The luminescence properties of the heteroleptic [Re(CO)3(N∩N)Cl] and [Re(CO)3(N∩N)(CH3CN)](+) complexes in view of the combined Marcus-Jortner and Mulliken-Hush formalism.

The luminescence properties of the heteroleptic fac-Re(CO)3(+) complexes with α-diimine N∩N ligands, neutral [Re(CO)3(N∩N)Cl] and cationic [Re(CO)3(N∩N)(CH3CN)](+) species, have been studied in acetonitrile solutions at room temperature. The investigated complexes exhibit the metal to ligand charge-transfer (MLCT) phosphorescence with the emission characteristics strongly affected by the nature of coordinated α-diimine N∩N ligands. The observed trends can be quantitatively described by invoking the electronic interactions between (3)*LC and (3)*MLCT states as well as the spin-orbit interactions between (3)*MLCT and (1)*MLCT states, respectively. All quantities necessary for the description can be straightforwardly accounted from analysis of the radiative (1)*MLCT ← S0 and (3)*MLCT → S0 charge transfer processes. It is also demonstrated that the radiative kr and non-radiative knr decay rate constants of the excited (3)*MLCT states can be interpreted within the same set of parameters. As expected from the Mulliken-Hush formalism the both processes are strictly related that allows prediction of the non-radiative knr rate constants using the parameters available from analysis of the radiative (1)*MLCT ← S0 and (3)*MLCT → S0 charge transfer processes.