Ultra-small Luminescent Copper Nanoclusters Catalyzed C-S Cross Coupling Reactions: Effect of Ligand Substituents in Modulating Catalytic Efficiency

Abstract

Ultra-small copper nanoclusters (CuNCs) have attracted attention as efficient and sustainable catalysts due to their large surface area, quantum-size effects, readily available active sites, and cost-effective synthesis. In this work, we report the gram-scale, one-pot synthesis of orange-emitting CuNCs@2MB, stabilized by thiolate ligands, exhibiting a long lifetime (~ 3 µs). The chemical composition, surface characteristics and spectroscopic properties of the synthesized CuNCs@2MB were analyzed using MALDI-TOF MS, TEM, UV-vis, and fluorescence spectroscopy. These ultra-small CuNCs act as a robust heterogeneous catalyst for C-S cross-coupling reactions, enabling the formation of diverse thioethers. The nanoclusters demonstrated high functional group tolerance and good yields across a wide range of aryl iodides and thiols. Furthermore, a comparative study with a newly synthesized nonyl chain appended copper nanoclusters (CuNCs@2MB-NB) and other CuNCs previously reported by our group demonstrates that ligand engineering significantly influences the catalytic efficiency and product yield. Considering the significance of thioethers in the fields of pharmaceuticals, functional materials, and polymer science, this approach provides a green and scalable method for constructing C-S bonds, offering distinct advantages over conventional copper catalysts.