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, C-2')(2,4-pentanedionato0,0) (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 x 10(9) 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 E-T 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. (c) 2005 Elsevier B.V. All rights reserved.