Nuclear motions of transition metal complexes and their impact on photoinduced electron transfer dynamics

Direct access to charge transfer excited states through photon absorption can induce redox potential in transition metal complexes (TMCs), rendering them effective catalysts for driving subsequent electron transfer reactions in solar energy conversion. While strong vibronic coupling is known to drive ultrafast excited state relaxations in TMCs, its influence on photoinduced electron transfer (PET) remains largely unexplored. This study investigates the impact of molecular vibrations on PET reactions in donor-acceptor systems featuring Pt(II) dimer or Cu(I) diimine complex as donors and naphthalene diimide (NDI) as the acceptor. Coherent vibrational wavepacket (CVWP) motions triggered by selective photoexcitation of TMCs provides new insights into the interplay between electronic and nuclear motions and their effects on PET outcomes. Particularly, certain CVWP motions are observed to directly modulate the spectral shape and intensity of NDI radical anions during PET reactions, indicating significant coupling between molecular vibrations and PET reaction. These findings highlight the importance of nuclear motions in shaping optimal trajectories for efficient charge separation.