Aug. 2023, 北海道大学, 令和4年度 全学教育科目エクセレントティーチャーズ　　　　　　　　　　　　　　　
小林 厚志

Jan. 2017, Hokkaido University, Hokkaido University President's Award　　　　　　　　　　　　　　　
KOBAYASHI Atsushi

Jul. 2016, Hokkaido University, Excellent Teachers　　　　　　　　　　　　　　　
KOBAYASHI Atsushi

Jan. 2016, Chemical Society of Japan, Hokkaido Branch, Encouraging prize of the Chemical Society of Japan, Hokkaido Branch　　　　　　　　　　　　　　　
Development of new environmentally-responsive multichromic complexes
KOBAYASHI Atsushi

Jan. 2015, Hokkaido University, Hokkaido University President's Award　　　　　　　　　　　　　　　
KOBAYASHI Atsushi

Effect of Self-Assembled Structure on the Luminescence of Platinum(II) and Palladium(II) Complexes with a C^N^C Tridentate N-Heterocyclic Carbene
Daisuke Saito, Kaito Segawa, Maria Kikkawa, Masaki Yoshida, Atsushi Kobayashi, Masako Kato
Crystal Growth & Design, 24, 17, 7194, 7201, American Chemical Society (ACS), 13 Aug. 2024
Scientific journal

Thermo-responsive emission induced by different delocalized excited-states in isomorphous Pd(ii) and Pt(ii) one-dimensional chains
Tomoya Saito, Masaki Yoshida, Kaito Segawa, Daisuke Saito, Junichi Takayama, Satoshi Hiura, Akihiro Murayama, Nishshanka M. Lakshan, W. M. C. Sameera, Atsushi Kobayashi, Masako Kato
Chemical Science, Royal Society of Chemistry (RSC), 2024
Scientific journal, The emissions of isomorphous Pt(ii) and Pd(ii) one-dimensional chains exhibited distinct thermal responses, revealing the limiting factor for extending the excited-state delocalization across multiple molecules through metallophilic interactions.

Dual-productive photoredox cascade catalyst for solar hydrogen production and methylarene oxidation
Atsushi Kobayashi
Catalysis Science & Technology, Royal Society of Chemistry (RSC), 2024, [Peer-reviewed], [Lead author, Last author, Corresponding author]
English, Scientific journal, A photoredox cascade catalyst for concurrent organic synthesis and hydrogen production was developed by combining a dual-dye sensitized Pt-TiO₂ photocatalyst and an N-hydroxyphthalimide hydrogen atom transfer catalyst.

Controlled crystallisation of porous crystals of luminescent platinum(ii) complexes by electronic tuning of ancillary ligands
Takanari Mochizuki, Masaki Yoshida, Atsushi Kobayashi, Masako Kato
Dalton Transactions, Royal Society of Chemistry (RSC), 2024
Scientific journal, The selectivity of the porous crystal phase of luminescent platinum(ii) complexes with Pt⋯Pt interactions has been systematically controlled by the ancillary N-heteroaryl carboxylate ligand.

Vapoluminescent thin-film with unsaturated copper(i) complex for rapid light-on sensing of N-heteroaromatic vapour
Sae Kondo, Nobutaka Yoshimura, Atsushi Kobayashi, K. D. Charith Kuruppu, W. M. C. Sameera, Saki Fujii, Masaki Yoshida, Masako Kato
Journal of Materials Chemistry C, Royal Society of Chemistry (RSC), Dec. 2023, [Peer-reviewed]
English, Scientific journal, A vapoluminescent thin film including a coordinatively unsaturated Cu(i) complex acts as an efficient light-on sensor for N-heteroaromatic vapours and exhibits intense emission of different colours.

Photoredox Cascade Catalyst for Efficient Hydrogen Production with Biomass Photoreforming
Atsushi Kobayashi
Angewandte Chemie International Edition, Wiley, 21 Sep. 2023, [Peer-reviewed], [Lead author, Last author, Corresponding author]
Scientific journal, Biomass photoreforming is a promising method to provide both a clean energy resource in the form of hydrogen (H2) and valuable chemicals as the results of water reduction and biomass oxidation. To overcome the poor contact between heterogeneous photocatalysts and biomass substrates, we fabricated a new photoredox cascade catalyst by combining a homogeneous catalyst, 2,2,6,6‐tetramethylpiperidine 1‐oxyl (TEMPO), and a heterogeneous dual‐dye sensitized photocatalyst (DDSP) composed of two Ru(II)‐polypyridine photosensitizers (RuP6 and RuCP6) and Pt‐loaded TiO2 nanoparticles. During blue‐light irradiation (λ = 460 ± 15 nm; 80 mW), the DDSP photocatalytically reduced aqueous protons to form H2 and simultaneously oxidized TEMPO· radicals to generate catalytically active TEMPO+. It oxidized biomass substrates (water‐soluble glycerol and insoluble cellulose) to regenerate TEMPO·. In the presence of N‐methyl imidazole as a proton transfer mediator, the photocatalytic H2 production activities for glycerol and cellulose reforming reached 2670 and 1590 µmol H2 (gTiO2)‐1 h‐1, respectively, which were comparable to those of state‐of‐the‐art heterogeneous photocatalysts.

Vapor‐Induced Assembly of a Platinum(II) Complex Loaded on Layered Double Hydroxide Nanoparticles
Tamami Morimoto, Masaki Yoshida, Ayana Sato-Tomita, Shunsuke Nozawa, Junichi Takayama, Satoshi Hiura, Akihiro Murayama, Atsushi Kobayashi, Masako Kato
Chemistry – A European Journal, Wiley, 15 Aug. 2023
Scientific journal, Controlled self‐assembly of Pt(II) complexes is key to the development of optical and stimuli‐responsive materials, but designing and precisely controlling them is still difficult owing to weak intermolecular interactions. Herein, we report the successful water‐vapor‐induced assembly of an anionic Pt(II) complex [Pt(CN)2(ppy)]– (Hppy = 2‐phenylpyridine) electrostatically loaded on cationically charged layered double hydroxide (LDH) nanoparticles consisting of Mg2+ and Al3+ ions. When the Pt(II) complexes were densely loaded onto the LDH nanoparticles, the assembly was maintained, even in dilute aqueous media. In the case of sparse loading, the Pt(II) complexes were loaded discretely in the dry state; however, when water vapor was adsorbed, the increased mobility of the Pt(II) complexes led to their assembly on the LDH nanoparticles. This resulted in a drastic change in luminescence from green to orange owing to the presence of water vapor.

Hydrogen Production from Hydrophobic Ruthenium Dye-Sensitized TiO₂ Photocatalyst Assisted by Vesicle Formation
Yusuke Higashida, Shin-ya Takizawa, Masaki Yoshida, Masako Kato, Atsushi Kobayashi
ACS Applied Materials & Interfaces, American Chemical Society (ACS), 25 May 2023, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal

Chromic triboluminescence of self-assembled platinum(II) complexes.
Kono Sasaki, Daisuke Saito, Masaki Yoshida, Fuka Tanaka, Atsushi Kobayashi, Kazuki Sada, Masako Kato
Chemical communications (Cambridge, England), 16 May 2023, [International Magazine]
English, Scientific journal, A series of Pt(II) complexes bearing N-heterocyclic carbenes, [Pt(CN)2(Rim-Mepy)] (Rim-MepyH+ = 3-alkyl-1-(4-methyl-(2-pyridinyl))-1H-imidazolium, R = Me, Et, iPr, or tBu), exhibits triboluminescence in the visible range from blue to red, as well as the corresponding intense photoluminescence. Remarkably, among the complexes, the iPr-substituted one exhibits chromic triboluminescence behaviour during the process of rubbing and also vapour exposure.

Efficient Hydrogen Production by a Photoredox Cascade Catalyst Comprising Dual Photosensitizers and a Transparent Electron Mediator
Nobutaka Yoshimura, Masaki Yoshida, Atsushi Kobayashi
Journal of the American Chemical Society, 145, 11, 6035, 6038, American Chemical Society (ACS), 13 Mar. 2023, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal

Importance of Electron Mediator Transparency: Photocatalytic Hydrogen Production from Polyoxometalate using Dye‐double‐layered Photocatalysts
Nobutaka Yoshimura, Osamu Tomita, Ryu Abe, Masaki Yoshida, Atsushi Kobayashi
ChemCatChem, 15, 4, Wiley, 26 Jan. 2023, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal

Elastic and bright assembly-induced luminescent crystals of platinum(ii) complexes with near-unity emission quantum yield
Yusuke Makino, Masaki Yoshida, Shotaro Hayashi, Toshiyuki Sasaki, Satoshi Takamizawa, Atsushi Kobayashi, Masako Kato
Dalton Transactions, Royal Society of Chemistry (RSC), 2023, [Peer-reviewed]
English, Scientific journal, Molecular crystals composed of platinum(ii) complexes exhibited elastic deformation without cracking and bright assembly-induced emission with an extremely high emission quantum yield of 0.94.

Efficient water reduction by ruthenium-picolinate dye-sensitized photocatalyst under red light illumination
Taku Shimamura, Nobutaka Yoshimura, Hiroki Otsuka, Masaki Yoshida, Atsushi Kobayashi
Journal of Photochemistry and Photobiology A: Chemistry, 436, 114412, 114412, Elsevier BV, Nov. 2022, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal

Recent developments of photoactive Cu(I) and Ag(I) complexes with diphosphine and related ligands
Hiroyuki Takeda, Atsushi Kobayashi, Kiyoshi Tsuge
Coordination Chemistry Reviews, 470, 214700, 214700, Elsevier BV, Nov. 2022, [Peer-reviewed], [Invited]
English, Scientific journal

Photofunctional molecular assembly for artificial photosynthesis: Beyond a simple dye sensitization strategy
Atsushi Kobayashi, Shin-ya Takizawa, Masanari Hirahara
Coordination Chemistry Reviews, 467, 214624, 214624, Elsevier BV, Sep. 2022, [Peer-reviewed], [Invited], [Lead author, Corresponding author]
English, Scientific journal

Photocatalyst–Mediator Interface Modification by Surface-Metal Cations of a Dye-Sensitized H₂ Evolution Photocatalyst
Nobutaka Yoshimura, Masaki Yoshida, Masako Kato, Atsushi Kobayashi
Inorganic Chemistry, 61, 29, 11095, 11102, American Chemical Society (ACS), 25 Jul. 2022, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal

Water Reduction Photocathodes Based on Ru Complex Dyes Covered with a Conjugated Polymer Nanosheet
Taku Shimamura, Atsushi Kobayashi, Yuya Oaki, Masaki Yoshida, Masako Kato
Energy & Fuels, American Chemical Society (ACS), 21 Jun. 2022, [Peer-reviewed], [Corresponding author]
English, Scientific journal

New aspects of vapochromic metal complexes: Cooperative phenomena in functions and structures
Masako Kato, Masaki Yoshida, Yu Sun, Atsushi Kobayashi
Journal of Photochemistry and Photobiology C: Photochemistry Reviews, 51, 100477, 100477, Elsevier BV, Jun. 2022, [Peer-reviewed]
English, Scientific journal

Fabrication of Ru-dye-sensitized Photoanodes Composed of a Prussian White-Prussian Blue Heterojunction toward Water Oxidation
Atsushi Kobayashi, Hiroki Otsuka, Masaki Yoshida, Masako Kato
Chemistry Letters, 51, 7, 697, 699, The Chemical Society of Japan, 07 May 2022
Scientific journal

Reversible and stepwise single‐crystal‐to‐single‐crystal transformation of a platinum(II) complex with vapochromic luminescence
Daisuke Saito, Tomasz Galica, Eiji Nishibori, Masaki Yoshida, Atsushi Kobayashi, Masako Kato
Chemistry – A European Journal, 28, 32, Wiley, 21 Apr. 2022, [Peer-reviewed]
English, Scientific journal

Thermo‐ and Mechano‐Triggered Luminescence ON/OFF Switching by Supercooled Liquid/Crystal Transition of Platinum(II) Complex Thin Films
Masaki Yoshida, Verner Sääsk, Daisuke Saito, Nobutaka Yoshimura, Junichi Takayama, Satoshi Hiura, Akihiro Murayama, Kaija Põhako‐Esko, Atsushi Kobayashi, Masako Kato
Advanced Optical Materials, 10, 7, 2102614, 2102614, Wiley, Apr. 2022, [Peer-reviewed]
English, Scientific journal

Interfacial Electron Flow Control by Double Nano-architectures for Efficient Ru-Dye-Sensitized Hydrogen Evolution from Water
Nobutaka Yoshimura, Atsushi Kobayashi, Tomoki Kondo, Ryu Abe, Masaki Yoshida, Masako Kato
ACS Applied Energy Materials, 4, 12, 14352, 14362, American Chemical Society (ACS), 27 Dec. 2021, [Peer-reviewed], [Corresponding author]
English, Scientific journal

Carbazole modification of Ruthenium Bipyridine–dicarboxylate Oxygen Evolution Molecular Catalyst
Hiroki Otsuka, Atsushi Kobayashi, Masaki Yoshida, Masako Kato
Dalton Transactions, 50, 44, 16233, 16241, Royal Society of Chemistry (RSC), Oct. 2021, [Peer-reviewed], [Corresponding author]
English, Scientific journal, We newly synthesised oxygen-evolving molecular Ru(II) catalysts with one or two carbazole moieties on the axial pyridyl ligands, namely [Ru(bda)(cbz-py)(py)] and [Ru(bda)(cbz-py)₂] [C1 and C2; bdaH₂ = 2, 2’-bipyridyl-6, 6’-dicarboxylic...

Halide Replacement Effect on Proton Conductivity and Vapochromic Luminescence of Pt(II) Complexes
Atsushi Kobayashi, Shin-ichiro Imada, Yuze Yao, Yuki Nagao, Yuto Kubota, Masaki Yoshida, Masako Kato
Bulletin of the Chemical Society of Japan, 94, 10, 2466, 2473, The Chemical Society of Japan, 28 Sep. 2021, [Peer-reviewed]
Scientific journal

Elastic deformability and luminescence of crystals of polyhalogenated platinum(ii)–bipyridine complexes
Masaki Yoshida, Yusuke Makino, Toshiyuki Sasaki, Shunichi Sakamoto, Satoshi Takamizawa, Atsushi Kobayashi, Masako Kato
CrystEngComm, 23, 34, 5891, 5898, Royal Society of Chemistry (RSC), Jun. 2021, [Peer-reviewed]
English, Scientific journal,

A series of polyhalogenated platinum(ii)–bipyridine complexes showed solvent-of-crystallisation-dependent elastic flexibility and luminescence.

Two Excited State Collaboration of Heteroleptic Ir(III)-Coumarin Complexes for H2 Evolution Dye-Sensitized Photocatalysts
Atsushi Kobayashi, Eiichirou Muramatsu, Masaki Yoshida, Masako Kato
Energies, 14, 9, 2425, 2425, MDPI AG, 24 Apr. 2021, [Peer-reviewed], [Corresponding author]
English, Scientific journal, Interfacial electron injection from a photoexcited surface-immobilized dye to a semiconductor substrate is a key reaction for dye-sensitized photocatalysts. We previously reported that the molecular orientation of heteroleptic Ir(III) photosensitizer on the TiO2 nanoparticle surface was important for efficient interfacial electron injection. In this work, to overcome the weak light absorption ability of heteroleptic Ir(III) photosensitizer and to improve the photoinduced charge-separation efficiency at the dye–semiconductor interface, we synthesized two heteroleptic Ir(III) complexes with different coumarin dyes, [Ir(C6)2(H4CPbpy)]Cl and [Ir(C30)2(H4CPbpy)]Cl [Ir-CX; X = 6 or 30; HC6 = 3-(2-enzothiazolyl)-7-(diethylamino)coumarin, HC30 = 3-(2-N-methylbenzimidazolyl)-7-N,N-diethylaminocoumarin, H4CPbpy = 4,4′-bis(methylphosphonic acid)-2,2′-bipyridine], as the cyclometalated ligands and immobilized them on the surface of Pt-cocatalyst-loaded TiO2 nanoparticles. Ultraviolet-visible absorption and emission spectroscopy revealed that the singlet ligand-centered (1LC) absorption and triplet 3LC emission bands of Ir-C30 occurred at shorter wavelengths than those of Ir-C6, while time-dependent density-functional-theory data suggested that the ligand-to-ligand charge transfer (LLCT) excited states of the two complexes were comparable. The photocatalytic H2 evolution activity of the Ir-C6-sensitized Pt-TiO2 nanoparticles (Ir-C6@Pt-TiO2) under visible light irradiation (λ > 420 nm) was higher than that of Ir-C30@Pt-TiO2. In contrast, their activities were comparable under irradiation with monochromatic light (λ = 450 ± 10 nm), which is absorbed comparably by both Ir-CX complexes. These results suggest that the internal conversion from the higher-lying LC state to the LLCT state effectively occurs in both Ir-CX complexes to trigger electron injection to TiO2.

Vapochromic behaviour of a nickel(ii)-quinonoid complex with dimensional changes between 1D and higher
Ryota Yano, Masaki Yoshida, Takahiro Tsunenari, Ayana Sato-Tomita, Shunsuke Nozawa, Youhei Iida, Noriaki Matsunaga, Atsushi Kobayashi, Masako Kato
Dalton Transactions, 50, 25, 8696, 8703, Royal Society of Chemistry (RSC), Apr. 2021, [Peer-reviewed]
English, Scientific journal,

The nickel(ii)–chloranilato complex shows reversible vapochromism with changes in dimensionality upon exposure to various vapours and subsequent drying by heating.

Enhancement of Photocatalytic Activity for Hydrogen Production by Surface Modification of Pt‐TiO 2 Nanoparticles with a Double Layer of Photosensitizers
Nobutaka Yoshimura, Atsushi Kobayashi, Masaki Yoshida, Masako Kato
Chemistry – A European Journal, 26, 70, 16939, 16946, Wiley, 15 Dec. 2020, [Peer-reviewed], [Corresponding author]
English, Scientific journal

Intense Red‐Blue Luminescence Based on Superfine Control of Metal–Metal Interactions for Self‐Assembled Platinum(II) Complexes
Daisuke Saito, Tomohiro Ogawa, Masaki Yoshida, Junichi Takayama, Satoshi Hiura, Akihiro Murayama, Atsushi Kobayashi, Masako Kato
Angewandte Chemie International Edition, 59, 42, 18723, 18730, Wiley, 12 Oct. 2020, [Peer-reviewed]
Scientific journal

Quantitative Thermal Synthesis of Cu(I) Coordination Polymers That Exhibit Thermally Activated Delayed Fluorescence
Atsushi Kobayashi, Tomoka Ehara, Masaki Yoshida, Masako Kato
Inorganic Chemistry, 59, 14, 9511, 9520, American Chemical Society (ACS), 20 Jul. 2020, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal

Bright Luminescent Platinum(II)‐Biaryl Emitters Synthesized Without Air‐Sensitive Reagents
Chuei Wakasugi, Masaki Yoshida, W. M. C. Sameera, Yasuhiro Shigeta, Atsushi Kobayashi, Masako Kato
Chemistry – A European Journal, 26, 24, 5449, 5458, Wiley, 24 Apr. 2020, [Peer-reviewed]
English, Scientific journal

Cooperative phenomenon of vapochromism and proton conduction of luminescent Pt(ii) complexes for the visualisation of proton conductivity
Atsushi Kobayashi, Shin-ichiro Imada, Dongjin Wang, Yuki Nagao, Masaki Yoshida, Masako Kato
Faraday Discussions, 225, 184, 196, Royal Society of Chemistry (RSC), Apr. 2020, [Peer-reviewed], [Lead author, Corresponding author], [International Magazine]
English, Scientific journal,

The cooperative phenomenon between proton conduction and vapochromism of luminescent Pt(ii) complexes, [PtCl(tpypy)]Cl and [PtCl(tpypyH)]Cl₂, is reported.

Aromatic versus Aliphatic α-Diimine Ligands in Heteroleptic Copper(I) Emitters: Photophysical and Electrochemical Properties.
Masaki Yoshida, Sae Yanagida, Daisuke Saito, Atsushi Kobayashi, Masako Kato
Analytical sciences : the international journal of the Japan Society for Analytical Chemistry, 36, 1, 67, 73, 10 Jan. 2020, [Peer-reviewed], [Domestic magazines]
English, Scientific journal, The electrochemical and photophysical properties of a heteroleptic Cu(I) complex bearing an aliphatic α-diimine ligand, [Cu(dab)(xantphos)]+ (Cu-dab; dab = N,N'-diphenyl-2,3-dimethyl-1,4-diazabutadiene, xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene), were evaluated together with those of complexes [Cu(dmp)(xantphos)]+ (Cu-dmp; dmp = 2,9-dimethyl-1,10-phenanthroline), [Cu(dmbpy)(xantphos)]+ (Cu-dmbpy; dmbpy = 5,5'-dimethyl-2,2'-bipyridine), and [Cu(bq)(xantphos)]+ (Cu-bq; bq = 2,2'-biquinoline), bearing aromatic diimine ligands. Cu-dab exhibited a two-step ligand-centered redox behavior, where the first wave corresponded to an electrochemically reversible one-electron reduction process. Although Cu(I)-aromatic diimine complexes Cu-dmp, Cu-dmbpy, and Cu-bq exhibited obvious luminescence from the metal-to-ligand charge transfer (MLCT) excited state, Cu-dab did not show any luminescence. Computational studies indicated that this non-luminescent property was caused by the large structural relaxation of Cu-dab during photoexcitation.

Vapochromic luminescence of a spin-coated copper(i) complex thin film by the direct coordination of vapour molecules
Sae Kondo, Nobutaka Yoshimura, Masaki Yoshida, Atsushi Kobayashi, Masako Kato
Dalton Transactions, 49, 46, 16946, 16953, Royal Society of Chemistry (RSC), 2020, [Peer-reviewed]
English, Scientific journal,

The spin-coated thin film fabricated with a simple Cu(i) complex exhibits luminescence colour changes in response to N-heteroaromatic vapours reversibly.

Liquid–liquid interface-promoted formation of a porous molecular crystal based on a luminescent platinum(ii) complex
Mari Kimura, Masaki Yoshida, Sho Fujii, Atsushi Miura, Kosei Ueno, Yasuhiro Shigeta, Atsushi Kobayashi, Masako Kato
Chemical Communications, 56, 85, 12989, 12992, Royal Society of Chemistry (RSC), 2020, [Peer-reviewed], [International Magazine]
English, Scientific journal,

A Pt(ii)-based luminescent porous molecular crystal was selectively crystallised at the liquid–liquid interface, allowing control of porosity and luminescence.

Photosensitizing ruthenium(ii)–dye multilayers: photoinduced charge separation and back electron transfer suppression
Nobutaka Yoshimura, Atsushi Kobayashi, Wataru Genno, Takashi Okubo, Masaki Yoshida, Masako Kato
Sustainable Energy & Fuels, 4, 7, 3450, 3457, Royal Society of Chemistry (RSC), 2020, [Peer-reviewed], [Corresponding author]
English, Scientific journal,

Photocatalytic H₂ evolution activity in iodide aqueous solution was improved by increasing the Ru(ii)–dye layer number on the Pt–TiO₂ surface.

Phosphorescence Properties of Anionic Cyclometalated Platinum(II) Complexes with Fluorine-substituted Tridentate Diphenylpyridine in the Solid State
T. Ogawa, W. M. C. Sameera, M. Yoshida, A. Kobayashi, M. Kato
Chem. Phys. Lett., 739, 137-24, Dec. 2019, [Peer-reviewed]
English, Scientific journal

Vapochromic Luminescent Proton Conductors: Switchable Vapochromism and Proton Conduction of Luminescent Pt(II) Complexes with Proton-exchangeable Sites　　　　　　　　　　　　　　　
A. Kobayashi, S. Imada, Y. Shigeta, Y. Nagao, M. Yoshida, M. Kato
J. Mater. Chem. C, 7, 14923, 14931, Oct. 2019, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal

Fast and Stable Vapochromic Response Induced Through Nanocrystal Formation of a Luminescent Platinum(II) Complex on Periodic Mesoporous Organosilica
H. Matsukawa, M. Yoshida, T. Tsunenari, S. Nozawa, A. Sato-Tomita, Y. Maegawa, S. Inagaki, A. Kobayashi, M. Kato
Sci. Rep., 9, 1, 15151, 15151, Oct. 2019, [Peer-reviewed], [International Magazine]
English, Scientific journal, A hybrid vapoluminescent system exhibiting fast and repeatable response was constructed using periodic mesoporous organosilica with bipyridine moieties (BPy-PMO) and a Pt(II) complex bearing a potentially luminescent 2-phenylpyridinato (ppy) ligand. An intense red luminescence appeared when the Pt(II)-complex immobilised BPy-PMO was exposed to methanol vapour and disappeared on exposure to pyridine vapour. The ON-OFF vapochromic behaviour occurred repeatedly in a methanol/pyridine/heating cycle. Interestingly, a rapid response was achieved in the second cycle and cycles thereafter. Scanning and transmission electron microscopies (SEM/TEM), absorption and emission, and nuclear magnetic resonance spectroscopies, mass spectrometry, and powder X-ray diffraction indicated that methanol vapour induced Si-C cleavage and thus liberated [Pt(ppy)(bpy)]Cl (bpy = 2,2'-bipyridine) from the BPy-PMO framework. Furthermore, the self-assembling properties of the Pt(II) complex resulted in the formation of highly luminescent micro/nanocrystals that were homogeneously dispersed on the porous support. The unique vapoluminescence triggered by the unprecedented protodesilylation on exposure to protic solvent vapour at room temperature is attributable to BPy-PMO being a giant ligand and an effective vapour condenser. Consequently, this hybrid system presents a new strategy for developing sensors using bulk powdery materials.

