2006 Fiscal Year Final Research Report Summary
Structure Induction and Functioning of Metal Complexes Due to Weak Interactions
| Project/Area Number |
16350036
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | Kansai University |
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Principal Investigator |
YAMAUCHI Osamu Kansai University, Faculty of Engineering, Professor, 工学部, 教授 (70029643)
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| Co-Investigator(Kenkyū-buntansha) |
NAKABAYASHI Yasuo Kansai University, Faculty of Engineering, Assoc.Professor, 工学部, 助教授 (70172385)
ODANI Akira Nagoya University, Research Center for Materials Science, Assoc.Professor, 物質科学国際研究センター, 助教授 (60143913)
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| Project Period (FY) |
2004 – 2006
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| Keywords | Noncovalent interactions / Aromatic amino acid / Aromatic ring stacking / Indole ring / Phenoxyl radical / Stability constant / Hydrogen bond / Bioinorganic Chemistry |
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| Research Abstract |
Amino acids are highly functional molecules with various side chain groups and essential components of proteins. Some of their functional groups are directly involved in enzyme activities, while others construct the microenvironment of the enzyme active center. We have been studying the weak interactions in metal complexes and revealed the presence of the hydrogen bonds and aromatic ring stacking interactions in metal complexes.
On the basis of the previous studies, we aimed at clarifying the structure determining ability of weak interactions, formation of molecular adducts, and their functions. In view of the biological significance of amino acids, we designed metal chelating agents incorporating the side chain groups of aromatic and aliphatic amino acids and synthesized their Cu(II), Pd(II), and Pt(II) complexes. Intramolecular aromatic ring stacking and other weak interactions in the complexes were investigated by various methods including stability constant determination and X-ray c
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rystal structure analysis. The studies revealed the following points : (1) the π-π stacking of the side chain aromatic ring with the metal-coordinated aromatic ring is stronger than that with an uncoordinated aromatic ring, and the large electron density difference between the interacting aromatic rings is favorable for the stacking ; (2) the binding of the indole ring with Pd(II) can occur at the N1 and the C3 atom in 3H-indole and gives rise to syn-anti isomers due to the binding at the tetrahedral C3 atom ; (3) the stability of the phenoxyl radical formed from metal-phenolate complexes by one-electron oxidation depends on both the central metal ion and the N-donor ability of the ligands ; (4) the methyl group from a branched alkyl side chain group often occupies the axial position with the C-metal distance of ca. 0.25 nm and shifts the redox potential of the Cu(II) center to a higher potential.
These results add to our understanding of the structure-function relationship in metal complexes and enzymes. Less
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