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Novel P-tert-butylcalix[4]arene derivatives (L-3-10) containing mixed donor atoms (O, N, S) have been synthesised in a two stage reaction, the first part of which involves the preparation of L-2 using 18-crown-6 as a phase transfer catalyst and K2CO3 as a weak base. These conditions lead to the removal of two distal protons from the lower rim, allowing the 1,3-bis-niethylethylthio ether derivative (L-2) to be synthesised in a reduced reaction time with greater yield and purity than previously published. The final two protons were removed using NaH, sites to which a variety of amine, amide and thiophene moieties were introduced. This thesis reports investigations on these new compounds detailed as follows, i) 1H and 13C NMR characterisation of these derivatives. In two cases, X-ray crystallograpliic structures have been determined, showing distortions from the symmetrical cone conformation of p-tert-butylcalix[4]arene caused by steric interactions of the lower rim substituents. ii) Solubility and derived Gibbs energies of these ligands in various solvents at 298.15 K. Using acetonitrile and methanol as reference solvents, Gibbs energy of transfer are calculated. iii)The acid-base properties of ligands L-3,4,6-8 were investigated by potentiometry. Equilibrium constants for the dissociation processes reveal relative proton affinities in methanol at 298.15 K. Data of individual species present as a function of pH are presented in diagrams. iv) Conductimetric measurements. These data are used to derive the stoichiometry of metal cation complexes of L-4 in methanol. v) 1H NMR studies of the complexation of L-4 with metal cations in CD3OD at 298 K. These reveal conformational change in the macrocycle cyclic structure as the substituents' arrangements are altered to accommodate the guests cations. vi) Determination of Gibbs energy of complexation for ligand L-4 and Ag+, Pb+2, Cd2+ and Cu2+ metal cations in methanol at 298.15 K, using a competitive potentiometric method. Cation selectivities are discussed.

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Cucurbit[8]uril (CB[8]) has attracted great interest in the cucurbit[n]uril (CB[\textit{n}]) family on account of its capability to simultaneously accommodate two guests inside its cavity, to form strong yet dynamic ternary complexes. Owing to the photo-induced \textit{trans} to \textit{cis} isomerisation property, azobenzene (Azo) derivatives have been widely employed in several host-guest systems, leading to various light-responsive materials. This thesis focuses on CB[8]-based ternary complexes, especially those involving Azo derivatives. These systems can be exploited as a platform to hierarchically fabricate supramolecular constructs, including crystalline structures and composite materials. Specifically, novel morphology-controlled (1D needle-like, 2D sheet-like) crystals have been prepared by adjusting the assembly of Azo-CB[8] complexes, which can be further developed to oriented macroscopic free-standing crystalline pillars grown from a glass surface. Next, a composite micelle-nanoparticle complex has been prepared utilising Azo-CB[8] assemblies, which demonstrates $\sim$90$\%$ efficiency in surfactant recycling. Finally, an organic CB[8]-mediated hydrogel reinforced by inorganic nanowires has been prepared. This hybrid structure shows increased stiffness due to various supramolecular interactions. Chapter 1 gives a brief introduction to CB[\textit{n}] host-guest chemistry with emphasis on CB[\textit{n}]-based crystalline structures and CB[8] ternary complexes. Recent progress of Azo-based host-guest chemistry is then reviewed. In addition, shape-controlled crystals formed \textit{via} supramolecular interactions are discussed at the end of the chapter. Chapter 2 focuses on the crystalline structure of the 1:2 homoternary complex formed between CB[8] and a methyl orange (MO) guest, which is the fastest CB[8]-based crystallisation to date. As a commonly used pH indicator, MO possesses an azobenzene moiety with both an electronically positive amino group and an anionic sulfonate group. At low pH values, formation of the homoternary complex 2MO@CB[8] occurs, serving as a 'tectonic' building block, which rapidly stacks into a herringbone arrangement. The intermolecular and intercomplex interactions inside 2MO@CB[8] crystals are discussed, whereby the CB[8] macrocycle orients the electrostatic charges on MO guests resulting in the repulsive interactions being shielded; this in turn leads to fast electrostatically-driven crystal growth. The 2MO@CB[8] system provides a promising approach for designing ultrarapid crystallisation systems derived from CB[\textit{n}] host-guest complexes. Moreover, the host-guest chemistry between CB[8] and a variety of Azo derivatives with different functional groups is discussed, demonstrating the influence of guest structures on their crystalline behaviours. Chapter 3 further explores the mechanism of 2MO@CB[8] crystallisation through a series of experimental and computational methods. Control over the crystal shape, length and growth rate can be achieved in a facile manner whilst maintaining the same (internal) unit cell. Therefore, the properties of the macro-scale crystals can be tuned at the molecular level through adjusting the assembly of 2MO@CB[8] building blocks. For example, tuning the ionic strength of the solution enables a second growth dimension, yielding 2D crystals with sheet-like and more complex morphologies. Furthermore, our understanding of oriented