研究者データベース

前田 理(マエダ サトシ)
理学研究院 化学部門 物理化学分野
教授

基本情報

所属

  • 理学研究院 化学部門 物理化学分野

職名

  • 教授

学位

  • 博士(理学)(東北大学)

ホームページURL

科研費研究者番号

  • 60584836

ORCID ID

J-Global ID

研究キーワード

  • 理論化学   人工力誘起反応法   遷移状態   量子化学計算   生化学反応   反応経路自動探索   酵素反応   自動探索   反応経路   

研究分野

  • ナノテク・材料 / 基礎物理化学

職歴

  • 2017年07月 - 現在 物質・材料研究機構 招聘主席研究員
  • 2017年04月 - 現在 北海道大学 理学(系)研究科(研究院) 教授
  • 2014年01月 - 2017年03月 北海道大学 理学(系)研究科(研究院) 准教授
  • 2012年02月 - 2013年12月 北海道大学 理学(系)研究科(研究院) 助教
  • 2010年04月 - 2012年01月 京都大学 白眉プロジェクト 特定助教
  • 2007年04月 - 2010年03月 日本学術振興会 特別研究員PD

研究活動情報

論文

  • Makito Takagi, Satoshi Maeda
    ACS Omega 2020年07月14日 [査読有り][通常論文]
  • Hitoshi Nabata, Makito Takagi, Kenichiro Saita, Satoshi Maeda
    RSC Advances 10 37 22156 - 22163 2020年 [査読有り][通常論文]
     

    In this study, we focused on the effect of pressure on the crystal structures of dioxides of group 14 elements, i.e. SiO2, GeO2, and CO2.

  • Matsuda, Yoshiyuki, Hirano, Yutaro, Mizutani, Shinichi, Sakai, Daichi, Fujii, Asuka, Maeda, Satoshi, Ohno, Koichi
    The Journal of Physical Chemistry A 2020年 [査読有り][通常論文]
  • Ikemoto, Koki, Tokuhira, Toshiki, Uetani, Akari, Harabuchi, Yu, Sato, Sota, Maeda, Satoshi, Isobe, Hiroyuki
    The Journal of Organic Chemistry 2020年 [査読有り][通常論文]
  • Sumiya, Yosuke, Maeda, Satoshi
    Chemistry Letters 2020年 [査読有り][通常論文]
  • Yorimoto, Sadaiwa, Tsubouchi, Akira, Mizoguchi, Haruki, Oikawa, Hideaki, Tsunekawa, Yoshiaki, Ichino, Tomoya, Maeda, Satoshi, Oguri, Hiroki
    Chemical Science 2019年 [査読有り][通常論文]
  • Ozen, Cihan, Shoji, Yoshiaki, Fukushima, Takanori, Maeda, Satoshi
    The Journal of Organic Chemistry 2019年 [査読有り][通常論文]
  • Suzuki, Kimichi, Maeda, Satoshi, Morokuma, Keiji
    ACS Omega 4 1 1178 - 1184 2019年 [査読有り][通常論文]
  • Hada, Masaki, Hada, Masaki, Hasegawa, Taisuke, Hasegawa, Taisuke, Inoue, Hirotaka, Inoue, Hirotaka, Takagi, Makito, Takagi, Makito, Omoto, Kazuki, Omoto, Kazuki, Chujo, Daiki, Chujo, Daiki, Iemoto, Shogo, Iemoto, Shogo, Kuroda, Taihei, Kuroda, Taihei, Morimoto, Taiga, Morimoto, Taiga, Hayashi, Takuma, Hayashi, Takuma, Iijima, Toru, Iijima, Toru, Tokunaga, Tomoharu, Tokunaga, Tomoharu, Ikeda, Naoshi, Ikeda, Naoshi, Fujimori, Kazuhiro, Fujimori, Kazuhiro, Itoh, Chihiro, Itoh, Chihiro, Nishikawa, Takeshi, Nishikawa, Takeshi, Yamashita, Yoshifumi, Yamashita, Yoshifumi, Kiwa, Toshihiko, Kiwa, Toshihiko, Koshihara, Shin-ya, Koshihara, Shin-ya, Maeda, Satoshi, Maeda, Satoshi, Hayashi, Yasuhiko, Hayashi, Yasuhiko
    ACS Applied Energy Materials 2 7700 - 7708 2019年 [査読有り][通常論文]
  • Kanami Sugiyama, Yosuke Sumiya, Makito Takagi, Kenichiro Saita, Satoshi Maeda
    Physical Chemistry Chemical Physics 21 14366 - 14375 2019年01月 [査読有り][通常論文]
  • Reyes, Ronald L., Iwai, Tomohiro, Maeda, Satoshi, Sawamura, Masaya
    Journal of the American Chemical Society 141 17 6817 - 6821 2019年 [査読有り][通常論文]
  • Kinoshita, Shin-nosuke, Inokuchi, Yoshiya, Onitsuka, Yuuki, Kohguchi, Hiroshi, Akai, Nobuyuki, Shiraogawa, Takafumi, Ehara, Masahiro, Yamazaki, Kaoru, Harabuchi, Yu, Maeda, Satoshi, Ebata, Takayuki
    Physical Chemistry Chemical Physics 21 36 19755 - 19763 2019年 [査読有り][通常論文]
  • Yamakita, Yoshihiro, Yokoyama, Nanae, Xue, Bing, Shiokawa, Naoyuki, Harabuchi, Yu, Maeda, Satoshi, Kobayashi, Takayoshi
    Physical Chemistry Chemical Physics 21 10 5344 - 5358 2019年 [査読有り][通常論文]
  • Satoshi Maeda, Harabuchi, Yu
    Journal of Chemical Theory and Computation 15 4 2111 - 2115 2019年 [査読有り][通常論文]
  • Yu Harabuchi, Miho Hatanaka, Satoshi Maeda
    Chem. Phys. Lett. X 2 100007  2019年01月 [査読有り][通常論文]
  • Yusuke KONDO, Rina TAKAHARA, Hirono MOHRI, Makito TAKAGI, Satoshi MAEDA, Takeshi IWASA, Tetsuya TAKETSUGU
    Journal of Computer Chemistry-japan 18 1 64 - 69 2019年 [査読有り][通常論文]
  • Maria Fumanal, Yu Harabuchi, Etienne Gindensperger, Satoshi Maeda, Chantal Daniel
    Journal of Computational Chemistry 40 1 72 - 81 2019年 [査読有り][通常論文]
  • Iwasa, Takeshi, Sato, Takaaki, Takagi, Makito, Gao, Min, Lyalin, Andrey, Kobayashi, Masato, Shimizu, Ken-ichi, Maeda, Satoshi, Taketsugu, Tetsuya
    The Journal of Physical Chemistry A 123 1 210 - 217 2019年 [査読有り][通常論文]
  • Tomoya Ichino, Makito Takagi, Satoshi Maeda
    ChemCatChem 11 4 1346 - 1353 2019年 [査読有り][通常論文]
  • Yosuke Sumiya, Satoshi Maeda
    Chemistry Letters 48 1 47 - 50 2019年 [査読有り][通常論文]
  • Sreekanta Debnath, Xiaowei Song, Matias Fagiani, Marissa Weichman, Min Gao, Satoshi Maeda, Tetsuya Taketsugu, Wieland Schöllkopf, Andrey Lyalin, Daniel Neumark, Knut Asmis
    The Journal of Physical Chemistry C 2018年12月 [査読有り][招待有り]
  • Shunsuke Sato, Kenichiro Saita, Keita Sekizawa, Satoshi Maeda, Takeshi Morikawa
    ACS Catalysis 8 5 4452 - 4458 2018年05月04日 [査読有り][通常論文]
     
    Electrocatalytic CO2 reduction over a Mn-complex catalyst in an aqueous solution was achieved at very low energy with a combination of multiwalled carbon nanotubes (MWCNTs) and K+ cations. Although the bare Mn-complex did not function as a catalyst in an aqueous solution, the combined Mn-complex/MWCNT cathode promoted electrocatalytic CO2 reduction at an overpotential of 100 mV where neither the bare MWCNTs nor bare Mn-complex were catalytically active. The Mn-complex/MWCNT produced CO at a constant rate for 48 h with a current density of greater than 2.0 mA cm-2 at -0.39 V (vs RHE). The MWCNTs with electron accumulation properties, together with surface adsorbed K+ ions, provided an environment to stabilize CO2 adjacent to the Mn-complex and significantly lowered the overpotential for CO2 reduction in an aqueous solution, and these results were consistent with density functional theory (DFT) calculations. Experiments clarified that the synergetic effect of the MWCNTs and K+ ions was also applicable to Co and Re complexes that were almost inert with regard to CO2 reduction in an aqueous solution.
  • Ayako Furuhama, Takashi Imamura, Satoshi Maeda, Tetsuya Taketsugu
    Chemical Physics Letters 692 111 - 116 2018年01月16日 [査読有り][通常論文]
     
    We performed a systematic reaction path search for the initial reactions of methyl amine with ozone (O3) in gas phase, by using a single-component artificial force induced reaction (SC-AFIR) method. The reaction rate constants calculated by UCCSD(T) energies and UM062X frequencies, agreed well with the experimental observation. This agreement could support the proposed reaction pathway for H-abstraction from amine as an initial step. The high rate constant for the reaction of trimethyl amine with O3 could be explained by a formation of the cyclic transition state structure.
  • Satoshi Maeda, Yu Harabuchi, Makito Takagi, Kenichiro Saita, Kimichi Suzuki, Tomoya Ichino, Yosuke Sumiya, Kanami Sugiyama, Yuriko Ono
    Journal of Computational Chemistry 39 4 233 - 250 2018年 [査読有り][通常論文]
     
    This article reports implementation and performance of the artificial force induced reaction (AFIR) method in the upcoming 2017 version of GRRM program (GRRM17). The AFIR method, which is one of automated reaction path search methods, induces geometrical deformations in a system by pushing or pulling fragments defined in the system by an artificial force. In GRRM17, three different algorithms, that is, multicomponent algorithm (MC-AFIR), single-component algorithm (SC-AFIR), and double-sphere algorithm (DS-AFIR), are available, where the MC-AFIR was the only algorithm which has been available in the previous 2014 version. The MC-AFIR does automated sampling of reaction pathways between two or more reactant molecules. The SC-AFIR performs automated generation of global or semiglobal reaction path network. The DS-AFIR finds a single path between given two structures. Exploration of minimum energy structures within the hypersurface in which two different electronic states degenerate, and an interface with the quantum mechanics/molecular mechanics method, are also described. A code termed SAFIRE will also be available, as a visualization software for complicated reaction path networks. (c) 2017 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.
  • Satoshi Maeda, Kanami Sugiyama, Yosuke Sumiya, Makito Takagi, Kenichiro Saita
    Chemistry Letters 47 4 396 - 399 2018年 [査読有り][通常論文]
     
    In this study, artificial force induced reaction (AFIR) method, which has been utilized extensively in molecular systems, was applied to surface adsorbed species. A systematic strategy for obtaining path networks for surface adsorbed species is described for future applications to various surface reactions. As a case study, global reaction route mapping on the potential energy surface (PES) of H2O adsorbed on Cu(111) surface was performed.
  • Yu Harabuchi, Kenichiro Saita, Satoshi Maeda
    Photochemical and Photobiological Sciences 17 3 315 - 322 2018年 [査読有り][通常論文]
     
    Radiative and nonradiative decay paths from the first excited singlet electronic state (S1) in four heteroaromatics, indole, isoindole, quinoline, and isoquinoline, were systematically explored. Three decay processes, i.e., internal conversion (IC), intersystem crossing (ISC), and fluorescence emission (FE), were compared. Minimum energy conical intersection structures between the electronic ground and first excited states were investigated to determine the most preferred IC path. The minimum energy seam of crossing (MESX) geometries between S1 and the lowest-lying triplet states and the spin-orbit couplings at these MESX structures were computed to identify the most feasible ISC path. The oscillator strength was calculated at each S1 local minimum to reveal the contribution of the FE process. The calculations clearly showed that indole had the highest fluorescent quantum yield, consistent with the experimental data. The present calculations also explained other experimental properties of the heteroaromatics such as ISC quantum yields.
  • Takuro Tsutsumi, Yu Harabuchi, Yuriko Ono, Satoshi Maeda, Tetsuya Taketsugu
    Physical Chemistry Chemical Physics 20 3 1364 - 1372 2018年 [査読有り][通常論文]
     
    A methodology to analyze a trajectory on-the-fly (TOF) based on a global reaction route map consisting of intrinsic reaction coordinate (IRC) pathways is proposed. By using the distance functions in the configurational space, the location of each point on the trajectories is detected, providing a dynamical picture that the molecular system goes over several minima and transition states in the reaction path network. In its application to structural transformations of an Au5 cluster, a variety of reaction routes are obtained, and the hopping from one IRC to another IRC (IRC-jump) is analyzed. The branching of trajectories over many minima on the potential energy surface via valley-ridge transition points is also discussed.
  • Marciniak A, Yamazaki K, Maeda S, Reduzzi M, Despre V, Herve M, Meziane M, Niehaus T. A, Loriot V, Kuleff A. I, Schindler B, Compagnon I, Sansone G, Lepine F
    Journal of Physical Chemistry Letters 9 24 6927 - 6933 2018年 [査読有り][通常論文]
  • Ingle R. A, Roberts G. M, Rottger K, Marroux H. J. B, Sonnichsen F. D, Yang M, Szyc L, Harabuchi Y, Maeda S, Temps F, Orr-Ewing A. J
    Chemical Physics 515 480 - 492 2018年 [査読有り][通常論文]
  • Takuro Tsutsumi, Yu Harabuchi, Rina Yamamoto, Satoshi Maeda, Tetsuya Taketsugu
    Chemical Physics 515 564 - 571 2018年 [査読有り][通常論文]
  • Kenichiro Saita, Makito Takagi, Yu Harabuchi, Haruki Okada, Satoshi Maeda
    The Journal of Chemical Physics 149 7 2018年 [査読有り][通常論文]
  • Yosuke Sumiya, Satoshi Maeda
    Chemistry - A European Journal 24 47 12264 - 12268 2018年 [査読有り][通常論文]
  • Kinoshita, Shin-nosuke, Kinoshita, Shin-nosuke, Miyazaki, Yasunori, Miyazaki, Yasunori, Sumida, Masataka, Sumida, Masataka, Onitsuka, Yuuki, Onitsuka, Yuuki, Kohguchi, Hiroshi, Kohguchi, Hiroshi, Inokuchi, Yoshiya, Inokuchi, Yoshiya, Akai, Nobuyuki, Akai, Nobuyuki, Shiraogawa, Takafumi, Shiraogawa, Takafumi, Ehara, Masahiro, Ehara, Masahiro, Yamazaki, Kaoru, Yamazaki, Kaoru, Harabuchi, Yu, Harabuchi, Yu, Maeda, Satoshi, Maeda, Satoshi, Taketsugu, Tetsuya, Taketsugu, Tetsuya, Ebata, Takayuki, Ebata, Takayuki
    Physical Chemistry Chemical Physics 20 26 17583 - 17598 2018年 [査読有り][通常論文]
  • Kimichi Suzuki, Keiji Morokuma, Satoshi Maeda
    JOURNAL OF COMPUTATIONAL CHEMISTRY 38 26 2213 - 2221 2017年10月 [査読有り][通常論文]
     
    We propose a multistructural microiteration (MSM) method for geometry optimization and reaction path calculation in large systems. MSM is a simple extension of the geometrical microiteration technique. In conventional microiteration, the structure of the non-reaction-center (surrounding) part is optimized by fixing atoms in the reaction-center part before displacements of the reaction-center atoms. In this method, the surrounding part is described as the weighted sum of multiple surrounding structures that are independently optimized. Then, geometric displacements of the reaction-center atoms are performed in the mean field generated by the weighted sum of the surrounding parts. MSM was combined with the QM/MM-ONIOM method and applied to chemical reactions in aqueous solution or enzyme. In all three cases, MSM gave lower reaction energy profiles than the QM/MM-ONIOM-microiteration method over the entire reaction paths with comparable computational costs. (c) 2017 Wiley Periodicals, Inc.
  • Xiaowei Song, Matias R. Fagiani, Sreekanta Debnath, Min Gao, Satoshi Maeda, Tetsuya Taketsugu, Sandy Gewinner, Wieland Schoellkopf, Knut R. Asmis, Andrey Lyalin
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 19 34 23154 - 23161 2017年09月 [査読有り][通常論文]
     
    The mechanism of dissociative D-2 adsorption on Ti2O4-, which serves as a model for an oxygen vacancy on a titania surface, is studied using infrared photodissociation spectroscopy in combination with density functional theory calculations and a recently developed single-component artificial force induced reaction method. Ti2O4- readily reacts with D-2 under multiple collision conditions in a gas-filled ion trap held at 16 K forming a global minimum-energy structure (DO-Ti-(O)(2)-Ti(D)-O)(-). The highly exergonic reaction proceeds quasi barrier-free via several intermediate species, involving heterolytic D-2-bond cleavage followed by D-atom migration. We show that, compared to neutral Ti2O4, the excess negative charge in Ti2O4- is responsible for the substantial lowering of the D-2 dissociation barrier, but does not affect the molecular D-2 adsorption energy in the initial physisorption step.
  • Eiji Yamamoto, Satoshi Maeda, Tetsuya Taketsugu, Hajime Ito
    Synlett 28 11 1258 - 1267 2017年07月03日 [査読有り][通常論文]
     
    Silylboranes are used as borylation reagents for organohalides in the presence of alkoxy bases without transition-metal catalysts. PhMe 2 Si-B(pin) reacts with a variety of aryl, alkenyl, and alkyl halides, including sterically hindered examples, to provide the corresponding organoboronates in good yields with high borylation/silylation ratios, showing good functional group compatibility. Halogenophilic attack of a silyl nucleophile on organohalides, and subsequent nucleophilic attack on the boron electrophile are identified to be crucial, based on the results of extensive theoretical and experimental studies. This borylation reaction is further applied to the first direct dimesitylboryl (BMes 2) substitution of aryl halides using Ph 2 MeSi-BMes 2 and Na(O- t -Bu), affording aryldimesitylboranes, which are regarded as an important class of compounds for organic materials. 1 Introduction 2 Boryl Substitution of Organohalides with PhMe 2 Si-B(pin)/Alkoxy Bases 3 Mechanistic Investigations 4 DFT Mechanistic Studies Using an Artificial Force Induced Reaction (AFIR) Method 5 Dimesitylboryl Substitution of Aryl Halides with Ph 2 MeSi-BMes 2 /Na(O- t -Bu) 6 Conclusion.
  • Ryohei Uematsu, Chihiro Saka, Yosuke Sumiya, Tomoya Ichino, Tetsuya Taketsugu, Satoshi Maeda
    CHEMICAL COMMUNICATIONS 53 53 7302 - 7305 2017年07月 [査読有り][通常論文]
     
