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|Title:||Electron spin resonance and optical studies of organic radicals.|
|Authors:||Verma, G. S. P.|
|Presented at:||University of Leicester|
|Abstract:||This thesis is in two parts. In Part I the electron spin resonance spectra of some organic radicals are reported. Studies of radicals produced by irradiating aromatic compounds are presented and factors contributing to resolution of hyperfine features in such spectra are discussed. The interaction of molecular oxygen with these radicals to give peroxy radicals is shown to be diffusion controlled. The line-width of such radicals is found to depend on the structure of the parent molecule, the nature of the solvent and the temperature. It is suggested that the effect of temperature on the line-width of the peroxy radicals can be understood in terms of the rotation of an O - O bond which involves a spin-orbit-lattice interaction. The 14N splitting for the methylene blue cation is determined and this is employed in calculating the spin density on nitrogen and other molecular parameters. Finally, alkali metal reduction of some organic compounds is reported. It is shown that the neutral radical formed by reduction of 1-methyl-4-cyanopyridinium iodide in dimethoxyethane is stable. The reduction of phenyltrimethyl-phosphonium iodide is found to result in cleavage of C-P bonds with the subsequent formation of biphenyl. In Part II the ultra-violet and visible absorption spectra and the electron spin resonance spectra of the tetracyanoquinodimethane anion and the methyl viologen cation are reported. The association process responsible for the concentration-dependent colour change is shown to involve dimersation rather than ion-pairing. The manner in which water favours such association is discussed and the concepts are used to analyse the dependence of the absorption spectrum of methylene blue on the solvent, dye concentration and the concentration of various solutes. The species responsible for a band at still higher energy is attributed to contact ion-pairs. Finally, it is shown that solvent polarities, as measured by Z-values, are not significantly dependent on temperature.|
|Rights:||Copyright © the author. All rights reserved.|
|Appears in Collections:||Theses, Dept. of Chemistry|
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