A reinvestigation of the ESR hyperfine splitting constants of 2,2'-Dipyridyl

Author.The electron spin resonance spectra of the lithium, sodium and potassium ion pairs of 2,2'-Dipyridyl have been investigated over a wide range of temperature and in various solvents. Results of the measurements are reported for the temperature as well as for the solvent dependence of the hyperfine splitting constants. In chapter one, several models are reviewed to explain the temperature and solvent dependence of the proton, nitrogen and alkali metal hyperfine splitting constants of alkali metal ion pairs. Three mechanisms for the occurrence of alkali metal hyperfine splitting constants are discussed. In chapter two, a description of the experimental procedure is presented. Tables and graphs for the experimental and simulated ESR spectra of the ions pairs and the variation of the hyperfine splitting constants with temperature are given. The least-square method is used to calculate the intercepts and slopes for the hyperfine splitting constants as a function of temperature and to estimate the precision of the results. In chapter three, a comparison is given between the results obtained in this thesis and those by other investigators. A discussion for the measured alkali metal hyperfine splittings is given in terms of the properties of the anion, the solvent and the cation. Two forms of ion pairs are assumed to coexist with an equilibrium constant that is a function of both temperature and solvent. The fact that the hyperfine splitting constants of 2,2'-dipyridyl-alkali metal ion pairs are slowly varying with temperature and solvents used suggests that the chemical equilibrium between the assumed two forms of ion pairs is almost completely shifted to the side of the tight ion pair