    An autocatalytic cycle was found in the mechanism of autoxidation of triethylborane using density functional theory calculations. The reaction starts with the generation of an ethyl radical via slow homolytic substitution. Fast radical propagation then takes place through a catalytic cycle in which the ethyl radical acts as a catalyst.
  • Takayoshi Yoshimura, Satoshi Maeda, Tetsuya Taketsugu, Masaya Sawamura, Keiji Morokuma, Seiji Mori
    CHEMICAL SCIENCE 8 6 4475 - 4488 2017年06月 [査読有り][通常論文]
     
    We explored the reaction mechanism of the cationic rhodium(I)-BINAP complex catalysed isomerisation of allylic amines using the artificial force induced reaction method with the global reaction route mapping strategy, which enabled us to search for various reaction paths without assumption of transition states. The entire reaction network was reproduced in the form of a graph, and reasonable paths were selected from the complicated network using Prim's algorithm. As a result, a new dissociative reaction mechanism was proposed. Our comprehensive reaction path search provided rationales for the E/Z and S/R selectivities of the stereoselective reaction.
  • Makito Takagi, Tetsuya Taketsugu, Hiori Kino, Yoshitaka Tateyama, Kiyoyuki Terakura, Satoshi Maeda
    PHYSICAL REVIEW B 95 18 2017年05月 [査読有り][通常論文]
     
    We propose an approach to perform the global search for low-lying crystal structures from first principles, by combining the artificial force induced reaction (AFIR) method and the periodic boundary conditions (PBCs). The AFIR method has been applied extensively to molecular systems to elucidate the mechanism of chemical reactions such as homogeneous catalysis. The present PBC/AFIR approach found 274 local minima for carbon crystals in the C-8 unit cell described by the generalized gradient approximation-Perdew-Burke-Ernzerhof functional. Among many newly predicted structures, three low-lying structures, which exhibit somewhat higher energy compared with those previously predicted, such as Cco-C-8 (Z-carbon) and M-carbon, are further discussed with calculations of phonon and band dispersion curves. Furthermore, approaches to systematically explore two- or one-dimensional periodic structures are proposed and applied to the C-8 unit cell with the slab model. These results suggest that the present approach is highly promising for predicting crystal structures.
  • Satoshi Maeda
    JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN 75 4 367 - 374 2017年04月 [査読有り][通常論文]
  • Yu Harabuchi, Tetsuya Taketsugu, Satoshi Maeda
    CHEMICAL PHYSICS LETTERS 674 141 - 145 2017年04月 [査読有り][通常論文]
     
    We report a new approach to search for structures of minimum energy conical intersection (MECIs) automatically. Gradient projection (GP) method and single component artificial force induced reaction (SC-AFIR) method were combined in the present approach. As case studies, MECIs of benzene and naphthalene between their ground and first excited singlet electronic states (S-0/S-1-MECIs) were explored. All S-0/S-1-MECIs reported previously were obtained automatically. Furthermore, the number of force calculations was reduced compared to the one required in the previous search. Improved convergence in a step in which various geometrical displacements are induced by SC-AFIR would contribute to the cost reduction. (C) 2017 Elsevier B.V. All rights reserved.
  • Min Gao, Daisuke Horita, Yuriko Ono, Andrey Lyalin, Satoshi Maeda, Tetsuya Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY C 121 5 2661 - 2668 2017年02月 [査読有り][通常論文]
     
    A systematic investigation is performed on structural transformations in small neutral gold clusters (Au-3-Au-12) induced by O-2 adsorption, with the use of the fully automated reaction path search techniques, i.e., anharrnonic downward distortion following (APDF) and artificial force induced reaction (AFIR) methods, implemented in the global reaction route mapping (GRRM) program. For each size of Au cluster, the most stable structure, low-energy isomers, and a network of isomerization pathways are determined. The located Au-n-O-2 adsorption forms can be classified into two groups: eta(1)-AunO2, where only one oxygen atom is adsorbed on Au-n, and eta(2)=AunO2, where both oxygen atoms are adsorbed on Au-n in a hridged manner. These two adsorption forms can be transformed to eath other with a low barrier. The isornerization pathways of gold clusters upon O-2 adsorption are compared with those obtained for the pure gold cluSters Without O-2. It is demonstrated that O-2 adsorption promotes structural transformations in gold clusters considerably by lowering the isomerization battlers. The presence of the unpaired electron is a necessary condition for O-2 adsorption in the eta(1)-Au O-2 form, as well as the subsequent cluster isomerization and the O-O bond activation. These conclusions ate consistent with the recent experimental resits by Fielicke et al.
  • Yosuke Sumiya, Tetsuya Taketsugu, Satoshi Maeda
    JOURNAL OF COMPUTATIONAL CHEMISTRY 38 2 101 - 109 2017年01月 [査読有り][通常論文]
     
    The branching ratio of unimolecular decomposition can be evaluated by solving the rate equations. Recent advances in automated reaction path search methods have enabled efficient construction of the rate equations based on quantum chemical calculations. However, it is still difficult to solve the rate equations composed of hundreds or more elementary steps. This problem is especially serious when elementary steps that occur in highly different timescales coexist. In this article, we introduce an efficient approach to obtain the branching ratio from a given set of rate equations. It has been derived from a recently proposed rate constant matrix contraction (RCMC) method, and termed full-RCMC (f-RCMC). The f-RCMC gives the branching ratio without solving the rate equations. Its performance was tested numerically for unimolecular decomposition of C3H5 and C4H5. Branching ratios obtained by the f-RCMC precisely reproduced the values obtained by numerically solving the rate equations. It took about 95 h to solve the rate equations of C4H5 consisting of 234 elementary steps. In contrast, the f-RCMC gave the branching ratio in less than 1 s. The f-RCMC would thus be an efficient alternative of the conventional kinetic simulation approach. (C) 2016 Wiley Periodicals, Inc.
  • Kenward King Ho Vong, Satoshi Maeda, Katsunori Tanaka
    CHEMISTRY-A EUROPEAN JOURNAL 22 52 18865 - 18872 2016年12月 [査読有り][通常論文]
     
    Alkyl esters, such as propargyl esters, typically lack the electron-withdrawing inductive effects needed to participate in nucleophilic acyl substitution reactions. Herein, we report an unusual observation in which glycine propargyl ester derivatives displayed selective, base-independent reactivity towards linear alkylamines under mild, metal-free conditions. Through global reaction route mapping (GRRM) modeling calculations, it is predicted that these observations may be governed by factors related to hydrogen-bonding and intermolecular interactions, rather than electron-withdrawing inductive effects. Based on this concept of propargyl-assisted selective amidation, a direct application was made to develop a novel site-specific C-terminal glycine peptide bioconjugation technique as a proof-of-concept, which relies upon the selective reactivity of glycine propargyl esters over that of aspartate and glutamate side-chainlinked propargyl esters.
  • Yu Harabuchi, Rina Yamamoto, Satoshi Maeda, Satoshi Takeuchi, Tahei Tahara, Tetsuya Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY A 120 44 8804 - 8812 2016年11月 [査読有り][通常論文]
     
    Ab initio molecular dynamics (AIMD) simulations were carried out for pi pi*-excited 1,1'-dimethylstilbene (dmSB) at the spin-flip time-dependent density functional theory (SF-TDDFT) level with the T-sF-index technique, to get insights into the substitution effects on the photoisomerization dynamics of stilbene (SB). It is found that the reaction path from the Franck-Condon structure of cis-dmSB is oriented toward the 4,4-dihydrophenanthrene (DHP) side from the beginning, which is in contrast to the case of SB where the pathway is oriented toward the twist side in the initial stage. The optimized geometries of minima and the minimum-energy conical intersection (MECI) suggested that molecules in the DHP region could easily decay to the ground state. On the other hand, S-1/S-0-MECI and S-1-minimum in the twist region have a relatively different geometry from each other, which is consistent with the experimental observation of the long lifetime of the perpendicular structure. AIMD simulations showed that more trajectories enter the well of the DHP side than the well of the twist side and that all of the trajectories going to the DHP side reached the S-1/S-0-CI region within similar to 0.2 ps on average, while very few trajectories reached S-1/ S-0-CI even after 1 ps in the twist region. Decrease in the S-1 population in the cis and twist regions qualitatively reproduced the temporal profiles of the transient absorption bands of dmSB observed in the visible and ultraviolet regions, respectively.
  • Guixiang Zeng, Satoshi Maeda, Tetsuya Taketsugu, Shigeyoshi Sakaki
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 138 41 13481 - 13484 2016年10月 [査読有り][通常論文]
     
    Two theoretically designed and one experimentally reported pincer-type phosphorus compounds are found to be active for the hydrogenation of carbon dioxide with ammonia borane. DFT, ONIOM(CCSD-(T):MP2), and CCSD(T) computational results demonstrated that the reaction occurs through phosphorus ligand cooperative catalysis, which provides an unprecedented protocol for metal-free CO2 conversion. The phosphorus compounds with the NNN ligand are more active than those with the ONO ligand. The planar conjugate ligand considerably improves the efficiency of the catalyst.
  • W. M. C. Sameera, Akhilesh Kumar Sharma, Satoshi Maeda, Keiji Morokuma
    CHEMICAL RECORD 16 5 2349 - 2363 2016年10月 [査読有り][通常論文]
     
    Nowadays, computational studies are very important for the elucidation of reaction mechanisms and selectivity of complex reactions. However, traditional computational methods usually require an estimated reaction path, mainly driven by limited experimental implications, intuition, and assumptions of stationary points. However, the artificial force induced reaction (AFIR) method in the global reaction route mapping (GRRM) strategy can be used for unbiased and automatic reaction path searches for complex reactions. In this account, we highlight applications of the AFIR method to a variety of reactions (organic, organometallic, enzymatic, and photochemical) of complex molecular systems. In addition, the AFIR method has been successfully used to rationalise the origin of stereo- and regioselectivity. The AFIR method can be applied from small to large molecular systems, and will be a very useful tool for the study of complex molecular problems in many areas of chemistry, biology, and material sciences.
  • Satoshi Maeda, Yu Harabuchi, Makito Takagi, Tetsuya Taketsugu, Keiji Morokuma
    CHEMICAL RECORD 16 5 2232 - 2248 2016年10月 [査読有り][通常論文]
     
    In this account, a technical overview of the artificial force induced reaction (AFIR) method is presented. The AFIR method is one of the automated reaction-path search methods developed by the authors, and has been applied extensively to a variety of chemical reactions, such as organocatalysis, organometallic catalysis, and photoreactions. There are two modes in the AFIR method, i.e., a multicomponent mode and a single-component mode. The former has been applied to bimolecular and multicomponent reactions and the latter to unimolecular isomerization and dissociation reactions. Five numerical examples are presented for an Aldol reaction, a Claisen rearrangement, a Co-catalyzed hydroformylation, a fullerene structure search, and a nonradiative decay path search in an electronically excited naphthalene molecule. Finally, possible applications of the AFIR method are discussed.
  • D. T. Ha, K. Yamazaki, Y. Wang, M. Alcami, S. Maeda, H. Kono, F. Martin, E. Kukk
    JOURNAL OF CHEMICAL PHYSICS 145 9 2016年09月 [査読有り][通常論文]
     
    The fragmentation of doubly charged gas-phase methionine (HO2CCH(NH2) CH2CH2SCH3) is systematically studied using the self-consistent charge density functional tight-binding molecular dynamics (MD) simulation method. We applied graph theory to analyze the large number of the calculated MD trajectories, which appears to be a highly effective and convenient means of extracting versatile information from the large data. The present theoretical results strongly concur with the earlier studied experimental ones. Essentially, the dication dissociates into acidic group CO2H and basic group C4NSH10. The former may carry a single or no charge and stays intact in most cases, whereas the latter may hold either a single or a double charge and tends to dissociate into smaller fragments. The decay of the basic group is observed to follow the Arrhenius law. The dissociation pathways to CO2H and C4NSH10 and subsequent fragmentations are also supported by ab initio calculations. Published by AIP Publishing.
  • Guixiang Zeng, Satoshi Maeda, Tetsuya Taketsugu, Shigeyoshi Sakaki
    ACS CATALYSIS 6 8 4859 - 4870 2016年08月 [査読有り][通常論文]
     
    Catalysis of phosphorus compound 10-P-3(2)3,7-di(tert-butyl)-5-aza-2,8-dioxa-l-phosphabicyclo[3.3.0]octa-2,4,6-triene 1P and its analogues in transfer hydrogenation of azobenzene with ammonia-borane (NH3BH3) using DFT, CCSD(T), and ONIOM(CCSD(T):MP2) methods. Theoretical calculations clearly reveal that this transfer hydrogenation reaction occurs through the phosphorus ligand cooperative catalysis function with a change in the phosphorus oxidation state between +I and +III. It is noteworthy that the change in phosphorus oxidation state is a characteristic feature of the cooperative catalysis by 1P: it is not easy for a main -group element to change its oxidation state. This characteristic feature differs from that of metal ligand cooperative catalysis in which the metal oxidation state does not change. Theoretical calculations also disclose that the catalytic activity of IP-like compound is improved by introducing electron -withdrawing substituents to the ligand and using the conjugated planar framework of the ligand. The best catalyst here is predicted to be active for transfer hydrogenations of various ketones and acetaldehyde with NH3BH3, indicating that IP-like compound exhibit a wide application scope as a catalyst.
  • Yu Harabuchi, Tetsuya Taketsugu, Satoshi Maeda
    CHEMISTRY LETTERS 45 8 940 - 942 2016年08月 [査読有り][通常論文]
     
    Automated searches for minimum energy conical intersection structures between the lowest two singlet electronic states (S-0/S-1-MECIs) of furan and dibenzofuran were made. In total, eight and sixty S-0/S-1-MECIs were found for furan and dibenzofuran, respectively, around their Franck-Condon (FC) regions. The difference in their experimental fluorescence quantum yields was discussed based on the barrier heights to reach S-0/S-1-MECIs from the FC regions. It was found that the stability of the FC region is the major factor giving the difference in their fluorescence quantum yields.
  • Kenichiro Saita, Yu Harabuchi, Tetsuya Taketsugu, Osamu Ishitani, Satoshi Maeda
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 18 26 17557 - 17564 2016年07月 [査読有り][通常論文]
     
    The mechanism of the CO ligand dissociation of fac-[Re-I(bpy)(CO)(3)P(OMe)(3)](+) has theoretically been investigated, as the dominant process of the photochemical ligand substitution (PLS) reactions of fac-[Re-I(bpy)(CO)(3)PR3](+), by using the (TD-)DFT method. The PLS reactivity can be determined by the topology of the T-1 potential energy surface because the photoexcited complex is able to decay into the T-1 state by internal conversions (through conical intersections) and intersystem crossings (via crossing seams) with sufficiently low energy barriers. The T-1 state has a character of the metal-to-ligand charge-transfer ((MLCT)-M-3) around the Franck-Condon region, and it changes to the metal-centered ((MC)-M-3) state as the Re-CO bond is elongated and bent. The equatorial CO ligand has a much higher energy barrier to leave than that of the axial CO, so that the axial CO ligand selectively dissociates in the PLS reaction. The single-component artificial force induced reaction (SC-AFIR) search reveals the CO dissociation pathway in photostable fac-[ReI(bpy)(CO)(3)Cl]; however, the dissociation barrier on the T-1 state is substantially higher than that in fac-[ReI(bpy)(CO)(3)PR3](+) and the minimum-energy seams of crossings (MESXs) are located before and below the barrier. The MESXs have also been searched in fac-[Re-I(bpy)(CO)(3)PR3](+) and no MESXs were found before and below the barrier.
  • Yu Harabuchi, Julien Eng, Etienne Gindensperger, Tetsuya Taketsugu, Satoshi Maeda, Chantal Daniel
    JOURNAL OF CHEMICAL THEORY AND COMPUTATION 12 5 2335 - 2345 2016年05月 [査読有り][通常論文]
     
    The mechanism of ultrafast intersystem crossing in rhenium(I) carbonyl bipyridine halide complexes Re(X)(CO)(3)(bpy) (X = Cl, Br, I) is studied by exploring the structural deformations when going from Franck-Condon (FC) to critical geometries in the low-lying singlet and triplet excited states and by selecting the key vibrational modes. The luminescent decay observed in [Re(Br)(CO)(3)(bpy)] is investigated by means of wavepacket propagations.based on the multiconfiguration time-dependent Hartree (MCTDH) method. The dominant coordinates underlying the nonradiative decay process are extracted from minima, minimum energy seam of crossing (MESX) and minimum energy conical intersection (MECI) geometries obtained by the seam model function (SME)/Single-component artificial force induced reaction (SC-AFIR) approach. By choosing the normal modes used in MCTDH from the MECI and MESX geometries, not only the degenerate energy points but also the low-energy-gap regions are included. For this purpose a careful vibrational analysis is performed at each critical geometry and analyzed under the light of the pertinent nonadiabatic coupling terms obtained from the linear vibronic coupling (LVC) model augmented by spin orbit coupling (SOC) in the electronic diabatic representation.
  • W. M. C. Sameera, Satoshi Maeda, Keiji Morokuma
    ACCOUNTS OF CHEMICAL RESEARCH 49 4 763 - 773 2016年04月 [査読有り][通常論文]
     
    CONSPECTUS: The artificial force induced reaction (AFIR) method in the global reaction route mapping (GRRM) strategy is an automatic approach to explore all important reaction paths of complex reactions. Most traditional methods in computational catalysis require guess reaction paths. On the other hand, the AFIR approach locates local minima (LMs) and transition states (TSs) of reaction paths without a guess, and therefore finds unanticipated as well as anticipated reaction paths. The AFIR method has been applied for multicomponent organic reactions, such as the aldol reaction, Passerini reaction, Biginelli reaction, and phase-transfer catalysis. In the presence of several reactants, many equilibrium structures are possible, leading to a number of reaction pathways. The AFIR method in the GRRM strategy determines all of the important equilibrium structures and subsequent reaction paths systematically. As the AFIR search is fully automatic, exhaustive trial-and-error and guess-and-check processes by the user can be eliminated. At the same time, the AFIR search is systematic, and therefore a more accurate and comprehensive description of the reaction mechanism can be determined. The AFIR method has been used for the study of full catalytic cycles and reaction steps in transition metal catalysis, such as cobalt-catalyzed hydroformylation and iron-catalyzed carbon-carbon bond formation reactions in aqueous media. Some AFIR applications have targeted the selectivity-determining step of transition-metal-catalyzed asymmetric reactions, including stereoselective water-tolerant lanthanide Lewis acid-catalyzed Mukaiyama aldol reactions. In terms of establishing the selectivity of a reaction, systematic sampling of the transition states is critical. In this direction, AFIR is very useful for performing a systematic and automatic determination of TSs. In the presence of a comprehensive description of the transition states, the selectivity of the reaction can be calculated more accurately. For relatively large molecular systems, the computational cost of AFIR searches can be reduced by using the ONIOM(QM:QM) or ONIOM(QM:MM) methods. In common practice, density functional theory (DFT) with a relatively small basis set is used for the high-level calculation, while a semiempirical approach or a force field description is used for the low-level calculation. After approximate LMs and TSs are determined, standard computational methods (e.g., DFT with a large basis set) are used for the full molecular system to determine the true LMs and TSs and to rationalize the reaction mechanism and selectivity of the catalytic reaction. The examples in this Account evidence that the AFIR method is a powerful approach for accurate prediction of the reaction mechanisms and selectivities of complex catalytic reactions. Therefore, the AFIR approach in the GRRM strategy is very useful for computational catalysis.
  • Yutaka Nagahata, Satoshi Maeda, Hiroshi Teramoto, Takashi Horiyama, Tetsuya Taketsugu, Tamiki Komatsuzaki
    JOURNAL OF PHYSICAL CHEMISTRY B 120 8 1961 - 1971 2016年03月 [査読有り][通常論文]
     
