination reduces the quasidegeneracy in the Q(x) state and then increases the spectral intensity. The disappearance of the Q(y) humps from the absorption spectrum of Pheo a, compared with that of Chlo a, is due to the red shift of the Q(y) state.

Theoretical study on the ionized states of ethylene by the SAC-CI(general-R)method "jointly worked"　　　　　　　　　　　　　　　
Chem. Phys., 230,23-30, 1998年

Excited states of free base phthalocyanine studied by the SAC-CI method
Kazuo Toyota, Jun-Ya Hasegawa, Hiroshi Nakatsuji
Journal of Physical Chemistry A, 101, 4, 446, 451, American Chemical Society, 1997年01月23日, ［査読有り］
英語, 研究論文（学術雑誌）, The SAC (symmetry adapted cluster)/SAC-CI method was used to calculate the ground and excited states of free base phthalocyanine (FBPc). This is the first accurate ab initio study of the excited states of FBPc. The calculated electronic spectrum agrees reasonably well with experimental results with regard to both energy and intensity. The relationships among the molecular structure, excitation energy, and spectral intensity are discussed, and the present results are compared with those for free base porphine (FBP) and free base tetrazaporphine (FBTAP) studied previously. Two important effects of skeletal changes are clarified
mesotetraaza substitution and tetrabenzo substitution cause a large splitting between the HOMO and next HOMO levels and lead to a breakdown of the quasi-degeneracy of the two main configurations of the Q band, resulting in strong visible absorption due to the incomplete cancellation of the individual contributions to the transition dipole moment. This explains why Pc's are so useful as pigments. Further, a new assignment of the B (Soret) band is proposed. The broad experimental B band is composed of at least four states. The main peak of the B band is due to transitions from the orbital lower than the so-called "four orbitals", and the transitions arising from the "four orbitals" constitute the shoulder in the lower energy side of the band.

Ground and excited states of carboxyheme: A SAC/SAC-CI study
H Nakatsuji, Y Tokita, J Hasegawa, M Hada
CHEMICAL PHYSICS LETTERS, 256, 1-2, 220, 228, ELSEVIER SCIENCE BV, 1996年06月, ［査読有り］
英語, 研究論文（学術雑誌）, The SAC (symmetry adapted cluster)/SAC-CI method is applied to calculations of the ground and excited states of carboxyheme (FeC24N6OH16). The excited statics are calculated up to 7.8 eV. The calculated excitation energies and oscillator strengths reproduce well the electronic spectrum. The Q bands are explained by the excitations within Gouterman's 4 orbitals. The B, N, L and A? bands are explained by the excitations within '6 orbitals', in which the lower porphyrin pi orbitals, 44a' and 45a', are added to the 4 orbitals, The B band shoulder in the higher energy side has a d, sigma-d*, sigma*, CO* nature, The states higher than the M band are characterized by the d-pi* and pi-d* states; therefore, the intensities are predicted to be small.

Ground and excited states of oxyheme: SAC/SAC-CI study
H Nakatsuji, J Hasegawa, H Ueda, M Hada
CHEMICAL PHYSICS LETTERS, 250, 3-4, 379, 386, ELSEVIER SCIENCE BV, 1996年03月, ［査読有り］
英語, 研究論文（学術雑誌）, The SAC(symmetrie adapted cluster)/SAC-CI(configuration interaction) mehtod is applied to the ground and low-lying excited states of oxyheme (FeC23N6O2H16). The ground state ((1)A') is suitably represented by the Pauling model, Fe(II) (S = 0) + O-2((1) Delta(g)). The SAC-CI result reproduces well the lower excitation spectrum of oxyhemoglobin. The lowest peak g observed at 1.34 eV is assigned to the (1) Delta(g) --> (1) Sigma(g)(+) excitation of the O-2 ligand. Many transitions originating from the iron d orbitals are calculated, although their intensities are very small. The lowest tripler state (1(3)A ''), which is due to the (1) Delta(g) --> (3) Sigma(g)(-) transition around the O-2 ligand, is calculated at 0.47 eV above the ground state, but its level is sensitive to the electron correlations included, In the geometry of the deoxy form, this 1(3)A '' state becomes more stable than the closed-shell singlet state ((1)A'), indicating a geometrical control of oxygen affinity of heme.

SAC-CI study of the excited states of free base tetrazaporphin
K Toyota, JY Hasegawa, H Nakatsuji
CHEMICAL PHYSICS LETTERS, 250, 5-6, 437, 442, ELSEVIER SCIENCE BV, 1996年03月, ［査読有り］
英語, 研究論文（学術雑誌）, The SAC (symmetry adapted cluster)/SAC-CI method is applied to calculations of the ground and excited states of free base tetrazaporphin (FBTAP). The electronic spectrum is reproduced in fairly good agreement with experiments, and unknown absorption bands in the energy region higher than 4 eV are predicted. The effect of meso-tetraaza-substitution on the excited states of porphin macrocycle explains why the compound is colored, as in the closely related compounds, phthalocyanines, used as pigments.

Ground and excited states of Mg porphin studied by the SAC/SAC-CI method
J Hasegawa, M Hada, M Nonoguchi, H Nakatsuji
CHEMICAL PHYSICS LETTERS, 250, 2, 159, 164, ELSEVIER SCIENCE BV, 1996年02月, ［査読有り］
英語, 研究論文（学術雑誌）, The SAC (symmetry adapted cluster)/SAC-CI method is applied to the ground and excited states of magnesium porphin (MgP). The pi interaction between the Mg atom and the porphin ring is small and, therefore, the essential difference between MgP and free base porphin (FBP) lies in symmetry; the former is D-4h and the latter D-2h. The degenerate excited states in MgP split into two in FBP. The SAC-CI results for the excitation energy and the oscillator strength compare reasonably well with the experimental spectra for Mg etioporphyrin (MgEtio) and Mg tetraphenylporphin (MgTPP) and the natures of the excited states are clarified. Gouterman's four-orbital model holds well for the Q band, but the excitations from the 2a(2u) MO below the four orbitals mix in the B band, as was found previously for FBP. The natures of the N bands are different between MgP and FBP.

Excited and ionized states of free base porphin studied by the symmetry adapted cluster-configuration interaction (SAC-CI) method
H Nakatsuji, JY Hasegawa, M Hada
JOURNAL OF CHEMICAL PHYSICS, 104, 6, 2321, 2329, AMER INST PHYSICS, 1996年02月
英語, 研究論文（学術雑誌）, The SAC(symmetry adapted cluster)/SAC-CI method is applied to the calculations of the ground, excited, and ionized states of the free base porphin. The electronic spectrum of porphin is well reproduced and new assignments for the B (Soret), N, L, and M bands are proposed. The present result shows that the four-orbital model is strongly perturbed for the B and N bands by the excitations from the lower 4b(1u) MO and that the cr electron correlations are important for the description of the excited states. The absorption peaks in the ionization spectrum are assigned and the reorganization effect is found to be large especially for the n and sigma electron ionizations. (C) 1996 American Institute of Physics.

