研究者データベース

小西 克明(コニシ カツアキ)
地球環境科学研究院 物質機能科学部門 分子材料化学分野
教授

基本情報

所属

  • 地球環境科学研究院 物質機能科学部門 分子材料化学分野

職名

  • 教授

学位

  • 博士(工学)(東京大学)

ホームページURL

ORCID ID

J-Global ID

研究キーワード

  • 超分子化学   有機・無機ハイブリッド   金属クラスター   Orgrnic - lnorganic hybrid   Metal Clrster   

研究分野

  • ナノテク・材料 / エネルギー化学
  • ナノテク・材料 / 複合材料、界面
  • ナノテク・材料 / 機能物性化学
  • ナノテク・材料 / 高分子化学
  • ナノテク・材料 / 有機合成化学
  • ナノテク・材料 / ナノ構造物理
  • ナノテク・材料 / ナノ構造化学
  • 環境・農学 / 環境材料、リサイクル技術
  • 環境・農学 / 環境負荷低減技術、保全修復技術

職歴

  • 2008年10月 - 現在 北海道大学 大学院地球環境科学研究院 教授
  • 2000年 - 2008年09月 Associate Professor, Hokkaido University
  • 2000年10月 - 2003年09月 JST PRESTO (さきがけ) 変換と制御 Researcher
  • 2000年 - 2003年 JSTさきがけ研究 研究員
  • 2000年 - 2002年 北海道大学 助教授(准教授)
  • 2000年 - 2000年 東京大学工学部 講師
  • 1991年 - 2000年 東京大学工学部 助手
  • 1991年 - 2000年 Research Associate, faculty of Engineering.

学歴

  •         - 1991年   東京大学   工学系研究科   合成化学
  •         - 1991年   東京大学
  •         - 1987年   東京大学   工学部   工業化学科
  •         - 1987年   東京大学

所属学協会

  • 高分子学会   日本化学会   The Society of Synthetic Organic Chemistry, Japan   The Society of Polymer Science, Japan   Chemical society of Japan   

研究活動情報

論文

  • Takuya Sagawa, Hirokazu Kobayashi, Chinatsu Murata, Yukatsu Shichibu, Katsuaki Konishi, Mineo Hashizume, Atsushi Fukuoka
    Bulletin of the Chemical Society of Japan 2022年05月27日
  • Yukatsu Shichibu, Fan Zhang, Yuxiang Chen, Masafumi Konishi, Susumu Tanaka, Hiroaki Imoto, Kensuke Naka, Katsuaki Konishi
    The Journal of Chemical Physics 155 5 054301 - 054301 2021年08月07日
  • Yuting Wang, Nabin Maity, Liming Zhao, Maximilian Krämer, Jun-ya Hasegawa, Yukatsu Shichibu, Katsuaki Konishi, Xiaoyuan Wang, Zhiyi Song, Masayoshi Bando, Tamaki Nakano
    Chemistry Letters 2021年04月15日
  • Yuki Saito, Yukatsu Shichibu, Katsuaki Konishi
    Nanoscale 13 22 9971 - 9977 2021年 

    Covalent crosslinking of Au25(SR)18 nanoclusters through reversible disulfide bond formation, which was promoted by the Au25 nanocluster itself, occurred under the control of dynamic covalent chemistry, affording free-standing nanocluster films.

  • Yukatsu Shichibu, Yuri Ogawa, Mizuho Sugiuchi, Katsuaki Konishi
    Nanoscale Advances 3 4 1005 - 1011 2021年 

    The profound chiroptical nature of Au13 clusters was revealed from systematic experimental and theoretical investigations.

