Ethynyl π-coordinated and non-coordinated mononuclear Cu(i) halide diphosphine complexes: synthesis and photophysical studies

Abstract

Highly emissive copper(I) diphosphine halide complexes and their alkynyl clusters have attracted great attention, but mononuclear copper(I) halide alkynyl diphosphine complexes and their photophysical properties are rarely reported. Here, seven mononuclear copper(I) halide ethynyl diphosphine complexes, CuX(L1), CuX(L2) and CuX(L3) [L1 = (2-PPh₂-C₆H₄)₂(CC), X = I (1), B (2), Cl (3); L2 = (4,5-OMe-2-PPh₂-C₆H₂)CC(2-PPh₂-C₆H₄), X = I (4), Br (5), Cl (6); and L3 = (4,5-OMe-2-PPh₂-C₆H₂)₂(CC), X = I (7)], were successfully prepared and their structures and photophysical properties were systematically characterized. In 1–3, ethynyl is non-coordinated with Cu(I), while in 4–7, ethynyl π coordinates with the Cu(I) center. Complexes 4 and 5 emit yellow green delayed fluorescence (λ_max = 536–539 nm, τ = 0.43–21.02 μs, and Φ_PL = 0.08–0.30%) and complexes 1–3 and 6 and 7 show yellow green to greenish yellow prompt fluorescence (λ_max = 549–583 nm, τ = 1.7–11.0 ns, and Φ_PL = 0.16–3.43%). The emissions of 1–7 are from the (metal + halide) to the ligand and intra-ligand charge transitions. Complex 4 shows photocatalytic H₂ evolution activity under visible-light irradiation.