    Markovian dynamics on complex reaction networks are one of the most intriguing subjects in a wide range of research fields including chemical reactions, biological physics, and ecology. To represent the global kinetics from one node (corresponding to a basin on an energy landscape) to another requires information on multiple pathways that directly or indirectly connect these two nodes through the entire network. In this paper we present a scheme to extract a hierarchical set of global transition states (TSs) over a discrete time Markov chain derived from first-order rate equations. The TSs can naturally take into account the multiple pathways connecting any pair of nodes. We also propose a new type of disconnectivity graph (DG) to capture the hierarchical organization of different time scales of reactions that can capture changes in the network due to changes in the observation. The crux is the introduction of the minimum conductance cut (MCC) in graph clustering, corresponding to the dividing surface across the network having the "smallest" transition probability between two disjoint subnetworks (superbasins on the energy landscape) in the network. We present a new combinatorial search algorithm for finding this MCC. We apply our method to a reaction network of Claisen rearrangement of allyl vinyl ether that consists of 23 nodes and 66 links (saddles on the energy landscape) connecting them. We compare the kinetic properties of our DG to those of the transition matrix of the rate equations and show that our graph can properly reveal the hierarchical, organization of time scales in a network.
  • Yu Harabuchi, Yuriko Ono, Satoshi Maeda, Tetsuya Taketsugu, Kristopher Keipert, Mark S. Gordon
    JOURNAL OF COMPUTATIONAL CHEMISTRY 37 5 487 - 493 2016年02月 [査読有り][通常論文]
     
    A new type of reaction pathway which involves a nontotally symmetric trifurcation was found and investigated for a typical S(N)2-type reaction, NC-+CH3X NCCH3+X- (X=F, Cl). A nontotally symmetric valley-ridge inflection (VRI) point was located along the C-3v reaction path. For X=F, the minimum energy path (MEP) starting from the transition state (TS) leads to a second-order saddle point with C-3v symmetry, which connects three product minima of C-s symmetry. For X=Cl, four product minima have been observed, of which three belong to C-s symmetry and one to C-3v symmetry. The branching path from the VRI point to the lower symmetry minima was determined by a linear interpolation technique. The branching mechanism is discussed based on the reaction path curvature and net atomic charges, and the possibility of a nonotally symmetric n-furcation is discussed. (c) 2015 Wiley Periodicals, Inc.
  • Hongyan Xiao, Satoshi Maeda, Keiji Morokuma
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 18 35 24582 - 24590 2016年 [査読有り][通常論文]
     
    Photodissociation pathways of HNO3 involving the four lowest electronic singlet states (S-0, S-1, S-2 and S-3) were studied by the MS-CAS(12e,8o)PT2/6-31+G(star) method. All critical points, i.e. minima, transition states and minimum energy conical intersections, were explored systematically by the global reaction route mapping (GRRM) strategy utilizing the anharmonic downward distortion following (ADDF) method. Some key structures were also optimized at the MS-CAS(16e,12o)PT2/aug-cc-pVDZ level. Based on structures and relative energies of these critical points, we discussed the wavelength-dependent photodissociation mechanism of HNO3 in detail. The OH(X-2 Pi) dissociation was found to occur through four pathways on the S-1, S-2, and S-3 surfaces depending on the excitation energy, and one of the four pathways was shown to undergo the excited state roaming mechanism. The experimental appearance energy of the O(D-1) dissociation channel at 538.8 kJ mol(-1) was attributed to a conical intersection between the S-2 and S-3 surfaces. It has been shown experimentally that the O(D-1) channel was dominant at the higher excitation energy. In this study, its mechanistic reason was explained by the shape of the S-3 surface and locations of important critical points.
  • Jun Kawano, Satoshi Maeda, Takaya Nagai
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 18 4 2690 - 2698 2016年01月 [査読有り][通常論文]
     
    Mg2+ is considered to play an important role in the formation of calcium carbonate polymorphs; however, how it affects polymorph selection during the early stages of CaCO3 formation is not yet well understood. In the present study, in order to clarify the effect of Mg2+ on the nucleation of calcium carbonate polymorphs, the stable structures of anhydrous additive-free and Mg-containing calcium carbonate clusters are derived using the anharmonic downward distortion following method, based on quantum chemical calculations. Optimization is performed at the B3LYP/6-31+G(d) level and the solvent effect is induced by the self-consistent reaction field method using the conductor-like polarized continuum calculation model. Calculation results show that incorporating Mg2+ into clusters can change the clusters' stable configuration. In the case of dimers and trimers, a Mg ion strongly prefers to locate at the centre of the clusters, which suggests that Mg is easy to incorporate into the clusters once it is released from its tight hydration shell. Notably, structures similar to the crystalline phase appear when only four CaCO3 units aggregate into the cluster: in the stable structure of the additive-free CaCO3 tetramer, the arrangement of Ca and CO3 ions is almost the same as that of the calcite structure, while the structure of the Mg-containing CaCO3 tetramer resembles the aragonite structure in the way that CO3 ions are stacked. These results indicate that Mg can play a key role in aragonite formation not only by inhibiting calcite growth but also by directly promoting aragonite nucleation in the early stages of CaCO3 formation.
  • Tsuneda Takao, Maeda Satoshi, Harabuchi Yu, Singh Raman K
    Computation 4 3 2016年 [査読有り][通常論文]
  • Yamazaki, Kaoru, Miyazaki, Yasunori, Harabuchi, Yu, Taketsugu, Tetsuya, Maeda, Satoshi, Inokuchi, Yoshiya, Kinoshita, Shin-nosuke, Sumida, Masataka, Onitsuka, Yuuki, Kohguchi, Hiroshi, Ehara, Masahiro, Ebata, Takayuki
    Journal of Physical Chemistry Letters 7 19 4001 - 4007 2016年 [査読有り][通常論文]
  • Daniel Murdock, Rebecca A. Ingle, Igor V. Sazanovich, Ian P. Clark, Yu Harabuchi, Tetsuya Taketsugu, Satoshi Maeda, Andrew J. Orr-Ewing, Michael N. R. Ashfold
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 18 4 2629 - 2638 2016年01月 [査読有り][通常論文]
     
    The photoisomerisation dynamics following excitation to the S-1 electronic state of two structurally related heterocyclic molecules, alpha-pyrone and coumarin, in acetonitrile solution have been probed by time-resolved vibrational absorption spectroscopy. Following irradiation at 310 nm, alpha-pyrone relaxes rapidly from its initially excited state, with a quantum yield for parent molecule reformation of 68%. Probing the antisymmetric ketene stretch region between 2100 cm(-1) and 2150 cm(-1) confirms the presence of at least two isomeric ring-opened photoproducts, which are formed highly vibrationally excited and relax on a picosecond timescale. Following vibrational cooling, a secondary, thermally driven, isomerisation is observed with a 1.8(1) ns time constant. In contrast, coumarin reforms the parent molecule with essentially 100% efficiency following excitation at 330 nm. The conical intersections driving the non-radiative relaxation of alpha-pyrone have been investigated using an automated search algorithm. The two lowest energy conical intersections possess remarkably similar structures to the two energetically accessible conical intersections reported previously for coumarin, suggesting that the differing photochemistry is the result of dynamical effects occurring after passage through these intersections.
  • Yosuke Sumiya, Yutaka Nagahata, Tamiki Komatsuzaki, Tetsuya Taketsugu, Satoshi Maeda
    JOURNAL OF PHYSICAL CHEMISTRY A 119 48 11641 - 11649 2015年12月 [査読有り][通常論文]
     
    The significance of kinetic analysis as a tool for understanding the reactivity and selectivity of organic reactions has recently been recognized. However, conventional simulation approaches that solve rate equations numerically are not amenable to multistep reaction profiles consisting of fast and slow elementary steps. Herein, we present an efficient and robust approach for evaluating the overall rate constants of multistep reactions via the recursive contraction of the rate equations to give the overall rate constants for the products and byproducts. This new method was applied to the Claisen rearrangement of allyl vinyl ether, as well as a substituted allyl vinyl ether. Notably, the profiles of these reactions contained 23 and 84 local minima, and 66 and 278 transition states, respectively. The overall rate constant for the Claisen rearrangement of allyl vinyl ether was consistent with the experimental value. The selectivity of the Claisen rearrangement reaction has also been assessed using a substituted allyl vinyl ether. The results of this study showed that the conformational entropy in these flexible chain molecules had a substantial impact on the overall rate constants. This new method could therefore be used to estimate the overall rate constants of various other organic reactions involving flexible molecules.
  • Yu Harabuchi, Yuriko Ono, Satoshi Maeda, Tetsuya Taketsugu
    JOURNAL OF CHEMICAL PHYSICS 143 17 2015年11月 [査読有り][通常論文]
  • Satoshi Suzuki, Satoshi Maeda, Keiji Morokuma
    JOURNAL OF PHYSICAL CHEMISTRY A 119 47 11479 - 11487 2015年11月 [査読有り][通常論文]
     
    The quenching pathways were investigated for three types of multiluminescent acene derivatives, which show environment-dependent fluorescence. Spin-flip time dependent density functional theory (SF-TDDFT) combined with the Global Reaction Route mapping (GRRM) strategy is employed to locate minimum-energy conical intersections (MECIs). The energies and geometries of the MECIs relative to the Franck-Condon (FC) state control the difference in fluorescence behavior among the three derivatives. For the molecule with a phenyamide moiety, a MECI with energy lower than the FC state with large geometrical change from V-type to flat structure provides an efficient internal conversion (quenching) pathway in solution. For the same molecule, in a solid, this large geometrical change is inhibited, and the second MECI, with an energy lower than FC but higher than the first MECI requiring only a small geometry change of CH out-of-plane bending, contributes to the quenching. The molecule with the napthaleneimide moiety has only one low-energy MECI that requires large geometrical change from the V-type to flat structure. Although this MECI provides the quenching pathway in solution, in the solid, this large motion is inhibited, and the molecule will stay in the excited state and emit. The molecule with an anthraceneimide moiety has no conical intersection lower than the FC state, and no quenching pathway is available in solution or solid. In addition, in this molecule, at the local minimum of the excited state, the dipole transition to the ground state is allowed, and this molecule prefers emission rather than internal conversion.
  • Shin A. Moteki, Hiroki Maruyama, Keiji Nakayama, Hai-Bei Li, Galina Petrova, Satoshi Maeda, Keiji Morokuma, Keiji Maruoka
    CHEMISTRY-AN ASIAN JOURNAL 10 10 2112 - 2116 2015年10月 [査読有り][通常論文]
     
    The origin of higher reactivity in water-accelerated asymmetric aldol reactions with our designed primary amine organocatalyst was elucidated by both computational and experimental methods. As suggested by the calculated transition-state structures for water-promoted imine-enamine isomerization, anti-selective aldol reaction and hemiaminal formation, the rate of this aldol reaction was found experimentally to be even more accelerated by the addition of cis-2-butene-1,4-diol as additive.
  • Hiroaki Tokoyama, Hideo Yamakado, Satoshi Maeda, Koichi Ohno
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 88 9 1284 - 1290 2015年09月 [査読有り][通常論文]
     
    Isomers of benzene (C6H6) have been searched by quantum chemical calculations using the GRRM/SCC-DFTB program. Further optimization at the level of B3LYP/6-311G(d,p) gave 2004 equilibrium structures (EQ). Obtained EQs were assigned as 212 valence isomers, 928 nonvalence isomers, 798 two-component clusters, and 66 three-component clusters. Energies of EQs range from the most stable isomer of benzene to the highest EQ at 1237 kJ mol(-1). The low energy region below 380 kJ mol(-1) only includes valence isomers. Valence isomers are distributed between 0 and 807 kJ mol(-1), while nonvalence isomers are located in the range of 380-1180 kJ mol(-1). All of the experimentally known 30 isomers of benzene were searched as valence isomers by the ADDF/SCC-DFTB method. Formally hypervalent molecules including pentacoordinated carbon atoms were discovered among nonvalence isomers.
  • Yu Harabuchi, Yuriko Ono, Satoshi Maeda, Tetsuya Taketsugu
    JOURNAL OF CHEMICAL PHYSICS 143 1 2015年07月 [査読有り][通常論文]
     
    A global reaction route map is generated for Au-5 by the anharmonic downward distortion following method in which 5 minima and 14 transition states (TSs) are located. Through vibrational analyses in the 3N - 7 (N = 5) dimensional space orthogonal to the intrinsic reaction coordinate (IRC), along all the IRCs, four IRCs are found to have valley-ridge transition (VRT) points on the way where a potential curvature changes its sign from positive to negative in a direction orthogonal to the IRC. The detailed mechanisms of bifurcations related to the VRTs are discussed by surveying a landscape of the global reaction route map, and the connectivity of VRT points and minima is clarified. Branching of the products through bifurcations is confirmed by ab initio molecular dynamics simulations starting from the TSs. A new feature of the reaction pathways, unification, is found and discussed. (C) 2015 AIP Publishing LLC.
  • Min Gao, Andrey Lyalin, Makito Takagi, Satoshi Maeda, Tetsuya Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY C 119 20 11120 - 11130 2015年05月 [査読有り][通常論文]
     
    This work present results of a systematic investigation of adsorption and dissociation of H-2 on the neutral, positively, and negatively charged gold clusters Au-n(q) (n = 2-11; q = 0; +/- 1) using the global reaction route mapping (GRRM) technique combined with the anharmonic downward distortion following (ADDF) and the artificial force-induced reaction (AFIR) methods. An exhaustive search for H-2 dissociation pathways is performed not only on the most stable cluster structures but also on the large number of low-energy isomers, allowing structural transformations between them. The present strategy can automatically identify the structure-dependent lowest transition states (TS) for H-2 dissociation with a systematic procedure in the regime of the structural fluxionality of gold clusters at finite temperature. Temperature effects, cluster isomerization, and influence of the charge state of gold clusters on H-2 adsorption and dissociation are studied. It is demonstrated that the most stable structures of the gold clusters are not always highly reactive, and an ensemble of isomeric structures must be taken into account for adequate description of the reaction rates at finite temperatures. The proposed approach can serve as a promising tool for a systematic analysis and prediction of reactivity of small metal clusters.
  • Ryohei Uematsu, Eiji Yamamoto, Satoshi Maeda, Hajime Ito, Tetsuya Taketsugu
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 137 12 4090 - 4099 2015年04月 [査読有り][通常論文]
     
    Theoretical and experimental studies have been conducted to elucidate the mechanism of the formal nucleophilic boryl substitution of aryl and alkyl bromides with silylborane in the presence of potassium methoxide. Density functional theory was used in conjunction with the artificial force induced reaction method in the current study to determine the mechanism of this reaction. The results of this analysis led to the identification of a unique carbanion-mediated mechanism involving the halogenophilic attack of a silyl nucleophile on the bromine atom of the substrate. These calculations have, therefore, provided a mechanistic rationale for this counterintuitive borylation reaction. Furthermore, the good functional group compatibility and high reactivity exhibited by this reaction toward sterically hindered substrates can be understood in terms of the low activation energy required for the reaction of the silyl nucleophile with the bromine atom of the substrate and the subsequent rapid and selective consumption of the carbanion species by the in situ generated boron electrophile. The results of an experimental study involving the capture of the anion intermediate provided further evidence in support of the generation of a carbanion species during the course of this reaction. The anomalous formal nucleophilic borylation mechanism reported in this study could be used to provide new insights into silicon and boron chemistry.
  • Satoshi Maeda, Yu Harabuchi, Yuriko Ono, Tetsuya Taketsugu, Keiji Morokuma
    INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY 115 5 258 - 269 2015年03月 [査読有り][通常論文]
     
    The intrinsic reaction coordinate (IRC) approach has been used extensively in quantum chemical analysis and prediction of the mechanism of chemical reactions. The IRC gives a unique connection from a given transition structure to local minima of the reactant and product sides. This allows for easy understanding of complicated multistep mechanisms as a set of simple elementary reaction steps. In this article, three topics concerning the IRC approach are discussed. In the first topic, the first ab initio study of the IRC and a recent development of an IRC calculation algorithm for enzyme reactions are introduced. In the second topic, cases are presented in which dynamical trajectories bifurcate and corresponding IRC connections can be inaccurate. In the third topic, a recent development of an automated reaction path search method and its application to systematic construction of IRC networks are described. Finally, combining these three topics, future perspectives are discussed. (c) 2014 Wiley Periodicals, Inc.
  • Satoshi Maeda, Tetsuya Taketsugu, Koichi Ohno, Keiji Morokuma
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 137 10 3433 - 3445 2015年03月 [査読有り][通常論文]
     
    The photodissociation of small molecules occurs upon irradiation by ultraviolet visible light, and it is a very important Chemical process in Earth's atmosphere, in the atmospheres of other planets, and in interstellar media. Photodissociation is an important method used to thoroughly investigate the fundamental issues of chemical,reactivity. Photodissociation involves Molecules and reaction fragments moving over ground and excited-state potential surfaces (PESs). Molecules can move on a single PES (adiabatic pathway) or can cross over from one PES to another (nondiabatic pathways). For a full theoretical understanding Of a photodissociation mechanism, all of the important nonadiabatic and adiabatic pathway must be determined. This is not an easy task. We have developed an efficient computational method, called the global reaction route mapping (GRRM) strategy, that allows a, theoretical exploration of ground- and excited-state PESs and their crossing seams in an automatic manner. In this Perspective, we summarize our approaches and present examples of their application together with newly determined chemical insights. These include the complex photodissociation mechanism of the formaldehyde molecule,, the exclusive excited-state roaming dynamics of the nitrate radical, and all product channels and conformational memory in the photodissociation of the formic acid molecule. Finally, perspectives for the theoretical design of photofunctional molecules ate discussed.
  • Pooria Farahani, Satoshi Maeda, Joseph S. Francisco, Marcus Lundberg
    CHEMPHYSCHEM 16 1 181 - 190 2015年01月 [査読有り][通常論文]
     