  • Midori Murakami, Riku Matsumine, Takeya Ono, Katsuaki Konishi
    Chemistry Letters 49 10 1228 - 1231 2020年10月05日 [査読有り][通常論文]
  • Masaru Kato, Yukatsu Shichibu, Kazuya Ogura, Mitsuhiro Iwasaki, Mizuho Sugiuchi, Katsuaki Konishi, Ichizo Yagi
    The Journal of Physical Chemistry Letters 11 19 7996 - 8001 2020年10月01日 [査読有り][通常論文]
  • Mizuho Sugiuchi, Mingzhe Zhang, Yusaku Hakoishi, Yukatsu Shichibu, Noriko Nishizawa Horimoto, Yoshihiro Yamauchi, Yasuhiro Ishida, Katsuaki Konishi
    The Journal of Physical Chemistry C 124 29 16209 - 16215 2020年07月23日 [査読有り][通常論文]
  • Heshuang Dai, Yukatsu Shichibu, Yoshitane Imai, Nobuyuki Hara, Katsuaki Konishi, Yue Wang, Zhiyi Song, Tamaki Nakano
    POLYMER CHEMISTRY 11 6 1134 - 1144 2020年02月 
    Polyaddition between 2,2'-dihydroxy-1,1'-binaphthyl (BINOL) and 1,4-diisocyanatobenzene (14DIB) and that between BINOL and 1,3-diisocyanatobenzene (13DIB) were conducted leading to optically active, helical polyurethanes, poly(BINOL-alt-14DIB) and poly(BINOL-alt-13DIB), respectively. In BINOL-14DIB systems, cyclic dimers were formed along with helical, linear poly(BINOL-alt-14DIB) where the content of dimers was higher at a lower ee of BINOL and the yield of higher-molar-mass, linear polymers was higher at a higher ee of BINOL in feed. (R,R)-, (R,S)-, and (S, S)-Cyclic dimers were completely resolved and separated by chiral HPLC. The (R,S)-cyclic dimer was preferred over (R,R)-and (S, S)-cyclic dimers, while in the reaction using racemic BINOL, the (R,R)-cyclic dimer was preferred over the other isomers at 25-75% ee of (R)-BINOL in feed. Poly(BINOL-alt-14DIB) is proposed to be composed of sequences with rather contiguous (R)-BINOL units as the majority component with rather sporadically incorporated (S)-units as the minor component. Helical sense excess appears to be greater than expected from the ee of BINOL units in the chain, suggesting that (S)-BINOL units sporadically incorporated in a rather contiguous (R)-BINOL unit sequence become a part of the left-handed helical conformation controlled by the chiral influence of contiguous (R)-BINOL units. In addition, the chiral conformation of poly (BINOL-alt-14DIB) and BINOL-14DIB cyclic dimers appeared to be stabilized or enhanced in the solid state. The BINOL-13DIB systems produced linear dimers as major components of the dimer whose content was almost constant regardless of the ee of BINOL in feed. Poly(BINOL-alt-13DIB) is proposed to be composed of sequences with rather randomly distributed (R)- and (S)-BINOL units and may be characterized by sharp, left-handed turns based on BINOL chirality forming a longer-pitched, left-handed helix.
  • Takuya Sagawa, Hirokazu Kobayashi, Chinatsu Murata, Yukatsu Shichibu, Katsuaki Konishi, Atsushi Fukuoka
    ACS Sustainable Chemistry & Engineering 7 17 14883 - 14888 2019年09月 [査読有り][通常論文]
  • Md Jahidul Islam, Ken-ichi Yuyama, Kiyonori Takahashi, Takayoshi Nakamura, Katsuaki Konishi, Vasudevanpillai Biju
    NPG Asia Materials 11 31  2019年06月 [査読有り][通常論文]
     
    The development of new methods to engineer lead halide perovskite crystals with a controlled band gap and emission properties is an active subject in materials science and chemistry. We present the preparation of mixed-halide lead perovskites by spatially- and temporally- controlled chemical reactions and crystal growth under an optical potential in unsaturated precursor solutions. The crystals are characterized by transmission and photoluminescence spectral measurements and X-ray diffraction analysis. When compared with the spontaneous formation of multiple crystals in saturated precursor solutions, the optical potential creates large single crystals with a high chloride composition, providing distinct blue and green fluorescent crystals of chloride-bromide lead perovskites. We discuss the formation of mixed-halide perovskites from the viewpoints of an increased rate of chemical reaction via the formation and desolvation of precursor complexes and a decreased free energy potential.
  • Yukatsu Shichibu, Mingzhe Zhang, Takeshi Iwasa, Yuriko Ono, Tetsuya Taketsugu, Shun Omagari, Takayuki Nakanishi, Yasuchika Hasegawa, Katsuaki Konishi
    Journal of Physical Chemistry C 123 6934 - 6939 2019年03月21日 [査読有り][通常論文]
     
