Electron–Nuclear Dynamics Accompanying Proton-Coupled Electron Transfer

Although photoinduced proton-coupled electron transfer (PCET) plays an essential role in photosynthesis, a full understanding of the mechanism is still lacking due to complex nonequilibrium dynamics arising from strongly coupled electronic and nuclear degrees freedom. Here we report PCET biomimetic model system investigated by means transient IR two-dimensional electronic–vibrational (2DEV) spectroscopies, spectroelectrochemistry (IRSEC), calculations utilizing long-range-corrected hybrid density functionals. This collective experimental theoretical effort provides nuanced picture complicated synergistic motions involved PCET. In particular, evolution 2DEV line shape, which highly sensitive mixing vibronic states, interpreted accurate computational modeling charge separated state shown represent gradual change distribution associated with dihedral twist that occurs on 120 fs time scale.