A Systematic Study on the Double-layered Photosensitizing Dye Structure on the Surface of Pt-cocatalyst-loaded TiO2 Nanoparticles
N. Yoshimura, A. Kobayashi, M. Yoshida, M. Kato
Bull. Chem. Soc. Jpn., 92, 11, 1793, 1800, Oct. 2019, [Peer-reviewed]
English, Scientific journal

Insight into the Origin of Competitive Emission of Copper(I) Complexes Bearing Diimine and Diphosphine Ligands
S. Yanagida, M. Yoshida, W. M. C. Sameera, A. Kobayashi, M. Kato
Bull. Chem. Soc. Jpn., 92, 10, 1684, 1693, Jul. 2019, [Peer-reviewed]
English, Scientific journal

Control of Emissive Excited States of Silver(I) Halogenido Coordination Polymers by a Solid Solution Approach
M. Dosen, Y. Kawada, S. Shibata, K. Tsuge, Y. Sasaki, A. Kobayashi, M. Kato, S. Ishizaka, N. Kitamura
Inorg. Chem., 58, 8419, 8431, Jun. 2019, [Peer-reviewed]
English, Scientific journal

Stability tuning of vapor-adsorbed state of vapochromic Pt(II) complex by introduction of chiral moiety
Y. Shigeta, A. Kobayashi, M. Yoshida, M. Kato
Inorg. Chem., 58, 7385, 7392, May 2019, [Peer-reviewed], [Corresponding author]
English, Scientific journal

Robust Triplatinum Redox-chromophore for a Post-synthetic Color-tunable Electrochromic System
M. Yoshida, H. Shitama, W. M. C. Sameera, A. Kobayashi, M. Kato
Chem. Eur. J., 25, 7669, 7678, Mar. 2019, [Peer-reviewed]
English, Scientific journal

Quantitative solvent-free thermal synthesis of luminescent Cu(I) coordination polymers
A. Kobayashi, M. Fujii, Y. Shigeta, M. Yoshida, M. Kato
Inorg. Chem., 58, 4456, 4464, Mar. 2019, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal

Two-step vapochromic luminescence of proton-conductive coordination polymers composed of Ru(II)-metalloligands and lanthanide cations
A. Kobayashi, K. Shimizu, A. Watanabe, Y. Nagao, N. Yoshimura, M. Yoshida, M. Kato
Inorg. Chem., 58, 2413, 2421, Jan. 2019, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal

Effect of the Chirality of Counter Anions on the Vapochromic Behavior of Luminescent Pt(II) Complexes
Y. Shigeta, A. Kobayashi, M. Yoshida, M. Kato
Eur. J. Inorg. Chem., 1011, 1017, Jan. 2019, [Peer-reviewed], [Corresponding author]
English, Scientific journal

Phosphorescence Properties of Discrete Platinum(II) Complex Anions Bearing N-heterocyclic Carbenes in the Solid State
T. Ogawa, W. M. C. Sameera, D. Saito, M. Yoshida, A. Kobayashi, M. Kato
Inorg. Chem., 57, 14086, 14096, Oct. 2018, [Peer-reviewed]
English, Scientific journal

The effect of pyridyl anchoring groups at the surfaces of Ru(II)-dye-sensitized TiO2 nanoparticles on photocatalytic oxygen evolution
H. Otsuka, A. Kobayashi, M. Yoshida, M. Kato
J. Photochem. Photobiol. A: Chem., 369, 189, 194, Elsevier BV, Oct. 2018, [Peer-reviewed], [Corresponding author]
English, Scientific journal

Anionic platinum(II) complexes bearing N-heterocyclic carbenes in a discrete space: Intense luminescence and colour variation based on regioselective π-extension　　　　　　　　　　　　　　　
T. Ogawa, W. M. C. Sameera, M. Yoshida, A. Kobayashi, M. Kato
Inorg. Chem., 57, 14086, 14096, Oct. 2018, [Peer-reviewed]
English, Scientific journal

Photocatalytic hydrogen evolution driven by platinated CdS nanorods with a hexacyanidoruthenate redox mediator
H. Kitano, A. Kobayashi, M. Yoshida, M. Kato
Sustainable Energy&Fuels, 2, 2609, 2615, Aug. 2018, [Peer-reviewed], [Corresponding author]
English, Scientific journal

Mechanochromic Switching between Delayed Fluorescence and Phosphorescence of Luminescent Coordination Polymers Composed of Dinuclear Copper(I) Iodide Rhombic Cores
A. Kobayashi, Y. Yoshida, M. Yoshida, M. Kato
Chem. Eur. J., 24, 14750, 14759, Jul. 2018, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal

Crystal Engineering of Vapochromic Porous Crystals Composed of Pt(II)-Diimine Luminophores for Vapor-History Sensors
Yasuhiro Shigeta, Atsushi Kobayashi, Masaki Yoshida, Masako Kato
Crystal Growth and Design, 18, 6, 3419, 3427, American Chemical Society, 06 Jun. 2018, [Peer-reviewed], [Corresponding author]
English, Scientific journal, A novel Pt(II) diimine complex, [Pt(CN)2(H2dpcpbpy)] (1, H2dpcpbpy = 4,4′-di(p-carboxyphenyl)-2,2′-bipyridine), was synthesized, and its vapochromic behavior was investigated. The yellow amorphous form of 1, 1-Ya, transformed into the porous orange crystalline form, 1-Oc, upon exposure to ethanol vapor. This behavior is similar to that of the previously reported complex, [Pt(CN)2(H2dcphen)] (2, H2dcphen = 4,7-dicarboxy-1,10-phenanthroline). X-ray diffraction study showed that 1-Oc possessed similar but larger porous channels (14.3 × 8.6 Å) compared to the red crystalline form of 2, 2-Rc (6.4 × 6.8 Å). Although the porous structure of 2-Rc was retained after vapor desorption, that of 1-Oc collapsed to form the orange amorphous solid, 1-Oa. However, the orange color was unchanged in this process. The initial color was recovered by grinding 1-Oa and 2-Rc. These vapor-writing and grinding-erasing functions can be applied to both in situ vapor sensing and vapor-history sensing, i.e., sensors that can memorize the existence of previous vapors. A notable difference was observed for humid air sensitivity
the orange emission of 1-Oa was largely unaffected upon exposure to humid air, whereas the red emission of 2-Rc was significantly affected. The lesser sensitivity of 1-Oa toward humidity is important for stable vapor-history sensor applications.

Solvent-Free Thermal Synthesis of Luminescent Dinuclear Cu(I) Complexes with Triarylphosphines
Panyi Liang, Atsushi Kobayashi, W. M.C. Sameera, Masaki Yoshida, Masako Kato
Inorganic Chemistry, 57, 10, 5929, 5938, American Chemical Society, 21 May 2018, [Peer-reviewed], [Corresponding author]
English, Scientific journal, Luminescent [Cu2I2(pyrpy)2(PR3)2] complexes (pyrpy = 4-pyrrolidinopyridine
PR3 = triphenylphosphine (1), tri-m-tolylphosphine (2), tri-p-tolylphosphine (3)) were prepared by solution reactions and a rarely reported solvent-free thermal method. X-ray structure analyses reveal that complexes composed of dinuclear {Cu2I2} cores surrounded by two PR3 and two pyrpy ligands were formed. Although the melting point of pyrpy is the lowest among the organic units used in this study, the temperature required to form the luminescent dinuclear complex, prepared by the thermal synthesis method, depended strongly on the PR3 moiety. Two of the three complexes (1 and 3) were successfully prepared by the solvent-free thermal method. Complexes 1-3 exhibited blue emissions at around 450 nm with moderately high quantum yields (φ) of 0.24, 0.31, and 0.51, respectively. Emission-lifetime measurements and time-dependent density functional theory (TD-DFT) calculations suggest thermally activated delayed fluorescence (TADF) in each complex. This solvent-free thermal synthesis of TADF materials represents a promising method for the preparation of luminescent layers directly onto substrates of thin-layer electronic devices, such as organic light-emitting diodes.

Importance of the Molecular Orientation of an Ir(III)-heteroleptic Photosensitizer Immobilized on TiO2 Nanoparticles
A. Kobayashi, S. Watanabe, M. Yoshida, M. Kato
ACS Appl. Energy Mater., 1, 2882, May 2018, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal

Immobilization of luminescent Platinum(II) complexes on periodic mesoporous organosilica and their water reduction photocatalysis
Masaki Yoshida, Kento Saito, Hiroki Matsukawa, Sae Yanagida, Masanori Ebina, Yoshifumi Maegawa, Shinji Inagaki, Atsushi Kobayashi, Masako Kato
Journal of Photochemistry and Photobiology A: Chemistry, 358, 334, 344, Elsevier B.V., 01 May 2018, [Peer-reviewed]
English, Scientific journal, Pt(II) complexes have been immobilized on a periodic mesoporous organosilica (PMO) consisting of 2,2′-bipyridine (bpy) units bridged by siloxane bonds (BPy-PMO). Although these Pt(II) complexes are luminescent in their discrete molecular states, the luminescence properties of the immobilized complexes largely depend on the origin of the emission
luminescence is quenched when the emission originates from the 3ππ* excited state of bipyridine due to the coupling of the C–H bending vibration of the bpy and the Si-O stretching vibration of the siloxane framework, while luminescence is maintained when the 3ππ* excited state of bipyridine is not the lowest excited state. Although the simple coexistence of Pt(0) nanoparticles and Pt(II) complexes did not catalyze water reduction even in the presence of an electron relay, photocatalytic water reduction is observed when Pt(0)/Pt(II)-co-immobilized BPy-PMOs are used. This result clearly demonstrates the importance of the integration of photosensitizers and catalysts on the PMO for enhancing intermolecular electron-transfer processes.

Luminescent ionic liquids based on cyclometalated platinum(ii) complexes exhibiting thermochromic behaviour in different colour regions
Tomohiro Ogawa, W. M.C. Sameera, Masaki Yoshida, Atsushi Kobayashi, Masako Kato
Dalton Transactions, 47, 16, 5589, 5594, Royal Society of Chemistry, 2018, [Peer-reviewed]
English, Scientific journal, Luminescent ionic liquids, based on anionic Pt(ii) complexes, were developed. Depending on the cyclometalating ligands used, they exhibit thermochromic luminescence with different colours. The chromic properties in the flexible liquid and glass states emerge through the self-assembling character of the square-planar Pt(ii) complexes.

Two-way vapochromism of a luminescent platinum(II) complex with phosphonic-acid-functionalized bipyridine ligand
Atsushi Kobayashi, Naotaka Yamamoto, Yasuhiro Shigeta, Masaki Yoshida, Masako Kato
Dalton Transactions, 47, 5, 1548, 1556, Royal Society of Chemistry, 2018, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal, A luminescent Pt(ii) complex [Pt(CN)2(H4dpbpy)] (1P
H4dpbpy = 2,2′-bipyridine-4,4′-diphosphonic acid) bearing a phosphonic-acid-functionalized bipyridine ligand was successfully synthesized and its unique two-way vapochromic behaviour investigated. X-ray structure analyses of both the anhydrous 1P and penta-hydrated 1P·5H2O phases clearly reveal the activation of intermolecular Pt⋯Pt interactions through the adsorption of water vapour. Emission spectroscopy reveals that the penta-hydrated 1P·5H2O complex exhibits an orange emission at 585 nm that shifts in two directions, to a blue-green emission at 469 nm by drying at 100 °C or to a red emission at 701 nm by drying under vacuum at room temperature. Thermogravimetric analyses and powder X-ray diffraction studies clearly reveal that anhydrous 1P, with negligible intermolecular Pt⋯Pt interactions, is formed by drying at 100 °C whereas the monohydrate 1P·H2O phase, with effective Pt⋯Pt interactions, is formed by drying under vacuum.

Thermal and Mechanochemical Syntheses of Luminescent Mononuclear Copper(I) Complexes
Panyi Liang, Atsushi Kobayashi, Tatsuya Hasegawa, Masaki Yoshida, Masako Kato
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 44, 5134, 5142, WILEY-V C H VERLAG GMBH, Dec. 2017, [Peer-reviewed], [Corresponding author]
English, Scientific journal, Mononuclear Cu-I iodide complexes, [CuI(PPh3)(2)L] {PPh3 = triphenylphosphine; L = 4-aminoisoquinoline (4-aiq) (2), 5-aminoisoquinoline (5-aiq) (3), and 5-nitroisoquinoline (niq) (4)}, were prepared by three different methods: normally used reactions in the solution state, mechanochemical synthesis, and newly developed solvent-free thermal synthesis. Although no solvent was required for the mechanochemical synthesis of the parent complex [CuI(PPh3)(2)(iq)] (1; iq = isoquinoline), a minimal amount of assisting solvent (PhCN) was required for the mechanochemical syntheses of the three functionalized isoquinoline complexes. The amino-functionalized isoquinoline complexes were successfully synthesized by heating the ground mixture of three types of starting materials at ca. 100 degrees C, where the PPh3 ligand melted to promote complex formation by acting as the ligand and the solvent. The emission properties strongly depend on the L ligand: Complexes 2 and 3 showed vibronic emission spectra originating from the (3)* excited state localized on the L ligand, whereas complex 4 did not show any emission in the visible region.

Effects of phosphonate ester groups attached on a heteroleptic Ir(III) photosensitizer
Atsushi Kobayashi, Shuhei Watanabe, Masanori Ebina, Masaki Yoshida, Masako Kato
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY, 347, 9, 16, ELSEVIER SCIENCE SA, Oct. 2017, [Peer-reviewed]
English, Scientific journal, Two heteroleptic Ir(III) complexes bearing two diethyl phosphonate groups, [Ir(ppy-PE)(2)(bpy)(PF6) and [Ir(ppy)(2)(bpy-dPE)](PF6) (1pPE and 1bPE; Hppy = 2-phenylpyridine, Hppy-PE =4-(diethylphosphonomethyl)-2-phenylpyridine, bpy = 2,2'-bipyridine, bpy-dPE=4,4'-bis(diethylphosphonomethyl)-2,2'bipyridine), were successfully synthesized, and their photophysical properties were investigated by UV-vis absorption and emission spectroscopic and electrochemical measurements. Both IpPE and IbPE complexes exhibited similar IJV-vis absorption and emission spectra and cyclic voltammograms as those of nonmodified complex [Ir(ppy)2(bpy)](PF6) (1), indicating the suitability for photocatalytic H-2 evolution reaction. (MLCT)-M-3 emissions of both IbPE and 1pPE were quenched by electron transfer from triethylamine (TEA) sacrificial electron donor, but the quenching rate of IpPE was lower than that of nonmodified complex 1 and 1bPE. In contrast, the quenching rate of IbPE by an electron-accepting [Co (bpy)(3)](2+) moiety was slightly lower than 1 or IpPE. These results suggest that the two diethylphosphonate ester groups regulate the direction of photoinduced electron-transfer reaction at the (MLCT)-M-3 excited state due to their steric bulkiness. In addition, the photocatalytic activity for H-2 evolution in the presence of K2PtC14 precatalyst clearly showed remarkably extended longevity for both IpPE and 1bPE compared to that of 1, indicating that the two diethyl phosphonate groups attached on IpPE and IbPE also play an important role in the extended longevity of H-2-evolution activity of in-situ generated Pt colloidal catalyst from K2PtC14. The deactivation pathway of IpPE and 1bPE during photo H-2 evolution reaction is mainly due to the substitution of the bpy-type ligand by CH3CN solvent of the one electron reduced Ir(II) species like the non-substituted complex 1. (C) 2017 Elsevier B.V. All rights reserved.

Impact of Photosensitizing Multilayered Structure on Ruthenium(II)-Dye-Sensitized TiO2-Nanoparticle Photocatalysts
Sogo Furugori, Atsushi Kobayashi, Ayako Watanabe, Masaki Yoshida, Masako Kato
ACS Omega, 2, 7, 3901, 3912, American Chemical Society, 31 Jul. 2017, [Peer-reviewed]
English, Scientific journal, To improve the efficiency of photoinduced charge separation on the surface of dye-sensitized TiO2 nanoparticles, we synthesized the Ru(II)-photosensitizer-immobilized, Pt-cocatalyst-loaded TiO2 nanoparticles RuCP2@Pt-TiO2, RuCP2-Zr-RuP6@Pt-TiO2, and RuCP2-Zr-RuP4-Zr-RuP6@Pt-TiO2 (RuCP2 = [Ru(bpy)2(mpbpy)]2-, RuP4 = [Ru(bpy)(pbpy)2]6-, RuP6 = [Ru(pbpy)3]10-, H4mpbpy = 2,2′-bipyridine-4,4′-bis(methanephosphonic acid), and H4pbpy = 2,2′-bipyridine-4,4′-bis(phosphonic acid)) using phosphonate linkers with bridging Zr4+ ions. X-ray fluorescence and ultraviolet-visible absorption spectra revealed that a layered molecular structure composed of Ru(II) photosensitizers and Zr4+ ions (i.e., RuCP2-Zr-RuP6 and RuCP2-Zr-RuP4-Zr-RuP6) was successfully formed on the surface of Pt-TiO2 nanoparticles, which increased the surface coverage from 0.113 nmol/cm2 for singly layered RuCP2@Pt-TiO2 to 0.330 nmol/cm2 for triply layered RuCP2-Zr-RuP4-Zr-RuP6@Pt-TiO2. The photocatalytic H2 evolution activity of the doubly layered RuCP2-Zr-RuP6@Pt-TiO2 was three times higher than that of the singly layered RuCP2@Pt-TiO2, whereas the activity of triply layered RuCP2-Zr-RuP4-Zr-RuP6@Pt-TiO2 was less than half of that for RuCP2@Pt-TiO2. The photosensitizing efficiencies of these Ru(II)-photosensitizer-immobilized nanoparticles for the O2 evolution reaction catalyzed by the Co(II)-containing Prussian blue analogue [CoII(H2O)2]1.31[{CoIII(CN)6}0.63{PtII(CN)4}0.37] decreased as the number of Ru(II)-photosensitizing layers increased. Thus, crucial aspects of the energy- and electron-transfer mechanism for the photocatalytic H2 and O2 evolution reactions involve not only the Ru(II)-complex-TiO2 interface but also the multilayered structure of the Ru(II)-photosensitizers on the Pt-TiO2 surface.

A Coordination Network with Ligand-Centered Redox Activity Based on facial-[Cr-III(2-mercaptophenolato)(3)](3-) Metalloligands
Masanori Wakizaka, Takeshi Matsumoto, Atsushi Kobayashi, Masako Kato, Ho-Chol Chang
CHEMISTRY-A EUROPEAN JOURNAL, 23, 41, 9919, 9925, WILEY-V C H VERLAG GMBH, Jul. 2017, [Peer-reviewed]
English, Scientific journal, The design of redox-active metal-organic frameworks and coordination networks (CNs), which exhibit metaland/or ligand-centered redox activity, has recently received increased attention. In this study, the redox-active metalloligand (RML) [Me4N](3)fac-[CrIII(mp)(3)] (1) (mp= 2-mercaptophenolato) was synthesized and characterized by single-crystal X-ray diffraction analysis, and its reversible ligand-centered one-electron oxidation was examined by cyclic voltammetry and spectroelectrochemical measurements. Since complex 1 contains O/S coordination sites in three directions, complexation with K+ ions led to the formation of the two-dimensional honeycomb sheet-structured [K(3)fac{ Cr-III(mp)(3)}(H2O)(6)] n (2.6H(2)O), which is the first example of a redox-active CN constructed from a RML with o-disubstituted benzene ligands. Herein, we unambiguously demonstrate the ligand-centered redox activity of the RML within the CN 2.6H(2)O in the solid state.

Emission Tuning of Luminescent Copper(I) Complexes by Vapor-Induced Ligand Exchange Reactions
Tatsuya Hasegawa, Atsushi Kobayashi, Hiroki Ohara, Masaki Yoshida, Masako Kato
INORGANIC CHEMISTRY, 56, 9, 4928, 4936, AMER CHEMICAL SOC, May 2017, [Peer-reviewed]
English, Scientific journal, We have synthesized two luminescent mononuclear Cu(I) complexes, [Cu(PPh(2)Tol)(THF)(4Mepy)(2)](BF4) (1) and [Cu-(PPh(2)Tol) (4Mepy)(3)] (BF4) (2) (PPh(2)Tol = diphenyl(o-tolyl)phosphine, 4Mepy = 4-methylpyridine, THF = tetrahydrofuran), and investigated their crystal structures, luminescence properties, and vapor-induced ligand exchange reactions in the solid state. Both coordination complexes are tetrahedral, but one of the three 4Mepy ligands of complex 2 is replaced by a THF solvent molecule in complex 1. In contrast to the very weak blue emission of the THF-bound complex 1 (wavelength of emission maximum (lambda(em)) = 457 nm, emission quantum yield (Phi(em)) = 0.02) in the solid state at room temperature, a very bright blue-green emission was observed for 2 (lambda(em) = 484 rim, Phi(em) = 0.63), suggesting a contribution of the THF ligand to nonradiative deactivation. Time dependent density functional theory calculations and emission lifetime measurements suggest that the room-temperature emissions of the complexes are due to thermally activated delayed fluorescence from the metal-to-ligand charge transfer excited state. Interestingly, by exposing the solid sample of THF-bound 1 to 4Mepy vapor, the emission intensity drastically increased and the emission color changed from blue to blue-green. Powder X-ray diffraction measurements revealed that the emission change of 1 is due to the vapor-induced ligand exchange of THF for 4Mepy, forming the strongly emissive complex 2. Further emission tuning was achieved by exposing 1 to pyrimidine or pyrazine vapors, forming green (lambda(em) = 510 nm) or orange (lambda(em) = 618 rim) emissive complexes, respectively. These results suggest that the vapor-induced ligand exchange is a promising method to control the emission color of luminescent Cu(I) complexes.

Effect of Water Coordination on Luminescent Properties of Pyrazine-Bridged Dinuclear Cu(I) Complexes
Atsushi Kobayashi, Ryuya Arata, Tomohiro Ogawa, Masaki Yoshida, Masako Kato
INORGANIC CHEMISTRY, 56, 8, 4280, 4288, AMER CHEMICAL SOC, Apr. 2017, [Peer-reviewed]
English, Scientific journal, Two luminescent pyrazine-bridged dinuclear Cu(I) complexes, namely, [{Cu(PPh3)(2)(H2O)}(mu-MeOpyz){ Cu (PPh3)(2)(CH3CN)}] (BF4)(2) and [{Cu (PPh3)(2)(H2O)} (mu-MeOpyz){Cu(PPh3)(2)(H2O)}] (BF4)(2)(H2O-Cu(2-)AN PPh3 = triphenylphosphine, MeOpyz = 2-methoxypyrazine), were successfully synthesized and characterized by single-crystal X-ray diffraction and luminescence measurements. X-ray analysis revealed that the water molecules are coordinated to both Cu(I) ions to form almost the same P2N1O1 coordination structure in H2O-Cu-2-H2O, whereas one of the two Cu ions in H2O-Cu-2-AN was coordinated by acetonitrile instead of water to form a different P2N2 coordination environment. The asymmetric H2O-Cu-2-AN exhibits very bright yellow-green emission with a high emission quantum yield (lambda(em) = 550 nm, Phi= 0.70) at room temperature in the solid state in spite of the coordination of water molecule, which usually tends to deactivate the emissive state through O H vibration. The intense emission at room temperature is a result of thermally activated delayed fluorescence, and the remarkable temperature dependence of emission lifetimes indicates the existence of unique multiple emission states for the asymmetric dinuclear complex. In contrast, the emission of H2O-Cu-2-H2O was observed at longer wavelengths with remarkably a lower quantum yield (lambda(em) = 580 nm, Phi = 0.05). Time-dependent density functional theory calculations suggested that the emission could result from the metal-to-ligand charge-transfer transition state. However, it could be rapidly deactivated by the structural distortion around the Cu ion with a less-bulky coordination environment in H2O-Cu-2-H2O.

Reversible luminescent colour changes of mononuclear copper(I) complexes based on ligand exchange reactions by N-heteroaromatic vapours
Hiroki Ohara, Tomohiro Ogawa, Masaki Yoshida, Atsushi Kobayashi, Masako Kato
DALTON TRANSACTIONS, 46, 11, 3755, 3760, ROYAL SOC CHEMISTRY, Mar. 2017, [Peer-reviewed]
English, Scientific journal, [CuCl(PPh3)(2)(4-Mepy)] (PPh3 = triphenylphosphine, 4-Mepy = 4-methylpyridine), a highly blue-luminescent mononuclear copper(I) complex, shows reversible emission colour change ranging from blue-green to red by vapour exposure to N-heteroaromatics, such as pyridine, pyrimidine, and 2-methylpyrazine. The remarkable colour changes occur due the ligand exchange reaction between the solid and gas. Such ligand exchange reactions would be applicable to various vapours with coordination ability and be useful for the sensing of such volatile organic compounds as well as a new convenient methodology for the preparation of luminescent complexes.