    © Copyright 2019 American Chemical Society. The use of multidentate chelating ligands enriches the geometric diversity of coordinated gold clusters, offering much knowledge to benefit the understanding of their unique electronic structures and optical properties. Herein we report different behaviors of [core+exo]-type Au6 clusters bearing C3- and C4-bridged diphosphines (1 and 2), highlighting profound effects of the steric constraints of the ligand environments on the excited-state structural dynamics. Although the Au6 geometries of 1 and 2 in the crystalline states were somewhat different, their absorption spectra in solution were almost similar. However, marked differences were found in the photoluminescence properties; phosphorescent-type emission was dominantly observed for 1, whereas 2 gave both fluorescence- and phosphorescence-type emissions. Theoretical calculations showed that the bridging chains influence the geometries of the Au6 unit in the excited states, leading to the observed differences in emission behaviors.
  • Mitsuhiro Iwasaki, Yukatsu Shichibu, Katsuaki Konishi
    Angewandte Chemie International Edition 58 8 2443 - 2447 2019年02月18日 [査読有り][通常論文]
  • Taniguchi, Tohru, Suzuki, Takahiro, Satoh, Haruka, Shichibu, Yukatsu, Konishi, Katsuaki, Monde, Kenji
    Journal of the American Chemical Society 140 46 15577 - 15581 2018年 [査読有り][通常論文]
  • Konishi Katsuaki, Iwasaki Mitsuhiro, Shichibu Yukatsu
    Accounts of Chemical Research 51 12 3125 - 3133 2018年 [査読有り][通常論文]
  • Sugiuchi, Mizuho, Shichibu, Yukatsu, Konishi, Katsuaki
    Angewandte Chemie-International Edition 57 26 7855 - 7859 2018年 [査読有り][通常論文]
     
    2,3-bis(diphenylphosphino)butane enantiomers (chiraphos, L) used as chiral auxiliaries results in the preferential formation of an unprecedented Au24 framework with inherent chirality. The crystal structure of [Au24L6Cl4]2+ (1) has a square antiprism-like octagold core twinned by two helicene-like hexagold motifs, where the inherent chirality is associated with the helical arrangement. The clusters carrying (R,R)- and (S,S)- diphosphines had right- and left-handed strands, respectively. Circular dichroism spectra showed peaks in the visible to near-IR region, some of which did not coincide with absorption bands, suggesting the enantiomeric Au24 frameworks possess unique chiroptical properties. The Au24 frameworks were thermally robust, which could be attributed to the superatomic concept (18 e− system) and the steric constraint effects of the bridging ligand units.
  • Sugiuchi, Mizuho, Maeba, Junichi, Okubo, Nobuyuki, Iwamura, Munetaka, Nozaki, Koichi, Konishi, Katsuaki
    Journal of the American Chemical Society 139 49 17731 - 17734 2017年 [査読有り][通常論文]
     
    Aggregation-induced optical responses are ubiquitous among a wide range of organic and inorganic compounds. Here, we demonstrate an unprecedented effect of aggregation on the photoluminescence (PL) profiles of [core + exo]-type [Au-8](4+) clusters, which displayed a change in the dominant PL emission mode from fluorescence to phosphorescence-type upon aggregation. In solvents in which cluster molecules are highly soluble and exist as monomers, they displayed single PL bands at similar to 600 nm at ambient temperatures. However, in solvents in which cluster molecules are less soluble and cluster aggregation is induced, a new PL band at similar to 700 nm also emerged. Lifetime measurements revealed that the PL emissions at similar to 600 and similar to 700 nm had fluorescence and phosphorescence characters, respectively. Studies of the excitation spectra suggested that organized cluster assemblies were responsible for the lower-energy emission at similar to 700 nm and had exceptionally high emission activity. Accordingly, intense phosphorescence-type emissions were observed in the solid state in which the quantum efficiencies were higher by two orders of magnitude than those of the corresponding monomeric forms in solution. This work provides an example of the critical effects of cluster aggregation events on their optical properties and shows the potential of such effects in the design of cluster based materials with unique functions and properties.
  • Abu Bakar, Md., Sugiuchi, Mizuho, Iwasaki, Mitsuhiro, Shichibu, Yukatsu, Konishi, Katsuaki
    Nature Communications 8 2017年 [査読有り][通常論文]
     
