Coupled Electronic States in trans-Dioxo Complexes of Rhenium(V) and Osmium(VI) Probed by Near-Infrared and Visible Luminescence Spectroscopy

Abstract

trans-Dioxo complexes of rhenium(V) and osmium(VI) with ethylenediamine, imidazole, and oxalate ancillary ligands show luminescence maxima varying between 620 and 900 nm. The resolved vibronic progressions of the rhenium complexes have intensity distributions that cannot be rationalized with harmonic potential energy surfaces. The broadband spectra of the osmium(VI) complexes also show deviations from the band shapes expected for a harmonic ground-state potential surface. We use the large variation of luminescence energies and the vibronic features to show the influence of excited electronic states on the ground-state potential energy surface. The vibronic structure and band envelopes of the luminescence spectra are calculated using the lowest energy adiabatic surface obtained from three interacting electronic states.