Expansion of Superatom Synthesis, Substitution, and Fusion via Carbene Chemistry

This dissertation describes my efforts in the Nuckolls lab to expand synthetic methods of wet-chemistry superatom synthesis, superatom surface ligand and core modification, and assembly of superatoms into materials with useful, cumulative properties. This work builds off of previous work from the Nuckolls lab describing photolabile ligand substitution and use of this technique to covalently bind superatoms to form various materials such as polymers and weaved sheets. This work will focus on the Chevrel-type M₆E₈L₆ metal-chalcogenide cluster Co₆Se₈, modification of its outer stabilizing ligands, and fusion of its core with other Co₆Se₈ superatoms to form fused dimers. Chapter 1 consists of a review of background material that forms a foundational basis for this work. The field of superatoms and superatomic materials will first be covered to contextualize this work in the field at large. Then, the prior work on wet-chemistry synthesis of Co₆Se₈ superatoms with replaceable, photolabile carbonyl (CO) ligands will be discussed. Finally, previous dimensionally-controlled assembly of materials using these carbonylated superatoms will be covered. Chapter 2 consists of the discovery of a masking carbene ligand generated from trimethylsilyl diazomethane (TMSD) and its use to create a new, electronically-coupled superatom dimer species (Co₁₂Se1₆(PEt₃)₁₀) that shows evidence of quantum confinement akin to nanoparticles and nanoparticle assemblies. Chapter 3 consists of new ligand substitution and methods to synthetically functionalize the fused dimer introduced in Chapter 2. The reactive carbene-ligated cluster is used to add new functional groups that were previously inaccessible to these cobalt-selenide clusters. New multi-carbene clusters are demonstrated as well as the use of site-differentiated clusters to form functionalized fused dimers from bis-carbonyl clusters. Chapter 4 consists of an investigation of the carbene cluster and insights that may be used in the future to finally expand cluster fusion into a chain. A reversible bridging of the carbene ligand based on temperature and oxidation state is analyzed experimentally and computationally. This information is used to synthesize a series of new carbene clusters which are used to try and assemble electronically-coupled, fused Co₆Se₈ superatomic materials.