Ligand-centered to metal-centered activation of a Rh(iii) photosensitizer revealed by ab initio molecular dynamics simulations.

Excited state evolution of the rhodium(iii) complex [Rh(iii)(phen) 2 (NH 3 ) 2 ] 2+ (phen = 1,10-phenanthroline) has been investigated theoretically to gain a better understanding of light-driven activation of high-energy metal centered states. Ab initio molecular dynamics (AIMD) simulations show the significance of asymmetric motion on a multidimensional potential energy landscape around the metal center for activated crossover from triplet ligand centered ( 3 LC) to triplet metal centered ( 3 MC) states on picosecond timescales. Significant entropic differences arising from the structural distributions of the 3 LC and 3 MC states revealed by the simulations are found to favor the forward crossover process. Simulations at different temperatures provide further insight into the interplay between structural and electronic factors governing the 3 LC → 3 MC dynamics as a concerted two-electron energy transfer process, and the broader implications for photoinduced generation of high-energy 3 MC states of interest for emerging photocatalytic applications are outlined.