研究者データベース

七分 勇勝(シチブ ユウカツ)
地球環境科学研究院 物質機能科学部門 機能材料化学分野
准教授

基本情報

所属

  • 地球環境科学研究院 物質機能科学部門 機能材料化学分野

職名

  • 准教授

学位

  • 博士(材料科学)(北陸先端科学技術大学院大学)

J-Global ID

研究キーワード

  • ホスト・ゲスト   光応答   金属クラスター   形状制御   電子構造解析   

研究分野

  • ナノテク・材料 / 機能物性化学
  • ナノテク・材料 / ナノ構造化学
  • ナノテク・材料 / 基礎物理化学

職歴

  • 2015年02月 - 現在 北海道大学 地球環境科学研究院 物質機能科学部門 准教授
  • 2010年02月 - 2015年02月 北海道大学 地球環境科学研究院 物質機能科学部門 助教
  • 2012年02月 - 2013年05月 グラスゴー大学 化学科 客員研究員
  • 2008年04月 - 2010年02月 北海道大学 地球環境科学研究院 研究員
  • 2008年01月 - 2008年03月 北海道大学 触媒化学研究センター 研究員
  • 2006年04月 - 2007年12月 分子科学研究所 研究員

学歴

  •         - 2006年03月   北陸先端科学技術大学院大学大学院   材料科学研究科   機能科学専攻 博士後期課程
  •         - 2003年03月   東京理科大学大学院   理学研究科   物理学専攻 修士課程
  •         - 2001年03月   東京理科大学   理学部   物理学科

所属学協会

  • 分子科学会   日本化学会   

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
  • Zhiyi Song, Hiroyasu Sato, Adriana Pietropaolo, Qingyu Wang, Shuhei Shimoda, Heshuang Dai, Yoshitane Imai, Hayato Toda, Takunori Harada, Yukatsu Shichibu, Katsuaki Konishi, Masayoshi Bando, Naofumi Naga, Tamaki Nakano
    CHEMICAL COMMUNICATIONS 58 7 1029 - 1032 2022年01月 
    Optically active linear polyurethane and a cyclic dimer were synthesized from 2,7-diisocyanatofluorene and 2,2 '-dihydroxy-1,1 '-binaphthyl. The circular dichroism (CD) spectral intensity of the polymer was amplified at a higher concentration through aggregate formation, while circularly polarized light (CPL) emission was not enhanced. The cyclic dimer's CPL emission was largely amplified (g(lum) 1.1 x 10(-2)) due to intermolecular excimer formation through aggregation, while the CD intensity was not affected.
  • 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 [査読有り]
  • Yuki Saito, Yukatsu Shichibu, Katsuaki Konishi
    Nanoscale 13 22 9971 - 9977 2021年06月 [査読有り]
     

    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.

  • 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 [査読有り]
  • Yukatsu Shichibu, Yuri Ogawa, Mizuho Sugiuchi, Katsuaki Konishi
    Nanoscale Advances 3 4 1005 - 1011 2021年03月 [査読有り]
     

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

  • 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]
  • 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 [査読有り][通常論文]
     
