Trinuclear Copper(I) Furanyl ortho-Diphosphine Halide Clusters: Structure, Photophysical and Photocatalytic Hydrogen Production Properties

Abstract

In recent years, mono-and di-nuclear copper(I) ortho-diphosphine halide complexes have attracted much attention due to their excellent emissive properties. However, trinuclear copper(I) ortho-diphosphine halide clusters have not been reported so far. Herein, three trinuclear Cu(I) furanyl ortho-diphosphine halide clusters Cu 3 X 3 (dppf) 2 [X = I (1), Br (2), Cl(3), dppf = 3,4-bis(diphenylphosphino)furan] were successfully synthesized, and their molecular structures and photophysical properties were systematically studied. The structures of complexes 1-3 reveal that three Cu(I) and two μ 3 -X ions form a trigonal bipyramid, in which three Cu(I) form the plane, with two μ 3 -X ions above and below the plane, respectively.One side of the triangle is bridged by one μ 2 -X ion, while each of the other two sides is bridged by one dppf ligand. At 297 K, complexes 1 and 2 in powder emit yellowish orange light with broad bands (1: λ em = 644 nm, τ = 1.3 μs, Φ = 7.79%; 2: λ em = 614 nm, τ = 14.0 μs, Φ = 9.27%) and complex 3 in powder shows greenish blue delayed fluorescence (λ em = 472 nm; τ = 9.4 μs; Φ = 10.63%). The broad emission bands of complexes 1 and 2 at 297 K are due to 3 XLCT (halogen-to-ligand charge transfer) and cluster-centered phosphorescence ( 3 CC). The emission of complex 3 at 297 K mainly originate from MLCT (metal-to-ligand charge transfer) and ILCT (intraligand charge transfer). Under visible-light irradiation, complexes 1-3 displayed photocatalytic H 2 evolution activity. Complex 3 showed the highest hydrogen production rate of 223.2 μmol/g/h and good photostability.