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The Influence of Noncovalent Interactions Involving Sulfur on the Solid State Properties of Thiazyl-Based Molecular Materials

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Title: The Influence of Noncovalent Interactions Involving Sulfur on the Solid State Properties of Thiazyl-Based Molecular Materials
Author: R. Alex, Mayo
Department: Department of Chemistry
Program: Chemistry
Advisor: Preuss, Kathryn E.
Abstract: The temperature dependent phase behaviour of the small, organic molecule 4-benzoyl-1,2,3-dithiazol-5-one (BzDTAO), with an emphasis on the effects of noncovalent sulfur-oxygen interactions on its polymorphic crystal forms, is elucidated. Additional thermodynamic arguments are made to rationalize the relationship between the two forms of BzDTAO which undergo a solid-to-solid chiral resolution with increasing temperature at Ttr = 70 °C. Thermodynamic arguments are supported by the comparison of the solid state characteristics of the high temperature form of BzDTAO with those of 4-benzoyl-1,2,3-dithiazol-5-thione (BzDTAT). Both crystallize in P212121 and they are isomorphous. Improvements on the original synthesis of BzDTAO are presented which were successful in increasing the yield of the desired product by 300% and essentially eliminating the by-products (which had included BzDTAT). Finally, due to the interest in using BzDTAO as a radical anionic ligand, electrochemical data of BzDTAO, and coordination of the neutral species to La(hfac)3, are presented. The crystal packing and supramolecular assembly of three derivatives of DTANQ (1,2,3-dithiazolyl-p-naphthoquinone) that differ only in the position/presence of methyl groups is discussed to identify structural similarities and the influence of moderate steric pressures. Discussion of the structural and magnetic properties of the metal complexes of these radical ligands is then presented. The magnetic properties of the Co(II) and Mn(II) complexes of 5,8-Me2DTANQ, and the Nd(III) and Dy(III) complexes of 6,7-Me2DTANQ are presented for the first time. The steric pressure induced by the methyl groups on the supramolecular assembly of the Mn(II) complexes of two dimethyl derivatives of DTANQ results in subtle differences in the geometries of intermolecular S•••S and S•••O contacts in the crystal structures. The S•••S and S•••O contacts are the intermolecular pathways of magnetic exchange coupling which is sensitive to contact geometry, yielding dramatically different magnetic properties for the Mn(II) complexes of 6,7-Me2DTANQ and 5,8-Me2DTANQ. Prior issues with ferromagnetic impurities and synthetic abnormalities are also resolved.
Date: 2017-04
Rights: Attribution-NonCommercial-ShareAlike 2.5 Canada
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Attribution-NonCommercial-ShareAlike 2.5 Canada Except where otherwise noted, this item's license is described as Attribution-NonCommercial-ShareAlike 2.5 Canada