Bimetallic Au2Cu6 Nanoclusters: Strong Luminescence Induced by the Aggregation of Copper(I) Complexes with Gold(0) Species

The concept of aggregation-induced emission (AIE) has been exploited to render non-luminescent (CuSR)-S-I complexes strongly luminescent. The (CuSR)-S-I complexes underwent controlled aggregation with Au-0. Unlike previous AIE methods, our strategy does not require insoluble solutions or cations. X-ray crystallography validated the structure of this highly fluorescent nanocluster: Six thiolated Cu atoms are aggregated by two Au atoms (Au2Cu6 nanoclusters). The quantum yield of this nanocluster is 11.7%. DFT calculations imply that the fluorescence originates from ligand (aryl groups on the phosphine) to metal (Cu-I) charge transfer (LMCT). Furthermore, the aggregation is affected by the restriction of intramolecular rotation (RIR), and the high rigidity of the outer ligands enhances the fluorescence of the Au2Cu6 nanoclusters. This study thus presents a novel strategy for enhancing the luminescence of metal nanoclusters (by the aggregation of active metal complexes with inert metal atoms), and also provides fundamental insights into the controllable synthesis of highly luminescent metal nanoclusters.