Thesis (Ph. D.)--University of Hong Kong, 1994. / Includes bibliographical references (leaves 293-306).

<p> The preparation of compounds containing polyatomic cations of sulphur, selenium and tellurium has been investigated by using oxidising agents such as AsF5, SbF5, S2O6F2 and SO3. New compounds, containing polyatomic cations Se8 2+, Se4 2+, Te3n n+, Te4 2+ Ten n+, S16 2+, S8 2+ and S4 2+, and anions of very strong acids such as Sb2F11- and AsF6- were isolated and characterised by a combination of the stoichiometry of the preparation reactions, UV-visible spectrophotometry, Infrared and Raman spectroscopy and magnetic susceptibility measurements.</p> <p> Solutions of sulphur in various concentrations of oleum were investigated in detail by UV-visible spectrophotometry and e.s.r. spectroscopy. Evidence is presented for the formation of the sulphur cations S16 2+, S8 2+ and S4 2+ in these media, and for the presence of low concentrations of the radical cations S8+ and S4+.</p> / Thesis / Doctor of Philosophy (PhD)

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--Michigan State University. Dept. of Chemistry, 2007. / Title from PDF t.p. (viewed on Apr. 16, 2009) Includes bibliographical references. Also issued in print.

<p>The goal of this research project is to synthesize, characterize, and examine the properties of a material that undergoes a decrease in refractive index upon exposure to light. It is anticipated that such photoresponses could elicit previously unknown nonlinear phenomena including self-trapped black beams. An appropriate material for these investigations would be a polymer cross-linked by photocleavable groups causing a Δ<em>n</em> < 0. Organo-ditellurides, molecules that contain a Te-Te bond, would be appropriate for the crosslinks as their σ*_Te-Te ← n_Te transition usually absorbs light between 400 and 500 nm, and can lead to photodissociation of the chalcogen-chalcogen bond.</p> <p>Initial attempts to directly functionalize a polymer (polystyrene) resulted in intractable solids. A more promising approach relies on the preparation of cross-linking agents followed by co-polymerization. Despite literature claims, to date, there is no structurally authenticated photoresponsive molecule that simultaneously contains vinyl (CH=CH) and telluride (-Te-) functional groups. The work in this thesis has yielded what would be the first example, in addition to a crystal structure obtained by X-ray diffraction, the compound has been characterized by multinuclear NMR (¹H, ¹³C, ¹²⁵Te) and vibrational spectroscopy with the support of DFT calculations.</p> / Master of Science (MSc)