A theoretical investigation of the ground and excited states of selected Ru and Os polypyridyl molecular dyes

Density functional theory (DFT) is applied to analyze ground and excited-state properties of some M(bpy)₂L₂ complexes (M = Ru, Os, L = CN, SCN, bpy = 2,2′-bipyridine), both in the gas phase and in aqueous solution. In particular, vertical excitation energies were computed by the PBEO hybrid functional in the framework of a time dependent DFT (TDDFT) approach, whereas the polarizable continuum model (PCM) was used to take into account solvent effects. Our results in the gas phase show that the PBE0 functional provides accurate description of all the low lying electronic states considered and correctly reproduces the excitation spectra of such complexes. Some insights on the difference observed for these complexes in changing the central metal atom, the chemical environment, or the medium are given.