Very small noble metal nanoparticles, known as monolayer protected clusters (MPCs), are in fact molecules with definite molecular formulae and structures, which have been determined by mass spectrometry and single-crystal x-ray diffraction, respectively. We have found that current models are far too simple to account for the chemical properties of these complex and structurally diverse materials. For example, synthesis of MPCs remains empirical or even somewhat random since a fundamental understanding of the mechanisms of cluster formation is still lacking, despite sustained efforts and the existence of competing synthetic models. Here we present a new model for understanding synthetic reactions that provides new tools for controlling the outcomes of synthetic reactions. Further, many examples of single- or few-heteroatom substitutions exist in molecular nanoparticles, but true alloys with compositions varying over a wide range of substitutions are rare. Here we present studies of M4AuxAg44–x(p-MBA)30 alloy nanoparticles as a model system, where M is a countercation and p-MBA is a p-mercaptobenzoic acid ligand, and where 0 ≤ x ≤ 12 represents the full range of possible compositions, all of which are stable in solution. Experiment and density functional theory together provide insights into the variation in the chemistry, electronic structure, and reactivity of M4AuxAg(44–x)(p-MBA)30 nanoparticle alloys as a function of composition.

Synthetic and postsynthetic chemistry of silver monolayer-protected clusters

2019 Fall National Meeting

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