Development of Ion-Conductive and Vapoluminescent Porous Coordination Polymers Composed of Ruthenium(II) Metalloligand
Ayako Watanabe, Atsushi Kobayashi, Erika Saitoh, Yuki Nagao, Shun Omagari, Takayuki Nakanishi, Yasuchika Hasegawa, W. M. C. Sameera, Masaki Yoshida, Masako Kato
INORGANIC CHEMISTRY, 56, 5, 3005, 3013, AMER CHEMICAL SOC, Mar. 2017, [Peer-reviewed]
English, Scientific journal, We synthesized two new porous coordination polymers (PCPs) {Ln(7)(OH)(5)[Ru(dcbpy)(3)](4).4nH(2)O} (Ln(7)-Ru-4; Ln = Ce, Nd) composed of the luminescent ruthenium (II) metalloligand [Ru(4,4'-dcbpy)(3)](4-) ([4Ru]; 4,4'-dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) and lanthanide ions Ln(3+) (Ln = Ce, Nd). These two PCPs Ln7-Ru4 are isomorphous with the previously reported PCP La-7-Ru-4, and the lattice constants (a, c, and unit cell volume V) changed systematically according to the lanthanide contraction. All three Ln(7)-Ru-4 compounds have OW anion containing porous structures and a large number of hydrate water molecules within the pores, resulting in moderate ion conductivities (10(-6)-10(-7) S cm(-1)) at 90% relative humidity Wavelength / nm (RH) and 298 K. In contrast, the structural transformation of Ln(7)-Ru-4 associated with water-vapor adsorption/desorption strongly depends on the lanthanide ion; the Ln(7)-Ru-4 compounds with larger Ln(3+) ions recover the original porous structure at lower relative humidities (RH). A similar trend was observed for the ion conduction activation energy, suggesting that the bridging Ln(3+) ion plays an important role in the formation of the ion conductive pathways. La-7-Ru-4 and Ce-7-Ru-4 exhibit vapochromic luminescence associated with water vapor adsorption/desorption, arising from the (MLCT)-M-3 emission of [4Ru]. This vapochromic behavior is also affected by the replacement of the Ln3(+) ion; the vapochromic shift of Ce-7-Ru-4 was observed at RH values (near 100% RH) higher than that of La-7-Ru-4. (MLCT)-M-3 emissions of the [4Ru] metalloligand in Nd-7-Ru-4 were barely observable in the visible region, but sharp emission bands characteristic of 4f-4f transitions of the Nd3+ ion were observed in the near -infrared (NIR) region (arising from the (MLCT)-M-1 transition of [4Ru]), suggesting the transfer of energy from the [4Ru] (MLCT)-M-3 excited state to the 4f-4f transition state of the Nd3+ ions.

Rücktitelbild: Methanol-Triggered Vapochromism Coupled with Solid-State Spin Switching in a Nickel(II)-Quinonoid Complex (Angew. Chem. 9/2017)
Paramita Kar, Masaki Yoshida, Yasuhiro Shigeta, Akane Usui, Atsushi Kobayashi, Takaaki Minamidate, Noriaki Matsunaga, Masako Kato
Angewandte Chemie, 129, 9, 2556, Wiley, Feb. 2017, [Peer-reviewed]

Methanol-Triggered Vapochromism Coupled with Solid-State Spin Switching in a Nickel(II)-Quinonoid Complex
Paramita Kar, Masaki Yoshida, Yasuhiro Shigeta, Akane Usui, Atsushi Kobayashi, Takaaki Minamidate, Noriaki Matsunaga, Masako Kato
Angewandte Chemie, 129, 9, 2385, Wiley, Feb. 2017, [Peer-reviewed]

Back Cover: Methanol-Triggered Vapochromism Coupled with Solid-State Spin Switching in a Nickel(II)-Quinonoid Complex (Angew. Chem. Int. Ed. 9/2017)
Paramita Kar, Masaki Yoshida, Yasuhiro Shigeta, Akane Usui, Atsushi Kobayashi, Takaaki Minamidate, Noriaki Matsunaga, Masako Kato
Angewandte Chemie International Edition, 56, 9, 2514, Wiley, Feb. 2017, [Peer-reviewed]

Methanol-Triggered Vapochromism Coupled with Solid-State Spin Switching in a Nickel(II)-Quinonoid Complex
Paramita Kar, Masaki Yoshida, Yasuhiro Shigeta, Akane Usui, Atsushi Kobayashi, Takaaki Minamidate, Noriaki Matsunaga, Masako Kato
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 56, 9, 2345, 2349, WILEY-V C H VERLAG GMBH, Feb. 2017, [Peer-reviewed]
English, Scientific journal, A highly methanol-selective vapochromic response has been realized in a Ni-II-quinonoid complex, [Ni(HLMe)(2)] (H2LMe=4-methylamino-6-methyliminio-3-oxocyclohexa-1,4-dien-1-olate) which exhibits a reversible structural transformation including a coordination geometrical change between the square-planar and octahedral structure by the selective uptake of methanol vapor. This was accompanied by a remarkable color change between purple and orange, as well as temperature-robust spin-state switching in the solid state under ambient conditions. It is remarkable that the properties are derived by the fine structural modification of the quinonoid ligand such as methyl or ethyl analogues. Such a system has high potential for applications in memory devices as well as chemical sensors and smart responsive materials.

Aggregation-enhanced photocatalytic H-2 evolution activity of photosensitizing cadmium selenide quantum dots and platinum colloidal catalysts
Kana Sawaguchi-Sato, Atsushi Kobayashi, Masaki Yoshida, Masako Kato
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY, 335, 182, 189, ELSEVIER SCIENCE SA, Feb. 2017, [Peer-reviewed]
English, Scientific journal, We have synthesized CdSe (cadmium selenide) quantum dots (QDs) with three different surface-passivating ligands: 3-mercaptopropionic acid (MPA), 4-mercaptobenzoic acid (MBA), and 4-mercaptomethylbenzoic acid (MMBA). Although all the QDs possessed similar diameters and thiol-based ligands, the MPA-passivated QD exhibited the highest photocatalytic H2 evolution activity in the presence of a polyvinylpyrrolidone-protected Pt (Pt-PVP) colloidal catalyst. Moreover, dynamic light scattering and zeta potential measurements clearly indicated a significant difference in their dispersibility in water. Thus, CdSe-MPA, having the sterically smallest thiol ligand, displayed the largest negative zeta potential and the best dispersibility owing to the presence of negatively charged carboxylate groups on the QD surface. This was sufficient for the QD to disperse as single particles. In contrast, the bulkier MMBA ligand covered the surface of the CdSe QD with a smaller number of ligand moieties, resulting in a smaller zeta potential and the formation of large aggregates (similar to 126 nm in diameter). In the presence of a Pt-PVP colloid as the hydrogen evolution catalyst, CdSe-MPA formed large aggregates (similar to 1.6 mu m in diameter) with the Pt-PVP colloid by electrostatic interactions. Conversely, CdSe-MMBA did not form such large aggregates with the Pt-PVP colloid. Since the emission of the CdSe QD was effectively quenched in the presence of the Pt-PVP colloid, we concluded that CdSe-MPA exhibits the highest photocatalytic hydrogen evolution activity with the Pt-PVP colloidal catalyst because the electron transfer efficiency from the photosensitizing CdSe QD to the Pt-PVP colloidal catalyst is enhanced by the formation of aggregates. (C) 2016 Elsevier B.V. All rights reserved.

Stimuli-responsive Luminescent Copper(I) Complexes for Intelligent Emissive Devices
Atsushi Kobayashi, Masako Kato
CHEMISTRY LETTERS, 46, 2, 154, 162, CHEMICAL SOC JAPAN, Feb. 2017, [Peer-reviewed], [Invited]
English, Scientific journal, Extensive studies of luminescent copper(I) complexes were conducted, revealing that some of them exhibit interesting chromic luminescence in response to external stimuli such as temperature, vapor, light, and mechanical force. In this review, recent progress in the field of luminescent chromic copper(I) complexes is discussed. Tetranuclear copper(I) clusters with a cubane-type {Cu4I4} core are the most prominent group, which shows thermochromic, vapochromic, and mechanochromic luminescence, and their responsiveness to external stimuli greatly depends on coordinating organic ligands. Coordination polymerization of copper(I) cluster cores using organic linkers provides new luminescent thermochromic and vapochromic materials with behavior strongly dependent on the flexibility of the framework. The diversity of the cluster core structure and the lability to the ligand exchange are also useful to derive unique behaviors of photochromic and vapochromic response. In addition to such stimuli-responsive luminescence, the mechanochemical synthesis of highly luminescent copper(I) complexes is introduced, since the phenomenon is closely related to the mechanochromic luminescence and this approach allows the preparation of an emission layer directly on the substrate.

Reduction in Crystal Size of Flexible Porous Coordination Polymers Built from Luminescent Ru(II)-Metalloligands
Erika Saitoh, Atsushi Kobayashi, Masaki Yoshida, Masako Kato
CRYSTAL GROWTH & DESIGN, 16, 12, 7051, 7057, AMER CHEMICAL SOC, Dec. 2016, [Peer-reviewed]
English, Scientific journal, In this study, we examined the reduction in crystal size of the porous coordination polymers (PCPs) {Sr-4(H2O)(9)][4Ru](2)center dot 9H(2)O]} (Sr-2[4Ru]) and [Mg(H2O)(6)]-{[Mg, (H2O)(3)[4Ru]center dot 4H(2)O} (Mg-2[4Ru]) composed of a luminescent metalloligand [Ru(4,4'-dcbpy)](4-) ([4Ru]; 4,4'= 4,4'-dicarboxy-2,2'-bipyridine) using a coordination modulation method. Scanning electron microscopy measurements clearly show that the sizes of crystals of Sr-2[4Ru] and Mg-2[4Ru] were successfully reduced to the mesoscale (about 500 nm width and 10 nm thickness for Sr-2[4Ru] (abbreviated as m-Sr-2[4Ru]) and about 1 mu m width and 30 nm thickness for Mg-2[4Ru] (abbreviated as m-Mg-2[4Ru])) using lauric acid as a coordination modulator. Interestingly, the nanocrystals of m-Sr-2[4Ru] formed flower-like aggregates with diameters of 1 mu m, whereas flower-like aggregates were not formed in m-Mg-2[4Ru]. Water vapor adsorption isotherms of these nanocrystals suggest that the water adsorption behavior of m-Sr-2[4Ru], which has a three-dimensional lattice structure containing small pores, is significantly different from that of the bulk Sr-2[4Ru] crystal, as shown by the vapor adsorption isotherm. In contrast, m-Mg-2[4Ru], which has a two-dimensional sheet structure, had an adsorption isotherm very similar to that of the bulk sample. These contrasting results suggest that the dimensionality of the coordination framework is an important factor for the guest adsorption behavior of nanocrystalline PCPs.

Conducting Behavior and Valence Ordering of a One-Dimensional MMX-Type Coordination Polymer under High Pressure
Kazuya Otsubo, Tomohiko Suto, Atsushi Kobayashi, Ryuichi Ikeda, Masato Hedo, Yoshiya Uwatoko, Hiroshi Kitagawa
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 2016, 27, 4402, 4407, WILEY-V C H VERLAG GMBH, Sep. 2016, [Peer-reviewed]
English, Scientific journal, One-dimensional (1D) halogen-bridged mixed-valent binuclear metal compounds, the so-called MMX chains, are well known as highly conductive coordination polymers because of the high electronic flexibility within their metal-dimer unit. Herein, we report on the conducting behavior and electronic state of a highly conductive MMX-chain compound, Pt-2(dta)(4)I (dta: CH3CS2-) under high pressure. Electrical resistivity measurements showed that this compound exhibits semiconducting behavior in a broad pressure region, despite metallic conduction under ambient pressure. Raman spectra provided clear information about the semiconducting state of this compound under pressure, which was also supported by X-ray diffraction (XRD) studies. Moreover, we successfully clarified the pressure temperature phase diagram of this material. By comparing with an analogous material, we found that the difference in the alkyl chain length of the terminal ligand plays an important role for the conducting behavior and the electronic phase under pressure.

Core-Structure-Dependent Luminescence of Thiolato-Bridged Copper(I) Cluster Complexes
Kotaro Shimada, Atsushi Kobayashi, Yuriko Ono, Hiroki Ohara, Tatsuya Hasegawa, Tetsuya Taketsugu, Eri Sakuda, Soichiro Akagi, Noboru Kitamura, Masako Kato
JOURNAL OF PHYSICAL CHEMISTRY C, 120, 29, 16002, 16011, AMER CHEMICAL SOC, Jul. 2016, [Peer-reviewed]
English, Scientific journal, Thiolato-bridged dinuclear, tetranuclear, and hexanuclear Cu(I) complexes [Cu-2(P boolean AND S)(2)(PPh3)(2)], [Cu-4(P boolean AND S)(4)(CH3CN)(2)], and [Cu-6(P boolean AND S)(6)] (abbreviated as Cu-2, Cu-4, and Cu-6, respectively, P boolean AND S = 2-(diphenylphosphino)benzenethiolate, PPh3 = triphenylphosphine) were synthesized and characterized by elemental analyses and single-crystal X-ray diffraction measurements. These complexes had {Cu2S2}, {Cu4S4}, and {Cu6S6} cluster cores and exhibited strong luminescence at room temperature in solid states. Different luminescence properties were observed depending on the core structure. Cu-2, Cu-4, and Cu-6 exhibited blue-green (lambda(max) = 482 nm, Phi(em) = 0.52), green (lambda(max) = 526 nm, Phi(em) = 0.19), and yellow (lambda(max) = 553 nm, Phi(em) = 0.49) luminescence, respectively, at 298 K in the solid state; among them, only Cu6 showed luminescence thermochromism. Different radiative rate constants at room temperature and 78 K derived from the emission lifetimes and quantum yields indicate that the luminescence from Cu-2 and Cu-4 at room temperature originated from thermally activated delayed fluorescence (TADF), whereas the luminescence at low temperatures was attributed to the phosphorescence. The temperature dependence of the emission lifetimes was successfully analyzed by the singlettriplet two-state model with an energy difference (Delta ES1-T1) of 547 and 775 cm(-1) for Cu-2 and Cu-4, respectively. Based on the time-dependent density-functional theory calculations, the origin of the luminescence for Cu-2 and Cu-4 was attributed to the charge transfer from the cluster core to the ligand. Moreover, the small values of Delta ES1-T1 for Cu-2 and Cu-4 were supported by the excited state calculations. On the other hand, the emission origin of Cu-6 was attributed to the phosphorescence from the triplet cluster-centered (3CC) excited state in which the electron is located on a bonding in-phase orbital constructed from the 4s/4p orbitals of the Cu atoms because only Cu6 contains trigonal-planar Cu(I) ions in the cluster.

Photocatalytic Water Oxidation Driven by Functionalized Ru(II) Photosensitizers: Effects of Molecular Charge and Immobilization of Molecular Photosensitizer
Atsushi Kobayashi, Sogo Furugori, Masaki Yoshida, Masako Kato
CHEMISTRY LETTERS, 45, 6, 619, 621, CHEMICAL SOC JAPAN, Jun. 2016, [Peer-reviewed]
English, Scientific journal, We synthesized a novel tris(bipyridyl)Ru(II) complex with sulfonic acid groups, [Ru(dSbpy)(bpy)(2)] (RuCS2; H(2)dSbpy: 2,2'-bipyridine-4,4'-bis(methanesulfonic acid)). The photosensitizing efficiency of water oxidation in the presence of a Na2S2O8 sacrificial electron acceptor was higher than that of the widely used phosphonic acid analog, [Ru(H(4)dPbpy)(bpy)(2)]Cl-2 (RuCP2; H(4)dPbpy: 2,2'-bipyridine-4,4'-bis(methanephosphonic acid)). The photosensitizing efficiency of RuCP2 for water oxidation was remarkably enhanced by immobilization onto semiconducting TiO2 nanoparticles.

Systematic Introduction of Aromatic Rings to Diphosphine Ligands for Emission Color Tuning of Dinuclear Copper(I) Iodide Complexes
Yuka Okano, Hiroki Ohara, Atsushi Kobayashi, Masaki Yoshida, Masako Kato
INORGANIC CHEMISTRY, 55, 11, 5227, 5236, AMER CHEMICAL SOC, Jun. 2016, [Peer-reviewed]
English, Scientific journal, We have newly synthesized two solution-stable luminescent dinuclear copper(I) complexes, [Cu-2(mu-I)(2)(dpppy)(2)] (Cu-py) and [Cu-2(mu-I)(2)(dpppyz)(2)] (Cu-pyz), where dpppy = 2,3-bis(diphenylphosphino)pyridine and dpppyz = 2,3-bis(diphenylphosphino)pyrazine, using chelating diphosphine ligands composed of N-heteroaromatic rings. X-ray analysis clearly indicates that the molecular structures of Cu-py and Cu-pyz are almost identical with that of the parent complex, [Cu-2(mu-I)(2)(dppb)(2)] [Cu-bz; dppb = 2,3-bis(diphenylphosphino)benzene]. Complexes Cu-py and Cu-pyz exhibit luminescence [emission quantum yield (Phi(em)) = 0.48 and 0.02, respectively] in the solid state at 298 K. A wide emission color tuning, from 497 to 638 nm (energy = 0.55 eV, with an emission color ranging from green to reddish-orange), was achieved in the solid state by the introduction of pyridinic N atoms into the bridging phenyl group between the two diphenylphosphine groups. Density functional theory calculations suggest that the emission could originate from the effective combination of the metal-to-ligand charge-transfer excited state with the halide-to-ligand charge-transfer excited state. Thus, the emission color change is due to stabilization of the pi* levels of the central aryl group in the diphosphine ligand. Furthermore, these copper(I) complexes exhibit thermally activated delayed fluorescence at 298 K because of the small singlet-triplet energy difference (Delta E = 523 and 564 cm(-1) for Cu-py and Cu-pyz, respectively). The stability of these complexes in chloroform, due to the rigid bonds between the diphosphine ligands and the Cu-I ions, enables the preparation of emissive poly(methyl methacrylate) films by the solution-doping technique.

Environmentally Friendly Mechanochemical Syntheses and Conversions of Highly Luminescent Cu(I) Dinuclear Complexes
Atsushi Kobayashi, Tatsuya Hasegawa, Masald Yoshida, Masako Kato
INORGANIC CHEMISTRY, 55, 5, 1978, 1985, AMER CHEMICAL SOC, Mar. 2016, [Peer-reviewed]
English, Scientific journal, Luminescent dinuclear Cu(I) complexes, [Cu2X2(dpypp)(2)] [Cu-X; X = Cl, Br, I; dpypp = 2,2'(phenylphosphinediyl)dipyridine], were successfully synthesized by a solvent-assisted mechanochemical method. A trace amount of the assisting solvent plays a key role in the mechanochemical synthesis; only two solvents possessing the nitrile group, CH3CN and PhCN, were effective for promoting the formation of dinuclear Cu-X. X-ray analysis revealed that the dinuclear structure with no Cu center dot center dot center dot Cu interactions, bridged by two dpypp ligands, was commonly formed in all Cu-X species. These complexes exhibited bright green emission in the solid state at room temperature (phi = 0.23, 0.50, and 0.74; lambda(em) = 528, 518, and 530 nm for Cu-Cl, Cu-Br, and Cu-I, respectively). Emission decay measurement and TD-DFT calculation suggested that the luminescence of Cu-X could be assigned to phosphorescence from the triplet metal-to-ligand charge-transfer ((MLCT)-M-3) excited state, effectively mixed with the halide-to-ligand charge-transfer ((XLCT)-X-3) excited state, at 77 K. The source of emission changed to thermally activated delayed fluorescence (TADF) with the same electronic transition nature at room temperature. In addition, the CH3CN-bound analogue, [Cu-2(CH3CN)(2)(dpypp)(2)](BF4)(2), was successfully mechanochemically converted to Cu-X by grinding with solid KX in the presence of a trace amount of assisting water.

Shape-Memory Platinum(II) Complexes: Intelligent Vapor-History Sensor with ON-OFF Switching Function
Yasuhiro Shigeta, Atsushi Kobayashi, Tadashi Ohba, Masaki Yoshida, Takeshi Matsumoto, Ho-Chol Chang, Masako Kato
CHEMISTRY-A EUROPEAN JOURNAL, 22, 8, 2682, 2690, WILEY-V C H VERLAG GMBH, Feb. 2016, [Peer-reviewed]
English, Scientific journal, A novel platinum(II)-diimine complex, [Pt(CN)(2)(H(2)dcphen)] (1; H(2)dcphen=4,7-dicarboxy-1,10- phenanthroline), was synthesized and its vapochromic shape-memory behavior was evaluated. The as-synthesized amorphous purple solid, [Pt(CN)(2)(H(2)dcphen)]2H(2)O (1P), exhibited vapochromic behavior in the presence of alcoholic vapors through transformation to a red, crystalline, porous, vapor-adsorbed form, 1Rvapor. The obtained 1Rvapor complex released the adsorbed vapors upon heating without collapse of the porous structure. The vaporfree, porous 1Ropen could detect water or n-hexane vapor, although these vapors could not induce 1P-to-1Rvapor transformation, and 1Ropen could easily be converted to the initial 1P by manual grinding. These results indicate that 1 is a new shape-memory material that functions through formation and collapse of the porous framework with an emission change upon vapor-adsorption and grinding; this enables it to exhibit vapor history and ON-OFF switching sensing functions.

A Redox-Active Dinuclear Platinum Complex Exhibiting Multicolored Electrochromism and Luminescence
Masaki Yoshida, Naoki Yashiro, Hotaka Shitama, Atsushi Kobayashi, Masako Kato
CHEMISTRY-A EUROPEAN JOURNAL, 22, 2, 491, 495, WILEY-V C H VERLAG GMBH, Jan. 2016, [Peer-reviewed]
English, Scientific journal, A redox series of cyclometalated platinum complexes based on a dinuclear motif linked by acetamidato (aam) bridging ligands, [Pt-2(mu-aam)(2)(ppy)(2)] (ppy(-) = 2-phenylpyridinate ion), has been synthesized. The complexes in this series are easily oxidized and reduced by both electrochemical and chemical methods, and this is accompanied by multistep changes in their optical properties, that is, multiple color changes and luminescence. Isolation of the complexes and the structural determination of three oxidation states, +2, +2.33, and +3, have been achieved. The mixed-valent complex, with an average oxidation state of +2.33, forms a trimer based on the dinuclear motif. The mixed-valent complex has a characteristic color owing to intervalence transitions in the platinum chain. In contrast, the divalent complex exhibits strong red phosphorescence originating from a triplet metal-metal-toligand charge transfer ((MMLCT)-M-3) state. This study demonstrates the unique chromic behavior of a redox-active and luminescent platinum complex.

Colour tuning by the stepwise synthesis of mononuclear and homo- and hetero-dinuclear platinum(II) complexes using a zwitterionic quinonoid ligand
Paramita Kar, Masaki Yoshida, Atsushi Kobayashi, Lucie Routaboul, Pierre Braunstein, Masako Kato
DALTON TRANSACTIONS, 45, 36, 14080, 14088, ROYAL SOC CHEMISTRY, 2016, [Peer-reviewed]
English, Scientific journal, The stepwise reaction of a zwitterionic ligand, 4-methylamino-6-methyliminio-3-oxocyclohexa-1,4-dien-1-olate (QH(2)) with [Pt-2(mu-Cl)(2)(ppy)(2)] (Hppy = 2-phenylpyridine) afforded a mononuclear complex, [Pt(ppy)(QH)] (1), and a dinuclear complex, [{Pt(ppy)}(2)(mu-Q)] (2). Using [ Pd-2(mu-Cl)(2)(ppy)(2)] in the second step resulted in the formation of a heterodinuclear complex, [{Pt(ppy)}(mu-Q){Pd(ppy)}] (3), which is the first heterodinuclear complex bridged by a quinonoid ligand. Single crystal X-ray diffraction analysis revealed that all three complexes adopted double-decker structures in the crystal. For 1, intermolecular N-H center dot center dot center dot O interactions between uncoordinated N-H and O groups in two adjacent square-planar mononuclear units led to the formation of hydrogen-bonded dimers, which stacked to form a herringbone structure with a double-decker tetranuclear motif. For 2 and 3, dinuclear units bridged by Q(2) formed a double-decker motif similar to that of 1, but a tetranuclear chain in the herringbone pattern was characteristic of the dinuclear complexes. Pt. Pt (or Pt. Pd) distances were more than 3.5 angstrom, twice the van der Waals radii of Pt, suggesting weak electronic metal-metal interactions in the crystal structures. Thus, the different colours observed (brown, purple, and dark green for 1, 2, and 3, respectively) mainly originated from the molecular structures. In fact, the three complexes exhibited colourful solutions of yellow, red, and green. UV-vis absorption spectroscopy and time-dependent density-functional theory (TD-DFT) calculations revealed that colour variations occurred depending on the electronic states composed of metal ions and the quinonoid ligand.