    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.
  • Yukatsu Shichibu, Mingzhe Zhang, Takeshi Iwasa, Yuriko Ono, Tetsuya Taketsugu, Shun Omagari, Takayuki Nakanishi, Yasuchika Hasegawa, Katsuaki Konishi
    Journal of Physical Chemistry C 123 11 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.
  • Takuya Sagawa, Hirokazu Kobayashi, Chinatsu Murata, Yukatsu Shichibu, Katsuaki Konishi, Atsushi Fukuoka
    ACS Sustainable Chemistry & Engineering 7 17 14883 - 14888 2019年 [査読有り][通常論文]
  • Unusual Attractive Au-pi Interactions in Small Diacetylene-Modified Gold Clusters
    Mitsuhiro Iwasaki, Yukatsu Shichibu, Katsuaki Konishi
    Angewandte Chemie International Edition 58 8 2443 - 2447 2019年 [査読有り][通常論文]
  • Mizuho Sugiuchi, Yukatsu Shichibu, Katsuaki Konishi
    Angewandte Chemie - International Edition 57 26 7855 - 7859 2018年06月25日 [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.
  • Katsuaki Konishi, Mitsuhiro Iwasaki, Yukatsu Shichibu
    Accounts of Chemical Research 51 3125 - 3133 2018年 [査読有り][通常論文]
  • Tohru Taniguchi, Takahiro Suzuki, Haruka Satoh, Yukatsu Shichibu, Katsuaki Konishi, Kenji Monde
    Journal of the American Chemical Society 140 15577 - 15581 2018年 [査読有り][通常論文]
  • Md. Abu Bakar, Mizuho Sugiuchi, Mitsuhiro Iwasaki, Yukatsu Shichibu, Katsuaki Konishi
    NATURE COMMUNICATIONS 8 576  2017年09月 [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.
  • Katsuaki Konishi, Mitsuhiro Iwasaki, Mizuho Sugiuchi, Yukatsu Shichibu
    JOURNAL OF PHYSICAL CHEMISTRY LETTERS 7 21 4267 - 4274 2016年11月 [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.
  • Yukatsu Shichibu, Keisuke Yoshida, Katsuaki Konishi
    INORGANIC CHEMISTRY 55 18 9147 - 9149 2016年09月 [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.
  • Mitsuhiro Iwasaki, Naoki Kobayashi, Yukatsu Shichibu, Katsuaki Konishi
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 18 28 19433 - 19439 2016年07月 [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.
  • Tohru Taniguchi, Mai Asahata, Akihito Nasu, Yukatsu Shichibu, Katsuaki Konishi, Kenji Monde
    CHIRALITY 28 7 534 - 539 2016年07月 [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.
  • Prashant G. Gudeangadi, Takeshi Sakamoto, Yukatsu Shichibu, Katsuaki Konishi, Tamaki Nakano
    ACS MACRO LETTERS 4 9 901 - 906 2015年09月 [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.
  • Yutaro Kamei, Neil Robertson, Yukatsu Shichibu, Katsuaki Konishi
    JOURNAL OF PHYSICAL CHEMISTRY C 119 20 10995 - 10999 2015年05月 [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.
  • Mizuho Sugiuchi, Yukatsu Shichibu, Takayuki Nakanishi, Yasuchika Hasegawa, Katsuaki Konishi
    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.
  • Yukatsu Shichibu, Mingzhe Zhang, Yutaro Kamei, Katsuaki Konishi
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 136 37 12892 - 12895 2014年09月 [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.
  • Yukatsu Shichibu, Katsuaki Konishi
    INORGANIC CHEMISTRY 52 11 6570 - 6575 2013年06月 [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.
  • Takeshi Sakamoto, Kento Watanabe, Yukatsu Shichibu, Katsuaki Konishi, Shin-Ichiro Sato, Tamaki Nakano
    JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY 49 4 945 - 956 2011年02月 [査読有り][通常論文]
     
    2,7-Bis(4-t-butylphenyl)-9-methylfluoren-9-yl acrylate (BBPMFA) was synthesized and polymerized using alpha,alpha'-azobisisobutyronitrile or n-Bu(3)B-air as a radical initiator and using the complex of 9-fluorenyllithium with (S)-(+)-1-(2-pyrrolidinylmethyl)pyrrolidine as an optically active anionic initiator. Although the radical polymerization led to rather low-molecular-weight products at low yields, the anionic polymerization afforded polymers with higher molecular weights in higher yields. The poly(BBPMFA) obtained by the anionic polymerization was slightly rich in isotacticity (meso diad 57%) and showed an intense circular dichroism (CD) spectrum and large dextrorotation. The intensity of the CD spectrum and magnitude of optical activity increased with an increase in M(n), suggesting that the polymer possesses a preferred-handed helical conformation. The CD spectrum disappeared within 1 s on irradiation to the polymer in a CHCl(3) solution using a 500-W Hg-Xe lamp. This was ascribed to fast photolysis of the ester linkage leading to a loss of helical conformation of the entire chain. Photolysis products of poly(BBPMFA) were poly(acrylic acid) and 2,7-bis(4-t-butylphenyl)-9-methylenefluorene (2,7-bis(4-t-butylphenyl)dibenzofulvene). The photolysis reaction seemed to proceed through the "unzipping" mechanism. The rate constant of photolysis of poly(BBPMFA) under irradiation at monochromated 325 nm was around 0.01 s(-1) independent of molecular weight. Photolysis at 325 nm was approximately 2400 times faster than that for chemical ester solvolysis under a neutral condition in the dark. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 945-956, 2011
  • 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]
  • Nirmalya K. Chaki, Yuichi Negishi, Hironori Tsunoyama, Yukatsu Shichibu, Tatsuya Tsukuda
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 130 27 8608 - + 2008年07月 [査読有り][通常論文]
     
