Photoinduced charge transfer in solvated anthraquinones is facilitated by low-frequency ring deformations

Efficiency of photoinduced charge transfer (CT) reactions in supramolecular assemblies is often compromised due to the rigid parametrization of acceptable donor-acceptor (D-A) distances and orientations. Using a combined approach of time-resolved optical measurements and electronic structure studies guided by molecular dynamics (MD) simulations, we demonstrate that dynamic control on CT rate exists for quenching of hydroxy-anthraquinones in donor aniline-like solvents. We find that anthraquinone ring deformation modes control the kinetics of CT within ∼300-700 fs by modulating the D-A electronic couplings. Our work demonstrates that low-frequency motions have to be critically understood for all such D-A pairs, and generates a rational methodology for utilization of hydroxy-anthraquinone acceptors in numerous photoactive architectures.