    One route to break down halomethanes is through reactions with radical species. The capability of the artificial force-induced reaction algorithm to efficiently explore a large number of radical reaction pathways has been illustrated for reactions between haloalkanes (CX3Y; X=H, F; Y=Cl, Br) and ground-state ((2)sigma(+)) cyano radicals (CN). For CH3Cl+CN, 71 stationary points in eight different pathways have been located and, in agreement with experiment, the highest rate constant (10(8) s(-1)M(-1) at 298 K) is obtained for hydrogen abstraction. For CH3Br, the rate constants for hydrogen and halogen abstraction are similar (10(9) s(-1)M(-1)), whereas replacing hydrogen with fluorine eliminates the hydrogen-abstraction route and decreases the rate constants for halogen abstraction by 2-3 orders of magnitude. The detailed mapping of stationary points allows accurate calculations of product distributions, and the encouraging rate constants should motivate future studies with other radicals.
  • Mikhail N. Ryazantsev, Adeel Jamal, Satoshi Maeda, Keiji Morokuma
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 17 41 27789 - 27805 2015年 [査読有り][通常論文]
     
    Detailed kinetic models (DKMs) are the most fundamental "bottom-up'' approaches to computational investigation of the pyrolysis and oxidation of fuels. The weakest points of existing DKMs are incomplete information about the reaction types that can be involved in the potential energy surfaces (PESs) in pyrolysis and oxidation processes. Also, the computational thermodynamic parameters available in the literature vary widely with the level of theory employed. More sophisticated models require improvement both in our knowledge of the type of the reactions involved and the consistency of thermodynamic and kinetic parameters. In this paper, we aim to address these issues by developing ab initio models that can be used to describe early stages of pyrolysis of C-1-C-3 hydrocarbons. We applied a recently developed global reaction route mapping (GRRM) strategy to systematically investigate the PES of the pyrolysis of C-1-C-3 hydrocarbons at a consistent level of theory. The reactions are classified into 14 reaction types. The critical points on the PES for all reactions in the network are calculated at the highly accurate UCCSD(T)-F12b/cc-pVTZ//UM06-2X/cc-pVTZ level of theory. The data reported in this paper can be used for first principle calculations of kinetic constants and for a subsequent study on modeling the evolution of the species from the reaction network of the pyrolysis and oxidation of C-1-C-3 hydrocarbons.
  • Yu Harabuchi, Tetsuya Taketsugu, Satoshi Maeda
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 17 35 22561 - 22565 2015年 [査読有り][通常論文]
     
    Minimum energy conical intersection (MECI) geometries were searched for polycyclic aromatic hydrocarbons (PAHs) consisting of up to 26 atoms. The energy barriers to the obtained MECIs showed a correlation with their fluorescence quantum yields. This provides a theoretical rationale for the size dependence of the fluorescence quantum yields seen in these PAHs.
  • Mikhail N. Ryazantsev, Adeel Jamal, Satoshi Maeda, Keiji Morokuma
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 17 41 27789 - 27805 2015年 [査読有り][通常論文]
     
    Detailed kinetic models (DKMs) are the most fundamental "bottom-up'' approaches to computational investigation of the pyrolysis and oxidation of fuels. The weakest points of existing DKMs are incomplete information about the reaction types that can be involved in the potential energy surfaces (PESs) in pyrolysis and oxidation processes. Also, the computational thermodynamic parameters available in the literature vary widely with the level of theory employed. More sophisticated models require improvement both in our knowledge of the type of the reactions involved and the consistency of thermodynamic and kinetic parameters. In this paper, we aim to address these issues by developing ab initio models that can be used to describe early stages of pyrolysis of C-1-C-3 hydrocarbons. We applied a recently developed global reaction route mapping (GRRM) strategy to systematically investigate the PES of the pyrolysis of C-1-C-3 hydrocarbons at a consistent level of theory. The reactions are classified into 14 reaction types. The critical points on the PES for all reactions in the network are calculated at the highly accurate UCCSD(T)-F12b/cc-pVTZ//UM06-2X/cc-pVTZ level of theory. The data reported in this paper can be used for first principle calculations of kinetic constants and for a subsequent study on modeling the evolution of the species from the reaction network of the pyrolysis and oxidation of C-1-C-3 hydrocarbons.
  • Yu Harabuchi, Tetsuya Taketsugu, Satoshi Maeda
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 17 35 22561 - 22565 2015年 [査読有り][通常論文]
     
    Minimum energy conical intersection (MECI) geometries were searched for polycyclic aromatic hydrocarbons (PAHs) consisting of up to 26 atoms. The energy barriers to the obtained MECIs showed a correlation with their fluorescence quantum yields. This provides a theoretical rationale for the size dependence of the fluorescence quantum yields seen in these PAHs.
  • Satoshi Maeda, Yu Harahuchi, Tetsuya Taketsugu, Keiji Morokuma
    JOURNAL OF PHYSICAL CHEMISTRY A 118 51 12050 - 12058 2014年12月 [査読有り][通常論文]
     
    Locating accessible conical intersections (CIs), especially minimum energy CI (MECI) structures, near the Franck-Condon (FC) region is one of the most important tasks in theoretical analyses of photoreactions. Many MECIs may exist around a FC point in molecules with many vibrational degrees of freedom. Usually, MECIs are optimized one by one starting from arbitrary chosen initial structures. In order to eliminate the arbitrariness, we have developed automated MECI search methods. In this paper, a new approach is described. It combines the seam model function approach with the recently proposed single-component artificial force induced reaction method. Starting from a FC point, the present method finds MECIs systematically. It requires neither a Hessian nor a derivative coupling vector. In an example of the automated search, the spin-flip TDDFT was employed as an efficient electronic structure calculation method, which, together with an automated algorithm to recognize proper electronic states, allowed for evaluation of energy and gradient in a black-box fashion. The present approach was tested with trans- and cis-1,3-butadiene, thymine, and coumarin molecules. The usefulness of the present approach was demonstrated by comparing obtained MECIs with those in the literature. It is hoped that the present technique will be useful in exploration of unknown photoreaction pathways.
  • Satoshi Maeda, Tetsuya Taketsugu, Keiji Morokuma, Koichi Ohno
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 87 12 1315 - 1334 2014年12月 [査読有り][通常論文]
     
    This article gives a comprehensive review of the anharmonic downward distortion following (ADDF) method. The ADDF method has been developed as an automated reaction path search method. This method follows the anharmonic downward distortion (ADD) toward transition states and dissociation channels starting from a local minimum on the potential energy surface (PES). Systematic applications of the ADDF method to all local minima provide a global network of reaction pathways on the PES of given chemical formulas. Various extensions have been proposed and applied to many interesting chemical problems such as elucidation of photodissociation mechanisms, structure prediction of H-bonded clusters, mechanistic studies of organometallic catalysis, design of generation-conversion routes of amino acid molecules, and so on. It has also been employed in efficient construction of anharmonic PESs for highly accurate vibrational analysis. These developments and applications are illustrated with some representative results.
  • Miho Isegawa, Fengyi Liu, Satoshi Maeda, Keiji Morokuma
    JOURNAL OF CHEMICAL PHYSICS 141 15 2014年10月 [査読有り][通常論文]
     
    We report reaction paths starting from N(D-2) + H2O for doublet spin states, D-0 and D-1. The potential energy surfaces are explored in an automated fashion using the global reaction route mapping strategy. The critical points and reaction paths have been fully optimized at the complete active space second order perturbation theory level taking all valence electrons in the active space. In addition to direct dissociation pathways that would be dominant, three roaming processes, two roaming dissociation, and one roaming isomerization: (1) H2ON -> H-O(H)N -> H-HON -> NO((2)Pi) + H-2, (2) cis-HNOH. HNO-H -> H-HNO -> NO + H-2, (3) H2NO -> H-HNO -> HNO-H -> trans-HNOH, are confirmed on the D-0 surface. (C) 2014 AIP Publishing LLC.
  • Gen Luo, Yi Luo, Satoshi Maeda, Jingping Qu, Zhaomin Hou, Koichi Ohno
    ORGANOMETALLICS 33 14 3840 - 3846 2014年07月 [査読有り][通常論文]
     
    Methyltrioxorhenium (MTO)-catalyzed transfer of a methylene group to styrene has been computationally found to preferably follow a stepwise mechanism to give phenylcyclopropane via formation of a pseudo-metallacyclic intermediate and subsequent alkylative cyclization. The present result serves as the first theoretical evidence for d(0) transition metal mediated transfer of methylene as a terminal form rather than a metal carbene or carbenoid fashion, accompanied by the cleavage of a H2C=O double bond. The mechanism presented here is in contrast to the carbenoid or metal carbene promoted methylene transfer and to the MTO-catalyzed isoelectronic atom (group) transfer in MeRe(O)(2)(eta(2)-O-NH) or MeRe(O)(2)(eta(2)-O-O). This study not only enriches the chemistry of olefin cyclopropanation and the MTO-catalyzed group (atom) transfer event but also sheds new light on the reaction chemistry of formaldehyde.
  • Miho Isegawa, Fengyi Liu, Satoshi Maeda, Keiji Morokuma
    JOURNAL OF CHEMICAL PHYSICS 140 24 2014年06月 [査読有り][通常論文]
     
    Photodissociation pathways of nitromethane following pi -> pi* electronic excitation are reported. The potential energy surfaces for four lowest singlet states are explored, and structures of many intermediates, dissociation limits, transition states, and minimum energy conical intersections were determined using the automated searching algorism called the global reaction route mapping strategy. Geometries are finally optimized at CASSCF(14e, 11o) level and energies are computed at CAS(14o, 11e) PT2 level. The calculated preferable pathways and important products qualitatively explain experimental observations. The major photodissociation product CH3 and NO2 (B-2(2)) is formed by direct dissociation from the S-1 state. Important pathways involving S-1 and S-0 states for production of various dissociation products CH3NO + O (D-1), CH3O((XE)-E-2) + NO (X-2 Pi), CH2NO + OH, and CH2O + HNO, as well as various isomerization pathways have been identified. Three roaming processes also have been identified: the O atom roaming in O dissociation from CH3NO2, the OH radical roaming in OH dissociation from CH2N(O)(OH), and the NO roaming in NO dissociation from CH3ONO. (C) 2014 AIP Publishing LLC.
  • Hiroaki Tokoyama, Hideo Yamakado, Satoshi Maeda, Koichi Ohno
    CHEMISTRY LETTERS 43 5 702 - 704 2014年05月 [査読有り][通常論文]
     
    Huge numbers of structures, 7000 isomers and 26229 transition structures, have been searched for C6H6 in quantum chemical calculations by using a GRRM/SCC-DFTB program. The stability of benzene is outstanding. At B3LYP/6-311G(d,p) level, no isomers are found in a wide energy range of 260 kJ mol(-1) above the energy of benzene, except for fulvene at 148 kJ mol(-1). Other isomers are distributed between 260-1250 kJ mol(-1). Thirty experimentally known isomers are found in the energy range below ca. 600 kJ mol(-1).
  • Satoshi Maeda, Miho Hatanaka, Ryohei Uematsu, Tetsuya Taketsugu, Keiji Morokuma
    JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN 72 5 567 - 579 2014年05月 [査読有り][通常論文]
     
    Theory has become one of important tools in synthetic organic chemistry. The transition state (TS) of chemical reactions can be visualized by geometry optimizations. This helps to design novel reactions. However, there has been a serious problem. That is, how to prepare initial structures for all relevant TSs. An optimization starting from a bad structure fails to converge. Moreover, geometry optimization cannot find unexpected TSs. The latter prohibits reliable analysis and prediction of mechanisms in highly complicated, multistep reactions. In order to solve this problem, we have developed automated reaction path search methods. In this paper, the artificial force induced reaction (AFIR) method and some examples of its applications are described. The AFIR method would expand applicability of theory dramatically.
  • Guixiang Zeng, Satoshi Maeda, Tetsuya Taketsugu, Shigeyoshi Sakaki
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 53 18 4633 - 4637 2014年04月 [査読有り][通常論文]
     
    Main-group-element catalysts are a desirable alternative to transition-metal catalysts because of natural abundance and cost. However, the examples are very limited. Catalytic cycles involving a redox process and E-ligand cooperation (E=main-group element), which are often found in catalytic cycles of transition-metal catalysts, have not been reported. Herein theoretical investigations of a catalytic hydrogenation of azobenzene with ammonia-borane using a trivalent phosphorus compound, which was experimentally proposed to occur through P-III/P-V redox processes via an unusual pentavalent dihydridophosphorane, were performed. DFT and ONIOM(CCSD(T):MP2) calculations disclosed that this catalytic reaction occurs through a P-O cooperation mechanism, which resembles the metal-ligand cooperation mechanism of transition-metal catalysts.
  • Min Gao, Andrey Lyalin, Satoshi Maeda, Tetsuya Taketsugu
    JOURNAL OF CHEMICAL THEORY AND COMPUTATION 10 4 1623 - 1630 2014年04月 [査読有り][通常論文]
     
    A new theoretical approach to find metal-cluster-catalyzed single bond activation pathways is introduced. The proposed approach combines two automated reaction path search techniques: the anharmonic downward distortion following (ADDF) and the artificial force induced reaction (AFIR) methods, developed in our previous works [Maeda, S.; Ohno, K.; Morokuma, K. Phys. Chem. Chem. Phys. 2013, IS, 3683-3701]. A simple model reaction of the H-H bond activation catalyzed by Au-n (n = 7,8) clusters is considered as an example. We have automatically found 33 and 20 transition-state (TS) structures for H-2 dissociation on Au-7 and Au-8 clusters, respectively, and successfully identified the best dissociation pathways with the lowest barrier. Systematic analysis of the structure-dependent reactivity of small gold clusters is performed. It is demonstrated that the most stable structures of the gold clusters are not always highly reactive and several isomeric structures must be taken into account for adequate description of the reaction rates at finite temperatures. The proposed approach can serve as a promising tool for investigation of the chemical reactions catalyzed by small metal clusters.
  • Yu Harabuchi, Satoshi Maeda, Tetsuya Taketsugu, Koichi Ohno
    CHEMISTRY LETTERS 43 2 193 - 195 2014年02月 [査読有り][通常論文]
     
    A direct reaction pathway for water gas shift reaction (WGSR) in gas phase, H2O + CO -> H-2 + CO2, was discovered by using anharmonic downward distortion following method. The direct WGSR is accompanied by a roaming-like mechanism. To examine the initial conditions of the direct WGSR, we carried out ab initio molecular dynamics simulations and showed that cooperative excitations of OH-stretching vibrational modes and the orientational control of reactants are required for the direct WGSR.
  • Miho Isegawa, Satoshi Maeda, Dean J. Tantillo, Keiji Morokuma
    CHEMICAL SCIENCE 5 4 1555 - 1560 2014年 [査読有り][通常論文]
     
    Application of the Artificial Force Induced Reaction (AFIR) method to the prediction of cyclization/rearrangement pathways for carbocation precursors to sesquiterpenes is described. This method captures many of the features revealed in previous studies as well as new ones, including a pathway to a sesquiterpene not yet isolated in nature that we suspect will be isolated in time.
  • Ryohei Uematsu, Satoshi Maeda, Tetsuya Taketsugu
    CHEMISTRY-AN ASIAN JOURNAL 9 1 305 - 312 2014年01月 [査読有り][通常論文]
     
    A systematic search for reaction pathways for the vinylogous Mannich-type reaction was performed by the artificial force induced reaction method. This reaction affords -amino--butenolide in one pot by mixing 2-trimethylsiloxyfuran, imine, and water under solvent-free conditions. Surprisingly, the search identified as many as five working pathways. Among them, two concertedly produce anti and syn isomers of the product. Another two give an intermediate, which is a regioisomer of the main product. This intermediate can undergo a retro-Mannich reaction to give a pair of intermediates: an imine and 2-furanol. The remaining pathway directly generates this intermediate pair. The imine and 2-furanol easily react with each other to afford the product. Thus, all of these stepwise pathways finally converge to give the main product. The rate-determining step of all five (two concerted and three stepwise) pathways have a common mechanism: concerted SiO bond formation through the nucleophilic attack of a water molecule on the silicon atom followed by proton transfer from the water molecule to the imine. Therefore, these five pathways have comparable barriers and compete with each other.
  • Satoshi Maeda, Tetsuya Taketsugu, Keiji Morokuma
    JOURNAL OF COMPUTATIONAL CHEMISTRY 35 2 166 - 173 2014年01月 [査読有り][通常論文]
     
    Finding all required transition state (TS) structures is an important but hard task in theoretical study of complex reaction mechanisms. In the present article, an efficient automated TS search method, artificial force induced reaction (AFIR), was extended to intramolecular reactions. The AFIR method has been developed for intermolecular associative pathways between two or more reactants. Although it has also been applied to intramolecular reactions by dividing molecules manually into fragments, the fragmentation scheme was not automated. In this work, we propose an automated fragmentation scheme. Using this fragmentation scheme and the AFIR method, a fully automated search algorithm for intramolecular pathways is introduced. This version for intramolecular reactions is called single-component AFIR (SC-AFIR), to distinguish it from multicomponent AFIR for intermolecular reactions. SC-AFIR was tested with two reactions, the Claisen rearrangement and the first step of cobalt-catalyzed hydroformylation, and successfully located all important pathways reported in the literature. (c) 2013 Wiley Periodicals, Inc.
  • Wen Piao, Satoru Tsuda, Yuji Tanaka, Satoshi Maeda, Fengyi Liu, Shodai Takahashi, Yu Kushida, Toru Komatsu, Tasuku Ueno, Takuya Terai, Toru Nakazawa, Masanobu Uchiyama, Keiji Morokuma, Tetsuo Nagano, Kenjiro Hanaoka
    Angewandte Chemie - International Edition 52 49 13028 - 13032 2013年12月02日 [査読有り][通常論文]
     
    Let it shine: New hypoxia-sensitive fluorescent probes were developed they consist of a rhodamine moiety with an azo group directly conjugated to the fluorophore. Because of an ultrafast conformational change around the N=N bond, the compounds are nonfluorescent under normoxia. However, under hypoxia, the azo group is reduced, and a strongly fluorescent rhodamine derivative is released. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • Satoshi Maeda, Tetsuya Taketsugu, Keiji Morokuma
    ZEITSCHRIFT FUR PHYSIKALISCHE CHEMIE-INTERNATIONAL JOURNAL OF RESEARCH IN PHYSICAL CHEMISTRY & CHEMICAL PHYSICS 227 9-11 1421 - 1433 2013年11月 [査読有り][通常論文]
     
    The present study demonstrates a priori prediction of the mechanism of Paterno-Buchi (PB) reaction by automated search for reaction pathways using the artificial force induced reaction (AFIR) method, for the simplest set of reactants, H2CO + C2H4. The search found all previously suggested pathways automatically without using any guess about the reaction mechanism. Even the reaction product was not assumed. In addition, a comprehensive view of the reaction path network obtained in the present extensive search gave new insights into the mechanism. Barriers on excited states explained the preference of the initial bonding sites. A seam of crossing between the lowest triplet and first singlet excited state is suggested to make a significant contribution to an intersystem crossing and the reaction mechanism of the present system.
  • Yu Harabuchi, Satoshi Maeda, Tetsuya Taketsugu, Noriyuki Minezawa, Keiji Morokuma
    JOURNAL OF CHEMICAL THEORY AND COMPUTATION 9 9 4116 - 4123 2013年09月 [査読有り][通常論文]
     
