Total Structure and Optical Properties of a Phosphine/Thiolate-Protected Au24 Nanocluster

We report the synthesis and total structure determination of a Au-24 nanocluster protected by mixed ligands of phosphine and thiolate. Single crystal X-ray crystallography and elearospray ionization mass spectrometry (ESI-MS) unequivocally determined the cluster formula to be [Au-24(PPh3)(10)(SC2H4Ph)(5)X-2](+), where X = Cl and/or Br. The structure consists of two incomplete (i.e., one vertex missing) icosahedral Au-12 units joined by five thiolate linkages. This structure shows interesting differences from the previously reported vertex-sharing biicosahedral [Au-25(PPh3)(10)(SC2H4Ph)(5)X-2](2+) nanocluster protected by the same type and number of phosphine and thiolate ligands. The optical absorption spectrum of Au-24 nanocluster was theoretically reproduced and interpreted.