Computational Modeling Studies of the Structures and Properties of Organotin(IV) and Stannyl-Thioether Systems with Comparisons to X-ray Crystallography

Author

Michelle R. Stem Joseph, University of Texas at El PasoFollow

Date of Award

2009-01-01

Degree Name

Doctor of Philosophy

Department

Material Science and Engineering

Advisor(s)

M. Lawrence Ellzey

Abstract

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 thio_n 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 thio_n. 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-phenyl_xchloro_ystannane (thio_n, 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, thio_n: (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.

Language

en

Provenance

Received from ProQuest

Copyright Date

2009

File Size

105 pages

File Format

application/pdf

Rights Holder

Michelle R. Stem Joseph

Recommended Citation

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.
https://scholarworks.utep.edu/open_etd/363