Exposing the Delocalized Cu-S π Bonds on the Au24 Cu6 (SPhtBu)22 Nanocluster and Its Application in Ring-Opening Reactions.

Bimetallic nanomaterials are of major importance in catalysis. A Au-Cu bimetallic nanocluster was synthesized that is effective in catalyzing the epoxide ring-opening reaction. The catalyst was analyzed by SCXRD and ESI-MS and found to be Au24 Cu6 (SPhtBu)22 (Au24 Cu6 for short). Six copper atoms exclusively occupy the surface positions in two groups with three atoms for each, and each group was bonded with three thiolate ligands to give a planar motif reminiscent of a benzene ring. In the epoxide-ring opening reaction, Au24 Cu6 exhibited superior catalytic activity compared to other homometallic and Au-Cu alloy NCs, such as Au25 and Au38-x Cux . Control experiments and DFT calculations revealed that the π conjugation among the Cu-S bonds played a pivotal role. This study demonstrates a unique π conjugation established among the Cu-S bonds as a critical structural motif in the nanocluster, which facilitates the catalysis of a ring-opening reaction.