Many artificial photosynthetic systems employ multiple transition metal centers as functional building blocks for light harvesting, electron/energy transfer, and catalysis. Electronic couplings between the metal centers play a key role in determining the outcome of the reactions, and can be synthetically tuned. Using ultrafast optical and X-ray spectroscopies, effects of metal-metal interactions in bimetallic tetrapyridophenazine-bridged Os(II)/Cu(I) complex have been characterized. Excited-state coupling between the metal centers was evidenced by variations in the Os MLCT lifetime depending on the identity of the opposite metal center. This coupling results in concerted coherent vibrations observed that involve both metal centers. These vibrations are dominated by metal-ligand contraction at the Cu/Os centers, which are in-phase and linked through the conjugated bridging ligand. This study shows how vibronic coupling betweeen transition metal centers affects the ultrafast dynamics in bridged, multi-metallic systems, from the earliest times after photoexcitation to excited-state decay, presenting avenues for tuning charge transfer states through judicious choice of metal./ligand groups.

Excited state structural dynamics in photoactive bimetallic transition metal complexes for solar energy conversion

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.