2018 Theses Doctoral

Architecting Superatomic Metal Chalcogenide Clusters for Materials Design

Pinkard, Andrew

This dissertation describes and summarizes the research I performed as a member of the Roy group. The Roy group uses molecular clusters as nanoscale building blocks for new materials, in addition to several other topics of related interest including the design and synthesis of molecular wires to study the movement of electrons (conductance) at the molecular level.

Chapter 1 introduces molecular clusters as superatomic nanoscale building blocks and describes how superatomic crystals, analogous to ionic crystals, can be controllably assembled from these building blocks. Next, Chapter 2 examines how the atomic properties of ionization energy and electron affinity can be extended to superatoms by investigating the Co₆Se₈(PEt₃)₆(CO)₆₋ₓ family of clusters. As the degree of cabonylation increases, the superatom moves from alkali-like to halogen-like behavior; i.e., it becomes harder to ionize and easier to add an electron to the superatom as PEt₃ ligands are replaced with CO ligands while still maintaining the overall electron count of the cluster. Chapter 3 then moves to discuss how the related building blocks, Co₆Te₈(PEt₃)₆ and its derivatives, can be assembled into superatomic crystals using the electron-accepting Fe₈O4pz₁₂C₁₄ cluster. Chapter 4 then uses this same Fe₈O4pz₁₂C₁₄ cluster as a probe for singlet fission triplet dynamics by functionalizing this cluster with a singlet fission chromophore. Chapter 5 continues the idea of ligand design by exploring a series of oligophenylenediamine molecules capable of binding to gold (and presumably other metals), and it is observed that the conductance dramatically increases by applying a high positive bias to the molecules when they are bound to the tips of two gold electrodes. This dissertation concludes with Chapter 6, which discusses how new cobalt chalcogenide materials prepared from superatomic precursors can be deployed as new battery electrode materials for lithium and sodium ion batteries. Each of these chapters help illustrate how synthetic chemistry can be used to both elucidate interesting chemical phenomena and to design new materials with tailored properties.