Carboxylate-Protected “Isostructural” Cu₂₀ Nanoclusters as a Model System: Carboxylate Effect on Controlling Catalysis

Abstract

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 Cu 20 nanoclusters, with the molecular formulae of Se@ Cu 20 (PhSe) 12 (PPh 3 ) 2 (C 6 H 5 COO) 6 (Cu 20 -1) and Se@Cu 20 (PhSe) 12 (PPh 3 ) 2 (CF 3 COO) 6 (Cu 20 -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 Cu 20 structures share an identical metal skeleton and similar ligand distributions with the only difference being in the carboxylate ligands on the surface: C 6 H 5 COO for Cu 20 -1 while CF 3 COO for Cu 20 -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.

An insight, at the atomic level, into the structure and catalytic properties of the isomers of the Cu22 cluster

“…The Se 2− in the clusters may be generated in situ by the decomposition of the PhSe − ligands, whose C–Se bonds are broken under the reducing atmosphere. 42,43 Interestingly, during the crystal culture process, Cu 22 -1 and Cu 22 -2 formed crystals with different crystal forms (Fig. S1†), enabling easy separation and subsequent analysis using single-crystal X-ray diffraction.…”

[Au9Ag6(CCR)10(DPPM)2Cl2](PPh4): a four-electron cluster with a bi-decahedral twisted metal core

“…1–6 With the advancement of sophisticated characterization techniques, numerous metal clusters with atomic-level resolved structures have been reported to date. 7–21 It has been observed that the metal core of many of these clusters shares the same polyhedral units, despite variations in peripheral ligands or metal–ligand motif structures. These polyhedral units encompass an M 13 centered icosahedron, 22–28 an M 6 octahedron, 29–35 an M 13 cuboctahedron 36 and an M 7 decahedron, 37–42 among others, where ‘M’ represents Au, Ag, Cu, or other metal atoms or their mixtures.…”