Self-assembly of synthetic zinc chlorins in a silicate micelle prepared by sol-gel process

Zinc methyl 3-devinyl-3-hydroxymethyl-pyropheophorbide-a (1), a good model compound of light-harvesting pigments of green photosynthetic bacteria, formed self-aggregates in the presence of octadecyltriethoxysilane and tetraethoxysilane in an aqueous solution to exhibit visible absorption spectra similar to the natural antenna. Base-catalyzed cross-linked polymerization of the additive Si-ORs (R=ethyl and H) afforded the formation of a siloxane network (Si-O-Si) on the surface of the self-assemblies of 1. The resulting microcapsules were stable to tolerate the deaggregation to monomeric 1 by addition of surfactant Triton X-100 more largely than the corresponding micelles before polymerization.