Photoisomerisation-coupled electron transfer

Photochromic molecular structures constitute a unique platform for constructing molecular switches, sensors and memory devices. One of their most promising applications is as light-switchable electron acceptor or donor units. Here, we investigate a previously unexplored process that we postulate may occur in such systems: an ultrafast electron transfer triggered by a simultaneous photoisomerisation of the donor or the acceptor moiety. We propose a theoretical model for this phenomenon and, with the aid of DFT calculations, apply it to the case of a dihydropyrene-type photochromic molecular donor. By considering the wavepacket dynamics and the photoisomerisation yield, we show that the two processes involved, electron transfer and photoisomerisation, are in general inseparable and need to be treated in a unified manner. We finish by discussing how the efficiency of photoisomerisation-coupled electron transfer can be controlled experimentally.