    It is well known that various transition elements can form M center dot center dot center dot H hydrogen bonds. However, for gold, there has been limited decisive experimental evidence of such attractive interactions. Herein we demonstrate an example of spectroscopically identified hydrogen bonding interaction of C-H units to Au atoms in divalent hexagold clusters ([Au6](2+)) decorated by diphosphine ligands. X-ray crystallography reveals substantially short Au-H/Au-C distances to indicate the presence of attractive interactions involving unfunctionalized C-H moieties. Solution H-1 and C-13 NMR signals of the C-H units appear at considerably downfield regions, indicating the hydrogen-bond character of the interactions. The Au center dot center dot center dot H interactions are critically involved in the ligand-cluster interactions to affect the stability of the cluster framework. This work demonstrates the uniqueness and potential of partially oxidised Au cluster moieties to participate in non-covalent interaction with various organic functionalities, which would expand the scope of gold clusters.
  • Wada, Satoshi, Kitagawa, Yuichi, Nakanishi, Takayuki, Fushimi, Koji, Morisaki, Yasuhiro, Fujita, Koji, Konishi, Katsuaki, Tanaka, Katsuhisa, Chujo, Yoshiki, Hasegawa, Yasuchika
    Npg Asia Materials 8 2016年 [査読有り][通常論文]
     
    The chiral nonanuclear Tb(III) clusters [Tb-9(sal-(R)-Bt)(16)(mu-OH)(10)]+[NO3]-(Tb-(R)-Bt: sal-(R)-Bt=(R)-2-butyl salicylate) and [Tb9 (sal-(S)-Bt)(16)(mu-OH)(10)](+)[NO3](-)(Tb-(S)-Bt: sal-(S)-Bt=(S)-2-butyl salicylate) were found to exhibit a unique magneto-optical property: the Faraday effect. The clusters were composed of 9 Tb(III) ions bridged by 10 mu-OHs and 16 chiral salicylic acid esters. The Faraday rotation angle of Tb-(R)-Bt was greater than that of Tb-(S)-Bt, indicating that the Faraday effect was affected by the chirality of the Tb(III) clusters. The chiroptical properties of the Tb(III) clusters were estimated using circular dichroism and circularly polarized luminescence. In this study, a new finding concerning chiral magneto-optical properties was investigated.
  • Konishi, Katsuaki, Iwasaki, Mitsuhiro, Sugiuchi, Mizuho, Shichibu, Yukatsu
    Journal of Physical Chemistry Letters 7 21 4267 - 4274 2016年 [査読有り][通常論文]
     
    Recent advances in the crystal structure determination of ligand-protected metal clusters have revealed that their electronic structures and optical features are essentially governed by the nuclearity and geometries of the inorganic frameworks. In this Perspective, we point out the definite effects of the exterior ligand moieties on the properties of small gold clusters. On the basis of systematic experimental studies on the optical properties of Au-8 and Au-13 clusters with various anionic ligands, it was shown that not only the "through-bond" electronic effects of coordinating atoms but also the nonbonding interaction with neighboring heteroatoms and the electronic coupling with pi-systems cause substantial perturbations. We also suggest that the steric rigidity of the ligand environments affects their photoluminescence efficiencies. These findings imply the feasibility of the facile modulation of the cluster properties through the appropriate choice of ligand modules, which may lead to the evolution of novel cluster-based materials with unique properties and functions.
  • Shichibu, Yukatsu, Yoshida, Keisuke, Konishi, Katsuaki
    Inorganic Chemistry 55 18 9147 - 9149 2016年 [査読有り][通常論文]
     
    The inclusion of a Ag-I ion by a hexanuclear platinum(II) thiolate macrocycle in solution was demonstrated, and the inclusion structure was determined by Xray crystallography. Unique host-guest intermetallic interactions driven by charge transfer were elucidated by optical absorption spectroscopy and theoretical calculations.
  • Iwasaki, Mitsuhiro, Kobayashi, Naoki, Shichibu, Yukatsu, Konishi, Katsuaki
    Physical Chemistry Chemical Physics 18 28 19433 - 19439 2016年 [査読有り][通常論文]
     