Theoretical study on the electronic spectrum of TcO4-
J Hasegawa, K Toyota, M Hada, H Nakai, H Nakatsuji
THEORETICA CHIMICA ACTA, 92, 6, 351, 359, SPRINGER VERLAG, 1995年12月, ［査読有り］
英語, 研究論文（学術雑誌）, The theoretical electronic spectrum of TcO4- calculated by the SAC(symmetry adapted cluster)/SAC-CI method is presented. The spectrum is in good agreement with the experimental one. The observed peaks are assigned and the existence of several absorptions in the energy region higher than that observed is predicted. The difference and the similarity between the electronic spectra of TcO4- and MnO4- are clarified. The spectral difference between TcO4- and MnO4- is due to a remarkably high energy shift of the 3(1)T(2) state of TcO4-.

Theoretical study on the electronic spectrum of TcO4-
J Hasegawa, K Toyota, M Hada, H Nakai, H Nakatsuji
THEORETICA CHIMICA ACTA, 92, 6, 351, 359, SPRINGER VERLAG, 1995年12月
英語, 研究論文（学術雑誌）, The theoretical electronic spectrum of TcO4- calculated by the SAC(symmetry adapted cluster)/SAC-CI method is presented. The spectrum is in good agreement with the experimental one. The observed peaks are assigned and the existence of several absorptions in the energy region higher than that observed is predicted. The difference and the similarity between the electronic spectra of TcO4- and MnO4- are clarified. The spectral difference between TcO4- and MnO4- is due to a remarkably high energy shift of the 3(1)T(2) state of TcO4-.

CHIRAL AMINO-ACID RECOGNITION BY A PORPHYRIN-BASED ARTIFICIAL RECEPTOR
Y KURODA, Y KATO, T HIGASHIOJI, J HASEGAWA, S KAWANAMI, M TAKAHASHI, N SHIRAISHI, K TANABE, H OGOSHI
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 117, 44, 10950, 10958, AMER CHEMICAL SOC, 1995年11月, ［査読有り］
英語, 研究論文（学術雑誌）, Molecular recognition of amino acid methyl esters by doubly bridged porphyrin Zn complexes was investigated. A chiral, bridged porphyrin was prepared from the alpha,alpha,alpha,alpha-atropisomer of meso-tetrakis(o-aminophenyl)porphyrin and 4-nitroisophthaloyl chloride. The similar reactions using unsubstituted isophthaloyl, 5-nitroisophthaloyl, and 4,6-dinitroisophthaloyl chlorides as the bridging reagents gave corresponding nonchiral bridged porphyrins. The Zn complex of the chiral porphyrin exhibits significant chiral recognition toward amino acids. For example, the chiral receptor porphyrin shows D-/L-selectivity of 7.5 for valine methyl ester at 293 K in CH2Cl2. Comparison of binding behavior of four types of bridged porphyrin Zn complexes and H-1 NMR investigations reveal that the present chiral recognition observed for amino acid methyl esters is caused by favorable hydrogen bond formation between the carbonyl group of the guest and the 3-carboxyamide of the 4-nitroisophthalic bridging benzene. Thermodynamic parameters of the present complexation were also determined, and two types of very strong linear isoequilibrium relationships between the observed entropies and enthalpies were found. One is the linear correlation (R = 0.993) between Delta H and T Delta S values observed for host-guest combinations of bridged porphyrins-amino acid esters, and another is that (R = 0.997) observed for combinations of tetraphenylporphyrin-amino acid esters and bridged porphyrins-3-amino-2,4-dimethylpentane. The very large slopes observed for these linear correlations indicate that the significant amount of the conformational freedom of the guests is lost even during the process of simple coordination without hydrogen bond formation.

MOLECULAR TRENCH - HIGHLY COMPLEMENTARY BINDING-SITES FOR TARTARIC ACID DIALKYL ESTER
Y KURODA, Y KATO, M ITO, J HASEGAWA, H OGOSHI
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 116, 22, 10338, 10339, AMER CHEMICAL SOC, 1994年11月, ［査読有り］
英語

Tuning Transition Electric and Magnetic Dipole Moments: [7]Helicenes Showing Intense Circularly Polarized Luminescence (vol 12, pg 686, 2021)
Hiromu Kubo, Takashi Hirose, Takuya Nakashima, Tsuyoshi Kawai, Jun-ya Hasegawa, Kenji Matsuda, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 12, 4, 1124, 1124, 2021年02月
AMER CHEMICAL SOC, 英語, その他

ゼオライト固定化インジウム酸素クラスターの合成とメタン活性化能
前野禅, 安村駿作, りゅう冲, 鳥屋尾隆, 鳥屋尾隆, 今健一, 中山哲, 長谷川淳也, 清水研一, 清水研一, 触媒討論会討論会A予稿集(CD-ROM), 124th, 2019年

ビピリジル残基を主鎖に含むポリウレタンおよびポリエステルの合成と高分子配位子としての応用
中野環, 木村彰宏, 長谷川淳也, NAGEH Hassan, WANG Yue, 永直文, 高分子学会予稿集(CD-ROM), 67, 2, 2018年

触媒計算科学概観：理論計算はいかに活用できるか
長谷川 淳也, 触媒, 59, 4, 176, 180, 2017年
触媒学会, 日本語, 記事・総説・解説・論説等（学術雑誌）

キャタリストインフォマティクス
長谷川 淳也, 日本化学会情報化学部会誌(Web), 34, 4, 109, 109, 2016年, ［査読有り］
公益社団法人 日本化学会・情報化学部会, 日本語

Quantum mechanical molecular interactions for calculating excitation energy in molecular environments: A first-order interacting space approach
Kazuma Yanai, Kazuya Ishimura, Jun-ya Hasegawa, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 249, 2015年03月, ［査読有り］
AMER CHEMICAL SOC, 英語, 研究発表ペーパー・要旨（国際会議）

炭素へのセルロースオリゴマーの吸着における疎水性官能基の役割
藪下瑞帆, 小林広和, 長谷川淳也, 原賢二, 福岡淳, 触媒討論会討論会A予稿集, 114th, 411, 2014年09月18日
日本語

Adsorption of cellulosic molecules on carbon materials driven by their hydrophobicity
Mizuho Yabushita, Hirokazu Kobayashi, Jun-Ya Hasegawa, Kenji Hara, Atushi Fukuoka, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 248, 2014年08月, ［査読有り］
AMER CHEMICAL SOC, 英語, 研究発表ペーパー・要旨（国際会議）

マルチスケール・モデルによる複雑分子系の計算化学
長谷川 淳也, 化学, 68, 12, 12, 16, 2013年
化学同人, 日本語

Color-tuning in photo-functional proteins: electronic structure and interactions
Jun-ya Hasegawa, LUMINESCENCE, 27, 2, 121, 121, 2012年03月, ［査読有り］
WILEY-BLACKWELL, 英語, 研究発表ペーパー・要旨（国際会議）

光生物学システムの励起状態と機能への理論的アプローチ　　　　　　　　　　　　　　　
長谷川 淳也, 第２次先端ウオッチング調査：融合領域の創成, 41, 45, 2012年

光生物学システムの励起状態と機能：高精度電子理論の開発を基盤とする理論的研究　　　　　　　　　　　　　　　
長谷川 淳也, 「実在系の分子理論」ニュースレター, 20, 2010年