    Automated search for minimum energy conical intersection geometries between the lowest two singlet states (S-0/S-1-MECIs) was performed by combining the anharmonic downward distortion following (ADDF) method, the seam model function (SMF) approach, and the spin-flip (SF) TDDFT method. SMF/ADDF has been employed previously in automated searches for MECIs on potential energy surfaces (PESs) with expensive multireference methods. In this work, we adopt the SF-TDDFT method that enables efficient optimization of S-0/S-1-MECIs in the framework of TDDFT. To evaluate the performance of the present approach, it was applied to ethylene and 1,3-butadiene. The present method automatically gave unknown S-0/S-1-MECIs as well as all previously reported ones. Therefore, the present hybrid method of SMF/ADDF and SF-TDDFT is shown to be a promising approach to locate S-0/S-1-MECIs of large systems automatically with modest computational costs.
  • Hongyan Xiao, Satoshi Maeda, Keiji Morokuma
    JOURNAL OF PHYSICAL CHEMISTRY A 117 32 7001 - 7008 2013年08月 [査読有り][通常論文]
     
    The mechanism of various photodissociation channels of ketene involving the three lowest singlet states (S-0, S-1, and S-2) and the three lowest triplet states (T-1, T-2, and T-3) was investigated by means of the (MS-)CAS(8e,8o)PT2/6-31+G* method. Stationary structures, i.e., global minima (GMs), local minima (LMs), transition states (TSs), minimum energy conical intersections (MECIs), and minima on seam of crossing (MSXs), were explored systematically by the global reaction route mapping (GRRM) strategy. On the basis of these structures, we discussed related dissociation channels starting from S2 that have been studied experimentally with 193-215 nm excitation wavelength. Five working pathways were found for relaxation to the low-lying S-0, S-1, and T-1 potential energy surfaces (PESs) from the Franck-Condon region of S-2, and the relaxation is expected to occur very quickly. On these low-lying states, five dissociation channels are open: three CH2 + CO channels for different CH2 electronic states, H + HCCO, and H-2 + C2O. Pathways for all of these five channels were identified and discussed, including new minor paths leading to H-2 + C2O.
  • Miho Hatanaka, Satoshi Maeda, Keiji Morokuma
    Journal of Chemical Theory and Computation 9 7 2882 - 2886 2013年07月09日 [査読有り][通常論文]
     
    To predict the stereoselectivity of large and flexible reaction systems, structural sampling of many transition states (TSs) is required. We used an automated search method, the artificial force induced reaction (AFIR) method, for TS sampling and found 91 syn- and 73 anti-TSs for the diastereoselective C-C bond formation step of the aqueous lanthanide-catalyzed Mukaiyama aldol reaction. Among them 11 syn- and six anti-TSs are found to contribute significantly to the diastereomeric ratio at room temperature. © 2013 American Chemical Society.
  • Hongyan Xiao, Satoshi Maeda, Keiji Morokuma
    JOURNAL OF PHYSICAL CHEMISTRY A 117 28 5757 - 5764 2013年07月 [査読有り][通常論文]
     
    Various photodissociation pathways of methylamine involving the three lowest electronic states, namely, singlet ground S-0 state, singlet first excited S-1 state, and triplet ground T-1 state, were studied by the (MS-)CAS(8e,8o)PT2/6-31++G** method. All critical points, i.e., minima, transition states, minimum energy conical intersections, and minima on the seam of crossing, were explored systematically by the global reaction route mapping (GRRM) strategy utilizing the anharmonic downward distortion following (ADDF) and artificial force induced reaction (AFIR) methods. On the basis of obtained structures, we discuss the photodissociation mechanism of methylamine in the experimental excitation wavelength range 222-240 nm in detail. Especially, the T-1 potential energy surface was explored systematically for the first time. The N-H bond rupture is a primary channel on the S-1 state. Along the N-H dissociation path on S-1, there is a low-energy conical intersection (CI), and through this CI the system can go back to the S-0 state; from the CI the system can directly dissociate to CH3NH + H or reproduce the original CH3NH2 on S-0. There is a seam of crossing between S-0 and T-1 in a partially dissociated CH3-NH2 geometry, and through this seam the system may go up to the T-1. On the T-1 state, a roaming-like pathway giving CH4 + NH (X-3 Sigma(-)) products was found, which would explain the recently proposed intersystem crossing mediated roaming dynamics.
  • P. S. Krstic, J. P. Allain, C. N. Taylor, J. Dadras, S. Maeda, K. Morokuma, J. Jakowski, A. Allouche, C. H. Skinner
    PHYSICAL REVIEW LETTERS 110 10 2013年03月 [査読有り][通常論文]
     
    Lithium wall conditioning has lowered hydrogenic recycling and dramatically improved plasma performance in many magnetic-fusion devices. In this Letter, we report quantum-classical atomistic simulations and laboratory experiments that elucidate the roles of lithium and oxygen in the uptake of hydrogen in amorphous carbon. Surprisingly, we show that lithium creates a high oxygen concentration on a carbon surface when bombarded by deuterium. Furthermore, surface oxygen, rather than lithium, plays the key role in trapping hydrogen. DOI: 10.1103/PhysRevLett.110.105001
  • Bina Fu, Joel M. Bowman, Hongyan Xiao, Satoshi Maeda, Keiji Morokuma
    Journal of Chemical Theory and Computation 9 2 893 - 900 2013年02月12日 [査読有り][通常論文]
     
    We report new global potential energy surfaces (PESs) for the D0 and D1 states of NO3. The PESs are permutationally invariant fits to roughly 90 000 electronic energies (MS-CAS(17e,13o)PT2/aug-cc- pVTZ). Hundreds of thousands of quasiclassical trajectories are run from the D0 global minimum and one previously identified "roaming saddle point" as well as a roaming saddle point on D1, identified previously [Xiao, H. Maeda, S. Morokuma, K. J. Chem. Theory Comput. 2012, 8, 2600]. The calculations are done at a total energy of relevance to recent experiments where, together with theoretical analysis [Grubb, M. P. Warter, M. L. Xiao, H. Maeda, S. Morokuma, K. North, S. W. Science 2012, 335, 1075], point to roaming pathways to the O2+NO products on both D1 and D0. Detailed comparisons with experiment are made for the distributions of O2 vibrational and rotational states, the relative translational energy and the NO rotational states, and the NO v-j vector correlation. © 2012 American Chemical Society.
  • Satoshi Maeda, Koichi Ohno, Keiji Morokuma
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 15 11 3683 - 3701 2013年 [査読有り][通常論文]
     
    Global reaction route mapping (GRRM), a fully-automated search for all important reaction pathways relevant to a given purpose, on the basis of quantum chemical calculations enables systematic elucidation of complex chemical reaction mechanisms. However, GRRM had previously been limited to very simple systems. This is mainly because such calculations are highly demanding even in small systems when a brute-force sampling is considered. Hence, we have developed two independent but complementary methods: anharmonic downward distortion following (ADDF) and artificial force induced reaction (AFIR) methods. ADDF can follow reaction pathways starting from local minima on the potential energy surface (PES) toward transition structures (TSs) and dissociation channels. AFIR can find pathways starting from two or more reactants toward TSs for their associative reactions. In other words, ADDF searches for A -> X type isomerization and A -> X + Y type dissociation pathways, whereas AFIR finds A + B -> X (+ Y) type associative pathways. Both follow special paths called the ADDF path and the AFIR path, and these tend to pass through near TSs of corresponding reaction pathways, giving approximate TSs. Such approximate TSs can easily be re-optimized to corresponding true TSs by standard geometry optimizations. On the basis of these two methods, we have proposed practical strategies of GRRM. The GRRM strategies have been applied to a variety of chemical systems ranging from thermal-and photochemical-reactions in small systems to organometallic- and enzyme-catalysis, on the basis of quantum chemical calculations. In this perspective, we present an overview of the GRRM strategies and some results of applications. Their practical usage for systematic prediction is also discussed.
  • Satoshi Maeda, Erika Abe, Miho Hatanaka, Tetsuya Taketsugu, Keiji Morokuma
    JOURNAL OF CHEMICAL THEORY AND COMPUTATION 8 12 5058 - 5063 2012年12月 [査読有り][通常論文]
     
    Development of efficient methods for finding chemical reaction pathways has been one of the central subjects of theoretical chemistry. Recently, the artificial force induced reaction (AFIR) method enabled automated search for associative reaction pathways between multiple reactant molecules and has been applied to reactions involving a few tens of atoms. To expand its applicability to large systems, we combined it with the geometrical microiteration technique. With this extension, full optimization of transition state structures of enzymatic reactions in the protein became possible within the QM/MM framework. Performance of the microiteration-AFIR method was tested for a single water catalyzed Aldol reaction in (H2O)(299) cluster and for an enzymatic reaction of the isopenicillin N synthase, where the potential energy surfaces were calculated by the ONIOM(QM/MM) method. These numerical tests demonstrated that the present method is promising in predicting reaction pathways that take place within an active site (consisting of tens of atoms) in a very large environment such as protein and solution.
  • Predrag S. Krstic, Jean Paul Allain, Alain Allouche, Jacek Jakowski, Jonny Dadras, Chase N. Taylor, Zhangcan Yang, Keiji Morokuma, Satoshi Maeda
    FUSION ENGINEERING AND DESIGN 87 10 1732 - 1736 2012年10月 [査読有り][通常論文]
     
    Chemistry as well as sputtering and reflection dynamics of lithiated carbon material, bombarded by slow hydrogen atoms are studied. We present a realistic method for computational simulation of the dynamics of the polar Li-C-O-H material dynamics. It is based on an approximate, semi-empirical quantum mechanics of electrons and classical mechanics of nuclei. Results are validated qualitatively by comparison with experiments and with a first principle DFT computations. In particular, we explain observed details of the hydrogen bonding chemistry in lithiated carbon, showing that incoming hydrogen interacts preferably with Li-C rather than C structures. (C) 2011 Elsevier B.V. All rights reserved.
  • Hongyan Xiao, Satoshi Maeda, Keiji Morokuma
    JOURNAL OF CHEMICAL THEORY AND COMPUTATION 8 8 2600 - 2605 2012年08月 [査読有り][通常論文]
     
    We report analytical global potential energy surfaces (PESs) for three low-lying doublet states (D-0, D-1, and D-2) of NO3. The fits are made on roughly 74000 MS-CAS(17e,13o)PT2/aug-cc-pVTZ calculations of electronic energies, where these PESs are invariant of permutations of oxygen atoms. The surfaces describe two roaming pathways for NO3 -> NO2-O -> NO + O-2 involving different electronic states discovered in the photolysis of NO3 [Xiao, H. Y. et al. J Phys. Chem. Lett 2011, 2, 934]. These pathways become accessible at excess energy of similar to 210 kJ/mol above the ground-state global minimum of NO3. The ab initio data below 360 kJ/mol are reproduced very well by the fitted PESs with the fitting rms errors of less than 5.5 kJ/mol for all the three states. Moreover, key local minima and energy profiles along the roaming pathways on the fitted PESs are compared with those on the ab initio PESs. In addition, potential contour maps in the roaming region are also compared These careful evaluations of the fitted PESs suggest that the present fitted PESs are well suited for future dynamics calculations of this system.
  • Satoshi Maeda, Tetsuya Taketsugu, Keiji Morokuma
    JOURNAL OF PHYSICAL CHEMISTRY LETTERS 3 14 1900 - 1907 2012年07月 [査読有り][通常論文]
     
    To elucidate the photodissociation mechanism of HCOOH, we systematically explored reaction pathways starting from the first excited singlet state (S-1) by using automated reaction path search methods. All critical points, that is, minima, transition states, minimum energy conical intersections, and minima on seam of crossing, for the S-0, T-1, and S-1 potential energy surfaces (PESs) obtained in the present search were optimized at the CASPT2 level. The structure list obtained by the search explained all experimentally reported photolytic channels. A new mechanism for the previously suggested but unexplained conformational memory in the 193 nm photolysis is proposed, which involves two steps: partial dissociation and succeeding roaming of one of H atoms on the S-1 PES, followed by intramolecular recombination on the S-0 PES after radiationless transition through a conical intersection at a partially dissociated geometry. This is partially similar to the excited-state roaming recently discovered for the NO3 radical.
  • Michael P. Grubb, Michelle L. Warter, Hongyan Xiao, Satoshi Maeda, Keiji Morokuma, Simon W. North
    SCIENCE 335 6072 1075 - 1078 2012年03月 [査読有り][通常論文]
     
    Roaming mechanisms have recently been observed in several chemical reactions alongside trajectories that pass through a traditional transition state. Here, we demonstrate that the visible light-induced reaction NO3 -> NO + O-2 proceeds exclusively by roaming. High-level ab initio calculations predict specific NO Lambda doublet propensities (orientations of the unpaired electron with respect to the molecular rotation plane) for this mechanism, which we discern experimentally by ion imaging. The data provide direct evidence for roaming pathways in two different electronic states, corresponding to both previously documented photolysis channels that produce NO + O-2. More broadly, the results raise intriguing questions about the overall prevalence of this unusual reaction mechanism.
  • Satoshi Maeda, Keiji Morokuma
    JOURNAL OF CHEMICAL THEORY AND COMPUTATION 8 2 380 - 385 2012年02月 [査読有り][通常論文]
     
    Toward systematic prediction of reaction pathways in complex chemical reaction systems by quantum chemical calculations, a new automatic reaction path search approach has been proposed on the basis of the artificial force induced reaction (AFIR) method [J. Chem. Theory Comput. 2011, 7, 2335-2345.]. We demonstrate in this Letter that this approach enabled semiautomatic determination of the full catalytic cycle of the HCo(CO)(3)-catalyzed hydroformylation. The search was fully systematic; no initial guess was required concerning the entire reaction mechanism as well as each transition-state structure. This approach opens the door to nonempirical prediction of complex reaction mechanisms involving multiple steps in multiple pathways, such as full cycles of catalytic reactions.
  • Yoshiyuki Matsuda, Kunihito Hoki, Satoshi Maeda, Ken-ichi Hanaue, Keisuke Ohta, Keiji Morokuma, Naohiko Mikami, Asuka Fujii
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 14 2 712 - 719 2012年 [査読有り][通常論文]
     
    Ionization dynamics of acetone and its dimer in supersonic jets is investigated by a combination of experimental and theoretical techniques, both of which have recently been developed. In experiments, the neutral and the cationic structures are explored by infrared predissociation spectroscopy with the vacuum-ultraviolet photoionization detection schemes. Reaction paths following the one-photon ionization of the acetone monomer and its dimer have been studied by the joint use of several theoretical methods including the ab initio molecular dynamics, the global reaction route mapping, the intrinsic reaction coordinate, and the artificial force induced reaction calculations. Upon one-photon ionization, the dimer isomerizes to the H-bonded form, in which the enol cation of acetone is bound to the neutral molecule, while this enolization is energetically forbidden in the acetone monomer. The enolization of the dimer cation occurs through a two-step proton-transfer from the methyl group of the ionized moiety, and is catalyzed by the neutral moiety within the dimer cation.
  • Satoshi Maeda, Keiji Morokuma
    JOURNAL OF CHEMICAL THEORY AND COMPUTATION 7 8 2335 - 2345 2011年08月 [査読有り][通常論文]
     
    In these five decades, many useful tools have been developed for exploring quantum chemical potential energy surfaces. The success in theoretical studies of chemical reaction mechanisms has been greatly supported by these tools. However, systematic prediction of reaction mechanisms starting only from given reactants and catalysts is still very difficult. Toward this goal, we describe the artificial force induced reaction (AFIR) method for automatically finding reaction paths of type A + B -> X (+ Y). By imposing an artificial force to given reactants and catalysts, the method can find the reactive sites very efficiently. Further pressing by the artificial force provides approximate transition states and product structures, which can be easily reoptimized to the corresponding true ones. This procedure can be executed very efficiently just by minimizing a single function called the AFIR function. All important reaction paths can be found by repeating this cycle starting from many initial orientations. We also discuss perspectives of automated reaction path search methods toward the above goal.
  • Nicholas S. Shuman, Thomas M. Miller, Jeffrey F. Friedman, Albert A. Viggiano, Satoshi Maeda, Keiji Morokuma
    JOURNAL OF CHEMICAL PHYSICS 135 2 2011年07月 [査読有り][通常論文]
     
    The flowing afterglow technique of variable electron and neutral density attachment mass spectrometry (VENDAMS) has recently yielded evidence for a novel plasma charge loss process, electron catalyzed mutual neutralization (ECMN), i.e., A(+) + B- + e(-) -> A + B + e(-). Here, rate constants for ECMN of two polyatomic species (POCl3- and POCl2-) and one diatomic species (Br-2(-)) each with two monatomic cations (Ar+ and Kr+) are measured using VENDAMS over the temperature range 300 K-500 K. All rate constants show a steep negative temperature dependence, consistent with that expected for a three body process involving two ions and an electron. No variation in rate constants as a function of the cation type is observed outside of uncertainty; however, rate constants of the polyatomic anions (similar to 1 x 10(-18) cm(6) s(-1) at 300 K) are measurably higher than that for Br-2(-) [(5.5 +/- 2) x 10(-19) cm(6) s(-1) at 300 K]. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3605631]
  • Hongyan Xiao, Satoshi Maeda, Keiji Morokuma
    JOURNAL OF PHYSICAL CHEMISTRY LETTERS 2 9 934 - 938 2011年05月 [査読有り][通常論文]
     
    Roaming dynamics has been recognized as one of the key mechanisms in atmospheric and combustion processes. In this Letter, we report the first example of roaming dynamics that occurs on an excited-state potential energy surface. In the photodissociation of a nitrate radical, systematic CASPT2 reaction path search and DFT dynamics calculations show that the roaming dynamics occurs on the first excited doublet state (D(1)). The direct dissociation on D(1) gives the minor vibrationally cold O(2), while the indirect dissociation after the nonadiabatic transition to the ground doublet state (D(0)) produces the major vibrationally hot O(2); this proposal explains the recent experimental results.
  • Satoshi Maeda, Takashi Fujitomo, Takahiro Okabe, Shigeyuki Wakitani, Mutsumi Takagi
    Journal of Bioscience and Bioengineering 111 4 489 - 492 2011年04月 [査読有り][通常論文]
     
    Aiming for the clinical application of cartilage regeneration, a culture method for mesenchymal stem cells (MSCs) derived from human bone marrow to obtain scaffold-free cartilage-like disk-shaped sheet of uniform sizes without the shrinkage was investigated. A disk-shaped cell sheet having the same diameter as that of the membrane without the shrinkage was formed after the cultivation of MSCs (18.6×105cells/well) for 3weeks in a cell culture insert (CCI) containing a flat membrane whose porosity was 12%, while 6.2 and 31.0×105MSCs/well, respectively, resulted in the shrinkage of the aggregate and the hole formation in the center part of the sheet. Cell aggregates shrunk also in a 96-well plate and CCIs having lower porosity. The disk-shaped cell sheet showed the comparable thickness (1.2mm) and sulfated glycosaminoglycan (sGAG) density to those of the pellet formed in a pellet culture. The gene expression levels of aggrecan and type II collagen in the disk-shaped cell sheet were not lower than those in the pellet. In conclusion, the usage of CCI having 12% porosity and 18.6×105MSCs/well could avoid the shrinkage from the formation of the scaffold-free cartilage-like disk-shaped cell sheet. © 2010 The Society for Biotechnology, Japan.
  • Satoshi Maeda, Ryo Saito, Keiji Morokuma
    JOURNAL OF PHYSICAL CHEMISTRY LETTERS 2 8 852 - 857 2011年04月 [査読有り][通常論文]
     
