Copper Nanoclusters for Catalytic Carbon–Carbon and Carbon–Nitrogen Bond Formations

Abstract

Newly synthesized blue-emitting few-atom copper nanoclusters (CuNCs) have been successfully utilized for catalyzing C(sp2)–C(sp2) and C(sp2)–N(sp3) bond formations. Various substituted biphenyls and 2° aromatic amines have been synthesized in good yield using this copper catalyst at facile reaction conditions in dimethyl sulfoxide. The amount of required nanocatalysts is as low as merely 2 mol % for carrying out these reactions. These types of copper nanoclusters are promising as potential and cheap catalysts for replacing conventional metal nanoparticles and heavy-metal-ion-based organic catalysts. The optimized structure of Cu6(GS)2 [GS = C10H16N3O6S] from computational studies revealed the perfect arrangements of Cu atoms in CuNCs and their interactions with stabilizing ligands. It is evident from the structure that some free Cu sites are available in the nanocluster species. These kinds of coordinatively unsaturated sites are highly active toward the catalytic reactions. Matrix-assisted laser desorption ionization–time-of-flight (MALDI–TOF) analysis also supports the computational hypothesis. Interestingly, matrix-assisted laser desorption ionization–time-of-flight mass spectrometry (MALDI–TOF MS) and computational studies revealed the formation of several reaction key intermediates in catalyzing C(sp2)–C(sp2) bond formation.