This thesis describes the preparation and characterisation of a number of homochiral coordination and metallosupramolecular assemblies. These species were formed from the reaction of chiral pyridine and quinoline containing ligands and metal ions. The combination of traditional coordination chemistry and supramolecular interactions led to a range of polymeric and network structures being formed. The ligands used in this thesis can be divided into two broad categories: alkaloids and ligands derived from them, and amino acid-based ligands. In the first category three new ligands were synthesized, and a variety of routes towards alkaloid-based homochiral ligands were investigated. The second category focused on three ligand motifs, and resulted in the preparation of 16 ligands. These two categories of ligands were reacted with a range of metal salts to investigate their coordination and supramolecular chemistry. The structure of twenty complexes was determined by single crystal X-ray crystallography. The complexes had a range of structures, with discrete and polymeric species being formed. Hydrogen bonding was an important feature in the supramolecular chemistry of the complexes, playing a different role in different series of complexes. Two chiral coordination polymers and one chiral coordination network were synthesized. All three of these structures possessed directionality to some degree: in the coordination network and one of the polymers the directionality is counterbalanced by the opposite directionality being present in the crystal, while the second coordination polymer is generated by the screw axis present and has a high degree of overall directionality.

No description available.

This thesis describes the synthesis and anion recognition properties of a variety of interlocked host receptors and the application of metal nanoparticles in the areas of catalysis and sensing. <b>Chapter One</b> introduces the field of anion supramolecular chemistry, with particular emphasis on areas relevant to the research discussed in later chapters. Following this, the synthesis and applications of metal nanoparticles are outlined. <b>Chapter Two</b> details the synthesis of a range of halo-triazolium based rotaxanes and explores the effects of altering both the halogen bond donor atom and degree of preorganisation on the anion recognition properties of the interlocked host system. A halogen bond containing catenane is also prepared and its anion binding properties investigated. <b>Chapter Three</b> initially reports the anion-templated synthesis of a series of neutral pyridine N-oxide axle containing rotaxanes before their ability to recognise anions in aqueous solvent mixtures is studied. Attempts to enhance anion binding through the incorporation of a positive charge into the macrocyclic component of the rotaxane structure are also explored. <b>Chapter Four</b> outlines the preparation of β-cyclodextrin functionalised metal nanoparticles and investigations of their catalytic and sensing properties. <b>Chapter Five</b> describes in detail the synthetic and analytical procedures discussed in chapters two to four. <b>Chapter Six</b> summarises the conclusions of this thesis.

Symmetrical cage-annulated podands were synthesized via highly efficient synthetic strategies. Mechanisms to account for the key reaction steps in the syntheses are proposed; the proposed mechanisms receive support from the intermediates that have been isolated and characterized. An unusual complexation-promoted elimination reaction was studied, and a mechanism is proposed to account for the course of this reaction. This unusual elimination may generalized to other rigid systems and thus may extend our understanding of the role played by the host molecules in "cation-capture, anion-activation" via complexation with guest molecules. Thus, host-guest interaction serves not only to activate the anion but also may activate the leaving groups that participate in the complexation. Complexation-promoted elimination provides a convenient method to desymmetrize the cage while avoiding protection/deprotection steps. In addition, it offers a convenient method to prepare a chiral cage spacer by introducing 10 chiral centers into the host system in a single synthetic step. Cage-annulated monocyclic hosts that contain a cage-butylenoxy spacer were synthesized. Comparison of their metal ion complexation behavior as revealed by the results of electrospray ionization mass spectrometry (ESI-MS), alkali metal picrate extraction, and pseudohydroxide extraction with those displayed by the corresponding hosts that contain cage-ethylenoxy or cage-propylenoxy spacers reveals the effect of the length of the cage spacer upon the host-guest behavior. A series of cage-annulated cryptands, cavitands and the corresponding non-cage-annulated model compounds have been synthesized. These host molecules display unusual behavior when examined by using ESI-MS techniques, i.e., they bind selectively to smaller alkali metal ions (i.e., Li+ and Na+), a result that deviates significantly from expectations based solely upon consideration of the size-fit principle. It seems likely that this behavior results from the effect of the host topology on host-guest behavior. A series of non-cage-annulated cryptands also have been synthesized. These compounds can serve as starting materials for cavitand construction.

No description available.

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.

No description available.

