Synthesis of Au₁₃Cu₄ Nanoclusters with Isomeric Mercaptobenzoic Acid Ligands

Au-based alloy nanoclusters (NCs) have attracted significant interest due to their unique properties, including chirality, magnetism, luminescence, and size-dependent characteristics. Despite their promising potential, further efforts are required to explore a broader range of ligands and alloy NCs to fully unlock their capabilities. Here, [Au₁₃Cu₄(MBA)₁₂]^3- alloy NCs (MBA = mercaptobenzoic acid) were synthesized from [Au₂₅(MBA)₁₈]^- seed NCs using MBA isomers as etching agents. The [Au₂₅(MBA)₁₈]^- NCs were fragmented and reassembled with Cu ions into [Au₁₃Cu₄(MBA)₁₂]^3- NCs. This process, driven by MBA ligands, was monitored by time-dependent electrospray ionization mass spectrometry and optical spectroscopies. Theoretical calculations suggested a tetrahedral geometry for the [Au₁₃Cu₄(MBA)₁₂]^3- NCs stabilized by interligand interactions. Notably, the quantum yield of [Au₁₃Cu₄(p-MBA)₁₂]^3- NCs increased ∼14-fold compared to that of [Au₂₅(p-MBA)₁₈]^- NCs. These results offer a novel approach for synthesizing water-soluble, size-focused Au-based alloy NCs, opening up the investigation of new gold alloy clusters with enhanced properties and broader applications.