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

Abstract

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 k_r and non-radiative k_nr 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 k_nr rate constants using the parameters available from analysis of the radiative ¹*MLCT ← S₀ and ³*MLCT → S₀ charge transfer processes.