Proton-switchable vapochromic behaviour of a platinum(II)-carboxy-terpyridine complex
Atsushi Kobayashi, Shiori Oizumi, Yasuhiro Shigeta, Masaki Yoshida, Masako Kato
DALTON TRANSACTIONS, 45, 43, 17485, 17494, ROYAL SOC CHEMISTRY, 2016, [Peer-reviewed]
English, Scientific journal, We synthesized a carboxy-substituted Pt(II)-terpyridine complex, i.e. [PtCl(Hctpy)] Cl ([1H] Cl; Hctpy = 4'-carboxy-2,2': 6',2''-terpyridine), that shows interesting switchable vapochromic behaviour upon protonation/deprotonation of the carboxy group. The as-synthesized dark-blue amorphous-like solid [1H] Cl center dot 3H(2)O was converted to a yellow crystalline solid, [1H] Cl center dot H2O, upon exposure to various polar organic solvent vapours (e.g., acetonitrile, ethanol, 1-propanol, and dichloromethane), which promote the removal of water molecules. The reaction of [1H] Cl center dot 3H(2)O with aqueous ammonia afforded a deprotonated bright-yellow crystalline complex, i.e. [PtCl(ctpy)]center dot H2O (1 center dot H2O), which exhibits red luminescence with an emission maximum at 622nm. Although the colour of 1 center dot H2O was not affected by exposure to various polar organic solvent vapours, interesting vapochromic luminescence with a remarkable red-shift of the emission maximum from 622 to 652 nm was observed upon exposure to saturated water vapour to form orange crystalline 1 center dot 3.5H(2)O X-ray structural analysis revealed that the planar and neutral complex molecule 1 forms a one-dimensional columnar structure with an intermolecular Pt center dot center dot center dot Pt distance of 3.518(2) angstrom in the orange crystall 1 center dot 3.5H(2)O, while the cationic molecule [1H](+) in the protonated form, [1H] Cl center dot H2O, generates a dimeric structure with an intermolecular Pt center dot center dot center dot Pt distance of 3.439(2) angstrom. This difference suggests that the vapochromic behaviours of the protonated and deprotonated forms could be caused by structural changes induced by water-vapour adsorption/desorption, which affect the intermolecular Pt. Pt distance, thereby changing the energy of the metal-metal-to-ligand charge-transfer (MMLCT) transition. These contrasting results for the protonated and deprotonated complexes clearly indicate that the hydrophilicity of complex 1 is significantly affected by protonation/deprotonation of the carboxy group. In addition, quasi-reversible conversion between [1H] Cl center dot 3H(2)O and 1 center dot H2O was achieved by exposure of the protonated and deprotonated forms to triethylamine and humid hydrochloric acid vapours, respectively.

Photochemical hydrogen production from 3d transition-metal complexes bearing o-phenylenediamine ligands
Masaki Yoshida, Show Ueno, Yuka Okano, Akane Usui, Atsushi Kobayashi, Masako Kato
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY, 313, 99, 106, ELSEVIER SCIENCE SA, Dec. 2015, [Peer-reviewed]
English, Scientific journal, A series of 3d transition-metal complexes bearing o-phenylenediamine (opda) ligands [M(opda)(3)](2+) (M = Mn2+, Co2+, Ni2+, and Zn2+) were systematically synthesized as perchlorate salts and their structures were determined. All the opda complexes exhibited hydrogen-evolving activities under photoirradiation conditions as in the case of previously reported [Fe(opda)(3)](2+), whereas replacement of the opda ligands with other aromatic amine ligands caused a dramatic decrease of hydrogen-evolving activities. These results support a ligand-based reaction mechanism for photochemical hydrogen evolution from [M(opda)(3)](2+), which involves (1)pi pi* excitation of the opda ligand followed by homolytic N-H bond cleavage. In contrast to the non-catalytic reactions, an obvious metal-ion dependency was observed for the catalytic systems including hydroquinone as a proton/electron donor. The results of this work demonstrate a strategy for the design of a molecular photochemical hydrogen-production system under ambient temperature and pressure. (C) 2015 Elsevier B.V. All rights reserved.

Visualization of Ion Conductivity: Vapochromic Luminescence of an Ion-Conductive Ruthenium(II) Metalloligand-Based Porous Coordination Polymer
Ayako Watanabe, Atsushi Kobayashi, Erika Saitoh, Yuki Nagao, Masaki Yoshida, Masako Kato
INORGANIC CHEMISTRY, 54, 23, 11058, 11060, AMER CHEMICAL SOC, Dec. 2015, [Peer-reviewed]
English, Scientific journal, We synthesized a new porous coordination polymer {La-1.75(OH)(1.25)[RU(dcbpy)(3)]center dot 16H(2)O} (La-7-[4Ru](4); H(2)dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) composed of a luminescent ruthenium(II) metalloligand [Ru(4,4'-dcbpy)(3)](4-) and La3+ cations. X-ray analysis for La-7-[4Ru](4) revealed that the La3+ cations and [4Ru] metalloligands are crystallized in a molar ratio of 7:4 with OH- counteranions and a void fraction of similar to 25.5%. Interestingly, La-7-[4Ru](4) shows a reversible structural transition triggered by water ad/desorption, which affects not only the triplet metal-to-ligand charge-transfer ((MLCT)-M-3) emission energy but also the ion conductivity in the solid state. This correlation suggests that La-7-[4Ru](4) is an interesting material that enables visualization of the ion conductivity via the 3MLCT emission energy.

Coordination Structure Conversion of Hydrazone-Palladium(II) Complexes in the Solid State and in Solution
Fumi Kitamura, Kana Sawaguchi, Asami Mori, Shoji Takagi, Takayoshi Suzuki, Atsushi Kobayashi, Masako Kato, Kiyohiko Nakajima
INORGANIC CHEMISTRY, 54, 17, 8436, 8448, AMER CHEMICAL SOC, Sep. 2015, [Peer-reviewed]
English, Scientific journal, We prepared hydrazone palladium(II) complexes of [PdCl2(HLn)] and [PdCl(L-n)] (n = 1-3) by the reaction of [PdCl2(cod)] or [PdCl2(PhCN)(2)] and the hydrazone ligands of HLn {N'-(pyridin-2-ylmethylene)picolinohydrazide (HL1), N'-[1-(pyridin-2-yl)ethylidene]picolinohydrazide (HL2), and N'-[ (6-methylpyridin-2-yOmethylene]picolinohydrazide (HL3)}. The structures of the complexes were determined by X-ray analysis. The hydrazone ligands had kappa N(pyl), kappa N(imine) and kappa N(amidate) kappa N(py2) bidentate coordination modes in [PdCl2(HLn] (1, n = 1; 2, n = 2) and in [PdCl2(HL3)] (3), respectively. In contrast, tridentate coordination modes of kappa N(pyl)), kappa N(imine), kappa N(py2) and kappa N(py1), kappa N(amidate), kappa N(py2) were observed in [PdCl(L-n)] (4, n = 1; 5, n = 2) and in [PdCl(L-n)] (6, n = 1; 7, n = 2; 8, n = 3). Thermal conversion of complexes 1-3 to complexes 6-8 proceeded in acetonitrile. Complexes 4 and 5 were obtained from complexes 1 and 2, respectively, in a basic acetonitrile solution under dark conditions. Complex 4 reverted immediately to complex 1 in an acidic acetonitrile solution that included hydrochloric acid. However, under room light, in the basic acetonitrile solution that included trimethylamine, complex 4 converted photochemically to complex 6. The thermochromic or vapochromic structure conversion of these complexes also occurred in the solid state. On heating at 180 degrees C, the color of the crystals of complexes 1, 2, and 3 changed from yellow to orange in the solid state. H-1 NMR and/or UV vis absorption spectroscopy confirmed that the orange complexes 6-8 were produced. The reddish-orange crystals of complexes 4 and 5 were exposed to hydrogen chloride vapor to yield the yellow products of complexes 1 and 2, respectively.

Impact of a Carboxyl Group on a Cyclometalated Ligand: Hydrogen-Bond- and Coordination-Driven Self-Assembly of a Luminescent Platinum(II) Complex
Masanori Ebina, Atsushi Kobayashi, Tomohiro Ogawa, Masaki Yoshida, Masako Kato
INORGANIC CHEMISTRY, 54, 18, 8878, 8880, AMER CHEMICAL SOC, Sep. 2015, [Peer-reviewed]
English, Scientific journal, A new luminescent cyclometalated platinum(II) complex containing a carboxyl group, trans-[Pt(pcppy)(pic)] [1-COOH; Hpcppy = 2-(p-carboxyphenyl)pyridine and Hpic = picolinic acid] has been synthesized and characterized. The luminescence behavior of 1-COOH in the solid and solution states is completely different despite the similarity of the luminescence in both states for the nonsubstituted complex, [Pt(ppy)(pic)] (1-H; Hppy = 2-phenylpyridine). Interestingly, 1-COOH exhibits concentration-dependent absorption and emission behavior based on its aggregation in a basic aqueous solution despite the absence of amphiphilic character.

Vapochromic Luminescence and Flexibility Control of Porous Coordination Polymers by Substitution of Luminescent Multinuclear Cu(I) Cluster Nodes
Takahiro Hayashi, Atsushi Kobayashi, Hiroki Ohara, Masaki Yoshida, Takeshi Matsumoto, Ho-Chol Chang, Masako Kato
INORGANIC CHEMISTRY, 54, 18, 8905, 8913, AMER CHEMICAL SOC, Sep. 2015, [Peer-reviewed]
English, Scientific journal, Two luminescent porous coordination polymers (PCPs), i.e., [Cu-2(mu(2)-I)(2)ctpyz](n) and [Cu-4(mu(3)-I)(4)ctpyz](n) (Cu2 and Cu4, respectively; ctpyz = cis-1,3,5-cyclohexanetriyl-2,2',2 ''-tripyrazine), were successfully synthesized and characterized by single-crystal X-ray diffraction and luminescence spectroscopic measurements. Cu2 consists of rhombus-type dinuclear {Cu2I2} cores bridged by ctpyz ligands, while Cu4 is constructed of cubane-type tetranuclear {Cu4I4} cores bridged by ctpyz ligands. The void fraction of Cu4 is estimated to be 48.0%, which is significantly larger than that of Cu2 (19.9%). Under UV irradiation, both PCPs exhibit red luminescence at room temperature in the solid state (lambda(em) values of 660 and 614 nm for Cu2 and Cu4, respectively). Although the phosphorescence of Cu2 does not change upon removal and/or adsorption of EtOH solvent molecules in the porous channels, the solid-state emission maximum of Cu4 red-shifts by 36 run (lambda(em) = 650 nm) upon the removal of the adsorbed benzonitrile (PhCN) molecules from the porous channels (and vice versa). This large difference in the vapochromic behavior of Cu2 and Cu4 is closely related to the framework flexibility. The framework of Cu2 is sufficiently rigid to retain the porous structure without solvated EtOH molecules, whereas the porous structure of Cu4 collapses easily after removal of the adsorbed PhCN molecules to form a nonporous amorphous phase. The original vapor-adsorbed porous structure of Cu4 is regenerated by exposure of the amorphous solid to not only PhCN vapor but also tetrahydrofuran, acetone, ethyl acetate, and N,N-dimethylformamide vapors. The Cu4 structures with the various adsorbed solvents showed almost the same emission maxima as the original PhCN-adsorbed Cu4, except for DMF-adsorbed Cu4, which showed no luminescence probably because of weak coordination of the DMF vapor molecules to the Cu(I) centers of the tetranuclear {Cu4I4} core.

A dual-emissive ionic liquid based on an anionic platinum(II) complex
Tomohiro Ogawa, Masaki Yoshida, Hiroki Ohara, Atsushi Kobayashi, Masako Kato
Chemical Communications, 51, 69, 13377, 13380, Royal Society of Chemistry, 14 Jul. 2015, [Peer-reviewed]
English, Scientific journal, An ionic liquid fabricated from an anionic cyclometalated platinum(ii) complex and an imidazolium cation exhibits dual emission from the monomeric and aggregated forms of the platinum complex anions, leading to temperature-dependent color changes of luminescence.

Effects of N-heteroaromatic ligands on highly luminescent mononuclear copper(I)-halide complexes
Hiroki Ohara, Atsushi Kobayashi, Masako Kato
COMPTES RENDUS CHIMIE, 18, 7, 766, 775, ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER, Jul. 2015, [Peer-reviewed]
English, Scientific journal, A series of mononuclear Cu(I)-halide complexes, [CuX(PPh3)(2)(L)] (X= CI-, Br-, I-; PPh3 = triphenylphosphine; L = pyridine (py), isoquinoline (iq), 1,6-naphthyridine (nap)), were synthesized. The emission color of [CuX(PPh3)2(L)] varies from blue to red by changing the L ligands and the halide ions, and all the complexes exhibit high emission quantum yields (0.16-0.99) in the crystals. The emission studies revealed that the emissive states of [CuX(PPh3)(2)(L)] differ depending on the L ligand. Complexes [CuX(PPh3)(2)(py)] and [CuX(PPh3)2(nap)] mainly emit from the singlet metal-to-ligand charge transfer mixed with the halide-to-ligand charge transfer ((1)(M + X)LCT) state at room temperature. In contrast, emissions from [CuX(PPh3)(2)(iq)] at room temperature originate from both (3)(M + X)LCT and (3)pi pi* states. These results indicate that N-heterodomatic ligands play an important role in the emission properties of mononuclear Cu(I)-halide complexes. (C) 2015 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

Enhanced Electric Dipole Transition in Lanthanide Complex with Organometallic Ruthenocene Units
Yasuchika Hasegawa, Nao Sato, Yuichi Hirai, Takayuki Nakanishi, Yuichi Kitagawa, Atsushi Kobayashi, Masako Kato, Tomohiro Seki, Hajime Ito, Koji Fushimi
JOURNAL OF PHYSICAL CHEMISTRY A, 119, 20, 4825, 4833, AMER CHEMICAL SOC, May 2015, [Peer-reviewed]
English, Scientific journal, Enhanced luminescence of a lanthanide complex with dynamic polarization of the excited state and molecular motion is introduced. The luminescent lanthanide complex is composed of one Eu(hfa)(3) (hfa, hexafluoroacetylacetonate) and two phosphine oxide ligands with ruthenocenyl units Rc, [Eu(hfa)(3)(RcPO)(2)] (RcPO = diphenylphosphorylruthenocene). The ruthenocenyl units in the phosphine oxide ligands play an important role of switching for dynamic molecular polarization and motion in liquid media. The oxidation states of the ruthenocenyl unit (Rc(1+)/Rc(1+)) are controlled by potentiostatic polarization. Eu(III) complexes attached with bidentate phosphine oxide ligands containing ruthenocenyl units, [Eu(hfa)(3)(RcBPO)] (RcBPO = 1,1'-bis(diphenylphosphoryl)ruthenocene), and with bidentate phosphine oxide ligands, [Eu(hfa)(3)(BIPHEPO)] (BIPHEPO =1,1'-biphenyl-2,2'-diylbis(diphenylphosphine oxide), were also prepared as references. The coordination structures and electrochemical properties were analyzed using single crystal X-ray analysis, cyclic voltammetry, and absorption spectroscopy measurements. The luminescence properties were estimated using an optoelectrochemical cell. Under potentiostatic polarization, a significant enhancement of luminescence was successfully observed for [Eu(hfa)(3)(RcPO)(2)], while no spectral change was observed for [Eu(hfa)(3)(RcBPO)]. In this study, the remarkable enhanced luminescence phenomena of Eu(III) complex based on the dynamic molecular motion under potentiostatic polarization have been performed.

Systematic Syntheses and Metalloligand Doping of Flexible Porous Coordination Polymers Composed of a Co(III)-Metalloligand
Atsushi Kobayashi, Yui Suzuki, Tadashi Ohba, Tomohiro Ogawa, Takeshi Matsumoto, Shin-ichiro Noro, Ho-Chol Chang, Masako Kato
INORGANIC CHEMISTRY, 54, 6, 2522, 2535, AMER CHEMICAL SOC, Mar. 2015, [Peer-reviewed]
English, Scientific journal, A series of flexible porous coordination polymers (PCPs) RE-Co, composed of a Co(III)-metalloligand [Co(dcbpy)(3)](3-) (Co; H(2)dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) and lanthanide cations (RE3+ = La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Er3+), was systematically synthesized. X-ray crystallographic analysis revealed that the six carboxylates at the top of each coordination octahedron of Co(III)-metalloligand were commonly bound to RE3+ cations to form a rock-salt-type porous coordination framework. When RE-Co contains a smaller and heavier RE3+ cation than Nd3+, the RE-Co crystallized in the cubic Fm-3m space group, whereas the other three RE-Co with larger RE3+ crystallized in the lower symmetrical orthorhombic Fddd space group, owing to the asymmetric 10-coordinated bicapped square antiprism structure of the larger RE3+ cation. Powder X-ray diffraction and vapor-adsorption isotherm measurements revealed that all synthesized RE-Co PCPs show reversible amorphous-crystalline transitions, triggered by water-vapor-adsorption/desorption. This transition behavior strongly depends on the kind of RE3+; the transition of orthorhombic RE-Co was hardly observed under exposure to CH3OH vapor, but the RE-Co with smaller cations such as Gd3+ showed the transition under exposure to CH3OH vapors. Further tuning of vapor-adsorption property was examined by doping of Ru(II)-metalloligands, [Ru(dcbpy)(3)](4-), [Ru(dcbpy)(2)Cl-2](4-), [Ru(dcbpy)(tpy)Cl](-), and [Ru(dcbpy)(dctpy)](3-) (abbreviated as RuA, RuB, RuC, and RuD, respectively; tpy = 2,2':6',2?-terpyridine, H2dctpy = 4,4"-dicarboxy-2,2':6',2"-terpyridine), into the Co(III)-metalloligand site of Gd-Co to form the Ru(II)-doped PCP RuX@Gd-Co (X = A, B, C, or D). Three Ru(II)-metalloligands, RuA, RuB, and RuD dopants, were found to be uniformly incorporated into the Gd-Co framework by replacing the original Co(III)-metalloligand, whereas the doping of RuC failed probably because of the less number of coordination sites. In addition, we found that the RuA doping into the Gd-Co PCP had a large effect on vapor-adsorption due to the electrostatic interaction originating from the negatively charged RuA sites in the framework and the charge-compensating Li+ cations in the porous channel.

Syntheses and Structures of Molybdenum-Oxo Complexes Prepared by the Reactions of [Mo-2(II)(OAc)(4)] with tert-Butyl- or Bromo-Substituted Catechols
Takeshi Matsumoto, Hirokazu Yano, Masanori Wakizaka, Atsushi Kobayashi, Masako Kato, Ho-Chol Chang
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, 88, 1, 74, 83, CHEMICAL SOC JAPAN, Jan. 2015, [Peer-reviewed]
English, Scientific journal, The reactions of [Mo-2(II)(OAc)(4)] (OAc-: acetato) with catecholato derivatives (R-Cat(2-)), possessing electron-donating t-Bu groups (3,6-DTBCat(2-)) or electron-withdrawing Br groups (Br(4)Cat(2-)), results in the formation of a mononuclear complex [Na(THF)(6)][Mo-V(3,6-DTBCat)(3)] (1) and a dinuclear complex either [Na-6(Br(4)SQ)(2)][Mo-2(IV)(mu-O)(2)-(Br(4)Cat)(4)] or [Na-6(Br(4)Cat)(2)][Mo-2(V)(mu-O)(2)(Br(4)Cat)(4)] (3). Complex 3 has a [Mo(mu-O)(2)Mo] core as part of a dimer of [O=Mo-m(Br(4)Cat)(2)](n-) (m = IV or V, n= 2 or 1) moieties assembled in a head-to-tail arrangement, which has been structurally characterized as the a bis-mu-oxo molybdenum dinuclear complex containing catecholato ligands. The bond distance between the Mo atoms (2.4286(17) angstrom) strongly suggests that a Mo-IV=Mo-IV or Mo-V-Mo-V bonding character exists in 3. Differences in the substituent groups on the catecholato ligand affect not only the product formed but also the reactivity of both complexes. Complex 3 shows O-atom abstraction reactivity with dimethyl sulfoxide (DMSO) and forms dimethyl sulfide (DMS). These results support a high oxophilicity of the Mo center in 3.

Interactions between the trianionic ligand-centred redox-active metalloligand [Cr-III(perfluorocatecholato)(3)](3-) and guest metal ions
Masanori Wakizaka, Takeshi Matsumoto, Atsushi Kobayashi, Masako Kato, Ho-Chol Chang
DALTON TRANSACTIONS, 44, 32, 14304, 14314, ROYAL SOC CHEMISTRY, 2015, [Peer-reviewed]
English, Scientific journal, The redox-active metalloligand (RML) (Et3NH)(3)[Cr-III(F(4)Cat)(3)] (F(4)Cat = perfluorocatecholato) (1) was synthesized and its interactions with guest metal ions Li+, Mn2+, Fe2+, Co2+, Cu2+, and Zn2+ were examined. Cyclic voltammetry measurements and spectroelectrochemical studies revealed that complex 1 shows three-step ligand-centred one-electron oxidation to consecutively generate [Cr-III(F(4)Cat)(2)(F(4)SQ)](2-) (F(4)SQ = perfluorosemiquinonato), [Cr-III(F(4)Cat)(F(4)SQ)(2)](-), and [Cr-III(F(4)SQ)(3)] at -0.12, 0.23, and 0.53 V vs. Ag/Ag+ in dichloromethane, or at -0.21, 0.08, and 0.50 V in acetonitrile (MeCN), respectively. Titration experiments in MeCN revealed that treatment of 1 with Cu2+ leads to the formation of [Cr-III(F(4)Cat)(2)(F(4)SQ)](2-) and Cu+ via a redox reaction. However, when 1 was treated with Li+, Mn2+, Fe2+, Co2+, and Zn2+, further titration experiments revealed that these metal ions coordinated via the lone pairs on the coordinating oxygen atoms of the F(4)Cat(2-) moieties in a one-to-one ratio, and binding constants of 3.7 (+/- 0.3) x 10(4) (Li+), 1.5 (+/- 0.2) x 10(5) (Mn2+), 2.2 (+/- 0.4) x 10(5) (Fe2+), 1.9 (+/- 0.2) x 10(5) (Co2+), and 3.8 (+/- 0.4) x 10(5) M-1 (Zn2+) were established. Moreover, the oxidation potentials of 1 were positively shifted by 0.08-0.33 V upon addition of guest metal ions. Spectroelectrochemical studies of 1 in the presence of guest metal ions suggested that ligand-centred one- and two-electron oxidation of the RML occurred for Li+, Mn2+, Co2+, and Zn2+, respectively, while guest metal-centred one-electron oxidation was observed for Fe2+. Considering all the aforementioned results, this study demonstrated for the first time the ability of [Cr-III(F(4)Cat)(3)](3-) to act as a RML in solution.

Simple and extremely efficient blue emitters based on mononuclear Cu(i)-halide complexes with delayed fluorescence
Hiroki Ohara, Atsushi Kobayashi, Masako Kato
Dalton Transactions, 43, 46, 17317, 17323, Royal Society of Chemistry, 14 Dec. 2014, [Peer-reviewed]
English, Scientific journal, Simple mononuclear Cu(i)-halide complexes, [CuX(PPh3)2(4-Mepy)] (X = Cl-, Br-, I-
PPh3 = triphenylphosphine
4-Mepy = 4-methylpyridine), were prepared. They exhibit blue light emission, with extremely high photoluminescence quantum yields approaching 100% in the crystals. Emission lifetime analyses and density functional theory calculations revealed that the bright blue light emission at room temperature is mainly delayed fluorescence originating from the singlet metal-to-ligand charge transfer (MLCT) state combined with the halide-to-ligand charge transfer (XLCT) state, (1(M + X)LCT), while that at 77 K is phosphorescence from the 3(M + X)LCT transition state, due to the small singlet-triplet energy differences (ΔE = 940-1170 cm-1). The ternary ligand systems consisting of halide, bulky phosphine, and N-heteroaromatic ligands constitute inexpensive pure-blue-light-emitting materials, which can be fabricated by facile procedures such as simple manual grinding. This journal is

Tribo-, Thermo-, and Vapochromic Behavior of Hydrazone-Pt(II) Complexes Induced by Protonation-Deprotonation in the Solid State, and Their Luminescence Properties in Solution
Yurika Yamashita, Tomoya Tateishi, Kana Sawaguchi, Atsushi Kobayashi, Masako Kato, Kiyohiko Nakajima
CHEMISTRY LETTERS, 43, 12, 1912, 1914, CHEMICAL SOC JAPAN, Dec. 2014, [Peer-reviewed]
English, Scientific journal, Pt(II) complexes containing tridentate hydrazone ligands were prepared. Reversible protonation and deprotonation of the hydrazone complexes occurred in solution and in the solid state. On grinding and heating the yellow-colored crystals of the protonated complex [PtCl(HL)]Cl, the deprotonated red-colored product, [PtCl(L)], was produced, and HCl vapor was released. The deprotonated complex reverted to the yellow-colored protonated complex on exposure of the red-colored crystals to HCl vapor. Both [PtCl(HL)]Cl and [PtCl(L)] exhibited different luminescence colors in acetonitrile solution.

Vapochromic Platinum(II) Complexes: Crystal Engineering toward Intelligent Sensing Devices
Atsushi Kobayashi, Masako Kato
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 2014, 27, 4469, 4483, WILEY-V C H VERLAG GMBH, Sep. 2014, [Peer-reviewed], [Invited]
English, Scientific journal, Vapochromic materials that show reversible color change driven by vapor adsorption/desorption have drawn significant attention because of their potential applications in chemical sensors and chemical-switching modules. Among the vapochromic coordination complexes reported so far, a series of square-planar Pt-II complexes has been studied and represents one of the most promising systems for practical chemical sensors. For such systems, the color of the complexes strongly depends not only on the ligand-field splitting, but also on the intermolecular distance between the Pt-II ions. This microreview presents recent results of vapochromic complexes centered on one-dimensionally stacked Pt-II systems from the viewpoint of the origin of their vapochromic behavior. The design of vapochromic materials has been facilitated because several useful chromophores, including metallophilic interaction between Pt-II ions, have been developed. However, it is still challenging to realize a specifically sensitive and selective response to targeted vapors. This review focuses on strategies to achieve assembled Pt-II complexes with selective vapochromic responses.

