X‑ray Crystal Structure and Optical Properties of Au_{38–<i>x</i>}Cu_<i>x</i>(2,4-(CH₃)₂C₆H₃S)₂₄ (<i>x</i> = 0–6) Alloy Nanocluster

In this work, we report the synthesis and crystal structure of Au_{38–<i>x</i>}­Cu_<i>x</i>­(2,4-DMBT)₂₄ (<i>x</i> = 0–6, 2,4-DMBTH = 2,4-dimethyl­benzene­thiol) alloy nanocluster for the first time. A variety of characterizations including ESI-MS, TGA, and XPS reveal the composition as Au_{38–<i>x</i>}­Cu_<i>x</i>­(2,4-DMBT)₂₄ (<i>x</i> = 0–6). The single crystal structure has been determined by an X-ray single crystal diffractometer. From the anatomy of the structure, a bi-icosahedral Au₂₃ core is protected by six dimeric [−SR–M–SR–M–SR−] units (M = Cu/Au) and three monomeric [−SR–Au–SR−] units. It is interesting that all the Cu atoms are selectively doped in the motifs of the Au_{38–<i>x</i>}­Cu_<i>x</i>­(2,4-DMBT)₂₄ nanocluster. This phenomenon is distinct from the exclusive core doping of the Ag atoms in the previously reported Au_{38–<i>x</i>}­Ag_<i>x</i> alloy. Both the experimental results and DFT calculations of UV–vis spectra imply that the optical property of the Au_{38–<i>x</i>}­Cu_<i>x</i>­(2,4-DMBT)₂₄ nanocluster is consistent with that of the Au₃₈­(2,4-DMBT)₂₄ nanocluster, because the Cu dopants make little contribution to the frontier orbitals of the alloy NC