X-ray crystal structure and doping mechanism of bimetallic nanocluster Au36−xCux(m-MBT)24 (x = 1–3)

Abstract

A novel Au_36−xCu_x(m-MBT)₂₄ (x = 1–3, m-MBT = 3-methylbenzenethiolate) nanocluster has been prepared. According to the X-ray single crystal diffractometer, the structure of Au_36−xCu_x(m-MBT)₂₄ is similar to that of Au₃₆(SPh^tBu)₂₄. The Au_36−xCu_x(m-MBT)₂₄ nanocluster contains a face-centered cubic (FCC) M₂₈ core, which is protected by 4 M₂S₃ (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.