Research on Porphyrin-Chlorin Co-assemblies and Revival of Their Dioxygen-coordination Abilities Photoirradiation

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The aim of this investigation is to revive the dioxygen-coordination ability of the auto-oxidized amphiphilic porphyrinatoiron(III) (lipidporphyrinatoiron(III)) by photoirradiation of the co-assembled free-base chlorine or porphyrin derivatives.In the first year, a new lipidporphyrin with four phospholipid-like substituents was synthesizes, It can be easily dispersed and self-assembled in aqueous system, to give spherical bi layer membranes with a diameter of 100 nm. The obtained lipidporphyrin vesicles can reversibly bind and release dioxygen under physiological conditions. The IR and MCD spectroscopies showed the coordination structure of the dioxygen. The dioxygen-binding affinity and dioxygen association and dissociation rate constants were also carefully measured.In the second year. electron transfer process from the excited state of the incorporated protoporphyrin derivative in the lipidporphyrin bilayer membrane to the iron(III) center was investigated. Under the co-existence of the electron donor (sacrificial regent) in outer aqueous phase, this reaction became irreversible, which is photoreduction system of the lipidporphyrinatoiron(III).During the research period, we found some new phenomena related on this project. For example, in co-assembled bi layer vesicles made of Zn(II) complex and free-base lipidporphyrins, high-efficient energy transfer took place from the singlet state of the porphyricatozinc(II). It could be a new light-harvesting model in aqueous medium.