Mediation of ultrafast electron transfer in biological systems by conical intersections

Conical intersections between electronic-state potential energy surfaces are known to provide extremely efficient pathways for fast dynamical molecular processes. In this Letter, we describe theoretical work which, for the first time, identifies the existence of such a feature in the field of long-range inter-molecular photo-initiated electron transfer. This is the process at the heart of many biological processes. A typical case is studied here: the donor–acceptor pair porphyrin–quinone, which forms the basis for photosynthesis. This discovery brings a new aspect to the treatment of this fundamental process.