Effects of phenyl/thienyl substituents at acetylacetone auxiliary ligands on the properties of cyclometalated platinum(II) complexes

Abstract

2-(4-N,N-Diphenylaminophenyl)-5-trifluoromethylpyridine-based neutral cyclometalated Pt(II) complexes Pt1–Pt3 with acetylacetone derivatives as auxiliary ligands were synthesized and characterized. The photophysical and electrochemical properties of the complexes were investigated systematically. The phosphorescence maxima emission of complexes Pt1, Pt2 and Pt3 exhibit notable red-shifts at 568, 579 and 579 nm, respectively, compared with the model complex Pt(ppy)(acac) (λmax = 485 nm, ppy = 2-phenylpyridine). Relative to Pt(ppy)(acac), the photoluminescence quantum yields of complexes Pt1, Pt2 and Pt3 decrease at different extents, while their phosphorescence lifetimes are prolonged obviously (9.08 μs for Pt1, 30.76 μs for Pt2 and 27.01 μs for Pt3), much longer than that of Pt(ppy)(acac) (2.60 μs). Immobilized in the ethyl cellulose film, Pt2 bearing a diphenyl-substituted acetylacetone ancillary ligand demonstrates the highest oxygen sensitivity. Moreover, the phosphorescence quenching and recovery processes of the oxygen sensing films are reversible.