electrostatics provided by the homoternary tecton can then be exploited to prepare oriented macroscopic free-standing crystalline pillars grown from a glass surface at room temperature. Next, CB[8] ternary complexes have been employed as 'bridges' to link (organic) soft and (inorganic) hard materials together, resulting in composite materials. In chapter 4, a micelle-nanoparticle complex (\textbf{MNC}) structure has been assembled \textit{via} host-guest interactions between Azo-functionalised, cargo-loaded micelles and magnetic SiO$_2$ nanoparticles (NPs) functionalised with CB[8] catenanes. Owing to the photo-responsive and magnetic properties, \textbf{MNCs} can be exploited to recycle detergents (micelles) from aqueous solution. This is followed by the controlled release of the encapsulated hydrophobic molecules inside the micelle cavity. In this process, both the micelles and NPs can be recycled efficiently. The novel \textbf{MNC} structure provides a promising approach to recycle versatile drug carriers through host-guest chemistry. Chapter 5 introduces a CB[8]-based hydrogel in which inorganic nanowires (NWs) are employed to enhance the gel stiffness. The supramolecular hydrogel is comprised of methylviologen-functionalised poly(vinyl alcohol) (PVA-MV), hydroxyethyl cellulose with naphthyl moieties (HEC-Np) and CB[8]. The gel structure is effectively enhanced by the framework supporting effects of CePO$_4$ NWs and additional hydrogen bonding interactions between NWs and PVA-MV/HEC-Np polymers. The high aspect ratio NWs serve as a 'skeleton' for the network, providing extra physical crosslinks. This results in a single continuous phase hybrid supramolecular network with improved strength, showcasing a general approach to reinforce soft materials. Finally, this thesis closes with a summary and perspective chapter, concluding the present work and highlighting an insight towards future work. Utilising CB[8] ternary complexes, various supramolecular constructs can be prepared through hierarchical self-assemblies, leading to a wide variety of composite systems and functional materials in the future.

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Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The aim of the work presented in this thesis was to design ionic organic framework materials based on carboxylate salts with the intention of engineering interesting properties, such as porosity, into these framework materials. The first section focuses on the characterisation and porosity studies of an ionic framework material, 3,4-lutidinium pamoate hemihydrate, with THF-filled channels in the solid state. It was shown that this framework is able to exchange the THF in the channels for a wide variety of compounds, with many of these exchanges occurring in a single-crystal to single-crystal fashion. Competition experiments conducted with the framework, both by immersing crystals of the framework in solvent mixtures, as well as by exposing crystals of the framework to mixtures of solvent vapours, indicated that it is able to selectively exchange for one guest over another. The kinetics of exchange of this framework were studied, and it was possible to identify a kinetic model describing this process. A second novel framework-type material, 4-phenylpyridinium pamoate, was identified during the course of this study, as well as five isostructural frameworks containing different guest molecules. In this case the framework consists of discrete units that close-pack in such a way that guest molecules are included in constricted cavities in the solid state. Although this framework-type material is not porous, it is thermally quite stable and also highly selective. It is able to selectively encapsulate 1,4-dioxane when crystallised from various solvent combinations including 1,4-dioxane. In addition, eight novel structures with pamoic acid in combination with various pyridyl derivatives were obtained. A third novel framework material was obtained with N,N'-bis(glycinyl)pyromellitic diimide in which, due to the extended hydrogen-bonded network formed between the constituents of the framework, DMF molecules are aligned in channels. It was found that this framework material can also be formed by mechanochemical synthesis, and investigation of the thermal behaviour of this framework showed that it has the potential to be porous, since the framework appears to remain intact after desolvation. Furthermore, six novel structures with N,N'- bis(glycinyl)pyromellitic diimide in combination with various N-heterocycles were obtained. All structures obtained in this study were also further analysed to determine whether there are particular structural features that are required for framework formation. Insights gained from these investigations, in terms of degree of ionisation of the anion, packing arrangements and hydrogen bonding patterns as well as the molecular shape of the components are discussed. / AFRIKAANSE OPSOMMING: Die doel van die werk wat in hierdie tesis voorgelê word is om ioniese organiese raamwerkmateriale gebaseer op karboksilaatione te ontwerp, met die voorneme om interessante eienskappe in hierdie materiale te bewerkstellig. Die eerste afdeling fokus op die karakterisering en porositeit van ‘n ioniese organiese raamwerkmateriaal, 3,4-lutidiniumpamoaathemihidraat, wat kanale gevul met tetrahidrofuraan (THF) besit. Dit is aangetoon dat dit moontlik is vir hierdie raamwerkmateriaal om die THF in die kanale te verruil vir ‘n wye verskeidenheid stowwe, waarvan baie van hierdie uitruilings geskied as ‘n enkelkristal