PSII反応中心の励起状態と分子間相互作用　　　　　　　　　　　　　　　
長谷川 淳也, 北川 裕也, 松田 建児, 京都大学学術情報メディアセンター全国共同利用版「広報」, 9, 2, 12, 13, 2010年

光機能性蛋白質におけるカラー・チューニングの量子化学
長谷川 淳也, Mol. Sci., 4, 1, 31, 2010年, ［査読有り］
In visual systems and fluorescent proteins, controlling the photo-absorption/emission energy (color tuning) of the chromophore is the essentials to furnish a protein with the photo-functionality. Depending on the protein environment, the chromophores show a variety of colors, which are relevant to the character of the excited states and to the interactions between the chromophore and the environment. Here we summarize our recent studies on the spectral tuning mechanism of the human visual cone pigments and the fluorescent proteins. These studies elucidated a common feature in the color tuning, which also suggests a strategy to artificially control the color of proteins. We also explain our recent progress in developing the symmetry-adapted cluster-configuration interaction (SAC-CI) method and hybrid quantum mechanical/molecular mechanical (QM/MM) method particularly for studying the photo-functional proteins., Japan Society for Molecular Science, 日本語

錐体視物質におけるカラー・チューニング機構の解明：高精度量子化学計算による理論的研究　　　　　　　　　　　　　　　
長谷川 淳也, 藤本 和宏, 中辻 博, 京都大学学術情報メディアセンター全国共同利用版広報, 8, 2, 5, 6, 2009年

水素吸蔵体：分子間相互作用の解析と分子設計への展望　　　　　　　　　　　　　　　
長谷川 淳也, シーエムシー出版, 106, 113, 2009年, ［査読有り］

光合成・視覚・生物発光の初期過程--SAC-CI法による研究 (生物物質科学--金属を含む分子系を中心に 特集号) -- (生体分子系の電子状態解析)
長谷川 淳也, 中辻 博, 固体物理, 43, 11, 839, 847, 2008年11月
アグネ技術センタ-, 日本語

Exploring Photo-Biology and Bio-Spectroscopy with the SAC-CI (Symmetry-Adapted Cluster-Configuration Interaction) Method"jointly worked"　　　　　　　　　　　　　　　
Radiation Induced Molecular Phenomena in Nucleic Acid: A Comprehensive Theoretical and Experimental Analysis,Springer, 93-124, 2008年

A Review of the SAC-CI Applications to the Excited States of Porphyrin Compounds: How Q-band absorptions are controlled?"jointly worked"　　　　　　　　　　　　　　　
Comp. letters, in press, 2008年

紅色細菌光合成反応中心における励起状態と電子移動の量子化学　　　　　　　　　　　　　　　
光合成研究, 18, 43-49, 2008年

光合成・視覚・生物発光の初期過程：SAC‐CI法による研究,"jointly worked"　　　　　　　　　　　　　　　
固体物理, 43 (11), 147-155, 2008年

Spectral Tuning Mechanism in Photofunctional Proteins: A SAC-CI Theoretical Study "jointly worked"　　　　　　　　　　　　　　　
Frontiers of Computational Science 2008, 1-8, 2008年

生物による光吸収・発光色の多様性に関する電子論的起源について　　　　　　　　　　　　　　　
長谷川 淳也, 藤本 和宏, 中谷 直輝, 中辻 博, 京都大学学術情報メディアセンター全国共同利用版広報, 7, 2, 27, 28, 2008年

Exploring Photo-Biology and Bio-Spectroscopy with the SAC-CI (Symmetry-Adapted Cluster-Configuration Interaction) Method
J. Hasegawa, H. Nakatsuji, Radiation Induced Molecular Phenomena in Nucleic Acids: A Comprehensive Theoretical and Experimental Analysis, Springer, 93, 124, 2008年, ［査読有り］

光合成・視覚・生物発光の初期過程：SAC‐CI法による研究　　　　　　　　　　　　　　　
長谷川 淳也, 中辻 博, 固体物理, 43, 11, 147, 155, 2008年, ［査読有り］

Spectral Tuning Mechanism in Photofunctional Proteins: A SAC-CI Theoretical Study　　　　　　　　　　　　　　　
J. Hasegawa, K. Fujimoto, N. Nakatani, H. Nakatsuji, Frontiers of Computational Science 2008, 1, 8, 2008年, ［査読有り］

蛍ルシフェラーゼにおける発光色制御メカニズム　　　　　　　　　　　　　　　
長谷川 淳也, 中谷 直輝, 中辻 博, 京都大学学術情報メディアセンター全国共同利用版広報, 6, 2, 27, 28, 2007年

Photobiology and biospectroseopy studied by SAC-CI method
Jun-ya Hasegawa, RECENT PROGRESS IN COMPUTATIONAL SCIENCES AND ENGINEERING, VOLS 7A AND 7B, 7A-B, 1296, 1296, 2006年, ［査読有り］
VSP BV-C/O BRILL ACAD PUBL, 英語

Excited states and electron-transfer in bacterial photosynthetic reaction center: SAC-CI theoretical study
Jun-ya Hasegawa, Hiroshi Nakatsuji, RECENT PROGRESS IN COMPUTATIONAL SCIENCES AND ENGINEERING, VOLS 7A AND 7B, 7A-B, 790, 793, 2006年, ［査読有り］
The SAC-Cl calculations clarify the natures of the excited states and the electron-transfer (ET) processes in the photosynthetic reaction center (PSRC) of Rhodobactor (Rb.) sphaeroides. The absorption spectrum was assigned with the averaged error of 0.11 eV. The electronic factors calculated from the SACCI wave functions clarified the mechanism of the unidirectionality of the ET in Rh. sphaeroides. It is controlled by the ET step from bacteriochlorophyll (B) to bacteriopheophytin (11), not front the special pair (P) to B as in the Rhodopseudonzonas (Rps.) viridis reported previously: the electronic factor of the A-branch ET is 20 times larger than that of the B-branch. An analysis clarified that the unidirectionality originates from the inter-chromophore distances, and further that the hyperconjugations of the methyl groups with the R electrons of the chromophores have primary contributions to the electronic factor., VSP BV-C/O BRILL ACAD PUBL, 英語

2.3.4生体分子I(共著）　　　　　　　　　　　　　　　
実験化学講座 第5版、12巻 計算化学、丸善, 202-210, 2004年

2.3.4生体分子I　　　　　　　　　　　　　　　
長谷川 淳也, 中辻 博, 実験化学講座 第5版、12巻 計算化学, 丸善, 202, 210, 2004年, ［査読有り］

ノーベル賞と化学産業　　　　　　　　　　　　　　　
中辻 博, 長谷川 淳也, 江原 正博, 三洋化成ニュース, 417, 14, 18, 2003年

Excited states and electron transfer in the photosynthetic reaction center of Phodopseudomonas viridis: SAC-CI study "jointly worked"　　　　　　　　　　　　　　　
Protein, Nucleic acid and Enzyme, 45,587-594, 2000年

光合成反応中心の励起状態と電子移動
中辻博, 長谷川淳也, 大川和史, 蛋白質核酸酵素, 45, 4, 587, 594, 2000年, ［査読有り］
共立出版, 日本語

