Browsing by Author "Du Plessis, Marike"

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    Guest uptake in porous metallocyclic host compounds
    (2020-01-20) Du Plessis, Marike; Barbour, Leonard J.
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    Structural characterisation of coordination compounds incorporating Imidazole-based ligands
    (Stellenbosch : Stellenbosch University, 2012-03) Du Plessis, Marike; Barbour, Leonard J.; Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science.
    ENGLISH ABSTRACT: Crystal engineering is a relatively new and fast growing branch of science. It emanates from the field of supramolecular chemistry and involves the self assembly of molecular and/or ionic “building blocks” to form a crystal – i.e. a “supermolecule”. Ultimately, a crystal with a predetermined structure and properties may result from a shrewd choice of building blocks. The main objective of this study was to investigate the architectures formed by flexible imidazole derived ligands when combined with a range of transition metal salts. The specific architecture that we aim to obtain with these building blocks is the “doughnut”-shaped metallocycle. Stacking of metallocycles to form columns in the crystal is a design strategy for creating porous materials and it has proven to be successful on several occasions. The following organic ligands were synthesised as part of this work: - 1,4-bis(benzimidazol-1-ylmethyl)benzene - 4,4'-bis(benzimidazol-1-ylmethyl)biphenyl - 1,3-bis(benzimidazol-1-ylmethyl)-2,4,6-trimethylbenzene - 1,4-bis(benzimidazol-1-ylmethyl)tetrafluorobenzene - 1,4-bis-(2-methylimidazol-1-ylmethyl)benzene - 1,4-bis-(2-methylimidazol-1-ylmethyl)tetrafluorobenzene The coordination compounds that were obtained during the course of this study were mainly analysed using single-crystal X-ray diffraction (SCD). A total of 40 novel crystal structures were obtained, of which 13 are metallocycles, 26 are either 1D or 2D coordination polymers and one is a salt. Of the 13 metallocycles, seven have the conventional doughnut shape. However, the property of porosity was limited by certain factors, which are discussed. Preliminary results show that two of these metallocycles are potential candidates for porosity studies. Many of the crystal structures also provide excellent examples of isostructurality, solvatomorphism and supramolecular isomerism – i.e. different crystal forms. The latter terms refer to similarities in the packing arrangements of molecules in the solid state or different packing arrangements of the same molecules or building blocks, both common phenomena in supramolecular chemistry. In the context of crystal engineering, we are still far from being able to predict and control the outcome of a crystallisation experiment to obtain a specific crystal form.