Grant Johnson - Synthesis and Characterization of Gold Clusters Ligated with 1,3-Bis(dicyclohexylphosphino)propane

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  Publication Details (including relevant citation   information):


  Volume:   78

    Issue: 9

    Pages: 1033-1039

    Special Issue: SI


Published: SEP 2013


    In this multidisciplinary study the chemical reduction synthesis   of novel gold clusters in solution was combined with   high-resolution analytical mass spectrometry (MS) to gain insight   into the composition of the gold clusters and how their size,   ionic charge state, and ligand substitution influences their   gas-phase fragmentation pathways. Ultrasmall cationic gold   clusters ligated with 1,3-bis(dicyclohexylphosphino)propane   (dcpp) were synthesized for the first time and introduced into   the gas phase using electrospray ionization (ESI). Mass-selected   cluster ions were fragmented by employing collision-induced   dissociation (CID) and the product ions were analyzed using MS.   The solutions were found to contain the multiply charged cationic   gold clusters Au9L43+, Au13L53+, Au6L32+, Au8L32+, and Au10L42+   (L=dcpp). The gas-phase fragmentation pathways of these cluster   ions were examined systematically by employing CID combined with   MS. In addition, CID experiments were performed on related gold   clusters of the same size and ionic charge state but capped with   1,3-bis(diphenylphosphino)propane (dppp) ligands containing   phenyl functional groups at the two phosphine centers instead of   cyclohexane rings. It is shown that this relatively small change   in the molecular substitution of the two phosphine centers in   diphosphine ligands (C6H11 versus C6H5) exerts a pronounced   influence on the size of the species that are preferentially   formed in solution during reduction synthesis as well as the   gas-phase fragmentation channels of otherwise identical gold   cluster ions. The mass spectrometry results indicate that in   addition to the length of the alkyl chain between the two   phosphine centers, the substituents at the phosphine centers also   play a crucial role in determining the composition, size, and   stability of diphosphine-ligated gold clusters synthesized in   solution.

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