    The molecular formulas and charge state distributions of thus-far known ubiquitous alkanethiolate-protected gold clusters with core-masses of 8 and 29 kDa were assessed using electrospray ionization mass spectrometry. The 8 and 29 kDa clusters were determined to be composed of single species, [Au-38(SCn)(24)](z) and [Au-144(SCn)(59)](z), respectively, with charge states of z >= 0. Possible geometric structures for Au-38(SCn)(24) and Au-144(SCn)(59) are discussed, based on the structures of relevant systems that have been recently determined experimentally and theoretically: [Au-25(SR)(18)](-) and Au-102(SR)(44), in which the Au cores are protected by monomers [-SR-Au-SR-] and/or dimers [-SR-Au-SR-Au-SR-]. Their preferential formation and chemical robustness are proposed as being associated with high stability due to geometric factors, while the Au-thiolate interface takes on common motifs regardless of the underlying Au core.
  • Yuichi Negishi, Nirmalya K. Chaki, Yukatsu Shichibu, Robert L. Whetten, Tatsuya Tsukuda
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 129 37 11322 - + 2007年08月 [査読有り][通常論文]
     
    The present work aims to test the validity of the electronic shell model for Au-25(SC6H13)(18) by monitoring the charge state of the Au: S core and thereby to elucidate the origin of magic stability. Electrospray ionization mass spectrometry revealed that the Schiffrin method yields [Au-25(SC6H13)(18)](x) with a distribution of charge states, which shifts toward negative values with reduction time. The stable ions [Au-25(SC6H13)(18)](1+) and [Au-25(SC6H13)(18)](1-) can be synthesized by chemical oxidation and reduction of [Au-25(SC6H13)(18)](0), respectively. These findings lead us to conclude that electronic shell closing is not a crucial factor for the high stability of [Au-25 (SC6H13)(18)](x) (X = 1-, 0, 1+). We ascribe magic stability to the core-in-cage structure predicted theoretically.
  • Yukatsu Shichibu, Yuichi Negishi, Takahito Watanabe, Nirmalya K. Chaki, Hiroyuki Kawaguchi, Tatsuya Tsukuda
    JOURNAL OF PHYSICAL CHEMISTRY C 111 22 7845 - 7847 2007年06月 [査読有り][通常論文]
     
    The chemical reaction between [Au-11(PPh3)(8)Cl-2](+) and n-alkanethiol CnH2n+1SH (n = 2, 8, 10, 12, 14, 16, and 18) serendipitously yielded stable Au-25 cluster compounds with the formula, [Au-25(PPh3)(10)(SCnH2n+1)(5)Cl-2](2+). Single-crystal X-ray structural analysis of [Au-25(PPh3)(10)(SC2H5)(5)Cl-2](SbF6)(2) revealed that the Au-25 core is constructed by bridging two icosahedral Au-13 clusters with thiolates sharing a vertex atom. Optical absorption spectroscopy showed that coupling between the Au-13 building blocks gives rise to new electronic levels in addition to those of the Au-13 constituents.
  • Yukatsu Shichibu, Yuichi Negishi, Hironori Tsunoyama, Masayuki Kanehara, Toshiharu Teranishi, Tatsuya Tsukuda
    SMALL 3 5 835 - 839 2007年05月 [査読有り][通常論文]
  • H Zhang, Y Yasutake, Y Shichibu, T Teranishi, Y Majima
    PHYSICAL REVIEW B 72 20 2005年11月 [査読有り][通常論文]
     
