Speaker
Description
Ultrafast intersystem crossing (ISC) in transition metal complexes represents a challenging process for both experimental and theoretical investigation. Two computational approaches have been employed to study the relaxation processes during the ISC of complex [Re(bpy)(CO)$_\rm3$Cl] (bpy = 2,2’-bipyridine) in explicit dimethylsulfoxide solvent. Several relaxation processes has been identified along with their time scales and physical nature. Using state-of-the-art non-adiabatic molecular dynamics we have described the relaxation of molecular spin-orbit wave packet, and successive vibrational relaxation in non-adiabatic regime. We have connected the non-adiabatic simulations to the experiment through the fluorescence decay. An unconventional method for infrared spectra at sub-ps time scale was adapted. In accord with the experiment, we have observed the fast shift of frequencies and revealed the correlation with proximal solvent relaxation.
Next time scale, accounts for the vibrational relaxations. We restricted ourselves only to the monitoring of carbonyl modes, which provide connection to the experiment. Simulation results indicate that about 2 ps are needed for carbonyl modes to approach the new equilibrium frequencies. Longest time scale corresponds to the solvent relaxation. We found that 5 ps are enough to approach the new equilibrium distribution. Mechanistically, the redistribution of solvent follows the charge redistribution, i.e., negatively charged oxygen atoms are approaching closer to the carbonyl ligands and are pushed further from the bipyridine ligand.
