Mononuclear Cu(I) Halide Complexes Containing Asymmetric Diphosphine and Diphenyl Pyridyl Monophosphine: Structures And Photophysical Properties

Abstract

Thermally activated delayed fluorescent (TADF) Cu(I) halide complexes have attracted attention due to their highly emission and short lifetimes (several μs scale). Here, three mononuclear four-coordinate Cu(I) halide complexes containing asymmetric diphosphine and pyridyl phosphine, [CuX(L1)(L2)] (L1 = 2,3-bis(diphenylphoshino)thiophene, L2 = 2-(diphenylphosphino)pyridine, X = I (1), Br(2), Cl (3)), were synthesized and their structures and photophysical properties were characterized. At room temperature, complexes 1-3 in powder exhibit intense green to yellow green delayed fluorescence (λem = 497-523 nm, τ = 1.5-4.3 μs, Φ = 0.19-0.28 ). The emissions of the complexes 1-3 are originated from (metal+ halide)-to-ligand and intra-ligand charge transitions. More contributions from MLCT and XLCT can result in the shorter decay lifetimes (1.6 ~ 4.3 μs), which will prevent a roll-off of efficiency with increasing current density in OLED devices.

Keywords: Asymmetric diphosphine, pyridyl diphenyl phosphine, Cu(I) halide complex, Thermally activated delayed fluorescence, Structure, Photophysical properties