Artificial photosynthesis using chlorophyll based carotenoid quinone triads: Technical progress report, (16 June 1985 to 28 February 1986)

The purpose of this project is to design, synthesize, and study tripartite chlorophyll-carotenoid-quinone molecules which mimic the early, energy conserving steps of natural photosynthesis. The synthetic molecules should mimic the photodriven multistep electron transfer reactions of photosynthesis which generate high-energy, long-lived charge separated states. They should also mimic carotenoid antenna function, which involves transfer of singlet energy from the carotenoid to the chlorophyll derivative, and photoprotection from singlet oxygen damage, which involves transfer of triplet energy from the chlorophyll derivative to the carotenoid. This report describes the synthesis and study of chlorophyll-based carotenopyropheophorbide-quinone triad molecules which mimic all of the natural processes mentioned above. Irradiation of one of these molecules in methylene chloride solution initiates a two-step electron transfer leading to the formation of an energetic charge-separated state with a lifetime of 120 ns and a quantum yield of approx.4%. 12 refs., 17 figs.