Immobilization of a Redox-active Catecholato Pt(II) Complex on an Indium-doped Tin Oxide Electrode via Phosphonate Anchors
Hirotaka Honda, Takeshi Matsumoto, Ryo Tamura, Katsuhiko Kanaizuka, Atsushi Kobayashi, Masako Kato, Masa-aki Haga, Ho-Chol Chang
CHEMISTRY LETTERS, 43, 8, 1189, 1191, CHEMICAL SOC JAPAN, Aug. 2014, [Peer-reviewed]
English, Scientific journal, The reaction of tetraethyl [2,3-dihydroxy-1,4-phenylenebis-(methylene)]bisphosphonate (Et4LH2) with [PtCl2(DTBbPY)] (DTBbpy: 4,4'-di-tert-butyl-2,2'-bipyridine) afforded [Pt(Me4L)-(DTBbpY)] (1), [Pt(Bn4L-)(DTBbPY)] (2), Na-2[Pt(Me2L)-(DTBbpy)] (3), and [Pt(H4L)(DTBbpy)] (4) with tetramethyl-, tetrabenzyl-, half-protected, and fully-deprotected groups under different reaction conditions. The introduction of phosphonatomethyl groups at the 3,6-position of a redox-active catecholato unit led to slight shifts in charge-transfer bands and catecholato-centered redox processes in solution. The presence of deprotonated anchors in 3 resulted in the immobilization of the complex onto an indium-doped tin oxide electrode, demonstrating a well-defined redox response from the tethered complex.

Simple Manual Grinding Synthesis of Highly Luminescent Mononuclear Cu(I) Iodide Complexes
Hiroki Ohara, Atsushi Kobayashi, Masako Kato
CHEMISTRY LETTERS, 43, 8, 1324, 1326, CHEMICAL SOC JAPAN, Aug. 2014, [Peer-reviewed]
English, Scientific journal, Highly luminescent mononuclear copper(I) iodide complexes [CuI(PPh3)(2)(L)] have been synthesized by simple manual grinding of copper(I) iodide, PPh3, and N-heteroaromatic ligands (L = isoquinoline, 1,6-naphthyridine, and pyridine). They exhibit different colors of luminescence depending on L affording very high quantum yields (0.63-0.99).

Synthesis and Vapor-adsorption Behavior of a Flexible Porous Coordination Polymer Built from a Bis(bipyridyl)-Cu(I) Metalloligand
Atsushi Kobayashi, Akira Sugiyama, Tadashi Ohba, Yui Suzuki, Ho-Chol Chang, Masako Kato
CHEMISTRY LETTERS, 43, 7, 1070, 1072, CHEMICAL SOC JAPAN, Jul. 2014, [Peer-reviewed]
English, Scientific journal, A new porous coordination polymer (PCP), formulated as {[La-2(III)(mu(3)-OH)(CH3COO)(2)(H2O)][Cu-I(dmdcbpy)(2)]center dot 9H(2)O} (La2Cu center dot 9H(2)O; H(2)dmdcbpy: 6,6'-dimethyl-5,5'-dicarboxy-2,2'bipyridine), was synthesized and characterized by X-ray diffraction and vapor-adsorption isotherms. The porous framework of La2Cu consists of a 3-D coordination network of the Cu(I)-metalloligand and the tetranuclear La-4 cluster {La-4(mu(3)-OH)(2)(CH3COO)(4)(H2O)(2)}. La2Cu exhibits reversible guest adsorption desorption for various vapors, with reversible structural transformations.

Photoinduced Dimerization Reaction Coupled with Oxygenation of a Platinum(II)-Hydrazone Complex
Atsushi Kobayashi, Daisuke Yamamoto, Hiroyuki Horiki, Kana Sawaguchi, Takeshi Matsumoto, Kiyohiko Nakajima, Ho-Chol Chang, Masako Kato
INORGANIC CHEMISTRY, 53, 5, 2573, 2581, AMER CHEMICAL SOC, Mar. 2014, [Peer-reviewed]
English, Scientific journal, Photoreactivities of Ni(II)- and Pt(II)- hydrazone complexes, [NiCI(L)] (Ni1) and [PtCl(L)] (Pt1), respectively [HL = 2-(diphenylphosphino)benzaldehyde-2-pyridylhydrazone], were investigated in detail via UV-vis absorption, H-1 nuclear magnetic resonance (NMR) spectroscopy, and electrospray ionization time-of-flight (ESI-TOF) mass spectrometry; the two photoproducts obtained from the photoreaction of Pt1 were also successfully identified via X-ray analysis. The absorption bands of the Ni1 and Pt1 complexes were very similar, centered around 530 nm, and were assigned as an intraligand charge transfer transition of the hydrazone moiety. The absorption spectrum of Pt1 in a CH3CN solution changed drastically upon photoirradiation (lambda = 530 nm), whereas no change was observed for Ni1. H-1 NMR and ESI-TOF mass spectra under various conditions suggested that the photoexcited Pt1* reacts with dissolved dioxygen to form a reactive intermediate, and the ensuing dark reactions afforded two different products without any decomposition. In contrast to the simple photo-oxidation of HL to form a phosphine oxide HL(P=O), the X-ray crystallographic analyses of the photoproducts clearly indicate the formation of a mononuclear Pt complex with the oxygenated hydrazone ligand (Pt10) and a dinuclear Pt complex with the oxygenated and dimerized hydrazone ligand (Pt2). The photosensitized reaction in the presence of an O-1(2)-generating photosensitizer, methylene blue (MB), also produced Pt1O and Pt2, indicating that the reaction between O-1(2) and ground-state Pt1 is the important step. In a highly viscous dimethyl sulfoxide solution, Pt1 was slowly, but quantitatively, converted to the mononuclear form, Pt1O, without the formation of the dinuclear product, Pt2, upon photoirradiation (and in the reaction photosensitized by MB), suggesting that this photoreaction of Pt1 involves at least one diffusion-controlled reaction. On the other hand, the same complexes Pt1O and Pt2 were also produced in the degassed solution, probably because of the reaction of the photoexcited Pt1* with the biradical character and H2O.

Flexible Coordination Polymers Composed of Luminescent Ruthenium(II) Metalloligands: Importance of the Position of the Coordination Site in Metalloligands
Atsushi Kobayashi, Tadashi Ohba, Erika Saitoh, Yui Suzuki, Shin-ichiro Noro, Ho-Chol Chang, Masako Kato
INORGANIC CHEMISTRY, 53, 6, 2910, 2921, AMER CHEMICAL SOC, Mar. 2014, [Peer-reviewed]
English, Scientific journal, Coordination polymerization reactions between ruthenium(II) metalloligands [Ru(n,n'-dcbpy)](4-) ([nRu]; n = 4, 5; n,n'-dcbpy = n,n'-dicarboxy-2,2'-bipyridine) and several divalent metal salts in basic aqueous solutions afforded porous luminescent complexes formulated as [Mg(H2O)(6)]{[Mg(H2O)(3)][4Ru]center dot 4H(2)O} (Mg-2[4Ru]center dot 13H(2)O), [Mg-2(H2O)(9)][5Ru]center dot 10H(2)O (Mg-2[5Ru]center dot 19H(2)O), {[Sr-4(H2O)(9)][4Ru](2)center dot 9H(2)O} (Sr-2[4Ru]center dot 9H(2)O)(2), {[Sr-2(H2O)(8)][5Ru]center dot 6H(2)O} (Sr-2[5Ru]center dot 14H(2)O), and {[Cd-2(H2O)(2)][5Ru]center dot 10H(2)O} (Cd-2[5Ru]center dot 12H(2)O). Single-crystal X-ray structural analyses revealed that the divalent metal ions were commonly coordinated by the carboxyl groups of the [nRu] metalloligand, forming porous frameworks with a void fraction varying from 11.4% Mg-2[4Ru]center dot 13H(2)O to 43.9% Cd-2[5Ru]center dot 12H(2)O. M-2[4Ru]center dot nH(2)O showed a reversible structural transition accompanied by water and methanol vapor adsorption/desorption, while the porous structures of M-2[5Ru]center dot nH(2)O were irreversibly collapsed by the removal of crystal water. The triplet metal-to-ligand charge-transfer emission energies of M-2[4Ru]center dot nH(2)O were lower than those of [4Ru] in aqueous solution, whereas those of M-2[5Ru]center dot nH(2)O were close to those of [5Ru] in aqueous solution. These results suggested that the position of the coordination site in the metalloligand played an important role not only on the structure of the porous framework but also on the structural flexibility involving the guest adsorption/desorption properties.

Linkage and Geometrical Isomers of Dichloridobis(triphenylphosphine)ruthenium(II) Complexes with Quinoline-2-carbaldehyde (Pyridine-2-carbonyl)hydrazone: Their Molecular Structures and Electrochemical and Spectroscopic Properties
Asami Mori, Takayoshi Suzuki, Yukinari Sunatsuki, Atsushi Kobayashi, Masako Kato, Masaaki Kojima, Kiyohiko Nakajima
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 2014, 1, 186, 197, WILEY-V C H VERLAG GMBH, Jan. 2014, [Peer-reviewed]
English, Scientific journal, The reactions of quinoline-2-carbaldehyde (pyridine-2-carbonyl)hydrazone (HL) and [RuCl2(PPh3)(3)] in various solvents at different temperatures gave the three geometrical isomers trans(Cl,Cl)-, cis(Cl,Cl),trans(P,N)-, and trans(P,P)-[RuCl2(PPh3)(2){HL-O(amide),N(imine)}] (1, 2, and 3, respectively) as well as a linkage isomer trans(P,P)-[RuCl2(PPh3)(2){HL-N(imine),N(quin)}] (4). The molecular and crystal structures of 1-4, together with both E and Z configurational isomers (with respect to the C=N double bond) of the free ligand HL, were determined by X-ray analysis. The ligand HL adopted a Z form and acted as a O(amide),N(imine) bidentate ligand in 1-3, whereas it was an E isomer with a N(imine),N(quin) coordination mode in 4. The gradual thermal conversions of 1 to 2 and of 2 to 3 were observed in dichloromethane and ethanol, respectively, but an interconversion between 3 and 4 was not detected. In dichloromethane, all complexes have a reversible Ru-III/II redox couple in the range 110-412 mV (vs. Ag/Ag+), and the redox potential was largely dependent on the coordination mode of HL and on the mutual configuration of the two PPh3 ligands. Such a potential shift can be interpreted as a combination of Cl-/amide O -donor and PPh3/quinoline N -acceptor orbital contributions to the Ru-II d orbitals [highest occupied molecular orbitals (HOMOs)]. Complexes 3 and 4 in acetonitrile showed a gradual spectral change, probably because of the substitution of the Cl- ligand by the acetonitrile solvent. In addition, 2-4 showed solvatochromic behavior even in noncoordinating solvents that resulted from a blueshift of the metal-to-ligand charge-transfer (MLCT) transition band in polar solvents. These electrochemical and spectroscopic properties are also supported by DFT and time-dependent DFT (TD-DFT) calculations.

Variable-Rung Design for a Mixed-Valence Two-Legged Ladder System Situated in a Dimensional Crossover Region
Kazuya Otsubo, Atsushi Kobayashi, Kunihisa Sugimoto, Akihiko Fujiwara, Hiroshi Kitagawa
INORGANIC CHEMISTRY, 53, 2, 1229, 1240, AMER CHEMICAL SOC, Jan. 2014, [Peer-reviewed]
English, Scientific journal, Ladder systems situated in a crossover from one dimensionality to two dimensionalities have been an attractive research target, because the physical properties, which are associated with dimensionality, are strongly dependent on the number of constituent legs. However, control of the intraladder configuration and electronic properties based on the substitution of structural components remain challenging tasks in materials science. On the other hand, structural design using coordination chemistry offers crucial advantages for architectural and electronic variations through substitutions, of metal-organic building blocks. Here, we show the rational design and electronic properties of novel metal complex-based two-legged ladder compounds with several organic rung units: 4,4'-bipyridine, trans-1,4-diaminocyclohexane, and 4,4'-azopyridine. Single-crystal X-ray studies show that these two-legged ladder compounds are composed of halogen-bridged mixed-valence one-dimensional chains (MX chains) as their constituent legs. Depending on the molecular shape of the organic rung units, unique configurations of two-legged ladder lattices with periodic distortion of the legs are achieved. In addition, the electronic absorption spectra show that intervalence charge-transfer (IVCT) band gap of the two-legged ladder system increases with increasing degree of distortion of the leg. We have demonstrated for the first time that a two-legged ladder system shows a unique relationship between IVCT energy and the distortion parameter of the leg, as distinct from a single MX chain system. These systematic investigations, not only of configurations based on the rung variation but also of electronic states in metal-organic ladder system, provide the possibility for wide and rational tunings of physical and electronic properties of metal complex-based functional materials.

Hysteretic vapour response of a heterodinuclear platinum(II)-copper(II) complex derived from the dimer-of-dimer motif and the guest-absorbing site
Tadashi Ohba, Atsushi Kobayashi, Ho-Chol Chang, Takahiko Kouyama, Tatsuhisa Kato, Masako Kato
DALTON TRANSACTIONS, 43, 20, 7514, 7521, ROYAL SOC CHEMISTRY, 2014, [Peer-reviewed]
English, Scientific journal, A heterodinuclear complex, syn-[PtCu(mu-pyt)(2)(bpy)(2)](2+) (syn-[PtCu]; Hpyt = pyridine-2-thiol, bpy = 2,2 '-bipyridine), was synthesized by stepwise complexation. Three different crystal structures of the hexafluorophosphate salts with solvent molecules as guests at the axial sites of the Cu(II) ions, i.e. syn-[PtCu-G] (G = acetonitrile, acetone, and methanol), were determined by X-ray analyses. In the solid-state, these complexes adopt dimer-of-dimer motifs characteristic of the syn isomers of dinuclear complexes with two pyt bridging ligands arranged in a head-to-head configuration. These dinuclear complexes have a short Pt. Cu distance (2.75-2.81 angstrom) and slightly different intermolecular Pt...Pt distances (3.43-3.51 angstrom), which affect the colour of the solid complexes. All the syn-[PtCu-G] systems absorbed/desorbed vapour molecules; however, they exhibit different chromic changes because of the unique structural hysteresis of the desorbed form, i. e. syn-[PtCu], according to powder X-ray diffraction measurements. In addition, guest exchange occurred in the syn-[PtM-G] complexes upon exposure to the vapour of different solvents.

Self-association and columnar liquid crystalline phase of cationic alkyl-substituted-bipyridine benzenedithiolato gold(iii) complexes
Tomohiro Ogawa, Misaki Sakamoto, Hirotaka Honda, Takeshi Matsumoto, Atsushi Kobayashi, Masako Kato, Ho-Chol Chang
Dalton Transactions, 42, 45, 15995, 16005, 07 Dec. 2013, [Peer-reviewed]
English, Scientific journal, The introduction of a Au(iii) ion into a mesogenic core, [M(Bdt)(Cnbpy)]+ (Bdt = 1,2-benzenedithiolato and Cnbpy = 4,4′-di-alkyl-2,2′-bipyridine (n = 13 (4,4′-di-tridecyl-2, 2′-bipyridine (C13bpy)) and 8,10 (4,4′-di-(3-octyltridecyl)-2, 2′-bipyridine (C8,10bpy)))), leads to the formation of ionic molecular assemblies in crystalline and mesophases. Successive syntheses of precursor complexes, [AuCl2(Cnbpy)]PF6 (n = 13 (1) and 8,10 (2)), followed by the target complexes, [Au(Bdt)(Cnbpy)]PF6 (n = 13 (3) and 8,10 (4)), were achieved. The crystallographic analysis of 3 revealed that the central cationic cores form a characteristic one-dimensional columnar structure, which is an essential property for the formation of columnar structures in the liquid crystalline phase. The central cores of the [Au(Bdt)(C13bpy)]+ cations in 3 stack alternatively so as to cancel out their dipole moments and the counteranions lie between the cationic columns. Furthermore, the introduction of the branched alkyl tails in 4 induces the formation of a rectangular columnar liquid crystalline phase (Colr) with C2/m symmetry, and it melts to an isotropic liquid at 69 °C. The Colr phase of 4 is partially similar in its liquid crystalline structure to the neutral [Pt(Bdt)(C8,10bpy)] liquid crystal in a hexagonal columnar phase reported previously, while complex 4 shows a lower clearing point than that of the Pt analogue. Based on these results, the present study demonstrates the designability of the liquid crystalline structures of the [M(Bdt)(C8,10bpy)] skeleton together with their assembled structures and physico-chemical properties. © 2013 The Royal Society of Chemistry.

Effect of Ligand Polarization on Asymmetric Structural Formation for Strongly Luminescent Lanthanide Complexes
Yasuchika Hasegawa, Tomoki Ohkubo, Takayuki Nakanishi, Atsushi Kobayashi, Masako Kato, Tomohiro Seki, Hajime Ito, Koji Fushimi
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 2013, 34, 5911, 5918, WILEY-V C H VERLAG GMBH, Dec. 2013, [Peer-reviewed]
English, Scientific journal, The effect of ligand polarization on the formation of strongly luminescent lanthanide complexes with asymmetric structures is described for the first time. The lanthanide complexes are composed of Eu-III ions, three hexafluoroacetylacetonate (hfa) ligands, and two monodentate phosphine oxide ligands, namely, triphenylphosphine oxide (TPPO), p-tolyldiphenylphosphine oxide (TPPO-Me), tri-p-tolylphosphine oxide (TPPO-3Me) or o-phenoxyphenyldiphenylphosphine oxide (TPPO-OPh). The luminescence properties of the Eu-III complexes are characterized by their emission quantum yields, emission lifetimes, and their radiative (k(r)) and nonradiative (k(nr)) rate constants. The Eu-III complex with TPPO-OPh ligands offers a markedly high emission quantum yield (72% in [D-6]acetone, 85% in the solid state) owing to enhancement of the electric dipole transition and suppression of vibrational relaxation, which are directly related to k(r) and k(nr). The coordination geometries of the Eu-III complexes are categorized by shape-measure calculations. The Eu-III complexes exhibit characteristic square-antiprismatic or trigonal-dodecahedral structures, depending on the ligand polarization. Strongly luminescent Eu(hfa)(3)(TPPO-OPh)(2) has an asymmetric dodecahedron structure. The formation of distorted dodecahedral structures with low vibrational frequencies for the enhancement of luminescence is elucidated in terms of the ligand polarization of the monodentate phosphine oxide ligands in the Eu-III complexes.

Photo- and Vapor-Controlled Luminescence of Rhombic Dicopper(I) Complexes Containing Dimethyl Sulfoxide
Atsushi Kobayashi, Kahori Komatsu, Hiroki Ohara, Waka Kamada, Yuko Chishina, Kiyoshi Tsuge, Ho-Chol Chang, Masako Kato
INORGANIC CHEMISTRY, 52, 22, 13188, 13198, AMER CHEMICAL SOC, Nov. 2013, [Peer-reviewed]
English, Scientific journal, Halide-bridged rhombic dicopper(I) complexes, [Cu-2(mu-X)(2)(DMSO)(2)(PPh3)(2)] (X = I-, Br-; DMSO = dimethyl sulfoxide; PPh3 = triphenylphosphine), were synthesized, the iodide complex of which exhibited interesting photochromic luminescence driven by photoirradiation and by exposure to DMSO vapor in the solid state. Single-crystal Xray diffraction measurements revealed that the iodo and bromo complexes (abbreviated Cu2I2-[O,O] and Cu2Br2-[O,O]) were isomorphous, and that the two DMSO ligands were coordinated to the Cu(I) ion via the O atom in both complexes. Both complexes exhibited bright blue phosphorescence at room temperature (lambda(em) = 435 nm, Phi(em) = 0.19 and 0.14 for Cu2I2[O,O] and Cu2Br2-[O,O], respectively) with a relatively long emission lifetime (tau(em) similar to 200 mu s at 77 K) derived from the mixed halide-to-ligand and metal-to-ligand charge transfer ((XLCT)-X-3 and (MLCT)-M-3) excited state. Under UV irradiation, the blue phosphorescence of Cu2Br2-[O,O] disappeared uneventfully and no new emission band appeared, whereas the blue phosphorescence of Cu2I2-[O,O] rapidly disappeared with simultaneous appearance of a new green emission band (lambda(em) = 500 nm). On further irradiation, the green emission of the iodide complex gradually changed to bright yellowish-green (lambda(em) = 540 nm); however, this change could be completely suppressed by lowering the temperature to 263 K or in the presence of saturated DMSO vapor. The initial blue phosphorescence of Cu2I2-[O,O] was recovered by exposure to DMSO vapor at 90 degrees C for a few hours. IR spectroscopy and theoretical calculations suggest that the DMSO ligand underwent linkage isomerization from O-coordination to S-coordination, and both the occurrence of linkage isomerization and the removal of DMSO result in contraction of the rhombic Cu2O4-O-2 core to make the Cu.-Cu interaction more effective. In the contracted core, the triplet cluster-centered ((CC)-C-3) emissive state is easily generated by thermal excitation of the (XLCT)-X-3 and (MLCT)-M-3 mixed transition state, resulting in the green to yellowish-green emission. In contrast, the Cu"Cu distance in Cu2Br2-[O,O] is considerably longer than that of Cu2I2[O,O], which destabilizes the (CC)-C-3 emissive state, resulting in the nonemissive character.

Nonprecious-metal-assisted photochemical hydrogen production from ortho-phenylenediamine
Takeshi Matsumoto, Ho-Chol Chang, Masanori Wakizaka, Sho Ueno, Atsushi Kobayashi, Akira Nakayama, Tetsuya Taketsugu, Masako Kato
Journal of the American Chemical Society, 135, 23, 8646, 8654, 12 Jun. 2013, [Peer-reviewed]
English, Scientific journal, The combination of o-phenylenediamine (opda), which possesses two proton- and electron-pooling capability, with Fe(II) leads to the photochemical hydrogen-evolution reaction (HER) in THF at room temperature without addition of photosensitizers. From the THF solution, the tris(o-phenylenediamine) iron(II) complex, [FeII(opda)3](ClO4)2 (1), was isolated as a photoactive species, while the deprotonated oxidized species was characterized by X-ray crystallographic analysis, electrospray ionization mass spectrometry, and UV-vis NIR spectra. Furthermore, the HER is photocatalyzed by hydroquinone, which serves as a H+/e- donor. The present work demonstrates that the use of a metal-bound aromatic amine as a H+/e- pooler opens an alternative strategy for designing nonprecious-metal-based molecular photochemical H2 production/storage materials. © 2013 American Chemical Society.

Integration of Alkyl-Substituted Bipyridyl Benzenedithiolato Platinum(II) Complexes with Cadmium(II) Ion via Selective Dative Bond Formation
Hirotaka Honda, Takeshi Matsumoto, Misaki Sakamoto, Atsushi Kobayashi, Ho-Chol Chang, Masako Kato
INORGANIC CHEMISTRY, 52, 8, 4324, 4334, AMER CHEMICAL SOC, Apr. 2013, [Peer-reviewed]
English, Scientific journal, The presence of lone pairs on the Pt and S atoms of [Pt(Bdt)(DTBbpy)] (1) (Bdt = 1,2-benzenedithiolato and DTBbpy = 4,4'-di-tert-butyl-2,2'-bipyridine) and [Pt (Bdt) (C13bpy)] (2) (C13bpy = 4,4'-ditridecyl-2,2'-bipyridine) led to selective dative bond formation with Cd(II). Complexes 1 and 2 show no binding interaction with Zn(II), while they bind selectively with Cd(II) to give a twisted trinuclear complex, [Cd{Pt(Bdt)(DTBbpy)}(2)(ClO4)(H2O)](ClO4) (3), and a shuttlecock-shaped tetranuclear complex, [Cd{Pt(Bdt)(C13bpy)}(3)(H2O)](ClO4)(2)center dot CH2Cl2 (4), respectively, depending upon the alkyl groups substituted on the 2,2'-bipyridine. The two platinum moieties in 3 are connected to the seven-coordinated Cd atom through Pt -> Cd (2.7331(7) and 2.7936(7) angstrom) and S -> Cd (2.690(3), 2.940(3), and 3.067(3) angstrom) dative bonds, while the three moieties in 4 are connected to the tetrahedral Cd atom only by S -> Cd (2.552(4) angstrom) dative bonds. These structural variations found in 3 and 4 are caused not only by steric hindrance of the t-Bu groups but also by the microsegregation effect derived from the tridecyl chains. The three platinum moieties in 4 align so as to form a parallel orientation of their dipole moments, in contrast to the twisted arrangement found in 3. The dative bonds formed in 3 and 4 are commonly stable in the solid state and in less coordinative solvents such as dichloromethane, while dissociation behavior of platinum moieties with Cd(II) was observed in more coordinative THF. UV-vis and NMR spectroscopy unsealed the characteristic association/dissociation properties depending on the coordination abilities of solvents. Finally, the present study revealed that the formation of dative bonds between the platinum moieties with Cd(II) plays important roles not only in stabilizing the ground states, which leads to blue shifts in both absorption and emission energies, but also in electronic interactions between the moieties, which are revealed by electrochemical studies.

