Cu66 nanoclusters from hierarchical square motifs: Synthesis, assembly, and catalysis

Abstract

The elucidation of hierarchical assembly structure of metal nanoclusters is of fundamental importance in the context of bottom-up fabrication and functionalization. While recent studies have provided valuable insights into the multiscale assembly patterns of gold or silver-based nanoclusters, the success in achieving similar results for copper analogues has been notably limited. Herein, by virtue of a slow-ligand-release strategy, a copper nanocluster denoted as [Cu₆₆Cl₈(PPh₃)₈(SC₂H₅)₃₂H₂₄](SbF₆)₂ was synthesized, resulting in the formation of fresh hierarchical assembly structures in one-pot. The arrangement of the metal atoms within the cluster reveals an orderly of 16 Cu₄ squares, representing a rare copper nanocluster comprising square motifs. Additionally, the ligands (phosphine, thiolate, and halide) coordinate to the surface of the cluster in a regiospecific manner, displaying square patterns as well. The self-assembly facilitated by the C-H···F interaction between the cluster moieties and SbF₆⁻ anions further induces the formation of three-dimensional cubes and eventually large nanocrystals. Density functional theoretical (DFT) calculations reveal that hydride atoms with low chemical shifts typically exhibit short Cu-H distances. The cluster demonstrates moderate stability and high catalytic activity in the chemoselective hydrogenation of cyclohexanone under mild conditions.