The luminescence properties of heteroleptic [OsCl(CO)(N∩N)(P∩P)]+ complexes – radiative and non-radiative deactivation of the excited 3*MLCT state

Abstract

The luminescence properties of the heteroleptic [OsCl(CO)(N∩N)(P∩P)]⁺ complexes with bidentate phosphine P∩P and diimine N∩N ligands have been studied in acetonitrile solutions at room temperature and in methanol/ethanol (1 : 1) glasses at 77 K. At room temperature the investigated complexes feature strong (with the quantum yields ϕ_em from 0.17 up to 0.64), long-lived (with lifetimes τ_em in the range of 1.5–44.2 μs) ³*MLCT emission. Analysis of ³*MLCT emission band shapes leads to the quantities relevant for the radiative electron transfer (between the Os²⁺ central ion and the N∩N ligand) in the Marcus inverted region. It is also demonstrated that radiative k_r and non-radiative k_nr decay rate constants of the excited ³*MLCT states can be interpreted within the Mulliken–Hush formalism. Especially values of k_nr rate constants can be predicted using the parameters available from the analysis of the radiative ¹*MLCT ← S₀ and ³*MLCT → S₀ charge transfer processes.