Asymmetric alloying for heterogeneous metal-ion clusters of chiral-at-carbon CAu^I₄Ag^I₆ polyhedra exhibiting red to near-infrared photoluminescence.

Abstract

Well-defined subnano-sized metal clusters are highly susceptible to changes in the type, number and arrangement of the metals. Precise alloying and stereocontrol of metal clusters at the atomic level are therefore expected to elucidate unexplored structures and functions. Here, we report an asymmetric alloying method by adding silver trifluoroacetate to a highly symmetric C-centered hexagold(I) cluster protected by triphenylphosphine, and provide detailed descriptions of the structure and propertied of the resulting chiral-at-carbon hexasilver(I)-alloyed tetragoldmethane, CAu^I₄Ag^I₆, in a bicapped square antiprism. Theoretical calculations reveal the bonding natures of C-Au^I bonds and C···Ag^I interactions. By using homochiral carboxylate ligands, asymmetric induction to (R,Ʌ)- or (S,∆)-CAu^I₄Ag^I₆ species is quantitatively achieved, each of which exhibits red to near-infrared phosphorescence and distinct chiroptical activity. This asymmetric silver(I)-alloying involves etching of gold(I) ions from the hexagold(I) cluster, which will further lead to the development of heterometal ion clusters as chiral luminescent materials.