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)(NH3)(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 ((LC)-L-3) to triplet metal centered ((MC)-M-3) states on picosecond timescales. Significant entropic differences arising from the structural distributions of the (LC)-L-3 and (MC)-M-3 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 (LC)-L-3 -> (MC)-M-3 dynamics as a concerted two-electron energy transfer process, and the broader implications for photoinduced generation of high-energy (MC)-M-3 states of interest for emerging photocatalytic applications are outlined.

Automated summary

The excited state evolution of a rhodium(III) complex has been theoretically investigated to understand the light-driven activation of high-energy metal centered states. Ab initio molecular dynamics simulations reveal the significance of asymmetric motion for the activated crossover process on picosecond timescales. The simulations also show that entropic differences favor the forward crossover process. The interplay between structural and electronic factors in the dynamics and its implications for photoinduced generation of high-energy states are discussed.