Exploring the Enantioselective Mechanism of Pd Catalyst with Polyquinoxaline Ligand for Asymmetric Hydrosilylation of Styrene　　　　　　　　　　　　　　　
M. Ratanasak, T. Yamamoto, M. Suginome, J. Hasegawa
2019 National Symposium for Molecular Chirality, 2018年10月21日, 英語, 口頭発表（招待・特別）
Beijing University of Chemical Technology, ［招待講演］, ［国際会議］

Computational Chemistry with Constraint Force　　　　　　　　　　　　　　　
J. Hasegawa
A Satellite Symposium to celebrate Prof. Kenichi Fukui's 100th birthday, 2018年10月13日, 英語, 口頭発表（招待・特別）
京都大学, ［招待講演］, ［国際会議］

複雑系化学反応機構への計算化学アプローチ　　　　　　　　　　　　　　　
長谷川淳也
日本化学会東北支部青森地区講演会, 2018年10月05日, 口頭発表（招待・特別）
弘前大学, ［招待講演］, ［国内会議］

Methane to Ethane Conversion by Liquid Metal Indium: A DFT Mechanistic Study　　　　　　　　　　　　　　　
Y. Ohtsuka, Y. Nishikawa, H. Ogihara, I. Yamanaka, J. Hasegawa
2018 International Symposium on Advancement and Prospect of Catalysis Science & Technology, 2018年07月27日, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Theoretical Study on Reaction Mechanisms Involving Intersystem Crossing　　　　　　　　　　　　　　　
長谷川 淳也
Pure and Applied Chemistry International Conference 2018 (PACCON 2018), 2018年02月09日, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Constraint Structure Optimization for Minimum Energy Intersystem Crossing Point　　　　　　　　　　　　　　　
長谷川 淳也
The 8-th Asia Pacific Association of Theoretical and Computational Chemists (APATCC8), 2017年12月15日, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Constraint Structure Optimization for Minimum Energy Intersystem Crossing Point　　　　　　　　　　　　　　　
長谷川 淳也
Theoretical Design of Materials with Innovative Functions Based on Element Strategy and Relativistic Electronic Theory, 2017年12月08日, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Constraint Structure Optimization for Minimum Energy Intersystem Crossing Point　　　　　　　　　　　　　　　
長谷川 淳也
The XXII-th Quantum Systems in Chemistry, Physics, and Biology (QSCP), 2017年10月19日, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

系間交差を含む触媒反応経路に関する理論的研究　　　　　　　　　　　　　　　
長谷川 淳也
触媒・電池元素戦略研究拠点 第11回公開シンポジウム, 2017年10月04日, 日本語, 口頭発表（招待・特別）
［招待講演］, ［国内会議］

Theoretical Study of Frustrated Lewis Pair for Activation of Stable Chemical Bonds　　　　　　　　　　　　　　　
J. Hasegawa, M. Ohbo, Y. Hoshimoto, S. Ogoshi
The 21th International Annual Symposium on Computational Science and Engineering (ANSCSE 21), 2017年08月04日, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Excited-State Molecular Interactions: a First-Order Interacting Space Approach　　　　　　　　　　　　　　　
長谷川 淳也
3rd Japan-Thai workshop on Theoretical and Computational Chemistry 2017, 2017年07月14日, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Constraint Structure Optimization for a Particular Energy Minimum　　　　　　　　　　　　　　　
長谷川 淳也
2017 Summer Symposium of KCS-Physical Chemistry Division and 2017 Korea-Japan Molecular Science Symposium, 2017年07月11日, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Excited-State Molecular Interactions: a First-Order Interacting Space Approach　　　　　　　　　　　　　　　
J. Hasegawa, K. Yanai, K. Ishimura
International Symposium on Pure & Applied Chemistry (ISPAC) 2017, 2017年06月09日, 英語, 口頭発表（招待・特別）
Ho Chi Minh City, Vietnam, ［招待講演］, ［国際会議］

拘束条件を付したポテンシャル面上の最適化問題　　　　　　　　　　　　　　　
長谷川 淳也
スーパーコンピュータワークショップ2016 「これまでの理論・計算科学を振り返り今後を展望する」, 2017年02月01日, 口頭発表（招待・特別）
［招待講演］

Constraint Structure Optimization on Potential Energy Surface　　　　　　　　　　　　　　　
長谷川 淳也
Thai-Japan Symposium in Chemistry, 2016年11月15日, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

拘束条件を付したポテンシャル面上の最適化問題　　　　　　　　　　　　　　　
長谷川 淳也
第３回電子状態理論シンポジウム, 2016年11月05日, 口頭発表（招待・特別）
［招待講演］, ［国内会議］

Transition states of spin-crossing reactions　　　　　　　　　　　　　　　
長谷川 淳也
EMN Meeting on Computation and Theory, 2016年10月13日, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Transition states of spin-crossing reactions　　　　　　　　　　　　　　　
長谷川 淳也
International Symposium on Pure & Applied Chemistry (ISPAC) 2016 “Recent Advances in Pure & Applied Chemistry”, 2016年08月16日, 英語, 口頭発表（招待・特別）
［招待講演］

Theoretical Study of Excited States of Photosynthetic Reaction Center: Photoabsorption, electron transfer, and photoprotection　　　　　　　　　　　　　　　
長谷川 淳也
The 2016 Pure and Applied Chemistry Internati The onal Conference (PACCON 2016), 2016年02月11日, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

CO2 fixation mechanism of bifunctional porphyrin catalyst: a theoretical study　　　　　　　　　　　　　　　
長谷川 淳也
PACIFICHEM 2015, 2015年12月15日, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Theoretical Study of CO2 Fixation by a Bifunctional Porphyrin Catalyst　　　　　　　　　　　　　　　
長谷川 淳也
ICIQ-FIFC Spain-Japan Joint Symposium on Theoretical and Computational Chemistry of Comple Systems, 2015年11月25日, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Excited states and molecular interactions in photofunctional proteins　　　　　　　　　　　　　　　
長谷川 淳也
Computational Approaches for the Study of Chemical and Biological Systems, Centro de Investigaciones Biol?gicas, CIB-CSIC, 2015年11月23日, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Transition State of Spin-State Crossing Reactions　　　　　　　　　　　　　　　
J. Hasegawa
19th International Annual Symposium on Computational Science and Engineering (ANSCSE19), 2015年06月18日, 口頭発表（招待・特別）
Ubon Ratchathani University, Thailand, ［招待講演］, ［国際会議］

凝集系における分子の励起状態と分子間相互作用　　　　　　　　　　　　　　　
長谷川 淳也
理研シンポジウム「生体分子系量子化学計算の最前線」, 2015年01月22日, 口頭発表（招待・特別）
［招待講演］, ［国内会議］

Excited States and Molecular Interactions in Proteins and Solutions　　　　　　　　　　　　　　　
J. Hasegawa
The 2nd China-Japan-Korea Tripartite Workshop on Theoretical and Computational Chemistry, 2015年01月21日, 口頭発表（招待・特別）
Kobe, Japan, ［招待講演］, ［国際会議］

