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Title: Excited state processes of complexes of W(V) and U(VI) by laser photolysis and ESR spectroscopy
Author: Shand, Mark Alexander
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 1987
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This thesis deals with the reactions of two high-valent metal complexes. [UO2]2+ and [W(CN)8]3- in their excited states in which their one-electron reduction potentials are increased greatly, i.e. sufficiently for them to remove an electron from water. The studies with uranyl ion cover the following, (i) the ground state interaction with some simple amino acids, (ii) the excited-state interaction with a variety of amino acids including some containing sulphur, which gave results of particular interest and, in following up the latter, (iii) the excited state interaction with some simple organosulphur compounds. These three inter-related topics form Chapters 8, 9 and 10 of this thesis. In more detail, in Chapter 8 we characterise optically, three new complexes of 1:4 stoichiometry between [UO2]2+ and glycine and α- and β-alanine in acidic aqueous solution. The x-ray crystal structure of the glycine complex confirms it as tetrakis (glycine) dioxouranium (VI) nitrate. Chapter 9 covers the kinetics of luminescence quenching of *[U02]2+ by amino acids (indicating the level of reactivity) and the quant yields of [U(IV)] which indicate the degree of charge separation from the initial radical-pair configuration, while cryogenic ESR data reveal the nature of the primary ligand-derived radical. Interestingly we find that while much the greatest kinetic reactivity towards *[UO2]2+ is shown by the sulphur-containing amino acids, these show very low yields for [U(IV)] production. This pattern is repeated in our study of the photo-oxidation of dialkyl sulphides by excited uranyl ion, in which we believe to have demonstrated that a. recent report of high quantum yields in this system and published in Inorganic Chemistry is erroneous. Our brief study of the aqueous [W(CN)8]3- system confirms the quantum yields for [W(CN)8]4- of Samotus et al., as opposed to the earlier data of Balzani and Carassiti and characterises, using ESR, IR and UV-vis spectroscopy, new W(V)-cyanide 4 complexes obtained during irradiation into the C-T bands of [W(CN)8]4- and [W(CN)8]3- in aqueous solution. Three publications have resulted hitherto from the above work in the following journals: Chapter 8: J. Chem. Soc., Dalton Trans., 1985, 517. Chapter 9:, Inorgý Chim. Acta, 1986, 114, 215. Chapter 10: Inorg. Chem., 1986, 21, 3840. The results from the final chapter together with data from the photoreduction of [W(CN)8]3- 81 with many organic systems obtained by Dr. D. Rehorek during his visit to the Department, have been compiled and submitted for publication to the Journal of the Chemistry Society, Dalton Transactions (paper 6/2444).
Supervisor: Not available Sponsor: University of Warwick
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QD Chemistry