tot enkelkristal transformasie. Kompetisie-eksperimente is met hierdie raamwerkmateriaal uitgevoer deur die kristalle in mengsels van oplosmiddels te onderdompel, sowel as deur die kristalle aan mengsels van die oplosmiddeldampe bloot te stel. Die resultate het aangedui dat dit moontlik is vir hierdie raamwerkmateriaal om een gasstof selektief teenoor ‘n ander te verruil vir die THF in die kanale. Die kinetika van die uitruilingsproses van hierdie materiaal is ook bestudeer en dit was moontlik om ‘n kinetiese model te identifiseer wat die uitruilingsproses beskryf. ‘n Tweede nuwe raamwerk-tipe materiaal, 4-fenielpiridiniumpamoaat, is deur die loop van hierdie studie geïdentifiseer, sowel as vyf isostrukturele raamwerkmateriale waarvan net die gasstof verskil. In hierdie geval bestaan die raamwerk uit diskrete eenhede wat op so ‘n wyse saampak dat die gasstowwe in vernoude porieë ingesluit word. Alhoewel hierdie raamwerk-tipe materiaal nie poreus is nie, is dit termies stabiel en ook hoogs selektief. Die raamwerkmateriaal kan selektief 1,4-dioksaan enkapsuleer wanneer dit gekristalliseer word vanuit ‘n verskeidenheid oplosmiddel kombinasies met 1,4-dioksaan. Verder is agt nuwe strukture verkry met die pamoaat ioon in kombinasie met ‘n verskeidenheid piridien-derivate. ‘n Derde nuwe raamwerkmateriaal is verkry met N,N'-bis(glisiniel)piromellitiese diïmied waarin, danksy die uitgebreide waterstofgebinde netwerk tussen die komponente van die raamwerk, die DMF molekules in kanale aangetref word. Hierdie raamwerkmateriaal kan deur meganochemiese sintese berei word en verdere ondersoek na die termiese gedrag van hierdie raamwerkmateriaal dui aan dat dit die potensiaal het om porositeit te toon, aangesien die raamwerk behoue bly nadat die DMF molekules verwyder is. Ses nuwe strukture is ook met N,N'-bis(glisiniel)piromellitiese diïmied in kombinasie met ‘n wye verskeidenheid stikstof-bevattende heterosikliese verbindings verkry. Alle strukture wat tydens hierdie studie verkry is, is verder ondersoek om te bepaal of daar spesifieke strukturele kenmerke is wat benodig word vir die vorming van raamwerkmateriale. Insigte wat verkry is vanuit hierdie ondersoeke, in terme van die graad van ionisasie van die anioon, die rangskikking van molekules in die struktuur en waterstofbindingspatrone, sowel as die molekulêre vorm van die komponente, word bespreek.

Three different types of cage crown ethers have been prepared and their complexation properties with Ag(I) have been studied. Atomic absorption, fluorescence quenching, and UV absorption have been used to study the interaction between the hosts (cage crown ethers) and guests (Ag+). For the cage-annulated crown ethers that contain aromatic rings, cation-π and π-π interactions may contribute significantly to the overall complexation ability of the host system. Piperazine groups may cooperate, and the piperazine nitrogen atoms provide unshared electrons, which may form a complex with Ag+. In addition, relatively soft donor atoms (e.g., Br) are well-suited for complexation with Ag+, which is a softer Lewis acid than alkali metal cations.

Doctor of Philosophy / Department of Chemistry / Christer B. Aakeroy / A family of three 2-aminopyrazine derivatives were prepared and co-crystallized with thirty carboxylic acids. Our theoretical charge calculations and experimental results from 90 reactions demonstrated that decreasing the charge on the hydrogen-bond acceptor sites results in a decrease of the supramolecular yield (the frequency of occurrence of the desired outcome). However, synthon crossover (undesired connectivity) was observed 7/12 times and was unavoidable due to competitive binding sites present in the N-heterocyclic bases chosen. To avoid synthon crossover, we used a strategy based on geometric bias. We utilized hydrogen-bonding two-point contacts and halogen-bonding single-point contacts for supramolecular reactions with the 2-aminopyrazine family of compounds. The desired two-point contact and single-point contact (N•••I or N•••Br) appeared in 9/9 times even in the presence of other potentially interfering intermolecular interactions. In addition, the role of charge in controlling the presence/absence of proton transfer was also highlighted. To establish a hierarchy in halogen-bonding interactions we designed and synthesized a library of eight molecules equipped with two different halogen bond donors and combined with variety of halogen-bond acceptors. 11 Halogen-bonded co-crystals were obtained; however, positional disorder of I/Br atoms obscures a complete analysis. This problem was solved by introducing asymmetry in the halogen-bond donor molecules. Finally, successfully demonstrated an unprecedented hierarchy in halogen-bond interactions based on electrostatics. We developed high-yielding Suzuki-Miyaura coupling reactions of tetraboronic pinacolyl ester cavitand to iodoarenes with a range of functional groups (electron withdrawing/donating group and a heterocycle) that show robustness and versatility, making it a ‘launch pad’ for the synthesis of many new cavitands in a facile manner. We have also successfully demonstrated cavitand functionalization from tetraaldehyde to tetraoximes using ‘solvent assisted grinding’, irrespective of the position of the aldehyde. Finally, we prepared tetra-substituted pyridyl and carboxylic acid cavitands having an ellipsoidal cavity capable of encapsulating asymmetric guest molecules and was subsequently obtained the first of its kind, C[subscript]2v symmetric molecular capsule with encapsulated asymmetric guest molecule.