Excited States and Molecular Interactions in Proteins and Solutions　　　　　　　　　　　　　　　
J. Hasegawa
Quantum System in Chemistry and Physics, 2014年11月17日, 口頭発表（招待・特別）
Tamkang, Taiwan, ［招待講演］, ［国際会議］

Excited states and molecular interactions in photofunctional proteins　　　　　　　　　　　　　　　
J. Hasegawa
Ultrafast Processes in Proteins: Theory and Experiment, 247th American Chemical Society National Meeting & Exposition, 2014年03月, 口頭発表（招待・特別）
［招待講演］

Molecular Excited States in Proteins and Solutions: a Theoretical Study on Molecular Interactions　　　　　　　　　　　　　　　
J. Hasegawa
Molecular Science and Synthesis of Functional Molecules for Next Generation, 2014年03月, 口頭発表（招待・特別）
［招待講演］

Excited states of molecules in proteins and solutions　　　　　　　　　　　　　　　
Jun-ya Hasegawa
CRC-EC Joint International Symposium on Chemical Theory for Complex Systems, 2014年01月, 口頭発表（招待・特別）
［招待講演］

Molecular Excited States in Proteins and Solutions　　　　　　　　　　　　　　　
Jun-ya Hasegawa
5th JCS International Symposium on Theoretical Chemistry, 2013年12月, 口頭発表（招待・特別）

Electrostatic and Quantum Mechanical Molecular Interactions　　　　　　　　　　　　　　　
長谷川 淳也
The 15-th Asian Chemical Congress Singapore, 2013年08月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Computational Chemistry for Complex Systems: Environmental Effect in Proteins and Solutions　　　　　　　　　　　　　　　
J.Hasegawa
The Fourth Joint Symposium of PCOSS-CRC, 2013年05月09日, 英語, 口頭発表（招待・特別）
［国際会議］

Theoretical Study on the Color Tuning Mechanism of Photo-functional Proteins: Excited States and Molecular interactions　　　　　　　　　　　　　　　
J.Hasegawa
2012 HU - NU - SNU - NIMS/MANA Joint Symposium, ”Challenges in Advanced Chemistry of Asia”, 2012年12月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Configuration Interaction in Quantum Chemistry　　　　　　　　　　　　　　　
J.Hasegawa
MAterial Simulation in Petaflops era (MASP2012), Institute for Solid State Physics, 2012年06月25日, 英語, 口頭発表（招待・特別）
［国際会議］

Color-tuning in Photo-functional Proteins: Electronic Structure and Interactions　　　　　　　　　　　　　　　
J.Hasegawa
The 17-th International Symposium on Bioluminescence and Chemiluminescence, 2012年05月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Theoretical study on the excited states and molecular interactions of photo-functional proteins　　　　　　　　　　　　　　　
J.Hasegawa
The 14-th Asian Chemical Congress, 2011年09月, 英語, 口頭発表（招待・特別）
［招待講演］

Excited states of photo-functional proteins: SAC-CI study　　　　　　　　　　　　　　　
J.Hasegawa
The 16-th Quantum Systems in Chemistry and Physics, 2011年09月, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Excited states of photo-functional proteins　　　　　　　　　　　　　　　
J.Hasegawa
Fukui International Symposium for Theoretical Chemistry, 2011年08月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Quantum chemistry of the excited states of photo-functional proteins: physical, chemical, and biological origins of the color-tuning　　　　　　　　　　　　　　　
J.Hasegawa
BioInformatics in Torun - BIT11, 2011年06月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Excited states of photo-functional proteins: SAC-CI study　　　　　　　　　　　　　　　
J.Hasegawa
The 4-th Japan-Czech-Slovakia Symposium on Theoretical Chemistry, 2011年05月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Spectral tuning mechanism in photofunctional proteins: A SAC-CI theoretical study　　　　　　　　　　　　　　　
J.Hasegawa
BIT's 2nd Annual World Congress of Biosoft-2010, 2010年06月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Quantum Chemistry in the Primary Event of Photobiological Processes　　　　　　　　　　　　　　　
J.Hasegawa
Pure and Applied Chemistry International Conference 2010, 2010年01月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Excited states of photofunctional molecules in protein: Electronic structure and interaction　　　　　　　　　　　　　　　
J.Hasegawa
45th Symposium on Theoretical Chemistry, Excited States: From Photophysics to Photobiology, 2009年09月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Excited states of photofunctional molecules in protein environments　　　　　　　　　　　　　　　
J.Hasegawa
CREST International Symposium on Theory and Simulations of Complex Molecular Systems, 2009年07月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Spectral Tuning Mechanism in Photofunctional Proteins: A SAC-CI Theoretical Study　　　　　　　　　　　　　　　
J.Hasegawa
International Symposium on Frontiers of Computatinal Science 2008, 2008年11月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

SAC-CI study on the primary events in photobiological processes　　　　　　　　　　　　　　　
J.Hasegawa
第88回日本化学会春季年会アジア国際シンポジウム, 2008年03月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Color-tuning mechanism of human visual cone pigments　　　　　　　　　　　　　　　
J.Hasegawa
The 2-nd Japan-Czeck-Slovakia Joint Symposium for Theoretical/Computational Chemistry, 2007年12月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Quantum Chemical Approach to Photobiology: Excited States of Photosynthetic Reaction Centers, Fluorescent Proteins, and Human Visual Cone Pigments　　　　　　　　　　　　　　　
J.Hasegawa
Photosynthesis and Enzyme Reactions, 2007年11月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

SAC-CI study of the Color-tuning Mechanism in Photobiology　　　　　　　　　　　　　　　
J.Hasegawa
The Third Asian-Pacific Conference of Theoretical and Computational Chemistry (APCTCC), 2007年09月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Color-tuning in Photobiology: A SAC-CI study　　　　　　　　　　　　　　　
J.Hasegawa
International Symposium on Molecular Theory for Real Systems, 2007年07月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Exploring Photobiology with the SAC-CI method　　　　　　　　　　　　　　　
J.Hasegawa
Molecular Response to Electronic Excitation, 2007年04月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Exploring Photobiology with the SAC-CI method　　　　　　　　　　　　　　　
J.Hasegawa
Recent Trends in Many-Body Methods for Electronic Structure and Properties of Atoms and Molecules, 2007年01月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Polar Coordination Space for H2 Storage: Electronic Structure and Potential Surface　　　　　　　　　　　　　　　
J.Hasegawa
The second International Symposium on Chemistry of Coordination Space, 2006年12月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Excited States and Electron Transfer in Bacterial Photosynthetic Reaction Center: SAC-CI Theoretical Study　　　　　　　　　　　　　　　
J.Hasegawa
Computational Approaches to Supramolecular Chemistry, 2006年10月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Photobiology and biospectroscopy studied by the SAC-CI method　　　　　　　　　　　　　　　
J.Hasegawa
Electron Correlation for the Whole Periodic Table, 2006年10月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