    In the recent development of structurally defined ligand-stabilized gold clusters, it has been revealed that not only the inorganic units but also the surrounding organic ligands substantially affect their electronic/optical properties. In this work, a series of core + exo type Au-8 clusters decorated by dppp (Ph2P(CH2)(3)PPh2) and arylthiolate ligands ([Au-8(dppp)(4)(SR)(2)](2+), 1-5) were synthesized, and their optical properties were studied in order to gain insights into the perturbation effects of the organic ligands. 1-5 showed visible absorption and photoluminescence emission bands at longer wavelengths compared to their chloro-and acetylide-modified analogues, suggesting the contribution of weak non-bonding interactions of the Au framework with the ligand heteroatoms. Upon acid treatment, 2- and 4-pyridinethiolate clusters (R = Py, 2 and 4) showed larger red shifts of the absorption and emission bands than the 3-pyridyl isomer (3), implying the involvement of the resonance structures of the SPy units. On the other hand, all regioisomers (2-4) showed large photoluminescence enhancements upon pyridine protonation. X-ray crystallographic and NMR analyses of 4 and its protonated form (4') showed that the electron-deficient pyridinium rings of 4' form p-stacks with neighbouring phenyl groups of dppp, suggesting that the orientation of the surface aromatics is a plausible factor governing the emission efficiency. These observations provide examples of successful modulation of optical properties of small gold clusters through the electronic and/or steric perturbation by the proximal organic ligands, highlighting the importance of the ligand design in the fine tuning of cluster properties directed for optical chemosensors and luminescent materials.
  • Taniguchi, Tohru, Asahata, Mai, Nasu, Akihito, Shichibu, Yukatsu, Konishi, Katsuaki, Monde, Kenji
    Chirality 28 7 534 - 539 2016年 [査読有り][通常論文]
     
    Separation of the diastereomers of glycosyl sulfoxides differing in the sulfur chirality has been difficult. This article presents a fast and scalable method for their diastereoseparation using a chiral stationary phase. The usefulness of this method was demonstrated in a 500-mg scale separation within 20 min, and in the separation of trisaccharyl sulfoxide diastereomers. (C) 2016 Wiley Periodicals, Inc.
  • Fukunaga, Naoto, Konishi, Katsuaki
    Nanoscale 7 48 20557 - 20563 2015年 [査読有り][通常論文]
     
    Poly(ethylene glycol) (PEG) has been widely used for the surface protection of inorganic nanoobjects because of its virtually 'inert' nature, but little attention has been paid to its inherent electronic impacts on inorganic cores. Herein, we definitively show, through studies on optical properties of a series of PEG-modified Cd10Se4(SR)10 clusters, that the surrounding PEG environments can electronically affect the properties of the inorganic core. For the clusters with PEG units directly attached to an inorganic core (R = (CH2CH2O)nOCH(3), 1-PEGn, n = 3, similar to 7, similar to 17, similar to 46), the absorption bands, associated with the low-energy transitions, continuously blue-shifted with the increasing PEG chain length. The chain length dependencies were also observed in the photoluminescence properties, particularly in the excitation spectral profiles. By combining the spectral features of several PEG17-modified clusters (2-C-m-PEG17 and 3) whose PEG and core units are separated by various alkyl chain-based spacers, it was demonstrated that sufficiently long PEG units, including PEG17 and PEG46, cause electronic perturbations in the cluster properties when they are arranged near the inorganic core. These unique effects of the long-PEG environments could be correlated with their large dipole moments, suggesting that the polarity of the proximal chemical environment is critical when affecting the electronic properties of the inorganic cluster core.
  • Kamei, Yutaro, Robertson, Neil, Shichibu, Yukatsu, Konishi, Katsuaki
    Journal of Physical Chemistry C 119 20 10995 - 10999 2015年 [査読有り][通常論文]
     
    Electronic properties of ultrasmall gold clusters with defined nuclearity and geometrical structures have been a recent subject of interest not only with respect to the concept of molecularity but also because of their potential applicability as nanomaterials and catalysts. In this work, the electrochemical properties of dppp-protected octagold clusters ([Au8L4](n+) (L = dppp, n = 2 (1) and 4 (2), dppp = Ph2P(CH2)(3)PPh2) with charge-dependent geometrical structures were investigated. Unlike conventional spherelike centered clusters held by multiple spokes, the nonspoked Ails clusters displayed irreversible electrochemical profiles for the two-electron redox interconversion between 1 and 2, exhibiting a wide energy gap between the redox couples. This electrochemical irreversibility could be attributed to the significant alteration of electronic structures associated with the redox-coupled isomerization of the nonspoked cluster structures. In addition, we show that the coordinative interaction of Cl- anions with the Au-8 clusters notably affects both reduction and oxidation courses, providing an example of coordination-coupled electron transfer events.
  • Sugiuchi, Mizuho, Shichibu, Yukatsu, Nakanishi, Takayuki, Hasegawa, Yasuchika, Konishi, Katsuaki
    Chemical Communications 51 70 13519 - 13522 2015年 [査読有り][通常論文]
     