    A new theoretical approach is proposed for finding automatically minimum structures on the seam of crossing (MSX) in reactions of type A + B -> X, where the artificial-force-induced reaction (AFIR) method is combined with the seam model function (SMF) approach. Its application to reactions between triplet dioxygen and unsaturated hydrocarbons provided many MSX structures. In addition to known ignition pathways, we discovered a pathway through a new type of MSX in the reaction of dioxygen with aromatic hydrocarbons; for benzene, this new pathway requires a lower energy than those of three known ignition pathways and is likely to be the most important. This demonstrates that the AFIR-SMF approach has the ability to discover unknown/unexpected MSX structures without prejudice for presumed pathways or mechanisms.
  • Koichi Ohno, Satoshi Maeda
    CHEMICAL PHYSICS LETTERS 503 4-6 322 - 326 2011年02月 [査読有り][通常論文]
     
    An efficient technique constructing anharmonic potential energy functions was applied to ab initio vibrational analysis of benzene. Anharmonic potentials including the 6-order terms, much higher than the full quartic force field, were automatically generated by a second-order algorithm using the scaled hypersphere search method, and vibrational calculations were performed at the level of VQDPT[1+ 2]. In comparison with previously reported anharmonic calculations, the present approach gave an excellent ab initio result for in-plane modes including the b(2u) so called Kekule mode. Characteristic properties of various approaches were discussed in connection with the anharmonic effects and the strong vibronic effects. (C) 2011 Elsevier B.V. All rights reserved.
  • Satoshi Maeda, Shinsuke Komagawa, Masanobu Uchiyama, Keiji Morokuma
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 50 3 644 - 649 2011年 [査読有り][通常論文]
  • Narayan C. Bera, Satoshi Maeda, Keiji Morokuma, Al A. Viggiano
    JOURNAL OF PHYSICAL CHEMISTRY A 114 50 13189 - 13197 2010年12月 [査読有り][通常論文]
     
    Proton affinity and fluoride affinity of nerve agent VX at all of its possible sites were calculated at the RI-MP2/cc-pVTZ//B3LYP/6-31G* and RI-MP2/aug-cc-pVTZ//B3LYP/6-31+G* levels, respectively. The protonation leads to various unique structures, with H(+) attached to oxygen, nitrogen, and sulfur atoms; among which the nitrogen site possesses the highest proton affinity of -Delta E similar to 251 kcal/mol, suggesting that this is likely to be the major product. In addition some H(2), CH(4) dissociation as well as destruction channels have been found, among which the CH(4) + [Et-O-P(=O)(Me)-S-(CH(2))(2)-N(+)(iPr)=CHMe] product and the destruction product forming Et-O-P(=O)(Me)-SMe + CH(2)=N(+)(iPr)(2) are only 9 kcal/mol less stable than the most stable N-protonated product. For fluoridization, the S-P destruction channel to give Et-O-P(=O)(Me)(F) + [S-(CH(2))(2)-N-(iPr)(2)](-) is energetically the most favorable, with a fluoride affinity of -Delta E similar to 44 kcal. Various F(-) ion-molecule complexes are also found, with the one having F(-) interacting with two hydrogen atoms in different alkyl groups to be only 9 kcal/mol higher than the above destruction product. These results suggest VX behaves quite differently from surrogate systems.
  • Rebeka Nadasdi, Gabor L. Zuegner, Maria Farkas, Sandor Dobe, Satoshi Maeda, Keiji Morokuma
    CHEMPHYSCHEM 11 18 3883 - 3895 2010年12月 [査読有り][通常論文]
     
    Pulsed laser photolysis (PLP) at lambda = 248 and 308 nm coupled with gas-chromatographic analysis is applied to determine the photodissociation quantum yield (QY) of methyl ethyl ketone (MEK). Temperature dependent UV absorption cross-sections [sigma MEK(lambda,T)] are also determined. At 308 nm, the QY decreases with decreasing temperature (T = 323-233 K) and with increasing pressure (P = 67-998 mbar synthetic air). Stern-Volmer (SV) analysis of the T and P dependent QYs provides the experimental estimate of E-S1 = 398 + 9 kJmol(-1) (= 300 + 6 nm) for the barrier of the first excited singlet state (S-1). The QY at 248 nm is close to unity and independent of pressure (T = 298 K). Theoretical reaction pathways are examined systematically on the basis of CASPT2/6-31 + G* calculations. Among three possible pathways, a S-1/S-0-diradical mechanism, which involves H atom transfer on the S-1 surface, followed by a nonadiabatic transition at a diradical isomer of MEK, explains the experimental data very well. Therefore, this unusual mechanism, which is not seen in any smaller carbonyl compounds, is proposed as an important pathway for the MEK dissociation. Our study supports the view that both the absorption cross-sections and the QYs of carbonyls have significant temperature dependences that should be taken into account for accurate modelling of atmospheric chemistry.
  • Satoshi Maeda, Yoshiyuki Matsuda, Shinichi Mizutani, Asuka Fujii, Koichi Ohno
    JOURNAL OF PHYSICAL CHEMISTRY A 114 44 11896 - 11899 2010年11月 [査読有り][通常論文]
     
    The dynamics on the vacuum-ultraviolet one-photon ionization or a formamide-water cluster is investigated by a combination of theoretical reaction-path search and infrared spectroscopic methods A keto-enol tautomerization of the formamide moiety occurs after photoionization by a catalylic action of the water molecule accompanied with its long-distance migration, the water molecule in the cluster migrates almost one turn around the formamide moiety During the migration, the water molecule abstracts the proton or CH in the formamide moiety and carries it to the O atom side in the carbonyl group through a "catch and release" -type catalytic action,
  • Shin-ya Ohno, Ken-ichi Shudo, Masatoshi Tanaka, Satoshi Maeda, Koichi Ohno
    JOURNAL OF PHYSICAL CHEMISTRY C 114 37 15671 - 15677 2010年09月 [査読有り][通常論文]
     
    Structural, energetic, and mechanistic features of the initial steps of the reaction of an O atom with Si(001)-(2 x 1) were modeled by the use of a Si(9)H(12) + O system. Transition state structures (TSs) and equilibrium structures (EQs) as well as dissociation channels (DCs) were systematically searched using a global reaction route mapping (GRRM) technique on the potential energy surface (PES) based on the scaled hypersphere search (SHS) algorithm. The first six low-energy structures were consistent with known structure models for oxygen adsorption on the dimer of Si(001)-(2 x 1). Other structures with higher energies could be well interpreted as intermediates leading toward reaction paths for migration/dissociation occurring at high temperatures.
  • Satoshi Maeda, Keiji Morokuma
    JOURNAL OF CHEMICAL PHYSICS 132 24 2010年06月 [査読有り][通常論文]
     
    Search for transition structures (TSs) as first-order saddles is one of the most important tasks in theoretical study of chemical reaction. Although automated search has been established either by starting from a local minimum (MIN) or by connecting two MINs, there is no systematic method which can locate TSs of A+B -> X(+Y) type reactions starting from separated reactants. We propose such an approach for the first time; it was demonstrated to work very well in the SN2, Diels-Alder, and Wittig reactions. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3457903]
  • Koichi Ohno, Satoshi Maeda
    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 324 1-2 133 - 140 2010年06月 [査読有り][通常論文]
     
    Anharmonic downward distortion (ADD) of potential energy surfaces (PES) indicates the direction of reaction routes, and the ADD-following on PES has made it possible to perform global reaction route mapping (GRRM) of a given chemical formula. The GRRM method based on the ADD-following can be applied to real processes of catalytic reactions to elucidate the reaction mechanisms. A systematic analysis of a RuHCl-BINAP-catalyzed asymmetric hydrogenation reaction has given an insight into the role of important adsorption structures and the chirality determining transition state among numerous candidates. Computed reaction profiles for the total catalytic cycles with and without protonation demonstrated significance of the protonation for both high enantioselectivity and high catalytic-activity. (C) 2010 Elsevier B.V. All rights reserved.
  • Satoshi Maeda, Koichi Ohno, Keiji Morokuma
    JOURNAL OF PHYSICAL CHEMISTRY LETTERS 1 12 1841 - 1845 2010年06月 [査読有り][通常論文]
     
    Structures of transition states (TSs) and minima on seam of crossing (MSXs) for potential energy surfaces (PESs) of acetone of the S-0, S-1 and T-1 states were explored. On the basis of the results, we propose a new mechanism, slow intersystem crossing from S-1 to T-1 without seam of crossing, followed by CH3 dissociation via a TS on T-1 this slow pathway will be overtaken by a more efficient S-1 pathway for higher energy. This is consistent with the observed long lifetime of the S-1 species. Moreover, four channels, including three new ones, were found to regenerate the ground state acetone from the S-1 PES, and they all may be involved in the roaming channel that has been proposed recently as a new route of CO generation in a 230 nm photolysis There are significant differences in MSX structures and energies between the present CASPT2 results and previous CASSCF results.
  • Satoshi Maeda, Koichi Ohno, Keiji Morokuma
    JOURNAL OF CHEMICAL THEORY AND COMPUTATION 6 5 1538 - 1545 2010年05月 [査読有り][通常論文]
     
    The conical intersections (Cis) form a (f-2)-dimensional hyperspace on which two diabatic potential energy surfaces (PESs) belonging to the same symmetry cross, where f is the internal degree of freedom. The branching plane (BP) is a (two-dimensional) plane defined by the difference gradient vector (DGV) and the coupling derivative vector (CDV), and on the BP, the degeneracy of the two adiabatic PESs is lifted. The properties of the BP are often used in the exploration of the conical intersection hyperspace, such as determination of the minimum energy CI or the first-order saddle point in Cl. Although both DGV and CDV are necessary to construct the BP in general, CDV is not always available depending on ab initio methods and programs. Therefore, we developed an approach for optimizing critical points on the Cl hypersurface without CDV by using a BP updating method, which was shown to be accurate and very useful for minimum energy and saddle point optimization and for the minimum energy path following within the Cl hypersurface in numerical tests for C(6)H(6) and C(5)H(8)N(+).
  • Anthony J. Midey, Thomas M. Miller, A. A. Viggiano, Narayan C. Bera, Satoshi Maeda, Keiji Morokuma
    ANALYTICAL CHEMISTRY 82 9 3764 - 3771 2010年05月 [査読有り][通常論文]
     
    Room temperature rate constants and product ion branching ratios have been measured for the reactions of numerous positive and negative ions with VX chemical warfare agent surrogates representing the amine (triethylamine) and organophosphonate (diethyl methythiomethylphosphonate (DEMTMP)) portions of VX. The measurements have been supplemented by theoretical calculations of the proton affinity, fluoride affinity, and ionization potential of VX and the simulants. The results show that many proton transfer reactions are rapid and that the proton affinity of VX is near the top of the scale. Many proton transfer agents should detect VX selectively and sensitively in chemical ionization mass spectrometers. Charge transfer with NO+ should also be sensitive and selective since the ionization potential of VX is small. The surrogate studies confirm these trends. Limits of detection for commercial and research grade CIMS instruments are estimated at 80 pptv and 5 ppqv, respectively.
  • Takeaki Iwamoto, Nobuyoshi Ohnishi, Zhenyu Gui, Shintaro Ishida, Hiroyuki Isobe, Satoshi Maeda, Koichi Ohno, Mitsuo Kira
    NEW JOURNAL OF CHEMISTRY 34 8 1637 - 1645 2010年 [査読有り][通常論文]
     
    Four isolable dialkylsilanimines R(2)(H)Si=NR (R = CH(2)Ph (5a), Ph (5b), 1-adamantyl (5c) and SiMe(3) (5d), where R(2)(H) = 1,1,4,4-tetrakis(trimethylsilyl)butane-1,4-diyl) were synthesized as air-sensitive crystals by the reaction of isolable dialkylsilylene 4 with the corresponding azides. X-ray analysis shows that 5a-5d are base-free silanimines and 5a and 5b have a remarkable bent Si=N-R structure, while 5c and 5d have an almost linear structure. Distinct pi(Si=N) -> pi*(Si=N) and n(N) -> pi*(Si=N) transition bands of silicon-nitrogen double bonds were observed for 5a-5d in hexane. A mechanism for the formation of silanimine from the reaction of silylene and azide is discussed using theoretical calculations with the GRRM method for model reactions.
  • Satoshi Maeda, Koichi Ohno, Keiji Morokuma
    JOURNAL OF CHEMICAL THEORY AND COMPUTATION 5 10 2734 - 2743 2009年10月 [査読有り][通常論文]
     
    The global reaction route mapping (GRRM) method enabled an automated and a systematic search for routes of chemical reactions on a potential energy surface based on the anharmonic downward distortion following (ADDF) approach [Chem. Phys. Lett. 2004, 384, 277]. On the other hand, the microiteration technique [Mol. Phys. 2006, 104, 701] has been developed for full optimizations of transition state (TS) structures for reactions/transformations in large flexible molecular systems and successfully used in ONIOM(OM:MM) calculations. In the present paper, combining the GRRM method with the microiteration technique, we developed a microiteration-ADDF (mu-ADDF) method for automated and systematic TS exploration of large flexible molecular systems. We showed that the method works well with two test systems, (H(2)CO)(H(2)O)(100) and Si(6)(C(12)H(17))(6), in the ONIOM(QM:MM) framework. It is noted that the present mu-ADDF method can be used for pure quantum mechanics (QM) or molecular mechanics (MM) systems (without ONIOM) and has been tested successfully in C(6)H(10)O pure QM calculations.
  • Masahiro Moteki, Satoshi Maeda, Koichi Ohno
    ORGANOMETALLICS 28 7 2218 - 2224 2009年04月 [査読有り][通常論文]
     
    Isomerization pathways of hexasilabenzene (Si6H6) were theoretically searched by using the anharmonic-downward-distortion-following (ADD-following) method, which is a recently established systematic and automatic transition-state (TS) finding method. The search revealed the lowest barrier from the six-membered-ring structure in hexasilabenzene, and the barrier height was computed to be only 74 kJ mol(-1). It follows that the six-membered ring in hexasilabenzene can easily be deformed via the TS structure. The present study identified three lower-lying TS structures around hexasilabenzene by the systematic search. These TS structures will be useful for designing a suitable substituent in a hexasilabenzene derivative for its isolation in the future, since such a substituent should be designed so that all TSs deforming the six-membered-ring backbone in a hexasilabenzene derivative are destabilized.
  • Yi Luo, Satoshi Maeda, Koichi Ohno
    JOURNAL OF COMPUTATIONAL CHEMISTRY 30 6 952 - 961 2009年04月 [査読有り][通常論文]
     
    Isomers of protonated water clusters H+(H2O)(n) (n = 5-7) have been explored on ab initio potential energy surfaces by means of the anharmonic downward distortion following algorithm. Totally, 9, 24, and 131 isomers for n = 5, 6, and 7, respectively, were located by the automatic exploration, and all of known important isomers previously reported by conventional geometry optimization approaches have been included in the present results. Moreover, structure transitions depending on n and temperature, which were observed by experimental studies, could be reproduced via thermodynamic simulation on the basis of the superposition approach and the present isomer sets. (C) 2008 Wiley Periodicals, Inc. J Comput Chem 30: 952-961, 2009
  • Peng Zhang, Satoshi Maeda, Keiji Morokuma, Bastiaan J. Braams
    JOURNAL OF CHEMICAL PHYSICS 130 11 2009年03月 [査読有り][通常論文]
     
    Accurate ab initio calculations using the multireference configuration interaction method have been performed to characterize the potential energy surfaces (PESs) of low-lying excited states (S-1 and T-1) of formaldehyde (H2CO) and hydroxymethylene (HCOH) with emphasis on their isomerization, dissociation, and the possible role of the T-1 state in the nonadiabatic photodissociation of H2CO. Two regions on the T-1 PES are found to contribute to the nonadiabatic transition to the ground (S-0) state. Three minima on the seam of crossing (MSXs), 80-85 kcal/mol (above the S-0 global minimum), are located in the HCOH region; they, however, are blocked by a high-energy isomerization transition state at similar to 107 kcal/mol. The other MSX discovered in the H2CO region is reachable with energy <= 91 kcal/mol and strong spin-orbit interaction; this may be a more important pathway for the T-1 to S-0 transition. A full-dimensional PES is generated for the T-1 state, fitted by a weighted least-squares method employing a many-body expansion in which each term is a function of the internuclear distances and is invariant under permutations of like atoms. The single global function covers the formaldehyde and the HCOH regions as well as dissociation pathways. The high quality of the fitted PES is demonstrated by the small root-mean-square fitting error of 119 cm(-1) and the close agreement between the critical points from ab initio calculations and from the fitted PES.
  • Satoshi Maeda, Koichi Ohno, Keiji Morokuma
    JOURNAL OF PHYSICAL CHEMISTRY A 113 9 1704 - 1710 2009年03月 [査読有り][通常論文]
     
    Automated global mapping of minimal energy points on seams of crossing (MSX structures) were performed by using the anharmonic downward distortion following (ADD-following) method, which has previously been applied to the single potential energy surfaces (PESs) to perform automated global reaction route mapping. In this study, the ADD-following is applied to a penalty function based on two PESs of different electronic states. The present approach is effective not only for crossing seams between states with different symmetry but also for conical intersections for states with the same symmetry. Many new MSX structures were discovered on the S-0/T-1 and S-1/T-1 crossing seams and the S-0/S-1 conical intersections of H2CO by automated global mapping using the ADD-following method. A possible pathway for dissociation of formaldehyde excited to S, at low energy is discussed.
  • Yi Luo, Satoshi Maeda, Koichi Ohno
    CHEMICAL PHYSICS LETTERS 469 1-3 57 - 61 2009年02月 [査読有り][通常論文]
     
    The reaction of formic acid with hydroxyl radical, which is considered to be relevant to atmospheric chemistry, has been extensively studied. A water-catalyzed process of this reaction is computationally studied here for the first time. The scaled hypersphere search method was used for global exploration of pre-reaction complexes. Calculations were performed at high level of theory, such as CCSD(T)/ccpVTZ//B3LYP/6-311+G(2df,2p) and CCSD(T)/cc-pVTZ//MP2/aug-cc-pVDZ. It is found that the water-catalyzed process of this reaction is more kinetically favorable than its non-catalytic process. Such catalytic process may also be of interest for atmospheric chemistry, like the non-catalytic one. (C) 2008 Elsevier B.V. All rights reserved.
  • Satoshi Maeda, Koichi Ohno
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 130 51 17228 - + 2008年12月 [査読有り][通常論文]
     
