Excited-states of a rhenium carbonyl diimine complex: solvation models, spin-orbit coupling, and vibrational sampling effects

We present a quantum-chemical investigation of the excited states of the complex [Re(CO) (Im)(Phen)] (Im = imidazole; Phen = 1,10-phenanthroline) in solution including spin-orbit couplings and vibrational sampling. To this aim, we implemented electrostatic embedding quantum mechanics/molecular mechanics (QM/MM) in the Amsterdam Density Functional program suite, suitable for time-dependent density functional calculations including spin-orbit couplings. The new implementation is employed to simulate the absorption spectrum of the complex, which is compared to the results of implicit continuum solvation and frozen-density embedding. Molecular dynamics simulations are used to sample the ground state conformations in solution. The results demonstrate that any study of the excited states of [Re(CO) (Im)(Phen)] in solution and their dynamics should include extensive sampling of vibrational motion and spin-orbit couplings.