Synthesis, photophysical and theoretical studies of luminescent silver(i)–copper(i) alkynyl-diphosphine complexes

Abstract

The novel heterometallic aggregates [Ag₈Cu₂(C₂C₆H₄X)₆(PPh₂C₆H₄PPh₂)₆][PF₆]₄ (X = H, 1; OMe, 2; NMe₂, 3) were prepared by the self-assembly reactions starting from simple precursors. These compounds consist of the central [Ag₆Cu₂(C₂C₆H₄X)₆]²⁺ clusters capped by two tripodal fragments [Ag(diphosphine)₃]⁺. The solid state structures of complexes 1 and 3 have been determined by X-ray crystallographic studies, and NMR spectroscopy confirmed that the compounds remain intact in solution. In solution such as CH₃CN, complexes 1–3 show a weak to moderate room-temperature phosphorescence in the blue region with a maximum quantum yield of 0.038 (2), while strong phosphorescence was recorded in the solid film of 1 with a quantum yield of 0.26. Photophysical experiments revealed a relatively small effect of luminescence quenching by O₂ for 1, but more prominent quenching for 2 and 3 in solution. Computational approaches are in good agreement with the experimental data, supporting the proposed structural motif, and provide an additional insight into the electronic properties of these compounds to rationalize the different behavior of 1 compared to 2 and 3.