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

The novel heterometallic aggregates [Ag(8)Cu(2)(C(2)C(6)H(4)X)(6)(PPh(2)C(6)H(4)PPh(2))(6)][PF(6)](4) (X = H, 1; OMe, 2; NMe(2), 3) were prepared by the self- assembly reactions starting from simple precursors. These compounds consist of the central [Ag(6)Cu(2)(C(2)C(6)H(4)X)(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 con. rmed that the compounds remain intact in solution. In solution such as CH(3)CN, 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. lm of 1 with a quantum yield of 0.26. Photophysical experiments revealed a relatively small effect of luminescence quenching by O(2) 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.