Quantum Coherence Enhances Electron Transfer Rates to Two Equivalent Electron Acceptors.

When a molecular electron donor interacts with multiple electron acceptors, quantum coherence can enhance the electron transfer (ET) rate. Here we report photodriven ET rates in a pair of donor-acceptor (D-A) compounds that link one anthracene () donor to one or two equivalent 1,4-benzoquinone () acceptors. Subpicosecond ET from the lowest excited singlet state of to two s is about 2.4 times faster than ET to one at room temperature, but about 5 times faster at cryogenic temperatures. This factor of 2 increase results from a transition from ET to one of two acceptors at room temperature to ET to a superposition state of the two acceptors with correlated system-bath fluctuations at low temperature.