    A systematic search for transition state (TS) structures of the chirality-determining elementary step in a RUCl(2)-((R)-BINAP)-catalyzed asymmetric hydrogenation reaction was performed by using the anharmonic downward distortion following method. As many as 68 TS structures were found for the elementary step because of the complexity of its potential energy surface caused by the introduction of bulky ligands in BINAP for high selectivity. We were able to determine the lowest TS structures for each enantiomer among the 68 TSs, and one for the (R)-type product was found to be the more stable in agreement with the experiment, From a comparison of the lowest TSs for each enantiomer, a "lock-and-key" motif at the TS structure was discovered to be the origin of the high selectivity in the reaction.
  • Yi Luo, Satoshi Maeda, Koichi Ohno
    TETRAHEDRON LETTERS 49 48 6841 - 6845 2008年11月 [査読有り][通常論文]
     
    The B3LYP theory and scaled hypersphere search method are utilized to explore pathways of (HO)(2)PS2Cu-mediated CH3OOH decomposition, a model reaction of alkyl hydroperoxide with cuprous dialkyldithiophosphate [(RO)(2)PS2Cu]. It is found that the decomposition of CH3OOH mediated by the copper(I) complex may lead to formaldehyde and water molecules via O-O bond heterolysis and subsequent intramolecular hydrogen transfer, with retainment of the copper(I) complex. The subsequent hydrogen transfer event and formation of water may add new understanding to the (RO)(2)PS2Cu-mediated decomposition process of alkyl hydroperoxide. The oxygen transfer from CH3OOH to (HO)(2)PS2Cu moiety, as an O-O bond cleavage manner of CH3OOH, is also found to occur. (c) 2008 Elsevier Ltd. All rights reserved.
  • K. Ohno, S. Maeda
    PHYSICA SCRIPTA 78 5 2008年11月 [査読有り][通常論文]
     
    It has been a long standing problem to know all possible structures with a given set of atoms and their conversion channels. By noting anharmonic downward distortion of potential energy surfaces, reaction channels around a structure can be discovered as energy minima on a scaled hypersphere and traced by expanding the sphere size. The scaled hypersphere search (SHS) method enables us to find reaction channels one after another to explore the global reaction route map for a given atomic constituent. This account demonstrates some applications of the SHS method to the chirality control and the hydrogen migration near the dissociation limit.
  • Yu Watanabe, Satoshi Maeda, Koichi Ohno
    JOURNAL OF CHEMICAL PHYSICS 129 7 2008年08月 [査読有り][通常論文]
     
    Potential energy functions (PEFs) in the form of the sixth-order polynomial concerned with intramolecular motions of (H(2)O)(n) (n=2-5) were constructed by the scaled hypersphere search (SHS) based polynomial fitting (SHS-PF) method, in which the numbers of ab initio calculations can be considerably reduced via the selection of sampling directions by the SHS method. Concerning fundamental frequencies of the dimer cluster, the root mean square error from gas-phase experiments was only 10 cm(-1). For the trimer, tetramer, and pentamer, computed anharmonic frequencies reproduced available gas-phase experimental frequencies of HOH bending, donor-OH stretching, and free-OH stretching excellently with errors of approximately 10-20cm(-1) on average. It follows that the SHS-PF method is promising for highly accurate anharmonic vibrational analyses of intramolecular modes of H-bond clusters. (C) 2008 American Institute of Physics.
  • Mari Yokoyama, Hiroto Miwa, Satoshi Maeda, Shigeyuki Wakitani, Mutsumi Takagi
    Journal of Bioscience and Bioengineering 106 1 46 - 50 2008年07月 [査読有り][通常論文]
     
    Mesenchymal stem cells (MSCs) should be expanded in vitro while maintaining their multilineage potential before differentiation to one mesenchymal lineage for application to regeneration therapy. The effect of fetal calf serum (FCS) on undesirable differentiation during subcultivations for the expansion was investigated. The expression level of the aggrecan gene, which is a marker of chondrogenic differentiation, gradually and markedly increased during the subcultivations of MSCs with the addition of 10% FCS and without additional cytokines. The percentage of cells positive for CD90 and CD166, which are markers of MSCs, decreased, and the percentage of large polygonal cells and the average cell adhesion area increased during the expansion. There was a marked difference in the increase in the aggrecan expression level between the two expansion cultures employing different FCS lots, although their proliferation rates were almost the same. The decrease in FCS concentration resulted in a higher percentage of CD90+CD166+ cells, a lower percentage of large polygonal cells, and a lower level of aggrecan expression. Consequently, FCS components could stimulate MSC differentiation to chondrocytes and a lower concentration could decrease this differentiation. © 2008 The Society for Biotechnology, Japan.
  • Satoshi Maeda, Koichi Ohno
    CHEMICAL PHYSICS LETTERS 460 1-3 55 - 58 2008年07月 [査読有り][通常論文]
     
    The potential energy surface (PES) of H(2)CO has been revisited by the anharmonic downward distortion following algorithm, where an unrestricted ab initio method was employed during the automated exploration. Some structures previously reported on the PES of restricted theories were found to be open-shell species, and new local minima and first-order saddle points were discovered in high energy regions related to radical fragments which are important in high energy processes such as combustion. (C) 2008 Elsevier B. V. All rights reserved.
  • Yi Luo, Satoshi Maeda, Koichi Ohno
    JOURNAL OF PHYSICAL CHEMISTRY A 112 25 5720 - 5726 2008年06月 [査読有り][通常論文]
     
    The cuprous dialkyldithiophosphate [(RO)(2)PS2Cu, CuDDP] as an antioxidant has been industrially used in lubricating oil. In this paper, for the first time, a computational study has been carried out for CuDDP. The scaled hypersphere search method has been used to explore the isomerization and decomposition pathways of (HO)(2)PS2Cu, a model compound of CuDDP, and its reaction with CH3OO center dot radical. The calculations were performed at the B3LYP level of theory. The results show that the most stable structure of (HO)(2)PS2Cu has pseudo-C-2 nu, symmetry and a four-membered ring constructed by P, Cu, and two S atoms. The bondrearrangement isomerization leading to a (H)O-bridging structure is kinetically feasible. Three dissociation channels have been found for (HO)(2)PS2Cu, which require high energy (> 60 kcal/mol) under the investigated condition. The reaction of (HO)(2)PS2Cu with CH3OO center dot includes bond-rearrangement isomerization and the decomposition of CH3OO center dot moiety. The (HO)(2)PS2Cu-assisted CH3OO center dot decomposition occurs via its O-O bond cleavage or the C-O bond dissociation. The former decomposition manner has been computed to be preferable over the latter at low temperature, but calculations suggested for the latter decomposition manner at higher temperature. Such a decomposition reaction, which is endothermic but possible, may be related to the antioxidation process of CuDDP.
  • Satoshi Maeda, Koichi Ohno
    JOURNAL OF PHYSICAL CHEMISTRY A 112 13 2962 - 2968 2008年04月 [査読有り][通常論文]
     
    The scaled hypersphere search method was applied to ab initio potential energy surfaces of the H2S center dot(H2O)(n)/SH-center dot H3O+center dot(H2O)(n-1) system with n = 5-7. Local minima databases including 121, 326, and 553 structures for n = 5-7, respectively, were obtained based on calculations at the MP2/6-311++G(3df,2p)//B3LYP/631+G** level. In these small cluster sizes, the SH-center dot H3O+center dot H2O)(n-1) type is still unstable relative to the H2S center dot(H2O)(n) type, and the global minima for H2S center dot(H2O)(n-1) are very similar to those of pure water clusters of (H2O)(n+1). Thermodynamic simulations based on the present databases showed a structure transition from the wellmixed (H2O)(n+1)-like global minimum at low temperatures to unmixed complexes between H2S and (H2O)(n) at high temperatures.
  • Satoshi Maeda, Yu Watanabe, Koichi Ohno
    JOURNAL OF CHEMICAL PHYSICS 128 14 2008年04月 [査読有り][通常論文]
     
    A fitting method of the sixth-order potential energy function is proposed, where ab initio potential energy data for the fitting are sampled in directions containing maximal anharmonic downward distortions detected by the scaled hypersphere search (SHS) method. This technique has been applied to H2O, HCHO, HCOOH, C2H4, CH3OH, CH3CHO, CH3NH2, B2H6, (H2O)(2), and (H2O)(3), where, without using the symmetry, 176, 904, 1432, 2992, 2520, 2760, 3608, 6232, 768, and 1456 times single-point energy calculations, respectively, were required for obtaining anharmonic terms. Experimental IR peak positions of not only fundamentals but also overtones and combinations in the excitation energy range of 1000-4000 cm(-1) could be reproduced very accurately by the post-vibrational self-consistent field theory employing potential functions obtained by the present SHS based polynomial fitting method. (c) 2008 American Institute of Physics.
  • Satoshi Maeda, Koichi Ohno
    JOURNAL OF PHYSICAL CHEMISTRY A 111 50 13168 - 13171 2007年12月 [査読有り][通常論文]
     
    Automated exploration of adsorption structures of a molecule (CH3COCH2COOCH3) on an organometallic complex of (R)-RuH2-BINAP (BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl) has been performed by a combination of the ONIOM method and the scaled hypersphere search (SHS) method. As many as 135 potential minima have been obtained as candidates of adsorption structures. The most stable structure among the 135 is a precursor of the (R)-type product, which is about 30 kJ/mol more stable than the most stable structure among precursors of the (S)-type product. This unbiased search is theoretically showing the power of BINAP to distinguish (R)-type and (S)-type at the adsorption state. This result is in line with very high optical yield of the (R)-type product in the corresponding experiment.
  • Yi Luo, Satoshi Maeda, Koichi Ohno
    JOURNAL OF PHYSICAL CHEMISTRY A 111 42 10732 - 10737 2007年10月 [査読有り][通常論文]
     
    The structures of the protonated water cluster H+(H2O)(8) have been globally explored by the scaled hypersphere search method. On the Hartree-Fock potential energy surface 174 isomers were found, among which 168 were computed to be minima at the B3LYP/6-31+G** level, and their energies were further refined at the level of MP2/6-311++G(3df,2p). The global minimum on the potential energy surface computed at the B3LYP/6-31+G** level shows a cagelike structure with the "Eigen" motif, while the lowest-free-energy isomer has a five-membered-ring structure at 170 K and a chain form at 273 K. The present results are well in line with previous experimental findings. In addition, the, ADMP (atom-centered density matrix propagation) simulation indicates that the extra proton in the lowest-free-energy isomer ( 170 K), which has a five-membered ring and the "Zundel" feature, is often in an asymmetrical hydrogen bond.
  • Yu Watanabe, Satoshi Maeda, Koichi Ohno
    CHEMICAL PHYSICS LETTERS 447 1-3 21 - 26 2007年10月 [査読有り][通常論文]
     
    Dissociation and isomerization channels of C2H7+ and C3H9+ have been globally explored by the scaled hypersphere search (SHS) method, which discloses reaction routes in an automatic way by following the anharmonic downward distortion on the potential energy surfaces. New structures have been discovered in addition to all of reported ones. Branching ratios leading to C2H(5)(+) + CH4 -> C3H9+ -> C3H7+ + H-2 have been calculated based on microcanonical rate constants of all transition state structures elucidated by the SHS method. Generation of cyclic C3H7+ has been predicted to be responsible for this reaction in a certain collision energy range. (c) 2007 Elsevier B.V. All rights reserved.
  • Xia Yang, Satoshi Maeda, Koichi Ohno
    JOURNAL OF PHYSICAL CHEMISTRY A 111 23 5099 - 5110 2007年06月 [査読有り][通常論文]
     
    A detailed computational study is performed on the singlet potential energy surface (PES) for possible isomerization and dissociation reactions of CH3CHO at the DFT (B3LYP/6-311++G(d,p)) and CCSD(T)/cc-pVTZ//B3LYP/6-311++G(d,p) levels. The pathways around the equilibrium structures can be discovered by the scaled hypersphere search (SHS) method, which enables us to make a global analysis of the PES for a given chemical composition. Fourteen isomers inclusive of 11 single-molecules and three "non-stabilized" oxygen-based ylides, 5 energetically favored complexes, and 79 interconversion transition states have been found on the singlet PES. Four lowest lying isomers with thermodynamic stability are also kinetically stable with respect to metastable intermediates. It was revealed that vinyl alcohols, which could be generated by the tautomerization of acetaldehyde, could undergo dissociation to form acetylene and water. In addition, recombination channels between some fragments, such as H2CO + (CH2)-C-1 and (CHOH)-C-1 + (CH2)-C-1, are energetically accessible via collision complex or oxygen-based ylides. Most of available unimolecular decompositions are found to be responsible for favorable hydrogen abstraction processes.
  • Satoshi Maeda, Koichi Ohno
    JOURNAL OF PHYSICAL CHEMISTRY A 111 20 4527 - 4534 2007年05月 [査読有り][通常論文]
     
    The potential energy surface (PES) of water octamers has been explored by the scaled hypersphere search method. Among 164 minima on the PES (based on MP2/6-311++G(3df,2p)//B3LYP/6-311+G(d,p) calculations), the cubic structure with D-2d symmetry has been confirmed to be the global minimum. In a thermodynamic simulation using these 164 structures, the cubic structure with S-4 symmetry has the highest population at low temperature, though double rings can become dominant as temperature going up, in good accord with a recent Monte Carlo simulation using an empirical potential. A transition temperature from cubic to noncubic has significantly been underestimated when potential energy data of B3LYP/6-311+G(d,p) calculations are employed in the simulation. This serious discrepancy between the MP2 and the B3LYP results suggests an importance of dispersion interactions for discussions on thermodynamics of water octamers.
  • Takuya Horio, Satoshi Maeda, Naoki Kishimoto, Koichi Ohno
    JOURNAL OF PHYSICAL CHEMISTRY A 110 38 11010 - 11017 2006年09月 [査読有り][通常論文]
     
    Ionic-state-resolved collision energy dependence of Penning ionization cross sections for OCS with He*-(2(3)S) metastable atoms was measured in a wide collision energy range from 20 to 350 meV. Anisotropic interaction potential for the OCS-He*(2(3)S) system was obtained by comparison of the experimental data with classical trajectory simulations. It has been found that attractive potential wells around the O and S atoms are clearly different in their directions. Around the O atom, the collinear approach is preferred (the well depth is ca. 90 meV), while the perpendicular approach is favored around the S atom (the well depth is ca. 40 meV). On the basis of the optimized potential energy surface and theoretical simulations, stereo reactivity around the O and S atoms was also investigated. The results were discussed in terms of anisotropy of the potential energy surface and the electron density distribution of molecular orbitals to be ionized.
  • Koichi Ohno, Satoshi Maeda
    JOURNAL OF PHYSICAL CHEMISTRY A 110 28 8933 - 8941 2006年07月 [査読有り][通常論文]
     
    Global reaction route mapping of equilibrium structures, transition structures, and their connections on potential energy surface ( PES) has been done for MCHO (M = H, Li, Na, Al, Cu) and HCO2M (M = H, Li). A one-after-another technique based on the scaled hypersphere search method has been successfully applied to exploring unknown chemical structures, transition structures, and reaction pathways for organometallic systems. Upon metal substitution, considerable changes of stable structures, reaction pathways, and relative heights of transition structures have been discovered, though some features are similar among the analogues. Al and Cu atoms were found to behave as very strong scissors to cut the CO double bond in MCHO. Energy profiles of the CO insertion into Li-H and Li-CH3 bonds were found to be very similar, especially around the structures where the Li atom is not directly connected with the methyl group, which indicates little effects of alkyl substitution on the reaction route topology.
  • Koichi Ohno, Satoshi Maeda
    CHEMISTRY LETTERS 35 5 492 - 493 2006年05月 [査読有り][通常論文]
     
    D-L conversion pathways of alpha-alanine have been discovered by theoretical search of potential energy surfaces at the level of B3LYP/6-311++G(d,p). No direct conversion channel via only one transition state could be found between D and L optical isomers of alanine. It is demonstrated that there are four types of conversion channels in chiral amino acids. The interconversion of four functional groups (H, CH3, NH2, and COOH) around the asymmetric carbon atom can occur as rotation of a single-bonded pair of two groups involving either NH2 or COOH together with H or CH3.
  • S Maeda, K Ohno
    JOURNAL OF CHEMICAL PHYSICS 124 17 2006年05月 [査読有り][通常論文]
     
    Conversion pathways from a fullerene to a ring and vice versa among C-20 clusters have been explored. A new technique has been developed for discovering multistep reaction pathways, which can be searched by finding constrained energy minima on spheres whose surfaces are contracting from the starting point to the terminal. Local landscapes that appeared on the pathways were found to be considerably different around the fullerene and the ring, from which one can make a new interpretation for no generation of the C-20 fullerene in laser vaporization of graphite. (c) 2006 American Institute of Physics.
  • S Maeda, K Ohno
    ASTROPHYSICAL JOURNAL 640 2 823 - 828 2006年04月 [査読有り][通常論文]
     
    Generation mechanisms of amino acids in the interstellar medium ( ISM) are of great importance in connection with the chemical evolution and the origin of life. Ion-molecule reactions and radical-molecule reactions have been studied as possible reaction mechanisms that can occur in ultracold and high-vacuum conditions in the ISM. In this paper, new barrierless reaction pathways generating glycine and its analogs via reactions between closed-shell species have been predicted based on quantum chemical calculations of potential energy surfaces. The ammonium ylide molecule, which is a higher energy isomer of methylamine, can be produced by radiative association between ammonia and the methyl radical cation followed by recombination dissociation. Glycine and its analogs can be generated without thermal activation via a combination of ammonium ylide and some simple molecules such as carbon dioxide. The present results and discussion suggest that higher lying isomers of well-known molecules can be responsible for molecular evolution as well as amino acid generation in the ISM.
  • T Horio, T Hatamoto, S Maeda, N Kishimoto, K Ohno
    JOURNAL OF CHEMICAL PHYSICS 124 10 2006年03月 [査読有り][通常論文]
     
    State-resolved collision energy dependence of Penning ionization cross sections of acetylene (C2H2) and ethylene (C2H4) with He-*(2 S-3) metastable atoms was observed in a wide collision energy range from 20 to 350 meV. A recently developed discharge nozzle source with a liquid N-2 circulator was employed for the measurements in the low-energy range from 20 to 80 meV. Based on classical trajectory calculations for the energy dependence of the partial ionization cross sections, anisotropic potential energy surfaces for the present systems were obtained by optimizing ab initio model potentials for the chemically related systems Li+C2H2 and C2H4. In the case of C2H2, the global minimum was found to be located around the H atom along the molecular axis with a well depth of 48 meV (ca. 1.1 kcal/mol). On the other hand, a dominant attractive well with a depth of 62 meV (ca. 1.4 kcal/mol) was found in the pi(CC) electron region of C2H4. These findings were discussed in connection with orbital interactions between molecular orbitals of the target molecules and atomic orbitals of the metastable atom. It is concluded that sigma-type unoccupied molecular orbitals of C2H2 and a pi(CC)-type highest occupied molecular orbital of C2H4 play a significant role for the attractive-site preference of sigma direction in C2H2 and pi direction in C2H4, respectively. (c) 2006 American Institute of Physics.
  • Balazs Hajgato, Satoshi Maeda, Koichi Ohno
    ASTROCHEMISTRY: FROM LABORATORY STUDIES TO ASTRONOMICAL OBSERVATIONS 855 296 - + 2006年 [査読有り][通常論文]
     
