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Dissertation Information for Wade A. Neiwert

NAME:
- Wade A. Neiwert

DEGREE:
- Ph.D.

DISCIPLINE:
- Chemistry

SCHOOL:
- Emory University (USA) (2004)

ADVISORS:
- Craig L. Hill

COMMITTEE MEMBERS:
- Vincent P. Conticello
- Debra L. Mohler

MPACT Status: Fully Complete

Title: Polyoxometalates as nanoscale building blocks for the formation of fundamentally new materials

Abstract: This dissertation details research aimed at better understanding the chemistry and structures of anionic metal-oxygen clusters known as polyoxometalates (POMs) for their use as nanoscale building blocks in the formation of fundamentally new materials. Chapter one introduces the formation and characterization of POMs in general, with special attention paid to their structural elucidation by X-ray crystallography. The \"sandwich-type\" complexes are highlighted as a family of POMs, consisting of multiple POM fragments, a precursor to multi-POM-containing materials. Chapter two consists of four parts, each relating to Keggin heteropolyoxometalates: isomerization, dimerization, functionalization, and catalysis. Part one examines the relative stabilities of Keggin isomers with experimental confirmation of theoretical predictions. The second and third sections describe different methods to derivative Keggin anions, metal and ligand substitution, both techniques that could lead to POM-based synthons for the development of high nuclearity materials. The final part of chapter two illustrated the utility of a redox active metal salt of a Keggin anion to catalyze the oxidation of a chemical warfare simulant. Chapter three details an investigation into the rational design, preparation, and characterization of a fundamentally new POM-based material consisting of 1,3,5-trisubstituted benzene linkers bridged by bis(triesterified) hexavanadate clusters. Solid-state CP-MAS 13 C and 51 V NMR spectroscopy, X-ray crystallography, and atomic force microscopy all identify this material to be a nanoarray of 72 hexavanadate POMs with a diameter of approximately 20 nm. This porous gelatinous material possesses the ability to dramatically swell in various organic solvents as well as take up toxic agents. The heterogeneous catalytic activity of the solid material was investigated for the oxidation of a thiol to its corresponding less-toxic disulfide under ambient conditions (1 atm air and 25°C). Efforts to improve the catalytic activity of the gelatinous material were pursued through the replacement of the tetrabutylammonium cations (as prepared) with redox active metal cations, such as Ag I and Co II .

MPACT Scores for Wade A. Neiwert

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calculated 2008-03-22 22:51:40

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