Vapour and mechanically induced chromic behaviour of platinum complexes with a dimer-of-dimer motif and the effects of heterometal ions
Tadashi Ohba, Atsushi Kobayashi, Ho-Chol Chang, Masako Kato
DALTON TRANSACTIONS, 42, 15, 5514, 5523, ROYAL SOC CHEMISTRY, 2013, [Peer-reviewed]
English, Scientific journal, Heterodinuclear complexes, syn-[MPt(mu-pyt)(2)(bpy)(2)](n+) (syn-[MPt], M = Pd2+, Au3+, Hpyt = pyridine-2-thiol, bpy = 2,2'-bipyridine), were synthesized as a selective geometrical isomer by stepwise complexation. X-ray analyses of the hexafluorophosphate salts of these complexes proved their dinuclear structures with short M...Pt distances (2.9084(4) angstrom for syn-[PdPt] and 2.9071(4) angstrom for syn-[AuPt]), similar to the homodinuclear complex (2.9292(2) angstrom for syn-[PtPt]). In the syn-[PdPt] crystal, two dinuclear motifs are arranged closely in a head-to-head manner with a short Pt...Pt distance (3.3757(3) angstrom), forming a dimer-of-dimer structure as in the case of syn-[PtPt], whereas the corresponding crystal of syn-[AuPt] has a discrete arrangement of the dinuclear motifs. By the isomerisation of syn-[PdPt], anti-[PdPt] with equivalent environments of the Pd2+ and Pt2+ ions was also obtained successfully. Syn-[PdPt](PF6)(2) exhibits vapochromic behaviour based on the absorption/desorption of CH3CN vapour, similar to that observed for syn-[PtPt](PF6)(2). The reversible structural transformations induced by the uptake and release of CH3CN molecules were investigated by powder and single-crystal X-ray diffraction studies. These revealed that the vapochromic behaviour was based on the interconversion between two phases, the dimer-of-dimer structure with a short Pt. Pt distance and a p-p stacked arrangement with no Pt. Pt intermolecular interaction. The introduction of the heterometal ions enabled control of the colour region: orange. red for syn-[PdPt] vs. light red. dark red for syn-[PtPt], reflecting the weaker metal-metal interaction between Pd2+ and Pt2+ ions in the dinuclear motif. In addition, these complexes were found to exhibit mechanochromic behaviour based on a crystal-to-amorphous transformation upon grinding, and the reconstruction of the crystal structures by vapour sorption.

Chameleon Luminophore for Sensing Temperatures: Control of Metal-to-Metal and Energy Back Transfer in Lanthanide Coordination Polymers
Kohei Miyata, Yuji Konno, Takayuki Nakanishi, Atsushi Kobayashi, Masako Kato, Koji Fushimi, Yasuchika Hasegawa
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 52, 25, 6413, 6416, WILEY-V C H VERLAG GMBH, 2013
English, Scientific journal

Vapor-Controlled Linkage Isomerization of a Vapochromic Bis(thiocyanato)platinum(II) Complex: New External Stimuli To Control Isomerization Behavior
Atsushi Kobayashi, Yuki Fukuzawa, Ho-Chol Chang, Masako Kato
INORGANIC CHEMISTRY, 51, 14, 7508, 7519, AMER CHEMICAL SOC, Jul. 2012, [Peer-reviewed]
English, Scientific journal, We synthesized a novel Pt(II)-diimine complex with a typical ambidentate thiocyanato ligand, [Pt(thiocyanato)(2)(H(2)dcbpy)] (1; H(2)dcbpy =4,4'-dicarboxy-2,2'-bipyridine), and found that the complex 1 exhibits unique linkage isomerizations with drastic color and luminescence changes driven by exposure to volatile organic chemical (VOC) vapors in the solid state. Reaction between [PtCl2(H(2)dcbpy)] and KSCN in aqueous solution at 0 degrees C enabled successful isolation of an isomer with the S-coordinated thiocyanato ligand, [Pt(SCN)(2)(H(2)dcbpy)] (1SS center dot H2O), as a nonluminescent orange solid. Interestingly, 1SS center dot H2O was isomerized completely to one isomer with the N-coordinated isothiocyanato ligand, [Pt(NCS)(2)(H(2)dcbpy)] (1NN center dot 3DMF) by exposure to DMF vapor, and this isomerization was accompanied by significant color and luminescence changes from nonluminescent orange to luminescent red. IR spectroscopy and thermogravimetric analysis revealed that adsorption of the DMF vapor and transformation of the hydrogen-bonded structure both played important roles in this vapor-induced linkage isomerization. Another isomer containing both S- and N-coordinated thiocyanato ligands, [Pt(SCN)(NCS)(H(2)dcbpy)] (1SN), was obtained as a nonluminescent yellow solid simply by exposure of 1SS center dot H2O to acetone vapor at room temperature, and about 80% of 1SS center dot H2O was found to be converted to 1SN. In the solution state, each isomer changed gradually to an isomeric mixture, but pure 1SS was regenerated by UV light irradiation (lambda(irr) = 300 nm) of an MeOH solution of the mixture. In the crystal structure of 1SN, the complex molecules were hydrogen-bonded to each other through the carboxyl groups of the H(2)dcbpy ligand and the N site of the thiocyanato ligand, whereas the 1NN molecules in the 1NN.4DMF crystal were hydrogen-bonded to the solvated DMF molecules. Competition of the hydrogen-bonding ability among the carboxyl groups of the H(2)dcbpy ligand, N and S atoms of the thiocyanato ligand, and the vapor molecule was found to be one of the most important factors controlling linkage isomerization behavior in the solid state. This unique linkage isomerization controlled by vapor can provide an outstanding vapochromic system as well as a new molecular switching function driven by vapor molecules.

Thermostable Organo-phosphor: Low-Vibrational Coordination Polymers That Exhibit Different Intermolecular Interactions
Kohei Miyata, Tadashi Ohba, Atsushi Kobayashi, Masako Kato, Takayuki Nakanishi, Koji Fushimi, Yasuchika Hasegawa
CHEMPLUSCHEM, 77, 4, 277, 280, WILEY-V C H VERLAG GMBH, Apr. 2012
English, Scientific journal

Coordination site-dependent cation binding and multi-responsible redox properties of Janus-head metalloligand, [Mo-V(1,2-mercaptophenolato)(3)]
Takeshi Matsumoto, Masanori Wakizaka, Hirokazu Yano, Atsushi Kobayashi, Ho-Chol Chang, Masako Kato
DALTON TRANSACTIONS, 41, 27, 8303, 8315, ROYAL SOC CHEMISTRY, 2012, [Peer-reviewed]
English, Scientific journal, The redox-active fac-[Mo-V(mp)(3)](-) (mp: o-mercaptophenolato) bearing asymmetric O- and S-cation binding sites can bind with several kinds of metal ions such as Na+, Mn-II, Fe-II, Co-II, Ni-II, and Cu-I. The fac-[Mo-V(mp)(3)](-) metalloligand coordinates to Na+ to form the contact ion pair {Na+(THF)(3)[fac-Mo-V(mp)(3)]} (1), while a separated ion pair, n-Bu4N[fac-Mo-V(mp)(3)] (2), is obtained by exchanging Na+ with n-Bu4N+. In the presence of asymmetric binding-sites, the metalloligand reacts with (MnCl2)-Cl-II center dot 4H(2)O, (FeCl2)-Cl-II center dot 4H(2)O, (CoCl2)-Cl-II center dot 6H(2)O, and (NiCl2)-Cl-II center dot 6H(2)O to afford UV-vis-NIR spectra, indicating binding of these guest metal cations. Especially, for the cases of the MnII and CoII products, trinuclear complexes, {M(H2O)(MeOH)-[ fac-Mo-V(mp)(3)](2)}center dot 1.5CH(2)Cl(2) (3.1.5CH(2)Cl(2) (M = Mn-II), 4.1.5CH(2)Cl(2) (M = Co-II)), are successfully isolated and structurally characterized where the M are selectively bound to the hard O-binding sites of the fac-[Mo-V(mp)(3)](-). On the other hand, a coordination polymer, {Cu-I(CH3CN)[mer-MoV(mp)(3)]}(n) (5), is obtained by the reaction of fac-[Mo-V(mp)(3)]-with [Cu-I(CH3CN)(4)]ClO4. In sharp contrast to the cases of 1, 3.1.5CH(2)Cl(2), and 4.1.5CH(2)Cl(2), the Cu-I in 5 are selectively bound to the soft S-binding sites, where each CuI is shared by two [MoV(mp) 3]-with bidentate or monodentate coordination modes. The second notable feature of 5 is found in the geometric change of the [MoV(mp) 3]-, where the original fac-form of 1 is isomerized to the mer-[Mo-V(mp)(3)](-) in 5, which was structurally and spectroscopically characterized for the first time. Such isomerization demonstrates the structural flexibility of the [Mo-V(mp)(3)](-). Spectroscopic studies strongly indicate that the association/dissociation between the guest metal ions and metalloligand can be modulated by solvent polarity. Furthermore, it was also found that such association/dissociation features are significantly influenced by coexisting anions such as ClO4- or B(C6F5)(4)(-). This suggests that coordination bonds between the guest metal ions and metalloligand are not too static, but are sufficiently moderate to be responsive to external environments. Moreover, electrochemical data of 1 and 3.1.5CH(2)Cl(2) demonstrated that guest metal ion binding led to enhance electron-accepting properties of the metalloligand. Our results illustrate the use of a redox-active chalcogenolato complex with a simple mononuclear structure as a multifunctional metalloligand that is responsive to chemical and electrochemical stimuli.

Systematic structural control of multichromic platinum(II)-diimine complexes ranging from ionic solid to coordination polymer
Atsushi Kobayashi, Hirofumi Hara, Tsubasa Yonemura, Ho-Chol Chang, Masako Kato
DALTON TRANSACTIONS, 41, 6, 1878, 1888, ROYAL SOC CHEMISTRY, 2012, [Peer-reviewed]
English, Scientific journal, Reactions of a Pt(II)-diimine-based metalloligand Na-2[Pt(CN)(2)(4,4'-dcbpy)] (4,4'-H(2)dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) with alkaline-earth metal salts Mg(NO3)(2)center dot 6H(2)O, CaCl2, SrCl2 center dot 6H(2)O, and BaBr2 center dot 2H(2)O in aqueous solution gave luminescent complexes formulated as [Mg(H2O)(5)][ Pt(CN)(2)(4,4'-dcbpy)]center dot 4H(2)O (MgPt-4 center dot 9H(2)O), {[Ca(H2O)(3)][Pt(CN)(2)(4,4'-dcbpy)]center dot 3H(2)O}(infinity) (CaPt-4 center dot 6H(2)O), {[Sr(H2O)(2)][Pt(CN)(2)(4,4'-dcbpy)]center dot H2O}(infinity) (SrPt-4 center dot 3H(2)O), and {[Ba(H2O)(2)][ Pt(CN)(2)(4,4'-dcbpy)]center dot 3H(2)O}(infinity) (BaPt-4 center dot 5H(2)O), respectively. The crystal structures of all MPt-4 complexes were determined by X-ray crystallography. In these structures, the alkaline-earth metal ions are commonly coordinated to the carboxyl groups of the [Pt(CN)(2)(4,4'-dcbpy)](2-) metalloligand. In the case of MgPt-4 center dot 9H(2)O, the Mg(II) ion is bound by five water molecules and one oxygen atom of a carboxyl group to form a neutral complex molecule [Mg(H2O) 5][Pt(CN)(2)(4,4'-dcbpy)]. In contrast, the alkaline-earth metal ion and metalloligand form two-dimensional (CaPt-4 center dot 6H(2)O) and three-dimensional (SrPt-4 center dot 3H(2)O and BaPt-4 center dot 5H(2)O) coordination networks, respectively. All fully hydrated complexes exhibited a strong phosphorescence from the triplet pi-pi* transition state. Luminescence spectroscopy revealed that MgPt-4 center dot 9H(2)O exhibited interesting multichromic (i.e., thermo-, mechano-, and vapochromic) luminescence, whereas CaPt-4 center dot 6H(2)O showed only thermochromic luminescence. The other two complexes did not exhibit any chromic behaviour. Combination analysis of powder X-ray diffraction, thermogravimetry, and IR spectroscopy suggests that the dimensionality of the coordination network contributes considerably to both the structural flexibility and luminescence properties; that is, the low-dimensional flexible coordination network formed in MPt-4 complexes with smaller alkaline-earth metal ions enables a structural rearrangement induced by thermal and mechanical stimuli and vapour adsorption, resulting in the observed multichromic behaviour.

ON-OFF Switching of the Solvatochromic Behavior of a Copper(II)-Hydrazone Complex Induced by Protonation/Deprotonation
Mee Chang, Atsushi Kobayashi, Ho-Chol Chang, Kiyohiko Nakajima, Masako Kato
CHEMISTRY LETTERS, 40, 12, 1335, 1337, CHEMICAL SOC JAPAN, Dec. 2011, [Peer-reviewed]
English, Scientific journal, A new copper(II)-hydrazone complex, [Cu(paph)Cl(CH3-OH)] (Hpaph: 2-pyridinecarboxaldehyde 2-pyridylhydrazone) (1) has been synthesized and characterized by single-crystal X-ray diffraction and UV-vis spectroscopy. This complex shows distinctive color changes by the protonation/deprotonation and exhibits interesting ON OFF switching of solvatochromic behavior on the basis of the protonation/deprotonation of the hydrazone moiety.

Dimensionality Control of Vapochromic Hydrogen-Bonded Proton-Transfer Assemblies Composed of a Bis(hydrazone)iron(II) Complex
Mee Chang, Atsushi Kobayashi, Kiyohiko Nakajima, Ho-Chol Chang, Masako Kato
INORGANIC CHEMISTRY, 50, 17, 8308, 8317, AMER CHEMICAL SOC, Sep. 2011, [Peer-reviewed]
English, Scientific journal, We describe the novel synthesis of a bis(hydrazone)iron(B) complex in protonated [Fe(Hpbph)(2)]Cl-2 (1) and deprotonated [Fe(pbph)(2)] (2) forms and several hydrogen-bonded proton-transfer (HBPT) assemblies having different dimensionalities of hydrogen-bonded network structures, [Fe(Hpbph)2] (CA)center dot 2CH(3)OH (3), [Fe(Hpbph)(2)](HCA)(2)center dot 2THF (4), and [Fe(Hpbph)(2)](CA)(H(2)CA)(2)center dot 2CH(3)CN (5) (Hpbph = 2-(diphenylphosphino)benzaldehyde-2-pyridylhydrazone), consisting of a deprotonated Fe(II)-hydrazone complex (2) as a proton acceptor (A) and chloranilic acid (H2CA) as a proton donor (D). The deprotonated complex 2 exhibited two-step reversible protonation reactions to form the double-protonated form 1, and the acid-dissociation constants were determined to be 7.6 and 10.3 in methanol solution. Utilizing this proton-accepting ability of 2, we succeeded in synthesizing HBPT assemblies 3, 4, and 5 from the reactions in CH3OH, THF, and CH3CN, respectively, with the same D/A ratio of H(2)CA/[Fe(pbph)(2)] = 10:1. These assemblies were found to have one-dimensional (1-D), two-dimensional (2-D), and three-dimensional (3-D) hydrogen-bonded networks with D/A ratios of 1:1, 2:1, and 3:1 for 3, 4, and 5, respectively. In 3, a 1-D hydrogen-bonded chain composed of the alternate arrangement of [Fe(Hpbph)(2)](2+) and CA(2-), {center dot center dot center dot[Fe(Hpbph)(2)](2+)center dot center dot center dot CA(2-)center dot center dot center dot}(infinity), was surrounded by solvated methanol molecules to form isolated 1-D hydrogen-bonded chains. In the HBPT assembly 4, a 2-D hydrogen-bonded sheet was formed from two types of hydrogen-bonded chains, {center dot center dot center dot[Fe(Hpbph)(2)](2+)center dot center dot center dot HCA(-)center dot center dot center dot HCA(-)center dot center dot center dot}(infinity) and {center dot center dot center dot HCA(-)center dot center dot center dot HCA(-)center dot center dot center dot}(infinity), and solvated THF molecules did not form any hydrogen bonds. In 5, two orthogonal hydrogen-bonded chains constructed from the neutral chloranilic acid molecules, {center dot center dot center dot CA2(-)center dot center dot center dot 2(H(2)CA)center dot center dot center dot}(infinity), were formed in addition to the 1-D hydrogen-bonded chain similar to that in 3, resulting in the formation of a rigid 3-D hydrogen-bonded network structure. By controlling the dimensionality of the hydrogen bond network, we found that the 2-D HBPT assembly 4 is sufficiently flexible to exhibit interesting vapochromic behavior in response to various organic vapors.

Chromic Behaviors of Hexagonal Columnar Liquid Crystalline Platinum Complexes with Catecholato, 2-Thiophenolato, and Benzenedithiolato
Ho-Chol Chang, Kazuki Komasaka, Keisuke Kishida, Tomoki Shiozaki, Takeshi Ohmori, Takeshi Matsumoto, Atsushi Kobayashi, Masako Kato, Susumu Kitagawa
INORGANIC CHEMISTRY, 50, 10, 4279, 4288, AMER CHEMICAL SOC, May 2011, [Peer-reviewed]
English, Scientific journal, Liquid crystalline (LC) platinum(II) complexes with 1,2-thiophenolato and 1,2-benzendithiolato have been newly synthesized and investigated by spectroscopy together with the catecholato analogue. The variations in coordinating atoms (O or S or O/S mixed) lead to significant modulation in electrochemical properties in solution and absorption and emission properties of the complexes both in solution media and in the condensed phases. The asymmetric, polar mesogens/chromophores consisting of Pt(II), redox-active ligands, and alkyl-substituted bipyridine commonly play important roles not only in stabilizing the columnar LC phases, but also in fluctuations of the ground state energies. A key finding of the present work is the chromic properties of LC complexes induced by the interplay of self-association of the mesogens/chromophores and their fluctuating properties.

Ln-Co-Based Rock-Salt-Type Porous Coordination Polymers: Vapor Response Controlled by Changing the Lanthanide Ion
Atsushi Kobayashi, Yui Suzuki, Tadashi Ohba, Shin-ichiro Noro, Ho-Chol Chang, Masako Kato
INORGANIC CHEMISTRY, 50, 6, 2061, 2063, AMER CHEMICAL SOC, Mar. 2011, [Peer-reviewed]
English, Scientific journal, We synthesized new porous coordination polymers (PCPs) {Ln(III)[Co(III)(dcbpy)(3)]center dot nH(2)O} (Ln = Nd(3+), Gd(3+); H(2)dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) and characterized them by X-ray diffraction and vapor-adsorption measurements. These three Ln-Co-based PCPs have similar rock-salt types and highly symmetrical porous structure and show a reversible structural collapse regeneration accompanied by water-vapor desorption adsorption. Similar structural regeneration was also observed for the Gd-Co PCP upon exposure to MeOH and CH(3)CN vapors, whereas the remaining two PCPs barely responded to organic vapors.

Structures and Luminescence Properties of Cyclometalated Dinuclear Platinum(II) Complexes Bridged by Pyridinethiolate Ions
Rie Aoki, Atsushi Kobayashi, Ho-Chol Chang, Masako Kato
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, 84, 2, 218, 225, CHEMICAL SOC JAPAN, Feb. 2011, [Peer-reviewed]
English, Scientific journal, A series of cyclometalated dinuclear platinum(II) complexes bridged by pyridine-2-thiolate (pyt) ions, [Pt-2(L)(2)-(pyt)(2)] (HL = 2-(p-tolyl)pyridine (Hptpy), 2-(2-thienyl)pyridine (Hthpy), or benzo[h]quinoline (Hbzqn)), as well as their two-electron-oxidized dinuclear platinum(III) complexes, [Pt2Cl2(L)(2)(pyt)(2)], have been synthesized and characterized. The structures and luminescence properties have been investigated by comparing them with those of the corresponding 2-phenylpyridinato (ppy) complex. All divalent complexes have similar dinuclear frameworks, with short Pt center dot center dot center dot Pt distances (ca. 2.85 angstrom), and exhibit similar intense luminescence from the triplet metal metal-to-ligand charge-transfer ((MMLCT)-M-3) state in glassy solutions. However, they provide different luminescence features reflecting their dynamic behaviors in fluid solutions and their intermolecular interactions in the solid state. [Pt-2(bzqn)(2)(pyt)(2)] containing fused aromatic rings exhibits the most sensitive features to the environment, i.e., it shows the most red-shifted luminescence spectrum in the solid state due to the intermolecular pi-pi interaction. However, in fluid solution, it provides very weak luminescence based on a rapid nonradiative deactivation mainly caused by the fluctuation of the intramolecular pi-pi repulsion between the ligands. [Pt-2(Ptpy)(2)(pyt)(2)], on the other hand, is the most stable luminophore, which always exhibits intense luminescence with an almost constant emission maximum independent of its temperature and state.

Synthesis, structure and photophysical properties of a flavin-based platinum(II) complex
Atsushi Kobayashi, Korin Ohbayashi, Rie Aoki, Ho-Chol Chang, Masako Kato
DALTON TRANSACTIONS, 40, 14, 3484, 3489, ROYAL SOC CHEMISTRY, 2011, [Peer-reviewed]
English, Scientific journal, We synthesized a thiosemicarbazone-functionalized flavin (Fl-(H) TSC: 2-[2-(3,4-dihydro-7,8-dimethyl-2,4-dioxobenzo[g]pteridin-10(2H)-yl)ethylidene]-hydrazinecarbothioamide) and its Pt(II) complex [Pt(Fl-TSC)(2)], and characterized it using X-ray diffraction, UV-visible absorption and luminescence spectroscopy. X-ray structural analysis for [Pt(Fl-TSC)(2)] revealed that the structure of the isoalloxazine part was almost the same as that in lumiflavin (7,8,10-trimethylisoalloxazine), and the thiosemicarbazone moiety acted as a bidentate ligand to form a PtS2N2 planar conformation. UV-visible absorption and luminescence spectra of these compounds were very similar to those of riboflavin, but the emission intensity and the lifetime decreased considerably. Theoretical calculations suggested that the charge-separated state (Fl(center dot-)-TSC center dot+) contributed to the faster quenching from the (1)pi-pi* emission state.

Vapour-adsorption and chromic behaviours of luminescent coordination polymers composed of a Pt(II)-diimine metalloligand and alkaline-earth metal ions
Hirofumi Hara, Atsushi Kobayashi, Shin-ichiro Noro, Ho-Chol Chang, Masako Kato
DALTON TRANSACTIONS, 40, 31, 8012, 8018, ROYAL SOC CHEMISTRY, 2011, [Peer-reviewed]
English, Scientific journal, Four new bimetallic coordination polymers (CPs), {M[Pt(CN)(2)(5,5'-dcbpy)]center dot 4H(2)O}(n) (M = Mg(2+), Ca(2+), Sr(2+), Ba(2+); 5,5'-H(2)dcbpy = 5,5'-dicarboxy-2,2'-bipyridine) were synthesized using four alkaline-earth metal ions and a Pt(II)-diimine metalloligand [Pt(CN)(2)(5,5'-H(2)dcbpy)]. All four CPs are isomorphous with the Zn complex, {Zn[Pt(CN)(2)(5,5'-dcbpy)]center dot 4H(2)O}(n), which exhibits effective metallophilic interactions between Pt(II) ions. These CPs exhibited colourful thermochromic behaviour and solid-state solvatochromic-like behaviours when suspended in various solvents. Thermogravimetric analysis and vapour-adsorption measurements revealed that the CPs can reversibly adsorb water and MeOH vapours. The emission energy of the triplet metal-metal-to-ligand charge-transfer ((3)MMLCT) state varied markedly upon guest adsorption/desorption. The chromic and vapour-adsorption properties of these CPs depend strongly on the cross-linking M(2+) ions.

Construction and Mechanistic Studies of Vapochromic Metal Complexes
KOBAYASHI Atsushi, KATO Masako
X-RAYS, 53, 6, 402, 408, The Crystallographic Society of Japan, 2011
Japanese, Scientific journal, Recently, vapochromic materials have drawn increasing attention because of their promising vapor sensing functions. In this paper, from the viewpoint of structural chemistry, several types of vapochromic metal complexes are described. The first one is vapochromic materials composed of Pt (II)-diimine complexes in which the origin of vapochromic behavior is the modification of the intermolecular metallophilic interactions. Second are the materials utilizing porous frameworks to adsorb/desorb vapor molecules. Third is the vapochromic hydrogen-bonded proton-transfer assembly which can recognize the hydrogen-bonding ability of vapor molecules.

Synthesis of Metal-Hydrazone Complexes and Vapochromic Behavior of Their Hydrogen-Bonded Proton-Transfer Assemblies
Atsushi Kobayashi, Masa-aki Dosen, Mee Chang, Kiyohiko Nakajima, Shin-ichiro Noro, Masako Kato
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 132, 43, 15286, 15298, AMER CHEMICAL SOC, Nov. 2010, [Peer-reviewed]
English, Scientific journal, We synthesized and investigated a new series of metal-hydrazone complexes, including deprotonated [MX(mtbhp)] and protonated forms [MX(Hmtbhp)](ClO(4)) (M = Pd(2+), Pt(2+); X = Cl(-), Br(-); Hmtbhp = 2-(2-(2-(methylthio)benzylidene)hydrazinyl)pyridine) and hydrogen-bonded proton-transfer (HBPT) assemblies containing [PdBr(mtbhp)] and bromanilic acid (H(2)BA). The mtbhp hydrazone ligand acts as a tridentate SNN ligand and provides a high proton affinity. UV-vis spectroscopy revealed that these metal-hydrazone complexes follow a reversible protonation-deprotonation reaction ([MX(mtbhp)] + H(+) -[MX(Hmtbhp)](+)), resulting in a remarkable color change from red to yellow. Reactions between proton acceptor [PdBr(mtbhp)] (A) and proton donor H(2)BA (D) afforded four types of HBPT assemblies with different D/A ratios: for D/A = 1:1, {[PdBr(Hmtbhp)](HBA)center dot Acetone} and {[PdBr(Hmtbhp)](HBA)center dot 2(1,4-dioxane)}; for D/A = 1:2, [PdBr(Hmtbhp)](2)(BA); and for D/A = 3:2, {[PdBr(Hmtbhp)](2)(HBA)(2)(H(2)BA)center dot 2Acetonitrile}. The proton donor gave at least one proton to the acceptor to form the hydrogen bonded A center dot center dot center dot D pair of [PdBr(Hmtbhp)]+center dot center dot center dot HBA(-). The strength of the hydrogen bond in the pair depends on the kind of molecule bound to the free monoanionic bromanilate OH group. Low-temperature IR spectra (T < 150 K) showed that the hydrogen bond distance between [PdBr(Hmtbhp)](+) and bromanilate was short enough (ca. 2.58 A) to induce proton migration in the [pdgr(Hrhtbhp)](2)(BA) assembly in the solid state. The hydrogen bonds formed not only between [PdBr(Hmtbhp)](+) and HBA(-) but also between HBA(-) and neutral H(2)BA molecules in the {[pdBr(Hmtbhp)](2)(HBA)(2)(H(2)BA)center dot 2Acetonitrile} assembly. The H(2)BA-based flexible hydrogen bond network and strong acidic host structure result in an interesting vapor adsorption ability and vapochromic behavior in this assembly because the vapor-induced rearrangement of the hydrogen bond network, accompanied by changes in pi-pi stacking interactions, provides a recognition ability of proton donating and accepting properties of the vapor molecule.

