2000 Fiscal Year Final Research Report Summary
Construction of Large-scale Molecular Structures through Self-assembling Processes
| Project/Area Number |
10480150
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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 |
Bioorganic chemistry
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| Research Institution | Kyoto Institute of Technology |
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Principal Investigator |
KURODA Yasuhisa Kyoto Institute of Technology, Department of Polymer Science, Professor, 繊維学部, 教授 (00111930)
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| Project Period (FY) |
1998 – 2000
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| Keywords | Self-assembling / Porphyrin / Photosynthetic Center / Molecular Recognition / Energy Transfer |
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| Research Abstract |
Two types of porphyrin assemblies were constructed.
1. New types of self-organized porphyrin arrays were constructed. The systems contain dimeric TT and trimeric tartrates TTT connected with 1, 6-hexamethylendiol spacers and the trench porphyrin P bridged with 2, 4-dinitro-isophthalic acid. The TT-P and TTT-P systems exhibit unique exciton splitting bands at 437 nm and 440 nm upon allowing the temperature of the samples to lower, of which splinting energies are 507 cm-1 and 691 cm-1 respectively. The observed splitting of the Soret bands strongly indicates the formation of porphyrin arrays on the tartarate templates.
2. The new nonameric porphyrin assembly is constructed by using specific complexation between the dimeric zinc porphyrin assembly and pyrazine derivative. The spectroscopic titration experiment shows that the new porphyrin having four pyrazinyl moieties (Py_4TPP) specifically forms complexes with dimeric [meso-tetrakis (2-carboxy-4-nonylphenyl) porphyrinato]-zinc (II)(TCP_2) to give the nonameric porphyrin assembly Py_4TPP-(TCP_2) 4 where the central free base porphyrin is surrounded by eight zinc porphyrins. The electronic spectra of the assembly suggest that four pyrazinyl moieties of Py_4TPP act as the independent binding site and electronic interaction between component porphyrins in the assembly is weak. The assembly shows strongly enhanced fluorescence (λ_<ex>=564 nm) of Py_4TPP even though the absorbance ratio 1/TCP_2 opyrazine is 1/22 at the excitation wavelength, suggesting effective energy transfer from TCP_2-pyrazine to Py_4TPP within the assembly. The energy transfer efficiency in the present assembly is estimated to be 82%. The results demonstrate the antenna effect of eight zinc porphyrins arranged around the central energy acceptor, which enhance the light absorption efficiency of the system rather than the energy transfer efficiency.
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