In photosynthesis, solar energy conversion is achieved by a multi-step electron transfer reaction in which the initial charge separation between chlorophyll and primary acceptor is stabilized by a series of subsequent electron transfer steps that separate the two unpaired electrons. There are many reports of supramolecular complexes designed to mimic the light-induced charge separation processes of photosynthesis, but achieving highly efficient light-induced sequential electron transfer in such systems remains a significant challenge. Porphyrin (Por) derivatives are commonly used as both optical and redox active components in such complexes. A crucial factor in the function of any electron transfer system is the electronic coupling between the donors and acceptors, which depends to a large extent on their spatial arrangement and whether the bonds between them promote exchange coupling. The influence of the length, bonding and conformation of the bridges have been studied in porphyrin-based systems in which the components are linked via bridges to the periphery of the Por ring. However, there are fewer studies of these factors in complexes with the components linked axially via the central element of the Por ring. In this context recently we reported several axially assembled donor-aluminum(III) porphyrin-acceptor systems where electron donor and acceptor units are bound to the Al center on opposite faces of the porphyrin. By varying the different factors (bridge length, redox potentials, geometry, etc) we have investigated the electron transfer rates and the lifetime of the charge-separated state.

Axially linked donor – aluminum(III) porphyrin – acceptor self-assembled triads as artificial photosynthetic reaction center models

2019 Spring National Meeting

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