Phosphorescent 8-quinolinol metal chelates. Excited-state properties and redox behavior

Abstract

A number of metal complexes of 8-quinolinol (QOH) of general formula M(QO)n(n = 3, M = Al(III), Bi(III), Rh(III), Ir(III); n = 2, M = Pt(II), Pb(II)) have been synthesized and characterized. The heavy-metal complexes (M = Pt(II), Pb(II), Bi(III), Ir(III)) exhibit long-lived (τ ≃ 2–4 μs) phosphorescence and excited-state absorption (ESA) in fluid solution. The photophysics of these complexes (emission spectra and lifetimes, ESA spectra and lifetimes, emission quantum yields, efficiencies of formation of the long-lived state) has been studied in some detail. The long-lived emitting state is assigned as a metal-perturbed triplet state of the 8-quinolinol ligand. On the basis of their ground-state redox potentials and on their excited-state properties, the heavy-metal 8-quinolinol complexes are predicted to behave as powerful excited-state reductants (potentials in the-0.8 to-1.3 V range vs. SCE). Quenching studies verify these expectations. © 1986, American Chemical Society. All rights re...