    An organometallic Au-13 cluster having two sigma-bonded acetylide ligands was synthesized and its structure was determined by X-ray crystallography. Absorption spectral studies indicated the presence of electronic coupling between the superatomic Au-13 core and the acetylide pi-orbitals, which was supported by theoretical considerations.
  • Gudeangadi, Prashant G., Sakamoto, Takeshi, Shichibu, Yukatsu, Konishi, Katsuaki, Nakano, Tamaki
    Acs Macro Letters 4 9 901 - 906 2015年 [査読有り][通常論文]
     
    (R)-1,1'-Bi(2-naphthol) was reacted with 1,4-phenylene diisocyanate leading to a mixture of linear polyurethane and cyclic compounds including a cyclic dimer and a cyclic trimer. The structure of the cyclic dimer was elucidated by X-ray crystal structure analysis. The polymer was proposed to possess a rather stiff, pi-stacked, 2/1-helical conformation on the basis of NMR, CD, and UV spectra and molecular dynamics simulations. The conformation was stable in the range of temperature of 0-60 degrees C.
  • Konishi, Katsuaki
    GOLD CLUSTERS, COLLOIDS AND NANOPARTICLES I 161 49 - 86 2014年 [査読有り][通常論文]
     
    Synthetic techniques, geometrical structures, and electronic absorption spectra of phosphine-coordinated pure-gold molecular clusters (PGCs) accumulated over 40 years are comprehensively collected especially for those with unambiguous X-ray crystal structures available. Inspection of the electronic absorption spectra from geometrical aspects reveals that their optical properties are highly dependent on the cluster geometries rather than the nuclearity. Recent examples of unusual clusters that show unique color/photoluminescence properties and their utilization for stimuli-responsive modules are also presented.
  • Shichibu, Yukatsu, Zhang, Mingzhe, Kamei, Yutaro, Konishi, Katsuaki
    Journal of the American Chemical Society 136 37 12892 - 12895 2014年 [査読有り][通常論文]
     
    Ligand-stabilized ultrasmall gold clusters offer a library of diverse geometrical and electronic structures. Among them, clusters with four valence electrons form an exceptional but interesting family because of their unique geometrical structures and optical properties. Here, we report a novel diphosphine-ligated four-electron Au-7 cluster (2). In good agreement with previous theoretical predictions, 2 has a "core+one" structure to exhibit a prolate shape. The absorption spectrum showed an isolated band, similar to the spectra of Au-6 and Au-8 dusters with "core+two" structures. TD-DFT studies demonstrated that the attachment of only one gold atom to a polyhedral core is sufficient to generate unique electronic structures and characteristic absorptions. The present result fills the missing link between Au6 and Au8 in the four-electron cluster family, showing that the HOMO-LUMO gap increases with increasing nuclearity in the case of the tetrahedron-based "core+exo" clusters.
  • Naoki Kobayashi, Yutaro Kamei, Yukatsu Shichibu, Katsuaki Konishi
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 135 43 16078 - 16081 2013年10月 [査読有り][通常論文]
     
    A series of [core+exo]-type Au-8 clusters bearing two alkynyl ligands on the exo gold atoms ([Au-8(dppp)(4)(C CR)(2)](2+), 2-6) were synthesized by the reaction of [Au-8(dppp)(4)](2+) (1) with alkynyl anions. Although the C C moieties directly attached to the Au-8 units did not affect the optical properties arising from intracluster transitions, the pyridylethynyl-bearing clusters (4-6) exhibited reversible visible absorption and photoluminescence responses to protonation/deprotonation events of the terminal pyridyl moieties. The chromism behaviors and proton-binding constants of these clusters were highly dependent on the relative position of the pyridine nitrogen atom, such that the 2-pyridyl (4) and 4-pyridyl (6) isomers showed more pronounced responses than the 3-pyridyl isomer (5). These results suggest that the resonance-coupled movement of the positive charge upon protonation is involved in the optical responses, where the formation of extended charged resonance structures causes significant perturbation effects on the electronic properties of the Au-8 unit and also contributes to the high binding affinities.
  • Konishi, Katsuaki, Shichibu, Yukatsu
    Abstracts of Papers of the American Chemical Society 246 2013年
  • Shichibu, Yukatsu, Konishi, Katsuaki
    Inorganic Chemistry 52 11 6570 - 6575 2013年 [査読有り][通常論文]
     
