Excimer and electron transfer quenching studies of a cyclometalated platinum complex

Luminescence quenching studies of a cyclometalated complex, platinum(II) (2-(4′,6′-difluorophenyl)pyridinato-N,C2′)(2,4-pentanedionato-O,O) (FPt), in solution at room temperature are reported. The FPt complex undergoes efficient self-quenching in solution at room temperature that can be successfully modeled by a monomer/excimer phosphorescence mechanism with a diffusion limited rate constant (4.2 ± 0.3 × 109 M−1 s−1). The emission lifetimes for FPt monomer and excimer in 2-methyltetrahydrofuran at room temperature are 330 ns (±15 ns) and 135 ns (±10 ns), respectively. The excited state properties of FPt were also investigated. A triplet energy ET of 2.8 eV and excited-state reduction potential E(FPt*/−) of 0.81 V versus SCE were determined from quenching studies in agreement with values estimated from emission spectra and a thermochemical cycle. The excited-state oxidation potential E(FPt*/+) cannot be determined from electrochemical data since FPt undergoes irreversible oxidation. However, a value of E(FPt*/+) = −1.41 V versus SCE was established from an electron transfer quenching study and thus, a ground state oxidation potential for FPt can be estimated to be 1.30 V versus SCE.