A Mossbauer study of some industrial applications of organotin compounds.

The technique of high dilution Mossbauer spectroscopy using the isotope Sn has been employed to study the nuclear environment of several organotin compounds having important industrial applications. For each compound studied structural and co-ordination information has been obtained relating to the mode of action of the organotin compound in its application. Chapters one and two of this thesis describe the theory of the Mossbauer Effect and the instrumentation and computational methods of recording and processing the Mossbauer data. Chapter three provides the main area of study in the thesis and is concerned with the role of organotin compounds in the stabilisation of PVC. Two types of organotin compound, dialkyltin thioglycollates and dialkyltin maleates, have been investigated for their effectiveness in preventing thermal and photochemical degradation of PVC. The resulting changes in the Mossbauer parameters following degradation have led to the identification of the organotin degradation products from which a degradation/stabilisation mechanism has been suggested. In chapter four the observation of a room temperature Mossbauer resonance is used to indicate that dimethylchlorotin acetate has an associated structure. A subsequent X-ray crystallographic determination supports the implications from the Mossbauer data and reveals dimethylchlorotin acetate to be 6 co-ordinate with a polymeric structure.In chapter five Mossbauer data have been obtained for a series of trialkyltin derivatives of L-cysteine and L-homocysteines The tri-alkyltin moiety has been reported to be a biologically active species and the Mossbauer data have revealed the sulphur atom in the cysteine and homocysteine groups to be a specific site for binding to the trialkyl tin moiety.Finally, in chapter six a simple Debye model of the solid has been applied to variable temperature Mossbauer data to suggest possible structures for two bis(triaikyltin)compounds containing two electronically different tin sites.