    Coulomb staircases in double-barrier tunneling junctions consisting of a scanning-probe-vacuum-gap-alkanethiol-protected Au nanoparticle/Au (111) electrode have been measured as a function of the set point current of scanning tunneling spectroscopy. The tunneling resistances of the scanning probe-Au core of a nanoparticle (R-1) and the Au core-Au (111) electrode (R-2) are evaluated by fitting a theoretical Coulomb staircase into the experimental tunneling current-voltage characteristics measured by scanning tunneling spectroscopy. When a vacuum gap exists between the scanning probe and alkanethiol Au nanoparticles, R-1 is inversely proportional to the set point current. On the contrary, in the case of R-1 < R-2, the top of the tip of the scanning probe tends to penetrate the octanethiol-protecting molecule of an Au nanoparticle. R-2 is found to be independent of the set point current, and R-2 of octanethiol- and hexanethiol-protected Au nanoparticles are evaluated as 7.6 G Omega +/- 10% and 460 M Omega +/- 10%, respectively.
  • Y Shichibu, Y Negishi, T Tsukuda, T Teranishi
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 127 39 13464 - 13465 2005年10月 [査読有り][通常論文]
  • Y Shichibu, K Watanabe
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 42 9A 5472 - 5476 2003年09月 [査読有り][通常論文]
     
    The electronic structures of iodine-doped and rubidium-doped pentacene molecular crystals are investigated by ab initio calculation based on the ultrasoft pseudopotential method. We find from charge transfer analysis that iodine, an electron acceptor, generates hole carriers, and rubidium, an electron donor, generates electron carriers at the edge of pentacene molecules. The calculation results support the two-dimensional electric conduction along the dopant sheet and the edges of pentacene molecules, which are well compatible with experimental observations.
  • C Kanai, Y Shichibu, K Watanabe, Y Takakuwa
    PHYSICAL REVIEW B 65 15 2002年04月 [査読有り][通常論文]
     
    The segregation of a hydrogen (H) atom to the monohydride diamond C(100)2x1 surface from the subsurface, which consists of two elementary processes of lateral migration in the subsurface and migration to the surface from the bulk, has been investigated by ab initio pseudopotential method. Since the activation energy barrier (AEB) for H migration in the subsurface perpendicular to dimer rows markedly decreases due to the presence of an H defect on the surface, it becomes an easy diffusion path and the diffusing H atoms tend to approach a position under a hollow site. The AEB for H migration to the surface from the bulk also markedly decreases due to the H defect on the surface. Thus, the H defect on the monohydride surface is easily repaired by H atoms from the subsurface, resulting in the suppression of methane adsorption and diamond epitaxial growth. The theoretical results support the experimental observations.

その他活動・業績

特許

  • 特開2010-222333:Au13クラスタ及び金クラスタの製造方法  
    小西克明, 七分勇勝
  • 特開2007-45791:Au25クラスターの選択的大量合成方法  
    寺西利治, 七分勇勝, 佃達哉, 根岸雄一

受賞

  • 2017年03月 日本化学会 第31回 若い世代の特別講演会
     
    受賞者: 七分勇勝
  • 2016年02月 北海道大学 研究総長賞(奨励賞)
     
    受賞者: 七分勇勝
  • 2015年01月 日本化学会北海道支部 奨励賞
     
    受賞者: 七分勇勝

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
  • 環境物質科学基礎論Ⅰ
    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 : Chemical Bonding, Electronic Structure, Atomic Orbital, Molecular Orbital, Crystal Structure
  • 化学Ⅰ
    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 : 原子の構造、原子軌道、化学結合、混成軌道、物質の三態、電解質溶液
  • 自然科学実験
    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 : 自然科学実験、物理学、化学、生物学、地球惑星科学

大学運営

委員歴

  • 2017年 - 現在   錯体化学会第67回討論会   実行委員
  • 2017年 - 現在   ナノ学会第15回大会   実行委員
  • 2011年 - 現在   第5回分子科学討論会   実行委員


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