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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Synthetic, structural and spectroscopic studies of peri-substituted systems and their complexes

Diamond, Louise M. January 2014 (has links)
The family of polycyclic aromatic hydrocarbons naphthalene, acenaphthene and acenaphthylene, containing rigid organic backbones, allow the study of non-bonded intramolecular interactions. Due to the rigid framework, heteroatoms that are substituted at the peri-positions (positions 1- and 8- of the naphthalene ring and positions 5- and 6- of the acenaphthene and acenaphthylene rings) are forced to occupy space that is closer than the sum of their van der Waals radii, resulting in severe steric strain and unique interactions. In spite of this, a vast amount of peri-substituted naphthalenes have been prepared, however acenaphthene and acenaphthylene compounds have received much less attention. Preparation of these sterically crowded systems is possible because of the backbones ability to relieve strain as a result of both attractive and repulsive interactions. Attractive interactions relax the backbone via formation of weak or strong bonds between the substituents. Alternatively, repulsive interactions can result in the deformation of the backbone away from its natural geometry by buckling the ring system and causing the peri-bonds to distort in-plane and out-of-plane. Peri-substituted systems can also ease strain by forming compounds with bridging atoms or through bidentate coordination to form metal complexes with, for example, metal bis(phosphine) or bis(thiolate) moieties. The competition between attractive and repulsive forces, the method by which peri-substituted compounds relieve steric strain, is investigated in this thesis using a variety of different peri-moieties and the aforementioned organic backbones. Chapter 2 initially focuses on the formation of a series of platinum bis(phosphine) complexes, constructed from corresponding peri-substituted naphthalenes, 1,8-naphthosultone and 1,8-naphthosultam, the chemistry of which is outlined in Chapter 1. A corresponding study of platinum bis(phosphine) complexes, constructed from analogous 5,6-dihydroacenaphtho[5,6-cd]-1,2-dithiole and 5,6-dihydroacenaphtho[5,6-cd]-1,2-diselenole bidentate ligands is provided in Chapter 6. The chemistry of peri-substituted naphthalenes is well documented and a number of reviews have been written on this subject. Chapter 3, meanwhile, reviews the chemistry of related acenaphthene and acenaphthylenes which have seen increasing use in the literature over the last few years. Chapter 4 investigates the relationship between repulsive and attractive interactions that occur between the peri-substituents in a series of bis-chalcogen, mixed chalcogen-chalcogen and mixed halogen-chalcogen acenaphthylenes. By comparison with their known naphthalene and acenaphthene counterparts, the effect the rigid aromatic ring system has on the molecular geometry is examined. Finally, Chapter 5 looks at a series of acenaphthene and acenaphthylene compounds containing ArTe peri-substituents and explores how repulsive and attractive interactions affect molecular conformation and Te•••Te spin-spin coupling constants.
2

Correlation of Structure and Magnetic Properties in Charge-Transfer Salt Molecular Magnets Composed of Decamethylmetallocene Electron Donors and Organic Electron Acceptors

Tyree, William Stuart 05 September 2005 (has links)
Di-n-propyl dicyanofumarate (DnPrDCF) and di-isopropyl dicyanofumarate (DiPrDCF) have been used as one-electron acceptors in the synthesis of charge-transfer salt magnets with decamethylmetallocenes, MCp*2 (M = Mn, Cr). Salts of each acceptor with each metallocene have been characterized and the structures of the chromium analogues have been solved. The two acceptors are structurally similar to dimethyl dicyanofumarate (DMeDCF) and diethyl dicyanofumarate (DEtDCF), which have been previously studied and found to form charge-transfer salt magnets with the aforementioned decamethylmetallocenes. A typical structural motif is present in these types of charge-transfer salts which allows for the comparison of magnetic properties based on the length or size of the alkyl group of the dialkyl dicyanofumarate. Some trends were established based on the magnetic properties of the homologous series including ordering temperature/bulkiness of the alkyl group and intrastack distances/theta values. Correlation of magnetic and structural properties may give some insight into "through-space" magnetic coupling, of which little is understood. / Master of Science

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