UC Berkeley

Metal-oxo clusters are discrete molecular metal-oxides that are important for applications in catalysis, medicine, precursors for thin film deposition, flash memory devices, switchable transparent films, and high-resolution nanopatterning, to name a few. There are many factors that control the solution stability of metal-oxo clusters; the internal chemistry of the coordination complex as well as the solution conditions can influence the thermodynamic stability of the species. Currently, there is a lack of understanding surrounding how to best manipulate these factors in order to achieve a specific isomer, geometry, or size of metal-oxo cluster in solution. Therefore, the work presented in this dissertation contains an evaluation of the influence of heteroatoms, caps, ligands, pH, electrochemical potential, metal ion concentration, and counterions on stabilizing metal-oxo clusters. Quantum chemical computations were employed to model tin-based and zirconium-based clusters with varying factors, to determine their hydrolysis Gibbs free energies and electronic structures.

Sn-oxo clusters, specifically of Keggin geometry, have been shown to be an excellent photoresist candidate for next-generation extreme ultraviolet lithography manufacturing of advanced integrated circuits. I showed how changing the Sn-Keggin heteroatom, caps, and ligands impact the stability ordering of the five known Keggin isomers. This Sn-Keggin ion represents the only Keggin ion family thus far, that favors the lower-symmetry isomers. The computational results provide a means to isolate a single isomer to promote a pure and stable material for advanced lithography.

Zr-oxo clusters, specifically the Zr hexamer, has been shown to be a good node for a metal- organic framework (MOF) which is a 3D porous network that can act as a nanoscale carrying device. However the ”green” manufacturing of Zr-based MOFs requires that the Zr hexamer stabilize in an aqueous solution without organic ligation, which has yet to be successfully accomplished. I examined how the pH, electrochemical potential, metal ion concentration, and counterions all influence the aqueous solution stability of Zr(IV) ions clusters and solids. This study successfully elucidates the magnitude of and reason for the thermodynamic instability of the hypothetical Zr hexamer compared to the ubiquitous Zr tetramer.

The knowledge gained from these computational studies on Sn-oxo and Zr-oxo clusters can expedite experimental syntheses through implementation of the strategic tuning of chemistry and solution conditions.