    Unusual visible absorption properties of [core+exo]-type Au-6 (1), Au-8 (2), and Au-11 (3) clusters were studied from experimental and theoretical aspects, based on previously determined crystal structures. Unlike conventional core-only clusters having no exo gold atoms, these nonspherical clusters all showed an isolated visible absorption band in solution. Density functional theory (DFT) studies on corresponding nonphenyl models (1'-3') revealed that they had similar electronic structures with discrete highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) bands. The theoretical spectra generated by time-dependent DFT (TD-DFT) calculations agreed well with the experimentally measured properties of 1-3, allowing assignment of the characteristic visible bands to HOMO-LUMO transitions. The calculated HOMO-LUMO transition energies increased in the order Au-11 < Au-6 < Au-g, as was found experimentally. Frontier orbital analyses indicated that the HOMO and LUMO were both found in proximity to the terminal Au-3 triangles containing the exo gold atom, with the HOMO -> LUMO transition occurring in the core -> exo direction. The HOMO/LUMO distribution patterns of 1' and 3' were similar to each other but were markedly different from that of 2', which has longer core-to-exo distances. These findings showed that not only nuclearity (size) but also geometric structures have profound effects on electronic properties and optical transitions of the [core+exo]-type clusters.
  • Yukatsu Shichibu, Yutaro Kamei, Katsuaki Konishi
    CHEMICAL COMMUNICATIONS 48 61 7559 - 7561 2012年 [査読有り][通常論文]
     
    A novel dodeca-ligated undecagold cluster having a nonagold core plus two exo-attached gold atoms was synthesized. Unlike the conventional icosahedron-based "core-only" isomer, the [9 + 2] cluster showed an intense visible absorption band. Theoretical calculation showed the involvement of the exo gold atoms in the generation of the unique electronic structure.
  • Yukatsu Shichibu, Kai Suzuki, Katsuaki Konishi
    NANOSCALE 4 14 4125 - 4129 2012年 [査読有り][通常論文]
     
    Synthesis of molecular gold clusters through a post-synthetic scheme involving HCl-promoted nuclearity convergence was examined with various phosphine ligands. Systematic studies with a series of bis(diphenylphosphino) ligands (Ph2P-(CH2)(m)-PPh2) using electrospray ionization mass spectrometry (ESI-MS) and electronic absorption spectroscopy demonstrated that the use of dppp (m = 3), dppb (m = 4) and dpppe (m = 5) as the ligands resulted in the formation of [Au13P8Cl4](+) type clusters, whereas the [Au13P10Cl2](3+) type cluster was formed with dppe (m = 2). The cluster species did not survive the HCl treatment step when monophosphines PPh3, PMe2Ph, and POct(3) were employed, but [Au-13(POct(3))(8)Cl-4](+) was isolated as a minor product in the NaBH4 reduction of Au(POct(3))Cl in aqueous THF. Electronic absorption and photoluminescence studies of a series of Au-13 clusters revealed that their optical properties are highly dependent on the phosphine/chloride composition ratio, but are far less so on the phosphine structure.
  • Sakamoto, Takeshi, Watanabe, Kento, Shichibu, Yukatsu, Konishi, Katsuaki, Sato, Shin-Ichiro, Nakano, Tamaki
    Journal of Polymer Science, Part A: Polymer Chemistry 49 4 945 - 956 2011年02月15日 [査読有り][通常論文]
  • Katsuaki Konishi, Eri Takase, Naoto Fukunaga
    LANGMUIR 27 4 1332 - 1335 2011年02月 [査読有り][通常論文]
     
    A series of water-soluble cadmium sulfide clusters bearing an alkyl-chain layer between the inorganic core and the outer PEG layer were synthesized by the ligand-exchange reaction of Cd10S4(SPh)(12) with thiols functionalized by an N-(omega-PEGylated alkyl) amide moiety. The photoluminescence titration experiments in aqueous media revealed that clusters with a sufficiently hydrophobic inner environment exhibit definite emission enhancements upon the addition of bisphenol A or 4-nonylphenol. The dramatic effect of the alkyl chain length on the emission responses demonstrated that the hydrophobic layer around the inorganic surface serves as guest binding sites to facilitate the access of the lipophilic phenols. near the organic inorganic interface. A marked preference for the lipophilic phenols over related compounds, such as methylated bisphenol A, long-chain n-alkanol, and nonlipophilic phenols, was observed in the emission responses of the "hydrophobic" cluster, suggesting that not only the hydrophobic interaction but also the attractive force involving the phenolic OH group contributes to the positive responses. The results of control experiments and IR studies indicated that the hydrogen bonding interaction between the phenolic OH group and the amide group in the surface organic units is responsible for the positive emission responses. The present work shows that the precise tuning of the molecular recognition environments near the organic inorganic interface is useful for developing guest-specific functions.
  • Yutaro Kamei, Yukatsu Shichibu, Katsuaki Konishi
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 50 32 7442 - 7445 2011年 [査読有り][通常論文]
  • Yukatsu Shichibu, Katsuaki Konishi
    SMALL 6 11 1216 - 1220 2010年06月 [査読有り][通常論文]
  • Yoshitaka Murakami, Katsuaki Konishi
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 129 46 14401 - 14407 2007年11月 [査読有り][通常論文]
     
