Discovery of ultra-fast intersystem crossings (ISC) controlling the photochemical properties of 1rst, 2nd and 3rd row transition metal complexes motivated a number of recent studies. Singlet to triplet as well as triplet to quintet ISC rates were found to range from 10 fs to a few ps. Whatever the metal is, ISC processes are characterized by similar kinetics with no correlation with spin-orbit (SO) effects. In order to rationalize the photophysics of Re (I) carbonyl-bipyridine complexes substituted by halides X, SO absorption spectra have been calculated by quantum chemical methods. A high density of spin-mixed metal-to-ligand-charge-transfer MLCT / X-to-ligand-charge-transfer XLCT states, the composition of which depends strongly on the halide X, characterizes these spectra. The interpretation of the kinetics observed in this series of molecules is based on wavepacket simulations of the ultra-fast decay from the absorbing state to the lowest phosphorescent spin-mixed state with substantial singlet character.

Quantum chemical treatment of ultra-fast intersystem crossings in Rhenium(I) carbonyls bipyridine complexes: Dynamical effects

245th National Meeting (2013)

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