Modular Design and Synthetic Tuning of Ternary Molecular Nanoclusters

Abstract

The understanding of the nature of the metal/support interaction in catalytic systems is central todesigning better and more sustainable catalysts. The characterization of heterogeneous interfaces most relevant to catalysis is challenging and relies on techniques that provide limited atom-level information on processes at the surface. To better understand this complex chemistry, atomically precise nanoclusters can be used as a molecular analogue to study such surface chemistry with high precision. Here the chemistry of Co6Se8L6 (L = Ph2PR, Ph = phenyl) is studied as a means of reaching this goal by facilitating the formation of ternary nanoclusters with metal edge sites which sit upon the cluster core and are akin to single-atom catalysts on a surface. In the first chapter, the synthesis of a series of Cu/Co/Se molecular clusters is described, and their properties probed extensively through a bevy of techniques. Four highly isostructural clusters varying in overall charge from –3 to 0 are synthesized and found to exhibit robust charge separation between the copper edge sites and Co/Se core. The electronic interactions and redistribution of charge between the copper(I) edge sites and the electronically flexible core glean insights into the nature of the dopant/support interaction. In Chapter 2, synthetic explorations are undertaken to expand the scope of the supporting phosphine ligands on the cluster, elucidating the approaches and challenges associated with developing new ligand platforms of this type. By varying the identity of the R-group on the phosphine Ph2PR used in cluster syntheses, a library of homoleptic clusters Co6Se8L6 (L = Ph2PR) with various heteroatom functionalities is created. It is found that many functional groups will tolerate the conditions of cluster formation, allowing for the facile synthesis of several clusters with contrasting functionalities. The utility of these clusters is limited by their solubility profiles and challenges with metalation, but they serve as a promising example of synthetic versatility of Co6Se8 nanoclusters and hybrid phosphine ligands while providing important lessons for the future design of ternary nanocluster systems.