Date of Award
Doctor of Philosophy
Material Science and Engineering
M. Lawrence Ellzey
Controlling the toxic effects of organotin(IV) compounds involves engineering the structure of the molecules to optimize their properties. Molecular engineering, coupled with improved capabilities to generate reliable computational optimization models (COMs), will enable researchers to have greater success at harnessing the highly specific cytotoxicity of organotins. For example, as the thion ligand phenyl groups were replaced with Cl atoms, the S-Sn intramolecularity was strengthened, the bond distance decreased, and the stannyl tetrahedral structure was deformed from its triphenyl conformation. With each substitution, conformation deformations lowered the damaging bioactivity levels of thion. Bonding various ligands to organotin(IV) compounds to control structure and electron density, is a significant method of using steric or chemical effects to control the properties of these compounds.
Numerous computational optimization treatments (COTs) were applied to o-1-methylthio-benzyl-2-phenylxchloroystannane (thion, where x + y = 3). Exhaustive comparative analyses ascertained the accuracies of the computational optimized models (COMs) generated from each COT relative to experimental data, such as X-ray crystallography (XRC) and solid-state 119Sn NMR (NMR). Further analyses included: (a) three R2SnCl2 structures, (Me2SnCl2, MePhSnCl2, Ph2SnCl2) such that R = methyl or phenyl, and (b) MeSnCl3 and Me3SnCl, where Me = methyl, and (c) the bimolecular complex, Ph2POCH2Cl*Ph2SnCl2.
This research determined for organotin(IV) molecules, thion: (1) reliable COTs, (2) validation methods, (3) complexities of creating reliable models, (4) hyperconjugation extended to include unexpected thioether OT molecular features, (5) a substitution method to control intramolecularity and hypercoordination, and (6) pre-optimization COM treatments and pre-optimization conformation changes that may influence final conformations. As external validation of the methodology, research on molecules (a) and (b) (noted above) repeated published research by applying the same COTs to the same organotin(IV) molecules as did the original researchers. A comparison of the current COMs to the original computational values and experimental XRC determined that the current research generated COMs that were at least as reliable as published values. Additionally, it was determined that applying a reliable COT to the bimolecular complex, noted above as (c), enabled the quantification of the dipole moment changes and reduced energy of formation for the complex versus the separated molecules. Examining the combination of molecules listed above, the research methods applied, and the project goals, resulted in a substantially greater understanding of a type of molecule that is becoming increasingly important to materials development.
Received from ProQuest
Michelle R. Stem Joseph
Stem Joseph, Michelle R., "Computational Modeling Studies of the Structures and Properties of Organotin(IV) and Stannyl-Thioether Systems with Comparisons to X-ray Crystallography" (2009). Open Access Theses & Dissertations. 363.