Several
recent studies have demonstrated the great promise of ligand-protected
atomically precise copper nanoclusters in driving various chemical
transformation processes. The insights into key factors in controlling
the catalytic performance of copper clusters at the molecular level
are highly desirable but difficult to gain. Herein, we report the
synthesis and comprehensive characterization of two novel Cu20 nanoclusters, with the molecular formulae of Se@Cu20(PhSe)12(PPh3)2(C6H5COO)6 (Cu20-1) and Se@Cu20(PhSe)12(PPh3)2(CF3COO)6 (Cu20-2), which are proved to be great candidates in clarifying
the structure and property relationship in catalysis. As revealed
by single-crystal X-ray analysis, the two Cu20 structures
share an identical metal skeleton and similar ligand distributions
with the only difference being in the carboxylate ligands on the surface:
C6H5COO for Cu20-1 while CF3COO for Cu20-2. Surprisingly, such small distinctions
in the structure cause a 16-fold catalytic activity leap in the catalytic
reduction of 4-nitrophenol to 4-aminophenol. The electronic structures
of the resulting clusters are distinct, which accounts for their distinct
catalytic performances. This work not only provides a model system
to highlight the importance of the carboxylate structures on controlling
the catalysis of copper clusters but, more importantly, is also expected
to simulate research attention on carboxylate engineering to modulate
physicochemical properties of carboxylate-functionalized copper metal
nanoclusters beyond catalysis.