SAC-CI applied to photobiology and biospectroscopy　　　　　　　　　　　　　　　
J.Hasegawa
The XII-th International Congress of Quantum Chemistry, Satellite Symposium, “Reactions in Solution and Biological Systems: Potential Energy Surface and Dynamics”, 2006年05月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Excited States and Electron Transfer in Bacterial Photosynthetic Reaction Center: SAC-CI study　　　　　　　　　　　　　　　
J.Hasegawa
Czech-Japan Joint Symposium for Theoretical/Computational Chemistry, Institute of Organic Chemistry and Biological Chemistry, 2005年09月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Theoretical Bio-molecular Spectroscopy Studied by SAC-CI Method　　　　　　　　　　　　　　　
J.Hasegawa
Frontiers of Molecular Science Developed by Advanced Spectroscopy, 2004年12月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Theoretical Spectroscopy for Biomolecules: SAC-CI Study　　　　　　　　　　　　　　　
J.Hasegawa
Singapore International Chemistry Conference 3, 2003年12月, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

力学刺激環境を取り扱う理論化学計算手法の開発と新しい反応コンセプトの構築
科学研究費助成事業 基盤研究(B)
2020年04月01日 - 2024年03月31日
長谷川 淳也
日本学術振興会, 基盤研究(B), 北海道大学, 20H02685

生体触媒反応場の精密制御に資する理論計算手法の開発と応用　　　　　　　　　　　　　　　
科学研究費助成事業 新学術領域研究(研究領域提案型)
2015年06月29日 - 2020年03月31日
長谷川 淳也
１．ロジウム触媒によるオレフィンとケトンのヒドロシリル化反応経路： オレフィンやケトンのヒドロシリル化反応ついて、ロジウム触媒を用いた場合の反応経路の研究を行った。基質として、エチレンとアセトンのヒドロシリル化について、DFT法による計算を行い、これまで提唱されてきた機構に加え、新たな反応経路として、alternative Chalk-Harrod機構とdouble hydride(DH)機構を見出し、従来提唱されてきた機構との関連性について研究を行った。特に、DH機構においてロジウム上にある複数のヒドリドの効果によって、活性化エネルギーが低下するメカニズムがあることを見出した。
２．らせん高分子反応場による不斉ヒドロシリル化反応に関する研究： キノキサリンからなる不斉らせん高分子触媒反応場が高いエナンチオ選択性を示すことを、杉野目グループが明らかにしている。我々は、この反応場におけるPd錯体のヒドロシリル化反応を例に、エナンチオ選択性の起源に関する研究を行った。その結果、触媒活性中心であるPd錯体について、トリフェニルホスフィン配位子と結合したキノキサリンユニットとの相互作用がエナンチオ選択性の原因であることを示す結果を得た。
３．再生されたルイス対による水素分子の活性化機構に関する研究： 生越グループでは、NHCとホウ素化合物からなる化合物において、C-B結合を活性化することでfrustrated Lewis pair(FLP) が得られ、水素分子を活性化できることを見出した。我々は、DFT計算を行い、FLP生成と水素分子活性化に至るメカニズムを解析し、隣接するリン酸基の回転などを経て、段階的にFLPが生成する経路を得た。FLP生成が律速段階であり、一旦水素分子がFLPの酸―塩基対に隣接すると、わずかな活性化エネルギーによって、H-H結合が切断されるという結果を得た。
日本学術振興会, 新学術領域研究(研究領域提案型), 北海道大学, 15H05805

凝集系の励起状態を記述する波動関数理論と量子的分子力場の構築
科学研究費助成事業 基盤研究(B)
2012年04月01日 - 2015年03月31日
長谷川 淳也
蛋白質・溶液等の凝集系における分子の励起状態を正しく計算しなければ、光が関わる生命現象の分子メカニズムの解明や光増感太陽電池の分子設計は不可能である。その為には、分子環境の量子的効果をも記述できる理論を開発することが必要である。凝集系における溶質－溶媒分子複合系の励起波動関数の構造を明らかにし、分子間相互作用を効率的に記述する波動関数を構築した。更に、この波動関数を解くための方程式を導出し、数値計算を行うための計算プログラムを開発し、幾つかの分子に適用した。今後、このプログラムの効率化を進め、動力学との関わりに関する研究へと展開する計画である。
日本学術振興会, 基盤研究(B), 北海道大学, 研究代表者, 競争的資金, 24350008

相対論的 SAC-CI を中核とする磁気的分子物性と励起状態反応系に関する理論研究
科学研究費助成事業 基盤研究(B)
2010年 - 2012年
波田 雅彦, 長谷川 淳也, 藤井 浩
本研究プロジェクトの主目的は、重原子を含む化合物において、電子励起状態が関与する化学現象を定量的に解析するための理論的方法として高次相対論を含めたSAC-CI法の開発を進め、例えば、光化学反応の解析、スピン-軌道(SO)相互作用や交換交差など考慮した定量的なエネルギー曲面の記述、など実施することであった。SO-CASSCF法では化学的精度の達成は困難であるため、本研究では、Generalized UHFを参照としたCCSD法からSAC-CI理論と同等の方法GUHFCCSD-CIによって励起状態を計算する理論を提案し、その計算プログラムを作成した。幾つかの原子の励起エネルギーを計算することでこの理論・方法の精度を検討した。原子の一重項、三重項の最低励起エネルギーを、本方法と、RHFを参照するSAC-CI法と、CASPT2法で計算した。他の計算方法と比較して、本方法GUHF-CCSD-CIが、三重項励起に対する分裂の実験値を格段に良く再現していた。更に、相対論補正が重要となる幾つかの応用計算を実施した。(i)冷却分子を用いて新たな量子物性探査を支援するため、MgLi, CaLi, SrLi, BaLi分子における電子基底状態のPESとPDMをCCSD(T)法で求め、 v=0における放射寿命は短いもので22秒であった。これは冷却分子実験の時間スケールに対して十分に長く、物性測定の可能性を示唆した。(ii)鉛原子を含んだ5員環化合物Plumboleに、 THF、 Py、 NHCが配位した化合物の芳香族性や、 C-NMR, Pb-NMRの特徴について研究した。 NICSの観点からは対象分子が芳香属性をもつことを示した。通常は重原子に隣接する軽原子は高磁場シフトするのだが、Pbに隣接するC13-NMRはPbのSpinOrbit相互作用の影響を受けて低磁場シフトすることを示した。
日本学術振興会, 基盤研究(B), 首都大学東京, 22350010

励起状態における分子間相互作用理論の高度化
科学研究費助成事業 若手研究(A)
2009年 - 2011年
長谷川 淳也
周辺の分子環境に応じて光吸収・発光エネルギーを大きく変化させる光機能性蛋白質(ヒト錐体視物質・蛍光タンパク質)について、理論化学計算によりメカニズムを解析した。その結果、色素の電子励起に伴い電荷分布が大きく変化すること、蛋白質が偏った静電ポテンシャルを色素上に形成することを見出し、これらのシナジーにより励起エネルギー準位が変化することを明らかにした。また、いくつかのレチナール蛋白質では、周辺アミノ酸の電子状態が励起エネルギーに寄与することを見出した。このような蛋白質の電子的効果を解析するために、新たに分子軌道の局在化法を開発し、事前に定義した形状や領域に局在化した分子軌道を得ることが可能になった。この方法を応用し、励起エネルギー移動におけるsuper-exchange機構について移動経路の解析を行なった。
日本学術振興会, 若手研究(A), 京都大学, 研究代表者, 競争的資金, 21685002

