X-ray crystal structure and doping mechanism of bimetallic nanocluster AuCu(m-MBT) (x = 1-3).

A novel AuCu(m-MBT) (x = 1-3, m-MBT = 3-methylbenzenethiolate) nanocluster has been prepared. According to the X-ray single crystal diffractometer, the structure of AuCu(m-MBT) is similar to that of Au(SPhBu). The AuCu(m-MBT) nanocluster contains a face-centered cubic (FCC) M core, which is protected by 4 MS (M = Au/Cu) staple motifs and 12 bridging SR ligands. The Cu dopants could possibly occupy 14 sites (six in the sub-surface and eight in the staple motifs). Spectral monitoring indicates that the number of Cu dopants sequentially increased on increasing the amount of Cu precursors (relative to a Au control). Meanwhile, DFT calculations imply that the maximum doping number of Cu is 3, and doping occurs preferentially at the staple sites and sub-surface sites (instead of the centre of the core). Because the atomic orbital of the peripheral locations hardly contributes to the frontier molecular orbitals, the UV-vis of the AuCu alloy is almost the same as that of its homometallic Au counterpart.