(Invited) Axially Assembled Photosynthetic Antenna-Reaction Center Mimics

Abstract

A series of porphyrin based donor-acceptor conjugates in which the arrangement of various components are in perpendicular orientation to the porphyrin plane have been constructed and used to study the pathways of electron and energy transfer processes. The employed aluminum(III) porphyrin in these studies is found to be synthetically more advantageous as it provides reaction site on both faces of the porphyrin plane. The axial hydroxyl group on one side of the aluminum(III) porphyrin plane is able to form a covalent ester or ether bond with an energy harvester or electron acceptor while Lewis bases such as pyridine or an imidazole group form a metal-ligand axial coordination on other side of the plane hosting an electron donor or acceptor. The advantage of this configuration of the conjugates is that the donor and acceptor sides of the complex are located on opposite faces of the porphyrin which minimizes the rate of charge recombination. Moreover, the excited state \U0001d70b* orbital of porphyrin and axially coordinated ligand lie in the same space which causes an increase in the electronic coupling thus facilitating the electron/energy transfer processes. The distance dependence of sequential electron transfer in vertical, linear supramolecular triads constructed using tetrathiafulvalene (TTF), aluminum(III) porphyrin (AlPor) and fullerene (C60) entities will be discussed. Further, results of photoinduced energy transfer followed by electron transfer in antenna-reaction center mimicking BODIPY-AlPor-C60 supramolecular triads will be highlighted. Figure 1