アバランシェ型フォトクロミック反応系の構築
科学研究費助成事業 特定領域研究
2007年 - 2010年
松田 建児, 深港 豪, 長谷川 淳也, 東口 顕士
HOPG/octanoic acid界面でのSTM測定によるジアリールエテンダイマーの光配列制御について検討し、紫外光照射後に新たな配列構造が表れ、可視光を照射すると配列構造が元に戻ることが明らかとなった。溶液相で光異性化した分子が異なるパッキングで2次元配列し、光による可逆なドメインの変化をもたらしたものと考えられる。
日本学術振興会, 特定領域研究, 九州大学->京都大学, 連携研究者, 競争的資金, 19050009

光生物学における分子理論の展開:励起状態理論の開発を基盤として
科学研究費助成事業 特定領域研究
2008年 - 2009年
長谷川 淳也
光生物学の研究対象は、光合成や色覚などの基礎科学的解明から、分子イメージングなどの蛋白質工学に至る広い学問領域において重要になっている。光機能性蛋白質の励起状態の電子構造や色素-蛋白質相互作用は機能発現と密接に関わっており、理論・計算化学の手法を用いて研究することで、物理化学的メカニズムの詳細を明らかにすることができる。我々は高い精度で励起状態を計算できるSAC-CI法と蛋白質を計算できる実際的計算手法であるQM/MM法を結びつけることで、蛋白質中の機能性色素の励起状態について研究を行っている。当該年度に実施した研究の成果は以下の通りである。
(1) ヒト色覚に関与する赤・緑・青色光受容体におけるカラー・チューニング機構について、これまでの研究成果を発展させ、カラー・チューニング機構の鍵となるアミノ酸にミューテーション計算を行った。その結果、既報の実験結果を再現することに成功し、提案したメカニズムを確認できた。
(2) ホタル・ルシフェリンの発光色制御に関して、これまでの研究で明らかになった発光色の制御メカニズムを基に、赤色発光の可能性のあるミューテーションを提案した。
(3) 擬縮退電子系を計算するための単参照理論の開発を行った。幾つかの小分子の結合解離についてのベンチマーク計算の結果、厳密解を良好に再現できた。また、複数のQM領域を用いることが可能なQM/MM法を提案した。
日本学術振興会, 特定領域研究, 京都大学, 研究代表者, 競争的資金, 20038026

量子化学計算によるphotodynamic therapy増感剤の分子設計　　　　　　　　　　　　　　　
受託研究
2008年 - 2008年
競争的資金

励起生体分子の動的過程:電子理論からのアプローチ
科学研究費助成事業 若手研究(B)
2006年 - 2008年
長谷川 淳也
電子励起した生体分子がどのような挙動を示すかを研究するために、励起状態のポテンシャルエネルギー面を計算する方法を整備した。巨大な蛋白質-色素複合体を計算するために、量子-古典ハイブリッド法であるQM/MM 法のプログラムを開発した。その応用として、レチナール蛋白質、ホタルルシフェラーゼなどの励起状態を計算した。その結果、ヒト色覚で見られるレチナールのスペクトル制御メカニズムやホタルの黄緑色発光の起源などを明らかにし、人工的な発光色チュ-ニングの提案などを行った。また、ヘムにおける酸素分子吸着過程を明らかにした。
日本学術振興会, 若手研究(B), 京都大学, 研究代表者, 競争的資金, 18770130

DNA2重螺旋におけるCircular Dichroismの理論分光
科学研究費助成事業 特定領域研究
2007年 - 2007年
長谷川 淳也
量子・古典論を組み合わせた計算手法を開発し、同方法を光機能性蛋白質の励起状態に応用した。レチナール蛋白質はヒトの視覚やバクテリアのプロトンポンプ等で重要な機能を果たすが、蛋白質の環境に応じて、大きく光吸収エネルギーを変化させることが知られている。今回、我々の方法によりレチナール蛋白質の光吸収エネルギーを定量的かつ系統的に計算することに初めて成功した。これにより、レチナール蛋白質の光吸収特性に関する定量的な解析を行うことができた。種々のレチナール蛋白質における励起エネルギーを色素の構造ひずみ、蛋白質の静電的環境、カウンターイオンとの量子的相互作用の3点に分割して解析を行った。その結果、蛋白質との静電的な相互作用がスペクトル・チューニングに最も重要な役割を果たすことが明らかになった。レチナール蛋白質の励起状態は分子内電荷移動性が強いため、蛋白質による静電的な環境を敏感に反映する。レチナール結合サイトの静電環境は蛋白質により異なるため、多様な光吸収エネルギー示す原因になっている。
蛍の蛍光色は発色団であるオキシルシフェリンによる。オキシルシフェリンの発光色は化学発光に関する実験結果を基に、ケト・エノール互変異性により説明されてきた。しかし、近年、エノール型への変換が抑制されたケト型オキシルシフェリンの生物発光において、通常の黄緑色発光が観測されて、従来説が疑問視されてきた。我々の方法を蛍の発光に応用し、北アメリカ蛍のケト型ルシフェリンが、化学発光では赤色、生物発光では黄緑色発光することを理論計算により示した。基底・励起状態の電荷分布と蛋白質の静電ポテンシャルの相互作用が発光色の変化に重要な寄与をしていることが明らかになった。更にこの結果を基に、ルシフェリンの分子設計を行った。アミノ酸残基を置換することにより活性中心の静電場を制御し、赤オレンジ色の発色を示すと期待されるミューテーション実験を提案した。
日本学術振興会, 特定領域研究, 京都大学, 研究代表者, 競争的資金, 19029023

水素吸蔵の量子的原理:新規材料設計への展開
科学研究費助成事業 特定領域研究
2006年 - 2007年
長谷川 淳也
分散力・誘起力・軌道相互作用の制御系としての水素吸着場の設計
これまでに報告されている水素吸蔵系について、水素分子と吸着サイトとの分子間相互作用を研究した。金属や金属酸化物を含む系において、相互作用エネルギーの分割解析をおこなった。その結果、水素の吸着において、外的な静電場における水素分子の分極が重要であることがわかった。軌道間相互作用については、水素分子への電子流入は比較的小さいことが分かった。
これまでに報告されている水素吸蔵材料は、水素の解離吸着に至る金属や金属酸化物、弱いvan der Waals相互作用により分子状吸着する炭素材料の両極が知られている。その中間領域を開拓するためには軌道間相互作用を最適に制御する必要がある。
得られた結果を基に水素吸蔵に最適と考えられる分子間相互作用を有するモデル系を構築した。これに基づいて現実の配位空間の設計に用いる可能性がある材料分子をスクリーニングした。共同研究を行なう実験グループとのディスカッションを通して実現可能な材料分子の選択を行った。
日本学術振興会, 特定領域研究, 京都大学, 研究代表者, 競争的資金, 18033029

