Browsing by Author "Jacobs, Tia"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Self-assembly of new porous materials
    (Stellenbosch : University of Stellenbosch, 2009-03) Jacobs, Tia; Barbour, Leonard J.; Bredenkamp, M. W.; University of Stellenbosch. Faculty of Science. Dept. of Chemistry and Polymer Science.
    ENGLISH ABSTRACT: The primary objective of the work was to prepare and investigate new porous materials using the principles of crystal engineering. Both organic and metal-organic systems were studied and the work can best be divided into two separate sections: 1. The crystal engineering of Dianin’s Compound, a well-known organic host. 2. The design and synthesis of a series of related porous coordination compounds consisting of discrete, dinuclear metallocycles. The first section discusses the synthetic modification of Dianin’s compound in order to engineer a new clathrate host with an altered aperture size. Although this study ultimately failed to isolate the host material in its porous guest-free form, the work led to the discovery of a chiral host framework that aligns guest molecules in a polar fashion, and consequently displays non-linear optical properties. These findings are unprecedented in the long history of crystal engineering of Dianin’s compound and its analogues. This section also describes desorption studies of the new inclusion compound, as well as the known thiol analogue of Dianin’s compound. Systematic characterisation of these desorbed phases has raised interesting fundamental questions about desolvation processes in general. The second section constitutes the major portion of the work. A series of related isostructural coordination metallocycles were synthesised and their structure-property relationships were investigated using a variety of complementary techniques. These metallocyclic compounds all crystallise as solvates in their as-synthesised forms, and different results are obtained upon desolvation of the materials. In each case, desolvation occurs as a single-crystal to single-crystal transformation and three new “seemingly nonporous” porous materials were obtained. A single-crystal diffraction study under various pressures of acetylene and carbon dioxide was conducted for one of the porous metallocycles. This enabled the systematic study of the host deformation with increasing equilibrium pressure (i.e. with increasing guest occupancy). The observed differences in the sorption behaviour for acetylene and carbon dioxide are discussed and rationalised. Gravimetric gas sorption isotherms were also recorded for the three different porous materials and the diffusion of bulkier molecules through the host was also investigated structurally. Finally, a possible gas transport mechanism is postulated for this type of porous material (i.e. seemingly nonporous), and this is supported by thermodynamic and kinetic studies, as well as molecular mechanics and statistical mechanics simulations.