2003 Fiscal Year Final Research Report Summary
Regulation of Reactivity by Hydrogen Bond to Coordinating Ligand in Metal Complexes
| Project/Area Number |
12304040
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Inorganic chemistry
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| Research Institution | Osaka University |
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Principal Investigator |
UEYAMA Norikazu Osaka University, Osaka University, Graduate School of Science, Professor (80093376)
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| Co-Investigator(Kenkyū-buntansha) |
YAMAMOTO Hitoshi 大阪大学, Graduate School of Science, Associate Professor (20222383)
OKAMURA Taka-aki 大阪大学, Graduate School of Science, Assistant Professor (90252569)
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| Project Period (FY) |
2000 – 2003
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| Keywords | Metal complexes / Hydrogen bond / O-transfer reaction / Mo, W-oxidase model / P450 model complexes / pK_a shift / Formation constant / biominerals |
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| Research Abstract |
Hydrogen bond to coordinating atom in metal thiolate complexes varies the dπ-pπ M-S bonding character, the property and the reactivity as well as M-O bonding character in metal carboxylate complexes. The following five results were obtained by this project "Regulation of Reactivity by Hydrogen Bond to Coordinating Ligand in Metal Complexes".
1) NH-S hydrogen bond between amide NH and coordinating S in Mo(IV) thiolate complexes contributes to the facilitation of O-atom transfer reaction from organic substrates although the hydrogen bond shifts the redox potential positively. On the contrary, the hydrogen bond decreases the O-transfer reactivity in dioxoMo(VI) complexes.
2) A similar shift of redox potential occurs in P450 model Fe(III) complexes. The hydrogen bond stabilizes the Fe(III) form but not Fe(II) form. The switching mechanism works between Fe(III) and Fe(II) presumably using a hair-pin turn conformation with NH-S hydrogen bond and α-helix without the hydrogen bond in the P450 active site.
3) In the case of metal complexes with coordinating O atom like carboxylate and phenolate, the NH-O hydrogen bond affects the M-O covalency in the neutral form, even the Ca-O bond in Ca complexes.
4) The presence of intramolecularly prelocated amide NH near carboxylic acid, thiol and phenol in ground state prompts their protonation and results in the lowering of pK_a. The lowering shift of the pK_a contributes to the increase of formation constant according to a formula, logβ=logK-pK_a especially working in an aqueous micellar solution.
5) In biominerals, strong Ca-O bonding on the surface of CaCO_3 crystal is due to the pK_a shift and the partially covalent Ca-O bond character.
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[Journal Article] Stabilization of Calcium- and Terbium-Carboxylate Bonds by NH…O Hydrogen Bonds in a Mononuclear Complex : A Functional Model of the Active Site of Calcium-Binding Proteins2004
Author(s)
A.Onoda, Y.Yamada, Y.Nakayama, K.Takahashi, H.Adachi, T.Okamura, A.Nakamura, H.Yamamoto, N.Ueyama, D.Vyprachticky, Y.Okamoto
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Journal Title
Inorg.Chem. 43
Pages: 4447-4455
Description
「研究成果報告書概要(和文)」より
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[Journal Article] Rapid and Sensitive Amino-Acid Sequencing of Cloning Thermus themophilus HB8 Ferredoxin by Proteomics2004
Author(s)
M.Kaneko, R.Masui, K.Ake, Y.Kousumi, S.Kuramit u, M.Yamaguchi, H.Kuyama, E.Ando, S.Norioka, T.Nakazawa, T.Okamura, H.Yamamoto, N.Ueyama
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Journal Title
J. Proteome Res. 3
Pages: 983-987
Description
「研究成果報告書概要(和文)」より
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[Journal Article] Stabilization of Calcium- and Terbium-Carboxylate Bonds by NH---O Hydrogen Bonds in a Mononuclear Complex : A Functional Model of the Active Site of Calcium-Binding Proteins2004
Author(s)
A.Onoda, Y.Yamada, Y.Nakayama, K.Takahashi, H.Adachi, T.Okamura, A.Nakamura, H.Yamamoto, N.Ueyama, D.Vyprachticky, Y.Okamoto
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Journal Title
Inorg.Chem. 43
Pages: 4447-4455
Description
「研究成果報告書概要(欧文)」より
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[Journal Article] An unusual 2D→3D parallel interpenetration : synthesis and X-ray structure of compound [Ag_2titmb)_2][Hsal]_2 3H_2O (titmb=1,3,5-tris(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene and H_2sal=salicylic acid)2004
Author(s)
J.Fan, W.-Y.Sun, T.Okamura, Y.-Q.Zheng, B.Sui, W.-X.Tang, N.Ueyama
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Journal Title
Inorg.Chim.Acta 357
Pages: 2385-2389
Description
「研究成果報告書概要(欧文)」より
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[Journal Article] Rapid and Sensitive Amino-Acid Sequencing of Cloning Thermus themophilus HB8 Ferredoxin by Proteomics2004
Author(s)
M.Kaneko, R.Masui, K.Ake, Y.Kousumi, S.Kuramitu, M.Yamaguchi, H.Kuyama, E.Ando, S.Norioka, T.Nakazawa, T.Okamura, H.Yamamoto, N.Ueyama
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Journal Title
J.Proteome Res. 3
Pages: 983-987
Description
「研究成果報告書概要(欧文)」より
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