    We have investigated small carbon clusters. The main focus of this work has been the extrema on the potential energy surface (PES) of the clusters along with their corresponding reaction and dissociation channels. We also calculated spectroscopic parameters for the stable compounds to help remote sensing techniques to detect reactions taking place in outer space, even though it is very difficult to collect suitable sample materials.
  • Yang, X, S Maeda, K Ohno
    CHEMICAL PHYSICS LETTERS 418 1-3 208 - 216 2006年01月 [査読有り][通常論文]
     
    The potential energy surfaces involving 10 singlet minima and 28 transition states for the isomerization pathways of the HC3N isomers are explored by the scaled hypersphere search method at ab initio levels. In addition to seven known species, three new cyclic isomers, bicyclic-CCCN-H, C-cyclic-CCN-H, and cyclic-CCCN-H, are predicted at the CCSD(T)/cc-pVTZ//B3LYP/6-311++G(d,p)+ZPE level. They can interconvert to each other, isomerize to other low-lying isomers, or decompose into other fragments easily. All isomers can be considered as adducts via barrierless recombination channels between various fragments detected in interstellar space or favorable hydrogen-adding processes. (c) 2005 Elsevier B.V. All rights reserved.
  • T Horio, M Yamazaki, S Maeda, T Hatamoto, N Kishimoto, K Ohno
    JOURNAL OF CHEMICAL PHYSICS 123 19 2005年11月 [査読有り][通常論文]
     
    A low-temperature discharge nozzle source with a liquid-N-2 circulator for He-*(2 S-3) metastable atoms has been developed in order to obtain the state-resolved collision energy dependence of Penning ionization cross sections in a low collision energy range from 20 to 80 meV. By controlling the discharge condition, we have made it possible to measure the collision energy dependence of partial ionization cross sections (CEDPICS) for a well-studied system of CH3CN+He-*(2 S-3) in a wide energy range from 20 to 350 meV. The anisotropic interaction potential energy surface for the present system was obtained starting from an ab initio model potential via an optimization procedure based on classical trajectory calculations for the observed CEDPICS. A dominant attractive well depth was found to be 423 meV (ca. 10 kcal/mol) at a distance of 3.20 A from the center of mass of CH3CN in the N-atom side along the CCN axis. In addition, a weak attractive well (ca. 0.9 kcal/mol) surrounding the methyl group (-CH3) has been found and ascribed to the interaction between an unoccupied molecular orbital of CH3CN and 2s atomic orbital of He-*(2 S-3).
  • S Maeda, Y Watanabe, K Ohno
    CHEMICAL PHYSICS LETTERS 414 4-6 265 - 270 2005年10月 [査読有り][通常論文]
     
    An efficient interpolation technique was developed for constructing potential energy surfaces (PES) around equilibriums based on data sampling by the scaled hypersphere search (SHS) method. Energy functions on several sizes of hypersphere are interpolated using cosine functions expanded at the SHS path points located in directions having the largest anharmonicity. In an application to H2O molecule, wide range of PES including HOH inversion and OH dissociation channels could be constructed with only a Hessian matrix and energy values at 123 points. In vibrational state calculations, the present technique was found to be much more accurate than the fourth-order Taylor expansion. (c) 2005 Elsevier B.V. All rights reserved.
  • Yang, X, S Maeda, K Ohno
    JOURNAL OF PHYSICAL CHEMISTRY A 109 32 7319 - 7328 2005年08月 [査読有り][通常論文]
     
    An extensive quantum chemical study of the potential energy surface (PES) for all possible isomerization and dissociation reactions of CH3CN is reported at the DFT (B3LYP/6-311++G(d,p)) and CCSD(T)/ cc-pVTZHB3LYP/6-311++G(d,p) levels of theory. The pathways around the equilibrium structures can be discovered by the scaled hypersphere search (SHS) method, which enables us to make a global analysis of the potential energy surface for a given chemical composition in combination with a downhill-walk algorithm. Seventeen equilibrium structures and 59 interconversion transition states have been found on the singlet PES. The four lowest lying isomers with thermodynamic stability are also kinetically stable with the lowest conversion barriers of 49.69-101.53 kcal/mol at the CCSD(T)/cc-pVTZHB3LYP/6-311++G(d,p) level, whereas three-membered-ring isomers c-CH2NCH, c-CH2CNH, and c-CHNHCH can be considered as metastable intermediates which can further convert into the low-lying chainlike isomers and higher lying acyclic isomers with the lowest conversion energies of 21.70-59.99 kcal/mol. Thirteen available dissociation channels depending on the different initial isomers have been identified. A prediction can be made for the possible mechanism explaining the migration of a hydrogen atom in competition with the CC bond dissociation. Several new energetically accessible pathways are found to be responsible for the migration of the hydrogen atom. The present results demonstrate that the SHS method is an efficient and powerful technique for global mapping of reaction pathways on PESs.
  • S Maeda, K Ohno
    JOURNAL OF PHYSICAL CHEMISTRY A 109 25 5742 - 5753 2005年06月 [査読有り][通常論文]
     
    Technical details of a new global mapping technique for finding equilibrium (EQ) and transition structures (TS) on potential energy surfaces (PES), the scaled hypersphere search (SHS) method (Ohno, K.; Maeda, S. Chem. Phys. Lett. 2004, 384, 277), are presented. On the basis of a simple principle that reaction pathways are found as anharmonic downward distortions of PES around an EQ point, the reaction pathways can be obtained as energy minima on the scaled hypersphere surface, which would have a constant energy when the potentials are harmonic. Connections of SHS paths between each EQ are very similar to corresponding intrinsic reaction coordinate (IRC) connections. The energy maximum along the SHS path reaches a region in close proximity to the TS of the reaction pathway, and the subsequent geometry optimization from the SHS maximum structure easily converges to the TS. The SHS method, using the one-after-another algorithm connecting EQ and TS, considerably reduces the multidimensional space to be searched to certain limited regions around the pathways connecting each EQ with the neighboring TS. Applications of the SHS method have been made to ab initio surfaces of formaldehyde and propyne molecules to obtain systematically five EQ and nine TS for formaldehyde and seven EQ and 32 TS for propyne.
  • K Ohno, M Yamazaki, S Maeda, N Kishimoto
    JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA 142 3 283 - 293 2005年03月 [査読有り][通常論文]
     
    Collision-energy/electron-energy-resolved two-dimensional Penning ionization electron spectroscopy (2D-PIES) has been used to study outer characteristics of molecules. Anisotropic potential energy surfaces for collisional ionization of molecules with a metastable helium atom He*(2(3)S) have been determined starting from ab initio model potentials via optimization based on trajectory calculations. Since ionization widths in the theoretical model of Penning ionization are functionals of target molecular orbitals, outer electron distributions of molecular orbitals can be determined via optimization procedures of calculated ionization cross-sections by trajectory calculations with respect to observed 2D-PIES data. (C) 2004 Elsevier B.V. All rights reserved.
  • S Maeda, K Ohno
    CHEMICAL PHYSICS LETTERS 404 1-3 95 - 99 2005年03月 [査読有り][通常論文]
     
    A new method for finding a transition state (TS) between a reactant and a product on the potential energy surface has been proposed. The scaled hypersphere search (SHS) method, in which reaction pathways are found as minima on the hypersphere, has been applied to finding TS. Starting from a hypersphere centered at the product with a radius just including the reactant on its surface, successive contraction of the sphere radii gives a pathway leading to the TS region. Applications of this method to isomerization of HCN, (H2O)(2), and alanine dipeptide demonstrated highly accurate estimation of TS without any initial guess. (C) 2005 Elsevier B.V. All rights reserved.
  • M Yamazaki, S Maeda, N Kishimoto, K Ohno
    JOURNAL OF CHEMICAL PHYSICS 122 4 2005年01月 [査読有り][通常論文]
     
    The potential energy surface of benzene (C6H6) with a He*(2 S-3) atom was obtained by comparison of experimental data in collision-energy-resolved two-dimensional Penning ionization electron spectroscopy with classical trajectory calculations. The ab initio model interaction potentials for C6H6+He*(2 S-3) were successfully optimized by the overlap expansion method; the model potentials were effectively modified by correction terms proportional to the overlap integrals between orbitals of the interacting system, C6H6 and He* (2 S-3). Classical trajectory calculations with optimized potentials gave excellent agreement with the observed collision-energy dependence of partial ionization cross sections. Important contributions to corrections were found to be due to interactions between unoccupied molecular orbitals and the He* 2s orbital. A C6H6 molecule attracts a He*(2 S-3) atom widely at the region where pi electrons distribute, and the interaction of - 80 meV (ca. -1.8 kcal/mol) just cover the carbon hexagon. The binding energy of a CA molecule and a He* atom was 107 meV at a distance of 2.40 Angstrom on the sixfold axis from the center of a C6H6 molecule, which is similar to that of C6H6+Li and is much larger than those of the C6H6+[He,Ne,Ar] systems. (C) 2005 American Institute of Physics.
  • S Maeda, K Ohno
    CHEMICAL PHYSICS LETTERS 398 1-3 240 - 244 2004年11月 [査読有り][通常論文]
     
    A new synthetic route of glycine with no activation barriers, NH3 + CH2 + CO2 --> H2NCH2COOH, has been discovered by the scaled hypersurface search method for ab initio potential energy surfaces. The route is composed of two steps with no activation barriers, an addition reaction of ammonia with singlet methylene yielding ammonium ylide (NH3 + (1):CH2 --> HCNH3) followed by carboxylation of the ylide with carbon dioxide (H2CNH3 + CO2 --> H2NCH2COOH). A sideway reaction of the ylide decomposing into methyleneimine and hydrogen (HCNH3 --> H2CNH + H-2) via new transition state was found in addition to an isomerization route to methylamine (H2CNH3 --> CH3NH2). (C) 2004 Elsevier B.V. All rights reserved.
  • S Maeda, K Ohno
    CHEMISTRY LETTERS 33 10 1372 - 1373 2004年10月 [査読有り][通常論文]
     
    New synthetic routes of glycine, the simplest amino acid molecule, have been discovered by theoretical search of ab initio potential energy surfaces. One step reaction of an acetolactone molecule with an ammonia molecule can produce a glycine molecule without byproducts, and its activation energy is only 1.6kcal(.)mol(-1). Acetolactone can be produced from either carbon dioxide and singlet methylene (CO2 + CH2) or carbon monoxide and formaldehyde (CO + HCHO) with respective activation energies of 3.2 and 36.3 kcal(.)mol(-1).
  • Masakazu Yamazaki, Satoshi Maeda, Koichi Ohno
    Chemical Physics Letters 391 4-6 366 - 373 2004年06月21日 [査読有り][通常論文]
     
    Classical trajectory calculations for collision energy dependence of partial Penning ionization cross-sections (CEDPICS) of He*(2 3S)+(N2,CO) were performed to obtain molecular orbital (MO) functions based on the observed data coefficients in linear combination of atomic orbitals and orbital exponents for a minimal atomic basis set (STO-6G) were optimized in order to give good agreement between observed and calculated CEDPICS. Although a crude basis set was assumed, obtained MOs derived by experimental CEDPICS were found to be very similar in the outer characteristics to theoretically obtained SCF-MOs in terms of much larger basis sets (6-311+G*). © 2004 Elsevier B.V. All rights reserved.
  • S Maeda, M Yamazaki, N Kishimoto, K Ohno
    JOURNAL OF CHEMICAL PHYSICS 120 2 781 - 790 2004年01月 [査読有り][通常論文]
     
    An overlap expansion method is proposed for improving ab initio model potentials. Correction terms are expanded in terms of overlap integrals between orbitals of the interacting system. The method is used to improve ab initio model potentials for N-2+He*(2 S-3), CO+He*(2 S-3), and C2H2+He*(2 S-3). Physical meanings of the optimization are elucidated in terms of target orbitals. Correction terms are found to be dominated by the components of HOMO, LUMO, next-HOMO, and next-LUMO on the target molecule. The present overlap expansion method using a limited number of correction terms related to frontier orbitals provides an efficient and intuitive approach for construction of highly anisotropic intermolecular interaction potentials. (C) 2004 American Institute of Physics.
  • K Ohno, S Maeda
    CHEMICAL PHYSICS LETTERS 384 4-6 277 - 282 2004年01月 [査読有り][通常論文]
     
    An algorithm for finding pathways to transition states (TS) or dissociation channels (DC) from equilibrium structures (EQ) on the potential energy surface (PES) is presented. The pathways around an EQ can be discovered at minima on the scaled hypersphere which would have a constant energy when the potentials are harmonic. Topographic maps including all TS, DC, and EQ were obtained for ab initio PES of H2O and HCHO in the MP2/3-21G level. The present scaled hypersphere search technique in combination with a downhill-walk algorithm enables us to make a topographic analysis of the PES for a given chemical composition. (C) 2003 Elsevier B.V. All rights reserved.
  • S Maeda, K Ohno
    CHEMICAL PHYSICS LETTERS 381 1-2 177 - 186 2003年11月 [査読有り][通常論文]
     
    An interpolation technique was developed for constructing ab initio potential energy surfaces (PES) around the equilibrium structure efficiently and accurately, using polar coordinates coupled with systematic generation of sample points on the hypersphere. Test calculations were performed for H2O and HCHO molecules, and interpolated PES and direct ab initio data were compared for randomly chosen 1000 points. Root mean square errors were found to be 4.8 x 10(-5) (2.4 cm(-1)) for H2O and 1.7 x 10(-4) (8.4 cm(-1)) for HCHO with respect to the maximum energy of 50 000 cm(-1). The present approach was found to provide considerably more accurate PES than conventional methods. (C) 2003 Elsevier B.V. All rights reserved.
  • N Kishimoto, T Horio, S Maeda, K Ohno
    CHEMICAL PHYSICS LETTERS 379 3-4 332 - 339 2003年09月 [査読有り][通常論文]
     
    Collision-energy dependence of partial Penning ionization cross-sections (CEDPICS) of OCS was obtained from collision-energy/electron-energy-resolved two-dimensional spectrum with a highly sensitive electron energy analyzer. The negative CEDPICS for X(2)Pi and C(2)Sigma(+) states indicates attractive interaction around S and O atoms with He*(2(3)S), where the corresponding 3pi(S-3p-O-2p) and 8sigma(sigma(CO)) orbitals extend, respectively. Utilizing classical trajectory calculations for CEDPICS and optimization of model potential energy surface, a large ring-like attractive well with a depth of ca. 120 meV was found for perpendicular directions around C=S axis and smaller interaction was found in the collinear direction of the C=O axis with well depth of ca. 70 meV around the oxygen atom in the lone pair region by sp(2) hybridization. (C) 2003 Elsevier B.V. All rights reserved.
  • M Yamazaki, S Maeda, N Kishimoto, K Ohno
    JOURNAL OF CHEMICAL PHYSICS 117 12 5707 - 5721 2002年09月 [査読有り][通常論文]
     
    Collision-energy/electron-energy resolved two-dimensional Penning ionization electron spectra (2D-PIES) of N-2, CO, and CH3CN with metastable He*(2 S-3) atoms are measured, and classical trajectory calculations with anisotropic entrance and exit potential energy surfaces are performed for these systems. Numerical qualities of the entrance potential surfaces are decisively important to understand the collisional ionization dynamics as well as to reproduce observed 2D-PIES, whereas the exit potential surfaces are less sensitive to the collisional ionization dynamics and the electron spectra except for special cases in which a deep potential well is relevant in the entrance potential surface. Ab initio calculations of both entrance and exit potentials as well as ionization widths are found to be reliable in obtaining their anisotropy and radial dependence with good quantitative accuracy. (C) 2002 American Institute of Physics.
  • M Yamazaki, S Maeda, N Kishimoto, K Ohno
    CHEMICAL PHYSICS LETTERS 355 3-4 311 - 318 2002年04月 [査読有り][通常論文]
     
    Anisotropic potential energy surfaces were optimized for classical trajectory calculations in order to reproduce collision energy dependence of partial Penning ionization cross-sections for N-2 and CO molecules with a He*(2(3)S) atom. Ab initio model potentials using a Li(2(2)S) atom in place of a He*(2(3)S) atom based on the similarity of valence electronic configurations were found to be successfully corrected by addition of negative terms including an exponential function combined with Legendre expansions. Optimized sets of parameters demonstrate that the most important correction terms are related to attractive interactions due to electron transfer from He*(Li) to unoccupied molecular orbitals. (C) 2002 Elsevier Science B.V. All rights reserved.

その他活動・業績

共同研究・競争的資金等の研究課題

  • 化学反応創成研究拠点
    日本学術振興会(JSPS):世界トップレベル研究拠点(WPI)
    研究期間 : 2018年10月 -2026年03月 
    代表者 : 前田理
  • 化学反応創成知能
    科学技術振興機構(JST):戦略的創造研究推進事業(ERATO)
    研究期間 : 2019年10月 -2025年03月 
    代表者 : 前田理
  • レドックスメカノケミストリーによる固体有機合成化学
    科学技術振興機構(JST):戦略的創造研究推進事業(CREST)
    研究期間 : 2019年10月 -2025年03月 
    代表者 : 伊藤肇
  • 反応経路自動探索法を基盤とする化学反応の理論設計技術
    科学技術振興機構(JST):戦略的創造研究推進事業(CREST)
    研究期間 : 2014年10月 -2020年03月 
    代表者 : 前田理

教育活動情報

主要な担当授業

  • 分子化学A(分子理論化学)
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 総合化学院
    キーワード : シュレディンガー方程式,分子軌道法,ハートリー・フォック方程式,密度汎関数理論,ボルン・オッペンハイマー近似,ポテンシャルエネルギー曲面,振動回転状態,遷移状態,反応経路,ダイナミクス,凝縮系,分子シミュレーション
  • 基礎物理化学特論
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 総合化学院
    キーワード : 分子軌道法,対称,分光学,表面,平衡と速度論
  • 大学院共通授業科目(一般科目):自然科学・応用科学
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : 分子軌道法,対称,分光学,表面,平衡と速度論
  • 化学のための数学
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 理学部
    キーワード : 複素関数論 常微分方程式 フーリエ変換
  • 化学Ⅰ
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 原子の構造、原子軌道、化学結合、混成軌道、物質の三態、電解質溶液
  • 量子化学Ⅱ
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 理学部
    キーワード : 多原子分子の分子軌道、変分原理、ヒュッケル分子軌道法、構造最適化、反応経路、ハートリー・フォック法、基底関数

大学運営

学内役職歴

  • 2018年10月23日 - 2020年3月31日 創成研究機構化学反応創成研究拠点長


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