Electron Paramagnetic Resonance Studies of Some Systems of Chemical Interest

McConnell, Archibald A (1970) Electron Paramagnetic Resonance Studies of Some Systems of Chemical Interest. PhD thesis, University of Glasgow.

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This thesis is subdivided into four parts, which are summarised seperatly below. Part I: An elementary account of the principles of electron paramagnetic resonance spectroscopy and a brief description of the spectrometer system are contained in this, the introductory section, of this thesis. Part II: This section describes a study of nitroxide radicals obtained from caryophyllene nitrosite. Eight different nitroxide radicals have been derived from caryophyllene nitrosite. Two are obtained allowing caryophyllene nitrosite in chloroform solution to react with iodine or with bromine; two by irradiating lid caryophyllene nitrosite with red light, or by irradiating solutions of caryophyllene nitrosite in toluene or in benzene with red light; two are obtained by irradiating solutions of caryophyllene nitrosite in ethanol with red light; one by irradiating solid caryophyllene nitrosite with ultraviolet radiation, and one by dissolving the last radical in chloroform. Three of these radicals have been isolated as pure, stable solids. Electron paramagnetic resonance spectra of the eight radicals are described and spin Hamiltonian parameters, extracted from spectra of "glasses" formed at 77 K by dispersing them in chloroform:toluene (3:2) solution or from room-temperature spectra, are given. Structures for the nitroxide radicals, and some information about the mechanisms of the red and ultraviolet photolyses reactions, are deduced from the electron paramagnetic resonance data. Part III: This section deals with a study of the small free radical, di-tertiary-butylnitroxide, within the cavities of Polycrystalline and single crystal electron paramagnetic resonance spectra of di-tertiary-butylunitroxide in Dianin's compound have been examinedl over the temperature range 77°K≤ T ≤ 430°K. The orientations of the radicals in the crystal have been determined, and the motions of the radicals and the magnitudes of the energy barriers hindering these motions in the clathrate, have been characterised. Changes in van der Waals interactions as the temperature changes appear to affect hyperfine tensor components, but it has not been possible to obtain quantitative information about changes in the electron distribution responsible for these effects. Other radicals do not appear to be formed as the temperature is raised. At higher temperatures the lattice sublimes. Part IV In this section the effects of axial interactions on electron paramagnetic resonance spectra of copper(II) chelates re described . X-band e. p. r, spectra in chloroform:toluene (60:40) glasses at 77K show that chloroform forms weak complexes with some planar compounds of copper(II). Spin Hamiltonian parameters for some "isolated" cupric chelates and for some corresponding chloroform-chelate complexes are reported, and these Parameters are equted to the atomic orbital coefficients in some of the molecular orbitals involved in bonding in both types of compound. The relative ordering of the energies of the B2g and A1g levels in planar copper (II) compounds may change if the ligand is changed. Effects of axial perturbations which arise from two axial dipoles acting on planar cupric complexes are considered , and first order perturbation theory is used to obtain relationships which connect the spin Hamiltonian parameters for the "isolated" complexes with those for the perturbed complexes: experimental observations are in accord with the theoretical treatment. Relaxation arising from rotation about the long axis of these cupric complexes controls the line widths in their e. p. r. spectra recorded at 295° K: the effect of chloroform complexing on paramagnetic relaxation phenomena these complexes is noted. E. p. r. methods may be used to discriminate between different isomers of polyketone complexes of copper(ll).

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Analytical chemistry, Physical chemistry
Date of Award: 1970
Depositing User: Enlighten Team
Unique ID: glathesis:1970-78549
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 28 Feb 2020 12:09
Last Modified: 28 Feb 2020 12:09
URI: http://theses.gla.ac.uk/id/eprint/78549

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