Au21S(SAdm)(15): Crystal Structure, Mass Spectrometry, Optical Spectroscopy, and First-Principles Theoretical Analysis

Here we report X-ray crystal structure, spectroscopic and theoretical characterization of Au21S(SAdm)(18) (SAdm = adamantanethiol). Single-crystal X-ray diffraction shows that the Au21S(SAdm)(15) nanomolecule exhibits a Au-12 cuboctahedral core missing one vertex surrounded by a single mu(3) sulfur atom (sulfide), five bridging thiols, two additional Au atoms, one monomeric Au(SR)(2), and two trimeric Au-3(SR)(4) staples, with the two trimeric staples being linked through a Au-2(SR) unit with a thiolate ligand in mu(4) coordination. Compositional, electronic, optical, and structural features of this compound are clarified via nanoelectrospray ionization mass spectrometry (nESI-MS), matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS), low-temperature UV- vis spectroscopy, and first-principles analysis.