| Research Abstract |
Synthesis of Novel Chlorophyllous Pigments
Novel 3ィイD11ィエD1-hydroxy-13ィイD11ィエD1-oxo-chlorins possessing various substituents at 3ィイD11ィエD1-,7-,8-,13ィイD12ィエD1-,17ィイD14ィエD1-and 20-positions and their metal complexes were prepared by modification of naturally occurring chlorophylls.
2. Preparation of Artificial Chlorosomes
Synthetic metal-chlorins self-aggregated to give any oligomers in non-polar organic solvents. aqueous organic solution, aqueous solutions of detergents, solid thin films and solid powders. Supramolecular structures of the resulting oligomers were investigated by several spectroscopic techniques, indicating that a linear orientation among the hydroxy, keto groups and central metal along the Qy-axis in the molecule is requisite for formation of highly ordered supramolecules and also that magnesium, zinc and cadmium as the central metal were effective for the self-aggregation.
All the self-aggregates were built-up mainly by 13-C=・・・H(3-CHR)O・・・M and π-πinteraction of the chlorin chromophores, which are good structural models for natural chlorosomes, extramembranous antennae of photosynthetic green bacteria. Peripheral substituents affected slightly the supramolecular structures of the oligomers, but did not change the framework.
In an aqueous solution of a detergent, synthetic pigments self-aggregated at the hydrophobic sphere in the micelle. When a chromophore of a bacteriochlorin moiety was added to the aqueous solution, photoexcited energy of the oligomers was transferred to the added bacteriochlorin, indicating the in vitro self-aggregates are good functional model for natural chlorosomes.
Comparison of Natural Chlorosomes with Artificial Chlorosomes
Natural chlorophyllous pigments are consisted of several the homologues. It is not unclear how the homologues self-aggregate in the natural systems. In vitro self-aggregation of synthetic pigments gave any information for the mechanism of in vivo self-aggregation.
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