Coupled electronic states in trans-dioxo complexes of rhenium(V) and osmium(VI) probed by near-infrared and visible luminescence spectroscopy

trans-Dioxo complexes of rhenium(V) and osmium(VI) with ethylenediamine, im idazole, and oxalate ancillary ligands show luminescence maxima varying bet ween 620 and 900 nm. The resolved vibronic progressions of the rhenium comp lexes have intensity distributions that cannot be rationalized with harmoni c potential energy surfaces. The broadband spectra of the osmium(VI) comple xes also show deviations from the band shapes expected for a harmonic groun d-state potential surface. We use the large variation of luminescence energ ies and the vibronic features to show the influence of excited electronic s tates on the ground-state potential energy surface. The vibronic structure and band envelopes of the luminescence spectra are calculated using the low est energy adiabatic surface obtained from three interacting electronic sta tes.