Deep-Red Luminescence and Efficient Singlet Oxygen Generation by Cyclometalated Platinum(II) Complexes with 8-Hydroxyquinolines and Quinoline-8-thiol

The synthesis and photophysical study of (C^∧N)Pt^IIQ complexes, where C^∧N is a bidentate cyclometalating ligand and Q is 8-hydroxyquinoline or quinoline-8-thiol, are presented. The compounds were obtained as a single isomer with N atoms of the C^∧N and Q ligands trans-coordinated to the Pt^II center as shown by X-ray crystallography. These chromophores absorb intensely in the visible region and emit in the deep-red spectral region from a quinolate-centered triplet intraligand charge-transfer excited state. The emission maxima are in the range 675−740 nm, with the quantum yields and lifetimes of up to 0.82% and 5.3 μs, respectively, in deoxygenated organic solvents at room temperature. These complexes are efficient photosensitizers of singlet oxygen in air-saturated solutions, with yields up to 90%.