Intervalence excitation of the Creutz-Taube ion. Resonance Raman and time-dependent scattering studies of Franck-Condon effects

Franck-Condon effects associated with intervalence excitation of the Creutz-Taube ion (a prototypical delocalized mixed-valency system) have been evaluated via a time-dependent analysis of resonance Raman scattering intensities and the intervalence absorption lineshape. Quantitative studies in the extended near infrared (1320 nm excitation) revealed that at least eight, and possibly nine, vibrational modes are coupled to the intervalence transition. Numerical assessment of vibrational structural changes and reorganizational energy contributions showed that the most important modes, in a Franck-Condon sense, are metal-ligand stretches along the metal-bridge-metal axis (i.e. RuN(pyrazine) and trans-RuNH3). Also active, however, are several pyrazine localized vibrations.