Acid-Base Behavior of Substituted Hydrazone Complexes Controlled by the Coordination Geometry
Mee Chang, Hiroyuki Horiki, Kiyohiko Nakajima, Atsushi Kobayashi, Ho-Chol Chang, Masako Kato
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, 83, 8, 905, 910, CHEMICAL SOC JAPAN, Aug. 2010, [Peer-reviewed]
English, Scientific journal, A new series of substituted hydrazone complexes, [Cu(Hpbph)I] (1), [Cu(Hpbph)PPh3]PF6 (2-PF6), [NiCl-(Hpbph)]Cl (3-Cl), [PtCl(Hpbph)]ClO4 (4-ClO4), and [PtCl(pbph)] (4b) (Hpbph = 2-(diphenylphosphino)benzaldehyde 2-pyridylhydrazone) have been synthesized and characterized. X-ray crystallography revealed that the copper(1) complexes adopt pseudo-tetrahedral geometry, while the nickel(II) and platinum(II) complexes provide square-planar forms. All the complexes exhibit distinct color changes on the basis of the deprotonation/protonation on the ligand although their acid/base behaviors are largely different. The acidity constants (pK(a)) in methanol were determined to be 11.4 (1), 12.5 (2), 7.7 (3), and 6.7 (4). The results indicate that the dissociation of the proton on the ligand strongly depends on the ligand deformation controlled by the coordination geometry of the complexes and ancillary ligands also somewhat affect the acidity.

Vapour-Induced Amorphous-Crystalline Transformation of a Luminescent Platinum(II)-Diimine Complex
Atsushi Kobayashi, Tsubasa Yonemura, Masako Kato
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 2010, 17, 2465, 2470, WILEY-V C H VERLAG GMBH, Jun. 2010, [Peer-reviewed]
English, Scientific journal, A novel luminescent platinum(II)-diimine complex, Na(2)[Pt(CN)(2)(dcbpy)]center dot nH(2)O (H(2)dcbpy = 4,4 '-dicarboxy-2,2'-bipyridine, n = 2 or 5) was synthesized and investigated by using X-ray diffraction measurements and spectroscopy. Complex Na(2)[Pt(CN)(2)(dcbpy)]center dot 2H(2)O was first obtained as a red amorphous solid (IA) that exhibits bright luminescence at 623 nm. After recrystallization, two crystalline forms, the dihydrate form, 1C, and the pentahydrate form, Na(2)[Pt(CN)(2)(dcbpy)]center dot 5H(2)O (2), were obtained and analyzed by the single-crystal X-ray diffraction method. Upon exposure of the amorphous form 1A to hydrophilic vapours such as those of MeOH and acetone, 1A irreversibly changed to a yellow crystalline solid 1C that showed luminescence at 608 nm with a shoulder at 568 nm. This vapour-induced amorphous-crystalline transformation has never been observed either by exposing 1A to hydrophobic vapours nor by increasing the temperature up to 410 K. IR spectroscopy revealed that the amorphous-crystalline transformation did not involve the adsorption of the vapour. This phenomenon of irreversible structural transformation accompanied by change of luminescence is possibly applicable to vapour history sensors.

Multifunctional sensing ability of a new Pt/Zn-based luminescent coordination polymer
Atsushi Kobayashi, Hirofumi Hara, Shin-ichiro Noro, Masako Kato
DALTON TRANSACTIONS, 39, 14, 3400, 3406, ROYAL SOC CHEMISTRY, 2010, [Peer-reviewed]
English, Scientific journal, We synthesized a new Pt/Zn-based coordination polymer, {Zn[Pt(CN)(2)(5,5'-dcbpy)]center dot 4H(2)O}(n), (5,5'-H(2)dcbpy = 5,5'-dicarboxy-2,2'-bipyridine), which exhibits reversible colour changes in response to temperature change or exposure to chemical vapours and liquids. Such chromic behaviour shows promise for sensing not only changes in temperature but also for detecting chemical solvents and vapours. The single crystal X-ray structure indicates that one-dimensional coordination polymeric chains formed by an alternating arrangement of [Zn(H(2)O)(3)](2+) and [Pt(CN)(2)(5,5'-dcbpy)](2-) stacked to produce moderate metallophilic interactions between the Pt(II) ions. Thermogravimetric analysis and water vapour adsorption measurements show that both the crystal water and water coordinated to Zn(II) ions can be removed and re-adsorbed reversibly by heating or under vacuum. Emission spectra at various temperatures and/or in the presence of vapours or liquids reveal that the complex exhibits thermochromic and solvatochromic-like behaviours, with the emission band shifting between 616 and 671 nm. IR spectroscopy and powder X-ray diffraction measurements suggest that this multichromic behaviour is a result of the cooperative phenomena of water adsorption/desorption around the Zn(II) ions and the modi. cation of the metallophilic interaction.

Electroconductive Porous Coordination Polymer Cu[Cu(pdt)(2)] Composed of Donor and Acceptor Building Units
Shinya Takaishi, Miyuki Hosoda, Takashi Kajiwara, Hitoshi Miyasaka, Masahiro Yamashita, Yasuyuki Nakanishi, Yasutaka Kitagawa, Kizashi Yamaguchi, Atsushi Kobayashi, Hiroshi Kitagawa
INORGANIC CHEMISTRY, 48, 19, 9048, 9050, AMER CHEMICAL SOC, Oct. 2009
English, Scientific journal, We synthesized a new porous coordination polymer Cu[Cu(pdt)(2)], which shows relatively high electrical conductivity (6 x 10(-4) S cm(-1) at 300 K) by the introduction of electron donors and acceptors as building units. This compound is applicable as a porous electrode with high power density. In addition, this compound forms a triangular spin lattice and shows spin frustration.

Stepwise Vapochromism Observed for a Simple Terpyridine-Platinum(II) Complex with a Thiocyanato Ligand
Atsushi Kobayashi, Yuki Fukuzawa, Shin-ichiro Noro, Takayoshi Nakamura, Masako Kato
CHEMISTRY LETTERS, 38, 10, 998, 999, CHEMICAL SOC JAPAN, Oct. 2009, [Peer-reviewed]
English, Scientific journal, A simple Pt-II-terpyridine complex [Pt(NCS)(tpy)](SCN) (tpy = 2,2': 6', 2 ''-terpyridine) shows distinct two-step vapochromism from red to yellow through dark red in response to methanol vapor. The adsorption isotherm for methanol vapor reveals that the two-step vapochromic behavior originates from breathing-like structural transformations.

129I mössbauer spectroscopic study of a metallic MMX chain system
Atsushi Kobayashi, Shinji Kitao, Makoto Seto, Ryuichi Ikeda, Hiroshi Kitagawa
Inorganic Chemistry, 48, 16, 8044, 8049, 17 Aug. 2009, [Peer-reviewed]
English, Scientific journal, One-dimensional iodide-bridged mixed-valence binuclear platinum complexes (the so-called "MMX chains") and their Pt(III) dimer precursors were investigated with 129I Mössbauer spectroscopy. Spectra consisting of two sets of octuplets were observed at low temperatures for a neutral MMX chain complex, Pt2(dtp)4l (dtp = C 2H5CS2-), with various charge-ordering states at the Pt dimers, indicating that the charge-ordering state is in an alternate-charge-polarization phase (ACP: · · ·[Pt2+-Pt3+]-l0.4--[Pt 3+-Pt2+]- · · · -10.3-- · · ·), which is consistent with a previous low-temperature X-ray diffraction study. The estimated valence states of the bridging iodines of [ (C2H5)2NH2]4[Pt 2(pop)4l] (pop = H2P2O 52-), with a charge-polarization phase (CP: · · · [Pf-Pt3+]-I0-4-· · · [Pt2+-Pt3+]-I0.4--· · ·), and [H3N(CH2)6NH 3]2[Pt2(pop)4l], with a charge-density-wave phase (CDW: · · · [Pt 2+-Pt2+] · · ·I0.3- -[Pt3+-Pt3+]-I30.3- · · ·), suggest that the covalent bond interaction is dominant in the CDW phase, whereas the Coulomb interaction is dominant in the CP phase. The estimated absolute quadrupole coupling constant (QCC) values for negatively charged MMX chain complexes with pop ligands are larger than those for neutral MMX chain complexes with CH3CS2- (dta) ligands, implying that the Madelung potential formed by the more-negative pop ligands and countercations effectively contributes to the physical properties of the pop system. The three Pt(III) dimer complexes Pt2(dta)4l 2, Pt2(dtp)4l2, and K 4[Pt2(pop)4l2] showed almost the same isomer shifts, indicating that the valence state of the iodide ion (1 0.5-) depends negligibly on the terminal ligand. The QCC value observed for K4[Pt2(pop)4l2] was larger than those for Pt2(dta)4l2 and Pt 2(dtp)4l2, originating from the anisotropic arrangement of the iodide anions, which form layers lying on the ab plane in the crystal. © 2009 American Chemical Society.

Pressure-Induced Consecutive Phase Transitions of a Metallic MMX-Chain Complex, Pt-2(dtp)(4)I (dtp: C2H5CS2-)
Kazuya Otsubo, Atsushi Kobayashi, Masato Hedo, Yoshiya Uwatoko, Hiroshi Kitagawa
CHEMISTRY-AN ASIAN JOURNAL, 4, 11, 1673, 1676, WILEY-BLACKWELL, 2009, [Peer-reviewed]
English, Scientific journal

Ultrafast dynamical study of self-trapped excitons in ladder type of halogen-bridged Pt complexes
Tohru Suemoto, Youtarou Takahashi, Keizo Yasukawa, Daisuke Kawakami, Shinya Takaishi, Masahiro Yamashita, Atsushi Kobayashi, Hiroshi Kitagawa
Journal of Luminescence, 128, 5-6, 1081, 1083, May 2008
English, Scientific journal, The properties and the dynamics of the excited states in out-of-phase ladder-type halogen-bridged Pt complexes (Pt-Br-out and Pt-I-out) are studied using femtosecond luminescence spectroscopy. In both materials, Gaussian-shaped broad luminescence bands with large Stokes shifts are found around 0.8 eV and assigned to self-trapped excitons (STE). The wave-packet oscillations with periods of 290 and 306 fs were observed in Pt-Br-out and Pt-I-out, respectively. The higher oscillation frequency in Pt-I-out compared with the one-dimensional (1D)-type Pt-I is ascribed to the smaller lattice relaxation in the ladder system. Although the lifetime of the STE is almost the same as that of the 1D-type Pt-Br, the lifetime in Pt-I-out is one order of magnitude longer than that in the 1D-type Pt-I. This is ascribed to the phase locking of the charge density wave due to the interchain interaction. © 2007 Elsevier B.V. All rights reserved.

Pressure-induced metal-semiconductor-metal transitions in an MMX-chain complex, Pt-2(C2H5CS2)(4)I
Atsushi Kobayashi, Aya Tokunaga, Ryuichi Ikeda, Hajime Sagayama, Yusuke Wakabayashi, Hiroshi Sawa, Masato Hedo, Yoshiya Uwatoko, Hiroshi Kitagawa
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 18, 3567, 3570, WILEY-V C H VERLAG GMBH, Sep. 2006, [Peer-reviewed]
English, Scientific journal, The electrical conductivity and X-ray diffraction measurements were performed for a highlyconductive halogen-bridged binuclear-metal mixed-valence complex (the so-called MMX chain), Pt-2(C2H5CS2)(4)I, under high pressure up to 2.5 GPa. The complex exhibited pressure-induced metal-semiconductor-metal transitions at 0.5 and 2.1 GPa. The Xray diffuse scatterings were observed at k = n+0.5 (n: integer) under ambient pressure, which are derived from the charge-density wave (CDW:center dot center dot center dot Pt-2-Pt2+center dot center dot center dot I-Pt3+-Pt3+-I center dot center dot center dot) fluctuation in the MMX chain. Above 0.5 GPa, where the pressure-induced metal-semiconductor transition occurred, these scatterings disappeared. The electronic phases under high pressure (P) were found to be attributable to the metallic averaged-valence state (AV: -Pt2.5+-Pt2.5+-I-Pt2.5+-Pt2.5+-I-) with CDW fluctuation of P < 0.5 GPa, semiconducting charge-polarization state (CP:center dot center dot center dot Pt2+-Pt3+-I center dot center dot center dot Pt2+-Pt3+-I center dot center dot center dot) of 0.5 < P < 2.1 GPa, and metallic AV state of P > 2.1 GPa. The electronic state Of Pt-2(C2H5CS2)(4)I is very sensitive to pressure, which implies that the phase competition among the CP, CDW, and AV phases is present in the MMX chain.

Tuning of electronic structures of quasi one-dimensional iodide-bridged dinuclear platinum mixed-valence complexes
Masahiro Yamashita, Shinya Takaishi, Atsushi Kobayashi, Hiroshi Kitagawa, Hiroyuki Matsuzaki, Hiroshi Okamoto
COORDINATION CHEMISTRY REVIEWS, 250, 17-18, 2335, 2346, ELSEVIER SCIENCE SA, Sep. 2006, [Peer-reviewed]
English, Scientific journal, This review describes the tuning of electronic structures and variable phase transitions in quasi one-dimensional iodide-bridged dinuclear Pt compounds (MMX chains). These are classified into two types of MMX chain compounds, that is, Pt-2(dta)(4)(I) (dta = dithioacetate derivatives) and R-4[Pt-2(pop)(4)I].nH(2)O (R = alkylammonium, etc.; pop = P2O5H22-). These MMX chains compounds can take four electronic structures such as average valence (AV), charge-density-wave (CDW), charge-polarization (CP) and alternating charge-polarization (ACP) states. The Pt-2(dta)(4)I compounds show a phase transition from metallic AV, CP, to ACP state with decreasing temperature. The phase transition feature depends on the alkyl derivatives of the dta ligands. The R-4[Pt-2(pop)(4)I].nH(2)O exhibits three oxidation states, AV, CDW, and CP states, depending on the kind of cations. Some of these compounds show a phase transition by pressure, photo-irradiation, temperature, and humidity. (c) 2006 Elsevier B.V. All rights reserved.

Mixed-valence two-legged MX-ladder complex with a pair of out-of-phase charge-density waves
Atsushi Kobayashi, Hiroshi Kitagawa
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 128, 37, 12066, 12067, AMER CHEMICAL SOC, Sep. 2006, [Peer-reviewed]
English, Scientific journal

Most stable metallic phase of the mixed-valence MMX-chain, Pt 2(dtp)4l (dtp = C2H5CS2), in purely d-electronic conductors based on the transition-metal complex
Kazuya Otsubo, Atsushi Kobayashi, Hiroshi Kitagawa, Masato Hedo, Yoshiya Uwatoko, Hajime Sagayama, Yusuke Wakabayashi, Hiroshi Sawa
Journal of the American Chemical Society, 128, 25, 8140, 8141, 28 Jun. 2006, [Peer-reviewed]
English, Scientific journal, The electrical resistivity and X-rayoscillation photograph measurements for an MMX-chain complex, Pt2(dtp)4I (dtp = C2H5CS2-), under high pressure were performed. We observed the most stable metallic phase (TMI = 70 K, under 2.2 GPa) in the 1-D purely d-electronic conductors and pressure-induced metal-insulator transition including the structural phase transition at 3.0 GPa. Copyright © 2006 American Chemical Society.

Direct determination of low-dimensional structures: Synchrotron X-ray scattering on one-dimensional charge-ordered MMX-chain complexes
Yusuke Wakabayashi, Atsushi Kobayashi, Hiroshi Sawa, Hiroyuki Ohsumi, Naoshi Ikeda, Hiroshi Kitagawa
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 128, 20, 6676, 6682, AMER CHEMICAL SOC, May 2006, [Peer-reviewed]
English, Scientific journal, A powerful method to determine the hidden structural parameters in functional molecules has been developed. Local valence arrangements that dominate the material properties are sometimes not three-dimensionally ordered. This method that comprises diffuse X-ray scattering and resonant X-ray scattering is suitable in such cases. Using this method, we present clear evidence of the low-dimensional valence arrangement in two halogen-bridged one-dimensional metal complexes, so- called MMX chains. This family allows us to control many physical and structural parameters by chemical substitution of bridging halogen, counterions, or metal ions, and one of our samples carries an unusual metallic phase. It is demonstrated with this complex that the present method makes it possible to have microscopic insight to low-dimensionally ordered systems.

Synthesis of a one-dimensional metal-dimer assembled system with interdimer interaction, M-2(dtp)(4) (M = Ni, Pd; dtp = dithiopropionato)
A Kobayashi, T Kojima, R Ikeda, H Kitagawa
INORGANIC CHEMISTRY, 45, 1, 322, 327, AMER CHEMICAL SOC, Jan. 2006, [Peer-reviewed]
English, Scientific journal, A metal-dimer assembled system, M-2(dtp)(4) (M = Ni, Pd; dtp = dithiopropionate, C2H5CS2-), was synthesized and analyzed by the X-ray single-crystal diffraction method, UV-vis-near-IR spectra of solutions, solid-state diffuse reflectance spectroscopies, and electrical conductivity measurements. The structures exhibit one-dimensional metal-dimer chains of M-2(dtP)(4) with moderate interdimer contact. These complexes are semiconducting or insulating, which is consistent with the fully filled d(Z2) band of M-II(d(8)). Interdimer metal-metal distances were 3.644(2) angstrom in Ni-2(dtp)(4) and 3.428(2) angstrom in Pd-2(dtp)(4), each of which is marginally longer than twice the van der Waals radius of the metal. Interdimer charge-transfer transitions were nevertheless observed in diffuse reflectance spectra. The origin of this transition is considered to be due to an overlap of two adjacent d(a*) orbitals, which spread out more than the d(Z2) orbital because of the antibonding d(sigma*) character of the M(d(Z2))-M(d(Z2)). The Ni-2(dtp)(4) exhibited an interdimer charge-transfer band at a relatively low energy region, which is derived from the Coulomb repulsion of the 3d(sigma*). orbital of Ni.

Novel Alternating Dimer Chain System (CH3)2NH2CuCl3 Studied by X-ray Structural Analyses and Magnetization Process
Inagaki Yuji, Kobayashi Atsushi, Asano Takayuki, Sakon Takuo, Kitagawa Hiroshi, Motokawa Mitsuhiro, Ajiro Yoshitami
J Phys Soc Jpn, 74, 10, 2683, 2686, The Physical Society of Japan (JPS), 15 Oct. 2005
English, The ground-state properties of an $S=1/2$quasi-one-dimensional quantum spin system (CH3)2NH2CuCl3 were investigated by X-ray structure analyses and high-field magnetization measurements. X-ray studies confirmed that the structural phase transition from monoclinic to triclinic phases occurs between 300 and 200 K. The magnetic chain realized at low temperatures involves three types of chlorine-bridged pathways that result in bond alternation with $n=4$, where $n$is the period of the spatial structure. High-field magnetization measurements at the lowest temperature of 0.5 K revealed a unique magnetization process with an initial rapid increase in a low field and a relatively gradual increase in a high field, separated by the magnetization plateau with half of the saturation moment. On the basis of these experimental facts, a novel quantum chain model, which is characterized by the alternation of an $S=1$triplet dimer and an $S=0$singlet dimer is proposed for the ground state of the present system.

I-129 Mossbauer spectroscopic study of a one-dimensional halogen-bridged binuclear complex, Pt-2(dtp)(4)I (dtp = C2H5CS2-)
A Kobayashi, H Kitagawa, R Ikeda, S Kitao, M Seto, M Mitsumi, K Toriumi
SYNTHETIC METALS, 135, 1-3, 405, 406, ELSEVIER SCIENCE SA, Apr. 2003, [Peer-reviewed]
English, Scientific journal, I-129 Mossbauer spectroscopic measurement was made for the title complex to investigate the insulating phase below a metal-insulator transition (TM-I = 205 K). Two chemically independent sites of iodine were observed, suggesting that the insulating phase is in alternate charge-polarization state of -Pt2+-Pt3+-I-Pt3+-Pt2+-I-Pt2+-Pt3+-I-Pt3+-Pt2+-I-.

Structural and optical properties of Pt-2(dtp)(4)Br-2 (dtp=dithiopropionato) and its halogen-replacement effect
A Kobayashi, H Kitagawa, R Ikeda
MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 379, 315, 320, TAYLOR & FRANCIS LTD, 2002, [Peer-reviewed]
English, Scientific journal, A novel binuclear Pt(III) complex, Pt-2(dtp)(4)Br-2 (dtp = CH3CH2CS2-, dithiopropionato), was synthesized by a reaction of Pt-2(dtp)(4) and Br-2 in refluxing toluene, which could be used as starting material for a new MMX-chain system such as a possible mixed-valence Pt-2(dtp)(4)Br. The title complex has been characterized by X-ray single-crystal structure analysis, UV-Visible-NearIR, IR, and polarized Raman spectroscopies. The Pt-2(dtp)(4)Br-2 crystallized in monoclinic P2(1)/a and this structure is almost same as Pt-2(dtp)(4)I-2. Halogen-replacement effect from X = I to Br on Pt-2(dtp)(4)X-2 has been examined. The Pt-Pt distance in X = Br is slightly shorter than that in X = I. Raman peak of the v(Pt-Pt) mode is slightly shifted to higher wavenumber from X = I to Br. These changes are considered to be mainly caused by the difference of electron densities of antibonding d(sigma)* orbitals.

