Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2009. / 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. / AFRIKAANSE OPSOMMING: Die primêre doel van die werk was om nuwe poreuse materiale te berei en deur die
toepassing van beginsels van kristalmanipulasie (E. crystal engineering) te ondersoek.
Beide organiese- en metaal-organiese sisteme is bestudeer en die werk kan in twee
kategorieë verdeel word:
1. Die kristalmanipulasie van Dianin se verbinding, ’n bekende organiese
gasheer.
2. Die ontwerp en sintese van ’n reeks verwante poreuse koördinasieverbindings
wat uit diskrete, binukleêre metallosiklieseverbindings bestaan.
Die eerste deel handel oor die sintetiese verandering van Dianin se verbinding om ’n
nuwe klatraatgasheer met ’n veranderde spleetgrootte te vorm. Alhoewel hierdie
studie nie daarin geslaag het om die gasheer in sy poreuse “gas(E. guest)-vrye” vorm
te isoleer nie, het die werk ’n nuwe chirale gasheerraamwerk aan die lig gebring. Die
chirale gasheerraamwerk rig gas(E. guest)molekules in eendimensionele kolomme op
’n polêre wyse en gevolglik vertoon die materiaal nie-linieêre optiese eienskappe.
Hierdie resultaat is ongekend in die lang geskiedenis van kristalmanipulasie van
Dianin se verbindings en sy analoë. Hierdie afdeling beskryf ook die desorpsiestudies
van die nuwe gasheer, en die tiol-afgeleide van Dianin se verbinding. Die
sistematiese karakterisering van hierdie fases na desorpsie het fundamentale vrae na
vore gebring oor desorpsieprosesse oor die algmeen.
Die tweede afdeling maak die grootste gedeelte van die werk uit. ’n Reeks verwante
isostrukturele ringvormige koördinasieverbindings is gesintetiseer en hul struktuureienskap
verhoudings is deur ’n verskeidenheid komplementêre tegnieke ondersoek.
Hierdie metallosiklieseverbindings kristalliseer almal in gesolveerde toestand vanaf
sintese en verskillende resultate word verkry wanneer die verbinding desorpsie
ondergaan. In alle gevalle vind gas(E. guest)desorpsie as enkel-kristal na enkel-kristal
omsettings plaas en drie nuwe ‘oënskynlik nie-poreuse’ poreuse materiale is bekom.
’n Enkelkristal diffraksiestudie onder verskeie gasdrukke is met asetileen en
koolstofdioksied uitgevoer vir een van die poreuse metallosiklieseverbindings. Dit het die geleentheid geskep om die mate waartoe die gasheer as gevolg van verhoogde
ewewigsdruk vervorm (en dus toename in gasheerbesetting), sistematies te bestudeer.
Die waargenome verskille in sorpsie-optrede vir asetileen en koolstofdioksied word
bespreek en verklaar. Gravimetriese gassorpsie isoterme is ook vir die drie poreuse
materiale verkry en die diffusie van groter molekules deur die gasheer is struktureel
ondersoek. Laastens word ’n moontlike gasoordragmeganisme vir hierdie tipe
poreuse (i.e. oënskynlik nie-poreuse) materiale gepostuleer. Hierdie bespreking word
deur termodinamiese en kinetiese studies aangevul, sowel as molekulêre-meganika en
statisties-meganiese studies.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/3970 |
| Date | 03 1900 |
| Creators | Jacobs, Tia |
| Contributors | Barbour, L. J., Bredenkamp, M. W., University of Stellenbosch. Faculty of Science. Dept. of Chemistry and Polymer Science. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | Unknown |
| Type | Thesis |
| Rights | University of Stellenbosch |
Page generated in 0.1004 seconds