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High resolution MMR of organotin compounds and ESR study of X-ray irradiated organic single crystals

University of British Columbia

In part I of this thesis, orgimotin compounds were investigated, using high resolution proton and tin 119 nuclear magnetic resonance technique. The tin 119 chemical shift of about forty organotin compounds were measured by absorption mode for the first time. The tin chemical shift and tin 119-proton coupling constant in some methyltinhalides wore found, to be solvent and concentration dependent in electron donor solvents. This dependence was attributed to the formation of higher than four coordinated complexes with solvent molecules. Equilibrium constants of the complex formation, the tin chemical shifts, and the tin-proton coupling constants of the complexes, wore obtained in a few solvents. The second-order paramagnetic chemical shifts of methyltinhaiides, methyltin cations, and five coordinated compounds were calculated and compared with the observed tin chemical shifts. Good qualitative agreements between calculated values and observed values confirmed that the second-order paramagnetic term in tin chemical shifts is dominant in the chemical shift changes in those compounds. In part II, X-ray irradiated single crystals of malonamide and cyanoacetamide were studied by electron spin resonance technique. In both cases at least two types of radicals were found. One was the usual π -electron type radical the proton coupling tensor of which had been studied, quite extensively in the past. In this study, besides the proton coupling and in the case of cyanoaecetamide, the coupling tensor for the cyano-nitrogen was also measured and discussed. The second radical found both in X-ray irradiated malonamide and cyanoacetamide was a Ϭ-electron type radical which was produced by the loss of one of the amide protons (-COṄH). The proton hyperfine coupling constant was found to be almost isotropic and very large, more than 80 gauss in both compounds. The nitrogen coupling tensor for the amide- nitrogen was found to be axially symmetric with the unique principal value equal to 36.6 gauss in the one (malonamide) and 25.4 gauss in the other (cyanoacetamide). The principal value in perpendicular direction was found to be very small but could not be determined conclusively. A semi-empirical molecular orbital calculation was performed on the fragment of Ϭ-electron radical together with perturbation through configuration interaction; the large isotropic proton coupling constants were explained theoretically.

Text

2011-07-05

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http://hdl.handle.net/2429/35880

Chemistry

University of British Columbia

Graduate