Time-dependent Raman analysis of metal-to-ligand charge transfer excited states: Application to radiative and nonradiative decay
Journal of Physical Chemistry A
The photophysical properties of the emitting metal-to-ligand charge transfer (MLCT) excited states of the complexes, [Os(bpy)3]2+, [Os(bpy)2(py)2]2+, and [Os(bpy)(py)4]2+ (bpy = 4-4′-bipyridine, py = pyridine) have been characterized in aqueous solution at room temperature by absorption, emission, and Raman spectroscopies and by emission lifetimes and emission quantum yields. A spectroscopic model has been developed by using the time-dependent theory of Raman scattering, taking into account interference effects on resonance Raman profiles arising from interactions between the different ligands. A model based on the cylindrical model of Sension and Strauss provides a good fit to the data. The mode-specific vibrational parameters obtained from the spectroscopic analysis are used to calculate the vibrational contributions to the radiative and nonradiative decay rate constants for each of the complexes. These results and the experimental rate constants were used to calculate vibrationally induced electronic coupling matrix elements (Vk) for nonradiative decay and also transition moments, M, for radiative decay. For radiative decay, the average transition moment for the three complexes was 0.05Å, and for nonradiative decay, the average value of Vk was 910 cm-1. Within a reasonable margin of error, the Franck-Condon contributions are in agreement with values obtained in a previous study that used the single mode approximation and a Franck-Condon analysis of emission spectra.
Thompson, D., Schoonover, J., Timpson, C., & Meyer, T. (2003). Time-dependent Raman analysis of metal-to-ligand charge transfer excited states: Application to radiative and nonradiative decay. Journal of Physical Chemistry A, 107 (48), 10250-10260. https://doi.org/10.1021/jp0303366