    The effect of dodecanethiolate-protected metallic nanoclusters of gold (Au:SC12, 1), silver (Ag: SC12), palladium (Pd:SC12), and platinum (Pt:SC12) on the catalytic activity of Mn(TPP)Cl (TPP = tetraphenylporphinato) was investigated in styrene oxidation with iodosylbenzene. Among the four metal clusters, only Au:SC12 led to appreciable acceleration of the catalytic reaction. The major role of the Au cluster was to regenerate the active catalytic path involving Mn(III) and Mn(V) from the deactivated Mn(IV) species. The binary 1/Mn(TPP)Cl catalyst system showed an absorption spectrum characteristic of Mn-(III)-porphyrin after reaction, whereas a catalytically ineffective Mn(IV) species was observed as the sole porphyrin species in the absence of the Au cluster or in the presence of Pd, Ag, and Pt clusters. Accordingly, the slow oxidation reaction with Mn(TPP)Cl was accelerated by the addition of Au:SC12, and complete conversion of Mn(IV) into Mn(Ill) was observed in the absorption spectrum. H-1 NMR inspection of the reaction of Au:SC12 and iodosylbenzene revealed that the surface dodecyl groups were partially oxidized into dodecanal and eliminated from the cluster surface, thereby producing unprotected gold sites on the surface. A reactivation mechanism involving the reaction of the Mn-porphyrin and the oxidant activated on the gold surface is proposed.

その他活動・業績

受賞

  • 2015年03月 日本化学会 学術賞
     
    受賞者: 小西 克明

共同研究・競争的資金等の研究課題

  • 配位子保護金属クラスターの精密組織化と金属コア間相互作用による機能発現
    日本学術振興会:科学研究費助成事業 基盤研究(A)
    研究期間 : 2021年04月 -2025年03月 
    代表者 : 小西 克明
  • 金属クラスターと芳香族ユニットの間に働く引力相互作用の学理解明と機能開拓
    科学研究費補助金:基盤研究(B)
    研究期間 : 2018年04月 -2021年03月 
    代表者 : 小西 克明
  • 自己組織構造形成に駆動される二重ラセン型配位高分子の精密合成
    JSPS:科学研究費 挑戦的萌芽研究
    研究期間 : 2016年04月 -2017年03月 
    代表者 : 小西 克明
  • 有機小分子に誘発される発光性ナノ金属種の自己集合を利用した機能開拓
    JSPS:科学研究費 基盤研究(B)
    研究期間 : 2012年04月 -2015年03月 
    代表者 : 小西 克明
  • 無機クラスター高次ネットワーク構造の構築と機能創発
    文部科学省:科学研究費 新学術領域研究(計画)
    研究期間 : 2008年10月 -2013年03月 
    代表者 : 小西 克明
  • 有機・無機超分子複合体の設計と環境調和型システムへの応用
    科学研究費補助金
    研究期間 : 2004年 -2005年

教育活動情報

主要な担当授業

  • ナノ環境材料化学特論Ⅱ
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 環境科学院
    キーワード : 高分子、超分子、ナノクラスター、ナノ粒子 polymer, supramolecule, nanocluster, nanoparticle
  • 化学Ⅱ
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 有機化合物、官能基、分子構造、化学的性質、化学反応、機能性有機物、生体関連有機物質

大学運営

学内役職歴

  • 2019年4月1日 - 2019年9月30日 大学院環境科学院副学院長
  • 2019年10月1日 - 2021年9月30日 大学院環境科学院副学院長
  • 2021年10月1日 - 2023年9月30日 大学院環境科学院副学院長
  • 2019年4月1日 - 2019年9月30日 大学院地球環境科学研究院副研究院長
  • 2019年10月1日 - 2021年9月30日 大学院地球環境科学研究院副研究院長
  • 2021年10月1日 - 2023年9月30日 大学院地球環境科学研究院副研究院長


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