As a first step to producing a shape selective catalysts or enzyme mimic, two preorganized host molecules were synthesized. Binding studies of the two hosts with a variety of guests in three solvents demonstrated that an important driving force in the association was the formation of C-H???X-R hydrogen bonds (X = halogen). A deuterated host was utilized to further examine the formation of the C-H???X-R hydrogen bonds. In an effort to place functionality in the hydrophobic pocket of these hosts, two methods were developed. The first utilized directed ortho metallation to place electrophiles above and/or directed into the cavity. Perlithiation of the host could lead to sixty-nine products but reaction conditions and host rigidity limited product formation. This reaction technique led to the placement of carboxylic acid groups onto the host and the isolation of twelve products. Two different positions of the carboxylic acids (endoand exo-) direct the orientation of the guest. 1D- and 2D-NMR were utilized to examine how the was orientated inside the host. The second method employed to place functionality on the host, sited a tripodal zinc binding ligand on the side of the hydrophobic pocket of the host. The synthesized host was able to bind zinc strongly and in a 1:1 manner.

Water-soluble deep-cavity cavitands provide a rare opportunity to study self-assembly driven by the hydrophobic effect. These molecular hosts dimerize in the presence of certain guest molecules to form water-soluble molecular capsules. These systems have given rise to numerous novel chemical phenomena and have potential use in drug delivery. The host octaacid (OA) has been particularly well-characterized, but studies are limited to basic pH because of limited host solubility. Herein we report an improved synthesis of OA and the syntheses of three new water-soluble deep-cavity cavitands. The new hosts are soluble at neutral pH, increasing relevance for biological studies. The new syntheses are versatile enough to apply to the synthesis of additional water- soluble cavitands in the future. We also describe preliminary characterization of the molecular recognition properties of the new hosts. Binding of organic guest molecules to form 1:1 host:guest complexes and 2:1 host:guest capsules was qualitatively similar to that of OA. However, binding of anions spanning the Hofmeister series revealed interesting new behavior. The new hosts bound a wider range of anions inside the hydrophobic pocket with much higher association constants. Moreover, external binding of several anions to the cavitand pendant feet was observed. Looking towards biological applications, we desired to learn how these molecules interact with phospholipid membranes. Six water-soluble cavitands were tested for their ability to permeabilize liposomal POPC membranes. One host showed very high potency in permeabilizing membranes, while three other hosts showed moderate activity. Host binding of POPC was found to be at least one factor in host-induced permeabilization. A requenching assay to determine leakage mechanism strongly supported all-or-none leakage, whereby some vesicles lose all contents while others lose none. These results suggest that these cavitands induce partial transient leakage of vesicles by the formation of transient membrane pores. These findings show potential for the use of these hosts as drug delivery carriers, antimicrobial compounds, and tools in membrane alteration studies.

Thesis presented to the CAPE PENINSULA UNIVERSITY OF TECHNOLOGY for the degree of MASTER OF TECHNOLOGY Department of Chemistry, Cape Peninsula University of Technology, Cape Town Campus, Zonnebloem, October 2013 / In this thesis, the complexation behaviour of the host compounds, 1,1’-binaphthyl- 2,2’-dicarboxylic acid (BNDA) and 1,1’-binaphthyl-2,2’-diol (BINOL) were investigated. These hosts are large, bulky and scissor shaped; they contain functionalities to selectively interact with other molecules. A series of small organic compounds, particularly amines, were used in the preparation of the complexes. BNDA formed three complexes with acyclic amines, two complexes with the cyclic amines and two complexes with a racemic amine in different solvents. All the complexes formed were salts. The amines used were diethylamine, di-nbutylamine, cyclohexylamine, dicyclohexylamine, and sec-butylamine. For the studies with the acyclic amines and cyclic amines, crystals were grown in methanol as a co-solvent. Similar experiments were conducted with BINOL. Successful complexation only occurred with cyclohexylamine and dicyclohexylamine respectively. An amine host, 1,1’-binaphthyl-2,2’- diamine (BINDIA) was also considered with acidic and amide guests to extend the study of the binaphthyl derivatives, but from the array of guests used, the host only formed an inclusion compound with dimethylacetamide (DMA). The structures of all the complexes were elucidated using single crystal X-ray diffraction. Thermal analysis was performed in order to determine the thermal stability of the complexes, including techniques such as thermogravimetry, differential scanning calorimetry and hot stage microscopy. The kinetics of desolvation was investigated for some of the complexes.