Systematic synthesis of proton-conductive and vapochromic Pt(II) complexes
今田慎一郎, WANG Dongjin, 長尾祐樹, 吉田将己, 小林厚志, 加藤昌子, 錯体化学会討論会講演要旨集, 70th (Web), 2020

酸‐塩基性官能基を導入したルテニウム錯体配位子から成る多孔性配位高分子の合成と物性
清水建樹, 小林厚志, 長尾祐樹, 吉田将己, 加藤昌子, 錯体化学会討論会講演要旨集, 69th, 231, 02 Sep. 2019
Japanese

ホスホン酸基含有ルテニウム錯体配位子から成る多孔性配位高分子の二段階水蒸気応答型発光とプロトン伝導
清水建樹, 小林厚志, 長尾祐樹, 吉田将己, 加藤昌子, 錯体化学会討論会講演要旨集, 68th, 39, 10 Jul. 2018
Japanese

温度によって発光色が可変する希土類錯体ポリマー
長谷川靖哉, 宮田康平, 中西貴之, 小林厚志, 加藤昌子, 伏見公志, 錯体化学会討論会講演要旨集, 63rd, 54, 15 Oct. 2013
Japanese

o‐フェニレンジアミン3d金属錯体が示す光水素発生反応
張浩徹, 松本剛, 上野導, 中山哲, 武次徹也, 小林厚志, 加藤昌子, 配位化合物の光化学討論会講演要旨集, 24th, 41, 42, 06 Aug. 2012
Japanese

分子間相互作用を有する希土類配位高分子の発光特性
宮田康平, 大場惟史, 小林厚志, 加藤昌子, 中西貴之, 伏見公志, 長谷川靖哉, 化学系学協会北海道支部冬季研究発表会講演要旨集, 2012, 36, 31 Jan. 2012
Japanese

Terpyridine platinum(II) complexes containing triazine di- or tri-thiolate bridges: structures, luminescence, electrochemistry, and aggregation
Hua-Xin Zhang, Masako Kato, Yoichi Sasaki, Tadashi Ohba, Hiroto Ito, Atsushi Kobayashi, Ho-Chol Chang, Kohei Uosaki, DALTON TRANSACTIONS, 41, 37, 11497, 11506, 2012
Dinuclear complexes [{Pt(trpy)}(2)(L)](PF6)(2) (trpy = 2,2': 6',2 ''-terpyridine, L = 2-octylthio-1,3,5-triazine4,6- dithiolate ion (1), L = 2-octadecylthio-1,3,5-triazine-4,6-dithiolate ion (2), L = 2-di-n-butylamino1,3,5- triazine-4,6-dithiolate ion (3)) and a trinuclear complex [{Pt(trpy)}(3)(L)](PF6)(3) (L = 1,3,5-triazine2,4,6- trithiolate ion (4)) have been synthesized and characterized. The single crystal X-ray analysis revealed that the two {Pt(trpy)}(2+) fragments in 1 and 3 adopt a syn-configuration. The Pt...Pt distances are around 4.3 angstrom, suggesting no intramolecular Pt...Pt interactions. Complexes 1-4 in acetonitrile show broad absorption bands at around 470 nm, assigned to mainly the ligand-to-ligand charge transfer ((LLCT)-L-1) from triazine thiolates to trpy based on the comparison to the related complexes and the density functional theory (DFT) calculations. The red luminescence of 1-4 in acetonitrile is attributable to emission predominantly from (LLCT)-L-3. Cyclic voltammograms of 1-3 exhibit four redox couples from -2.0 V to 0 V vs. Ag/AgCl. The two consecutive processes at around -0.70 V are assigned to the sequential reduction of two trpy ligands. This assignment was further supported by the observation of the anion radical of trpy in spectroelectrochemical experiments. The splitting of the redox potentials of two trpy ligands evidences the moderate electronic coupling interactions mediated by the triazine dithiolate bridges. Complex 2 formed a transparent red gel in CH3CN, whereas 4 produced a gel-like solid in the mixtures of CH3CN and other solvents. The interactions dominating the aggregative behaviours have been discussed based on the results of electronic absorption and emission spectroscopy., ROYAL SOC CHEMISTRY, English

ホスフィンオキシドで架橋された希土類配位高分子の構造と発光特性
宮田康平, 大場惟史, 小林厚志, 加藤昌子, 伏見公志, 長谷川靖哉, 光化学討論会講演要旨集, 2011, 39, 01 Sep. 2011
Japanese

Syntheses and luminescent properties of lanthanide coordination polymers with cross-linked phosphine oxide ligands
MIYATA Kohei, OHBA Tadashi, KOBAYASHI Atsushi, KATO Masako, FUSHIMI Koji, HASEGAWA Yasuchika, 希土類 = Rare earths, 0, 58, 102, 103, 05 May 2011
Japanese

Metal-Dependent and Redox-Selective Coordination Behaviors of Metalloligand [Mo-V(1,2-benzenedithiolato)(3)](-) with Cu-I/Ag-I Ions
Takeshi Matsumoto, Ho-Chol Chang, Atsushi Kobayashi, Kohei Uosaki, Masako Kato, INORGANIC CHEMISTRY, 50, 7, 2859, 2869, Apr. 2011
The synthesis and characterization of two coordination polymers, {Cu[Mo-V(bdt)(3)]center dot 0.5Et(2)O)(n) (1.0.5Et(2)O, bdt: o-benzenedithiolato) and {Ag-I[Mo-V(bdt)(3)]}(n) (2), composed of redox-active [Mo-V(bdt)(3)](-) metalloligand with Cu-I and Ag-I ions are reported. The complexation reactions of [Mo-V(bdt)(3)](-) with Cu-II(ClO4)(2) or (AgClO4)-Cl-I commonly lead to the formation of one-dimensional (1-D) coordination polymers. The presence of Cu-I in 1.0.5Et(2)O strongly indicates that the Cu-II ion is reduced during the complexation reaction with [Mo-V(bdt)(3)](-), which acts as an electron donor. The total dimensionalities of the assembled structures of 1.0.5Et(2)O and 2 are significantly different and related to the type of additional metal ions, Cu-I and Ag-I In contrast to the isolated 1-D chain structure of 1.0.5Et(2)O, complex 2 has a three-dimensional (3-D) assembled structure constructed from additional pi-pi stacking interactions between adjacent [Mo-V(bdt)(3)](-) moieties. These structural differences influence the solubility of the complexes in organic solvents; complex 1.0.5Et(2)O is soluble as origomeric species in highly polar solvents, while 2 is insoluble in organic solvents and water. Coordination polymers 1.0.5Et(2)O and 2 were investigated by UV-vis spectroscopy in the solid state, and that in solution together with their electrochemical properties were also investigated for 1 because of its higher solubility in polar organic solvents. Complex 1 0.5Et(2)O dissolved in CH3CN demonstrates concentration-dependent UV-vis spectra supporting the presence of coordinative interactions between [Mo-V3(bdt)(3)](-) moieties and Cu-I ions to create the origomeric species even in solutions, an observation that is supported also by electrochemical experiments., AMER CHEMICAL SOC, English

Development of new sensor materials based on metal complexes with metallophilic interaction
小林 厚志, 加藤 昌子, Fine chemicals, 39, 3, 24, 32, Mar. 2010
シーエムシー出版, Japanese

27aYF-3 A unique vapochromism of luminescent Pt complex with hydrogen-bonding network
Kobayashi Atsushi, Yonemura Tsubasa, Kato Masako, Meeting abstracts of the Physical Society of Japan, 64, 1, 806, 806, 03 Mar. 2009
The Physical Society of Japan (JPS), Japanese

24aRC-6 Substitution effect of rung ligand on two-legged MX-Ladder system
Kobayashi Atsushi, Kitagawa Hiroshi, Meeting abstracts of the Physical Society of Japan, 62, 2, 898, 898, 21 Aug. 2007
The Physical Society of Japan (JPS), Japanese

18aZB-5 Ultrafast time-resolved luminescence spectroscopy in two-leg ladder Bromine bridged Pt complexes
Takahashi Youtarou, Kobayashi Atsushi, Kitagawa Hiroshi, Suemoto Tohru, Meeting abstracts of the Physical Society of Japan, 62, 1, 696, 696, 28 Feb. 2007
The Physical Society of Japan (JPS), Japanese

25aZB-2 Physical property and structural control of MX-Ladder complex
Kobayashi Atsushi, Otsubo Kazuya, Kitagawa Hiroshi, Wakabayashi Yusuke, Sawa Hiroshi, Meeting abstracts of the Physical Society of Japan, 61, 2, 691, 691, 18 Aug. 2006
The Physical Society of Japan (JPS), Japanese

28pTD-5 Physical property of MX-Ladder complex under high pressure
Kobayashi Atsushi, Otsubo Kazuya, Kitagawa Hiroshi, Hedo Masato, Uwatoko Yoshiya, Sagayama Hajime, Wakabayashi Yusuke, Sawa Hiroshi, Meeting abstracts of the Physical Society of Japan, 61, 1, 836, 836, 04 Mar. 2006
The Physical Society of Japan (JPS), Japanese

20pYB-4 Magnetic properties of quasi-1D alternating dimer system DMACuCl3
Inagaki Y., Kobayashi A., Asano T., Sakon T., Kitagawa H., Motokawa M., Ajiro Y., Meeting abstracts of the Physical Society of Japan, 60, 2, 301, 301, 19 Aug. 2005
The Physical Society of Japan (JPS), Japanese

20aWB-9 A study of MX-ladder complex bridged by organic molecule
Kobayashi Atsushi, Kitagawa Hiroshi, Meeting abstracts of the Physical Society of Japan, 60, 2, 687, 687, 19 Aug. 2005
The Physical Society of Japan (JPS), Japanese

20aWB-11 Electrical conductivity and electronic states of MMX complex, Pt_2(dtp)_4l under high pressure
Otsubo Kazuya, Ozawa Akio, Kobayashi Atsushi, Yamauchi Miho, Kitasawa Hiroshi, Hedo Masato, Uwatoko Yoshiya, Wakabayashi Yusuke, Sawa Hiroshi, Meeting abstracts of the Physical Society of Japan, 60, 2, 688, 688, 19 Aug. 2005
The Physical Society of Japan (JPS), Japanese

27pYK-9A study of anionic MMX-Chain complexes by ^<129>I Mossbauer spectroscopy
Kobayashi Atsushi, Kitagawa Hiroshi, Kitao Shinji, Seto Makoto, Meeting abstracts of the Physical Society of Japan, 60, 1, 823, 823, 04 Mar. 2005
The Physical Society of Japan (JPS), Japanese

13pWF-8 Pressure dependence of X-ray diffuse scattering in a one-dimensional halogen-bridged binuclear-metal complex, Pt_2(C_2H_5CS_2)_4I
Kobayashi Atsushi, Kitagawa Hiroshi, Wakabayashi Yusuke, Sawa Hiroshi, Meeting abstracts of the Physical Society of Japan, 59, 2, 758, 758, 25 Aug. 2004
The Physical Society of Japan (JPS), Japanese

13pWF-7 Charge-density-wave in the MMX complex [Pt_2(dtp)_4]I observed by synchrotron radiation
Wakabayashi Y., Sawa H., Kobayashi A., Kitagawa H., Meeting abstracts of the Physical Society of Japan, 59, 2, 758, 758, 25 Aug. 2004
The Physical Society of Japan (JPS), Japanese

Direct determination of charge-ordered phase in MMX-Chain complexes by 129I Mössbauer spectroscopy
A. Kobayashi, H. Kitagawa, S. Kitao, Y. Kobayashi, M. Seto, KURRI Progress Report, 56, 01 Apr. 2004

30aWL-9 X-ray diffuse scattering study on charge-density-wave and charge-polarized complexes
Wakabayashi Y., Sawa H., Kobayashi A., Kitagawa H., Meeting abstracts of the Physical Society of Japan, 59, 1, 870, 870, 03 Mar. 2004
The Physical Society of Japan (JPS), Japanese

In-chain atomic arrangement in quasi one-dimensional MMX, chain complexes [Pt_2(dta, dtp)_4]I
Wakabayashi Y., Sawa H., Kobayashi A., Ohsumi H., Ikeda N., Kitagawa H., Ikeda R., Meeting abstracts of the Physical Society of Japan, 58, 2, 763, 763, 15 Aug. 2003
The Physical Society of Japan (JPS), Japanese

129I Mössbauer spectroscopic study of a one-dimensional halogen-bridged mixed-ligand binuclear-metal complex, Pt 2(dta) 2(dtp) 2I (dta = CH 3CS 2, dtp=C 2H 5CS 2)
A. Kobayashi, H. Kitagawa, S. Kitao, Y. Kobayashi, M. Seto, KURRI Progress Report, 45, 01 Apr. 2003

Valence arrangement in MMX chain obtained by X-ray diffuse scattering
Wakabayashi Y, Sawa H., Kobayashi A., Kitagawa H., Ikeda R., Meeting abstracts of the Physical Society of Japan, 58, 1, 814, 814, 06 Mar. 2003
The Physical Society of Japan (JPS), Japanese

Electronic structure of a one-dimensional halogen-bridged mixed-ligands binuclear-metal complex
Kobayashi Atsushi, Kitagawa Hiroshi, Ikeda Ryuichi, Kitao Shinji, Kobayashi Yasuhiro, Seto Makoto, Meeting abstracts of the Physical Society of Japan, 58, 1, 815, 815, 06 Mar. 2003
The Physical Society of Japan (JPS), Japanese

8pSC-10 ハロゲン架橋混合配位子複核金属錯体の構造と物性(金属錯体(MX系・MMX系など),領域7)
小林 厚志, 北川 宏, 池田 龍一, 田崎 遼子, 若林 裕助, 澤 博, 日本物理学会講演概要集, 57, 2, 709, 709, 13 Aug. 2002
一般社団法人日本物理学会, Japanese

27pZC-4 I M6ssbauer spectroscopic study of a one-dimensional halogen-bridged binuclear metal complex, Pt_2(dtp)_4I
Kobayashi Atsushi, Kitagawa Hiroshi, Ikeda Ryuichi, Kitao Shinji, Seto Makoto, Meeting abstracts of the Physical Society of Japan, 57, 1, 814, 814, 01 Mar. 2002
The Physical Society of Japan (JPS), Japanese

Measurement of dielectric constant in MMX-chain complexes
Ishikawa T., Koshihara S., Kobayashi A., Kitagawa H., Ikeda R., Meeting abstracts of the Physical Society of Japan, 56, 2, 713, 713, 03 Sep. 2001
The Physical Society of Japan (JPS), Japanese

化学実験II　　　　　　　　　　　　　　　
北海道大学-理学部

化学実験I　　　　　　　　　　　　　　　
北海道大学-理学部

自然科学実験　　　　　　　　　　　　　　　
北海道大学-全学教育

無機化学特論　　　　　　　　　　　　　　　
北海道大学-総合化学院

錯体化学　　　　　　　　　　　　　　　
北海道大学-理学部

化学I　　　　　　　　　　　　　　　
北海道大学-全学教育

光レドックスカスケード水分解触媒系の創出
科学研究費助成事業 基盤研究(B)
Apr. 2023 - Mar. 2027
小林 厚志
日本学術振興会, 基盤研究(B), 北海道大学, Principal investigator, 23H01969

Development of flexible water splitting photoelectrochemical cells using conductive photocatalytic ink　　　　　　　　　　　　　　　
Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Research (Exploratory)
Jun. 2022 - Mar. 2024
Atsushi Kobayashi
Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Research (Exploratory), Hokkaido University, Principal investigator, 22K19039

機能性分子の自己集積能に基づくZスキーム水分解光触媒の開発　　　　　　　　　　　　　　　
第48回岩谷科学技術研究助成
Apr. 2022 - Mar. 2023
岩谷直治記念財団, Principal investigator

人工光合成を加速する固-固界面制御分子素子の開発　　　　　　　　　　　　　　　
Dec. 2021 - Nov. 2022
カシオ科学振興財団, Principal investigator

Development of water-splitting dye-sensitized photoelectrochemical cell with multilayered charge-separation membrane
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
Apr. 2020 - Mar. 2022
小林 厚志
【高活性光増感色素多層膜の開発】Ru色素多層膜の内部および表面構造を分子レベルで制御しつつ、Pt担持二酸化チタンまたは層状ニオブ酸ナノ粒子表面へ担持させることで、酸化還元可逆な電子伝達剤との反応性を向上させながら、高活性な水素生成光触媒の創出に成功した。470nmの青色光照射下における見かけの量子収率は1％を超え、色素増感光触媒として非常に高活性であることも確認でき、色素多層膜を用いた本手法が従来の単純な色素増感機構を刷新しうる有望性を持つことが明らかとなった。
【水素生成光カソードの開発】多孔質酸化ニッケル電極に対して、Ru色素複層膜を形成後に有機ポリマー触媒を蒸着することで、水素生成光カソードを創出した。このポリマー触媒と色素複層膜からなる新規光カソードは可視光照射下で水素を生成することが確認され、その効率向上には色素多層膜-ポリマー触媒間のエネルギー・電子移動過程の制御が重要であることがわかった。さらに、Ru色素がNiO電極表面から脱離することをポリマー触媒蒸着により効果的に抑制可能なこともわかり、本手法が水素生成光カソードの活性・耐久性向上に資する有望なものであることが実証できた。
【酸素生成光アノードの開発】多孔質二酸化チタン電極に対し、Ru色素と正孔輸送剤となるプルシアンホワイト類縁体やカルバゾール重合体を修飾し、酸素生成触媒となるプルシアンブルー類縁体やRu錯体触媒を結合させたヘテロ接合型光アノードを新たに創出した。これらの光電極は十分な正電位印加下で酸素生成活性を有することが明らかとなり、正孔輸送剤を導入した電極では光照射下における光電流がさらに増強される特性を有することがわかった。これらの結果は酸素生成光アノード構築において、色素-触媒界面に正孔輸送剤を導入することが、活性向上に有望であることを強く示唆するものと考えられる。
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), Hokkaido University, Principal investigator, 20H05082

固相合成法を用いた強発光性銅錯体の成膜プロセスにおけるその場合成法の開発　　　　　　　　　　　　　　　
Challenging Research(Exploratory)
2018 - 2019
KOBAYASHI Atsushi
Japan Society for the Promotion of Science, Principal investigator, Competitive research funding

色素-触媒界面にキャリヤー集約ナノ薄膜を形成させた水分解色素増感光電気化学セルの開発　　　　　　　　　　　　　　　
-
2018
KOBAYASHI Atsushi
ENEOS Hydrogen Trust Fund, Principal investigator, Competitive research funding

相対湿度の三次元可視化のための発光性ナノ集積体の構築　　　　　　　　　　　　　　　
Apr. 2016 - Mar. 2017
小林 厚志
島津科学技術振興財団, Principal investigator, Competitive research funding

Visualization of Proton Conductivity by Luminescence Energy of Nano-sized Coordination Polymer　　　　　　　　　　　　　　　
Apr. 2016 - Mar. 2017
KOBAYASHI Atsushi
Inamori Foundation, Principal investigator, Competitive research funding

A study on the photo-excitation energy dynamics in nanocrystals of luminescent coordination polymers
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
Apr. 2014 - Mar. 2017
Kobayashi Atsushi
To develop a new methodology to control of photo-excitation energy dynamics in the mesoscopic region, we have investigated the effect of meso-crystallization on the photoluminescence properties of coordination polymers (CPs), and the effect of surface modification of semiconductor nanoparticles on the photosensitization ability. We found that meso-crystallized CP exhibited different luminescence behavior from that of bulk crystals and molecular complexes. In the solar water splitting reaction driven by semiconductor nanoparticles, we found that the ligand covering the surface of the photosensitizing nanoparticle was involved in the formation of the catalyst-photosensitizer complex. In addition, we demonstrate that the efficiency of the interfacial electron transfer reaction on the dye-semiconductor interface was drastically improved by the formation of multilayers of sensitizing dyes. These results indicate the importance of the nanostructure in the photo-generated exciton dynamics.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, Principal investigator, 26410063

正孔の迅速拡散に立脚した新しい太陽光水分解セルの開発　　　　　　　　　　　　　　　
第32回研究助成
Sep. 2016
小林 厚志
村田学術振興財団, Principal investigator, Competitive research funding

Development of a self-assembled super-nanocrystal photocatalyst　　　　　　　　　　　　　　　
PRESTO
Dec. 2012 - Mar. 2016
KOBAYASHI Atsushi
JST, Principal investigator, Competitive research funding

発光性Pt(II)錯体配位子からなる環境マルチセンシングナノ集積体の構築　　　　　　　　　　　　　　　
Mar. 2016
小林 厚志
松籟科学技術振興財団, Principal investigator, Competitive research funding

Construction of Luminescent Chromic Metal Complexes with Dynamic Ordering
Grants-in-Aid for Scientific Research
01 Apr. 2011 - 31 Mar. 2014
KATO Masako, KOBAYASHI Atsushi, CHANG Ho-chol
The purpose of this project is to construct novel assembled metal complex systems with dynamical ordering by using various intermolecular interactions such as metal-metal, pai-pai, hydrophobic, and hydrogen bonding interactions. In this concept, we have developed luminescent metal complexes which exhibit unique chromic behaviors in response to the various environmental stimuli such as vapor, light, and heat: 1) Vapochromic coordination polymers and suplamolecular restorable systems based on luminescent platinum(II) or ruthenium(II) complexes; 2) Luminescent dinuclear copper(I) complexes which exhibit luminescence changes induced by light and vapor; 3) Vapor and mechanically induced chromic behavior of platinum(II) complexes with a dimer-of-dimer motif and the effect of hetero metal ions.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 23350025

Bistable-Crystal, -Liquid Crystals, and -Liquids based on Redox-active Metal Clusters
Grants-in-Aid for Scientific Research
23 Jul. 2009 - 31 Mar. 2014
CHANG Ho-Chol, KATO Masako, KOBAYASHI Atsushi, KANAIZUKA Katsuhiko
We have developed the design of redox-active liquid crystals which allow us to switch molecular and assembled states simultaneously by means of electrochemical redox processes. We experimentally demonstrate that [M(L)(C10,8bpy)]n (L = redox-active ligand, n = 0 or +) shows versatility not only for mesogen for LC but also for thermochromism, emission, Lewis-acid binding, and redox-activity at LC phase. These physicochemical functions of the skeleton, in particular, appear at columnar LC phase, where the functional moieties play an essential role for constructing their physical structures. Therefore, the results could be foundational for developing chemical devices with the aid of the Coordination programming. In addition to the above results, we uncover novel features of coordination complexes with redox-active ligand, for example, redox-active metalloligand, photocatalytic hydrogen production, valence tautomerism coupled with macroscopic phase, and multiresponsive chromism.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), 21108007

Research on a nano-size effect of luminescent metal-complex assembly
Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)
Apr. 2012 - Mar. 2014
KOBAYASHI Atsushi
The purpose of this project is to create a new photofunctional coordination polymer system composed of luminescent metalloligand in mesoscopic region where several unique properties based on the quantum confinement effect are well known. We successfully synthesized new coordination polymers composed of well-known photosensitizer, Ru(bpy)3 moiety, and found that the photosensitizing ability of the coordination polymer with ca. 100 nm diameter is remarkably higher than that of Ru(bpy)3 in the solution state or the bulk of coordination polymer.
Japan Society for the Promotion of Science, Grant-in-Aid for Young Scientists (B), Hokkaido University, Principal investigator, 24750049

配位環境が誘起する新規フォトクロミックシステムの創出
科学研究費助成事業
2009 - 2010
加藤 昌子, 小林 厚志
本研究の目的は、光により誘起された配位構造の変化が連鎖的もしくは協奏的に集積構造の変化に波及してクロミズム現象として現れる、新しいタイプのフォトクロミック系の構築である。22年度は光構造変換を誘起するために、チオシアン酸イオン等の両座配位子を含む錯体の光誘起結合異性化や中心金属イオンの光誘起酸化状態変化など、配位化合物特有の性質を利用した以下の3つの系の開発と機構解明を行った。
1.ジメチルスルホキシド銅(I)錯体のフォトクロミック挙動の解明と高性能化.昨年度までに見出した菱形骨格を有する銅(I)複核錯体、[Cu_2(μ-I)_2(dmso)_2(PPh_3)_2]のフォトクロミック発光の機構を解明するために、対応する臭素架橋錯体とともに構造化学的、分光学的検討を行った。また、ヨウ素架橋銅(I)複核錯体は加熱により二量化が起こり、強発光性の四核錯体[Cu_4(μ-I)_4(PPh_3)_4]が生成することが確認された。
2.チオシアナト白金(II)錯体の光誘起結合異性化によるフォトクロミズムの発現.以前に見出している[Pt(SCN)_2(bpy)]の光誘起結合異性化を基盤に、多孔性水素結合ネットワークを形成する[Pt(NCS)_2(H_2dcbpy)]および柔軟集積構造を形成する[Pt(NCS)_2(dCnbpy)]を構築した。これらが熱や蒸気に対して応答性を示すことを見出した。また、溶液中では光により結合異性化が誘起され、これに伴う発光変化を観測した。
3.白金複核錯体の酸化状態の光制御に基づくフォトクロミズムの発現.アミダト架橋シクロメタレート型白金(II)複核錯体がアセトン中可視光照射により紫色⇔無色の可逆的な色変化を示すことを見出した。光励起による酸化状態の変化と混合原子価状態生成に伴う集積構造変化が起こっていると考えられ、フォトクロミック挙動を示す混合原子価白金錯体として明確に示された初めての例である。
日本学術振興会, 特定領域研究, 北海道大学, 21021001

新規低次元電子系金属錯体の合成と物性解明　　　　　　　　　　　　　　　
Grant-in-Aid for Young Scientists (B)
Apr. 2007 - Mar. 2009
KOBAYASHI Atsushi
Japan Society for the Promotion of Science, Principal investigator, Competitive research funding

配位環境が誘起する新規フォトクロミックシステムの創出
科学研究費助成事業
2008 - 2008
加藤 昌子, 小林 厚志
本研究では, 環境感応型発光性金属錯体を基盤にして, 光により誘起された配位構造の変化が連鎖的もしくは協奏的に集積構造の変化に波及してクロミズム現象として現れる, 全く新しいタイプのフォトクロミックシステムの構築をめざしている。今年度は光による構造変換を誘起するために, ジメチルスルホキシド(dmso)、ニトロシル(NO)、チオシアン酸イオン(NCS^-)などの両座配位子を用いて新規系の探索を行った。
1. フォトクロミックな発光変化を示すハロゲン架橋銅(I)複核錯体. 銅(I)多核錯体はしばしば強発光性を示すため、近年、安価で高効率な発光材料として注目を集めている。今回、dmsoが配位した銅(I)複核錯体、[Cu2(μ-1) 2(dmso) 2(PPh3)2]の結晶の単離に成功し、構造を明らかにした。この錯体は強発光性を示すが、350nmの光を照射すると、発光色が青色から緑色に変化し、逆に、照射後の錯体をdmso雰囲気下で加熱すると元の青色に戻ることが見出された。この"光で発光色が変化する"ユニークなフォトクロミック挙動は、光励起によるdmso分子の動きに誘起された構造変化に基づくものと考えられる。
2. 光誘起結合異性化を示す白金(II)錯体の構築とフォトクロミズムの発現. ニトロシル錯体は光に鋭敏に反応して結合異性化が起こることが知られているが, 異性化状態 (M-ON) は一般に低温では安定であるものの室温ではもとの(M-NO)に容易に戻ってしまう。異性化状態も室温でも2つの異性体がともに比較的安定で, 異性化に伴って著しい色変化が起こるニトロシル白金錯体を構築する。今回、 [PtBr (NH3) 4 (NO) ] (PF6) 2を合成し、フォトクロミック挙動を調べた。その結果、対応するCl錯体より光異性化状態が安定になることが見出された。
日本学術振興会, 特定領域研究, 北海道大学, 20044001

An exploring study to find a new electronic phase in a cross-over region between one dimension and two dimension
Grants-in-Aid for Scientific Research
2007 - 2008
KOBAYASHI Atsushi
1-2次元の境界領域に位置する新規MX-Ladder 錯体を合成し、その電子状態を詳細に検討した。その結果、一次元系MX-Chain 錯体で観測されていた、電荷密度波相が梯子内だけでなく、梯子間でも秩序化した新たな電子相を発見し、また梯子内の物理パラメータを化学的に制御することで、梯子内の電子状態を逆位相電荷密度波から、同位相電荷密度波へと制御可能なことを見出した。
Japan Society for the Promotion of Science, Grant-in-Aid for Young Scientists (B), Hokkaido University, 19750050