α-Hydroxyalkynyl-protected copper(I) acetelyenediide nanoclusters with anion-dependent photoluminescence.

Photoluminescent copper(I) acetelyenediide nanoclusters [(C2)Cu15(CCC(OH)R21)10(ClO4)2(CH3OH)3](ClO4) (Cu15, HCCC(OH)R21 = ethinylestradiol) and [(C2)Cu17(CCC(OH)R22)10(CF3CO2)5] (Cu17, HCCC(OH)R22 = ethisterone) are synthesised via comproportionation reactions of Cu(0) powder and Cu(II) salts in methanol. The employed α-hydroxyalkynes not only form multidentate α-hydroxyalkynyl ligands to stabilise the clusters from outside, but also release acetelyenediide (C22-) under ambient conditions in situ to template the formation of clusters from inside. Notably, although Cu15 and Cu17 share quite similar overall structures, the latter exhibits a photoluminescence quantum yield (PLQY) 15 times higher than the former in ethanol. A full and rigid protection formed by inner μ9-C22-, outer μ5-CCC(OH)R22 ligands, and bridging CF3CO2- anions in Cu17 is responsible for such significantly enhanced photoluminescence, as confirmed by theoretical calculations. This work demonstrates a mixed inner-outer and hetero-multidentate-ligand strategy for synergistically stabilising metal nanoclusters and generating intense photoluminescence, and α-hydroxyalkynes are highly applicable in achieving alkynyl-protected metal acetelyenediide clusters in a two birds, one stone manner.