量子的化学原理の深化と実現
科学研究費助成事業 学術創成研究費
2002年 - 2006年
中辻 博, 加藤 重樹, 榊 茂好, 波田 雅彦, 江原 正博, 長谷川 淳也, 森田 明弘
シュレーディンガー方程式の解析解の一般的な解法:シュレーディンガー(SE)方程式とディラック・クーロン方程式の解析解の一般的な解法の研究をさらに推し進めた。Scaled-SEに基づくFree ICI法により、世界で最も正確な波動関数をヘリウムや水素分子イオンについて求めることに成功した。さらに積分操作を行うことなく解析解を求める方法、Local SE法(LSE法)を開発し、積分の困難を原理的に解消することに成功した。このLSE法により絶対エネルギーにおいて化学精度(kcal/mol)を超える正しい解を一般の原子・分子について計算できることを示した。
ファインなスペクトロスコピーと反応の量子ダイナミックス:精度が高く計算効率の上でも優れているdirect SAC-CI法を完成した。有機ELのIr錯体やアクリジン型バイオセンサーの光吸収・発光過程を定量的に明らかにした。最先端の実験と協力し、様々な内殻電子過程における励起ダイナミクスを解明した。
巨大分子系の電子状態理論の構築:巨大な分子性結晶・分子集合体・ポリマー等の電子状態を、構成分子の精密なSAC-CI波動関数と同程度の精度で構築する新たな理論-Giant SAC/SAC-CI理論を開発した。この方法を、幾つかの環状分子性結晶の基底状態と励起状態に応用し、光磁気センサーを設計することが可能であることを示した。
生体反応系の電子論とダイナミックスの解明:視覚で知られるレチナール蛋白質について研究し、レチナール色素のcolor-tuningメカニズムを定量的に明らかにした。蛍ルシフェリンの発光色制御メカニズムを研究し、蛋白質残基とそのクーロン場が発光色制御の要因であることを明らかにした。
凝縮系における反応の電子論とダイナミックス:溶液内光化学過程の研究において、自由エネルギー円錐交差点を求める方法を開発し、極性溶媒中での円錐交差の構造と溶媒効果について論じた。
表面-分子相互作用系と触媒反応の電子論:燃料電池で重要なPt表面上のアルコール酸化反応の反応メカニズムの研究を行った。Pd錯体によるアレンのシリルボリル化反応を理論的に研究し、幾つかの反応経路を検討した。
日本学術振興会, 学術創成研究費, 京都大学, 連携研究者, 競争的資金, 14GS0217

配位空間のポテンシャル面:計算化学によるアプローチ
科学研究費助成事業 特定領域研究
2005年 - 2005年
長谷川 淳也
本研究では、配位空間への水素吸蔵について、量子化学計算により水素吸着ポテンシャル面を解析することにより、水素吸着のメカニズムを明らかにし、水素吸蔵能を有する配位空間設計の指針となりうる基礎的な知見を得ることを目的としている。京大工・北川らによる配位高分子CPL-1を基点として理論解析を行った。
ポテンシャル面を記述する量子化学計算方法に関して、種々の基底関数、電子相関法、誤差の補正法について検討を行った。水素吸着には分散力の記述が不可欠であるので電子相関理論とdiffuse関数を用いる必要がある。最低でもaug-cc-pVDZ基底を用いたMP2計算が必要で、counterpoise法によるBSSE(基底関数重ね合わせ誤差)を補正することが望ましい。
次に、配位空間を構成する有機配位子と水素分子の相互作用について研究を行った。まず、CPL-1の基本骨格を形成するpyrazineについて、様々な方向から水素分子を吸着させ相互作用エネルギーを計算した。吸着エネルギーは0.19〜0.66kcal/molであり非常に弱い吸着型のポテンシャル面になっていることが分かる。水素分子は主に分散力により吸着していると考えられる。
ところがpyrazine-monocarboxylateと水素分子について計算を行ってみると、水素分子はcarboxylateの酸素原子にend-onで直線的に吸着し、吸着エネルギーは2.44kcal/molと算出された。この原因を解析するためにMP2法の電子密度から電荷分布を計算したところ、pyrazineから水素分子への若干の電子移動と、水素分子の分極が観られた。このことはpyrazineと水素分子の吸着は、単に分散力のみでなく、軌道間相互作用に起因する分極が駆動力となっていることを示唆している。
この結果を利用した配位空間の設計として、正に帯電したcationを導入し、水素分子をcarboxylateの酸素原子と挟み込むことが考えられる。モデル系について計算を行ったところ、吸着エネルギーは7.58kcal/molに達した。分散力のみでなく分子分極や軌道間相互作用を誘起できる配位空間の設計が実現すれば、分散力のみを駆動力とする炭素材料を超える水素吸蔵材料となる可能性がある。
日本学術振興会, 特定領域研究, 京都大学, 研究代表者, 競争的資金, 17036030

光合成反応におけるエネルギー変換の量子化学
科学研究費助成事業 特定領域研究(A)
2000年 - 2000年
長谷川 淳也
光合成反応中心におけるbacteriopheophytin(H)からubiquinone(UQ)への電子移動について、反応に伴う構造緩和と蛋白が色素の電子状態に及ぼす影響について量子化学的方法を用いて研究した。
種々の方法と基底関数を試験し、電子親和力の計算には密度汎関数法、6-31+g基底関数を採用した。構造最適化には6-31+g^*基底関数を用いている。
気相中ではmenaquinone(MQ)、UQの電子親和力はHより小さく電子が移動する方向と矛盾する結果を与えるが、蛋白の効果を含めると、電子親和力は気相中より30kcal/mol程度大きくなり、Hの電子親和力を上回り、現象を説明できる結果を与えることがわかった。即ち、蛋白が色素の電子親和力を調節し、電子移動に重要な役割を果たしている事が明らかになった。これはquinoneのアニオンでは酸素原子に大きな負電荷が生じ、蛋白からの水素結合がこれを安定化していることによる。
次に電子移動の後の色素の構造緩和について研究した。まず、色素の気相中における構造緩和を調べると、アニオン状態ではSOMOの軌道の性質に由来した構造変化が見られたが、変化の大きさ自体は小さかった。次に周辺アミノ酸残基を加えて、結合サイト中での色素と水素結合しうるプロトンの構造変化を調べた。アニオン状態の色素は水素結合距離がより短くなるよう、蛋白の極性残基の方向に約0.2Å移動するが、色素自体、プロトンの位置に大きい変化は見られなかった。最後に、QM/MM法で電子移動の各状態の蛋白の全構造を最適化したところ、アニオン状態では色素はより強く水素結合するよう移動するが、蛋白の溶媒和構造の変化、蛋白全体の構造変化は小さいことが分かった。以上により、本研究では電子移動後による主な構造変化は結合サイト中での色素の移動である事が分かった。
本研究で求めた、構造を用いて反応熱を計算したところ、実験で算出されている値によく一致するものが得られた。反応熱を解析したところ、反応の駆動力は主に色素の電子親和力にあるという結果を得た。
日本学術振興会, 特定領域研究(A), 京都大学, 研究代表者, 競争的資金, 12042245

光合成反応中心における電子移動メカニズムの理論的解明　　　　　　　　　　　　　　　
科学研究費助成事業 特別研究員奨励費
1998年 - 1998年
長谷川 淳也
日本学術振興会, 特別研究員奨励費, 京都大学, 97J03052