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Molecules with functional properties, especially ones that display spin crossover behaviour, are becoming increasingly well researched due to their potential applications as the active components in molecular memory, optical displays or sensors.1,2 To this end, a series of Fe(II) coordination compounds utilising imidazolylimine and pyridylimine based ligands have been synthesised and their spin crossover behaviour analysed through a variety of techniques including variable temperature X-ray crystallography, magnetic susceptibility, surface reflectivity and UV-Visible spectroscopy. Light-Induced Excited Spin-State Trapping (LIESST) effects have also been analysed via photomagnetic measurements. Particular attention was paid to the supramolecular interactions present within the solid-state and the effect that these interactions may have on spin crossover behaviour. Subtle changes to the complexes through counter-anion exchange, solvent effects and ligand design were explored and careful structural analysis completed. This study was separated into two distinct categories. The first describes the synthesis, structural characterisation and spin crossover behaviour of Fe(II) dinuclear triple helicates. Four dinuclear triple helicates have been synthesised, three of which display spin crossover behaviour. Weak LIESST effects were observed in two of these examples. Variation in the ligand field strength between the complexes was achieved through modification of the coordinating “head group” and differences between the flexibility of the ligand backbone were also explored. The latter part of this study describes the synthesis, structural characterisation and spin crossover behaviour of novel Fe(II) mononuclear complexes. A series of related ligands which differ in the p-substituent have been synthesised and their coordination chemistry with Fe(II) metal ions examined. Subtle changes to the counter-anion and crystallised solvent molecules were also explored during this study. Five mononuclear Fe(II) complexes were shown to undergo spin crossover and the structural changes associated with the spin-state conversion have been analysed via variable temperature X-ray crystallography and compared with magnetic susceptibility measurements. Two complexes were also analysed for LIESST behaviour and these complexes showed full photo-excitation into the high-spin state at 10 K.

Thirty four silver(I) complexes of azobenzene and derivatives have been synthesised, only two of which have been previously published. The azobenzene derivatives used are 2-bromo, 3-bromo, 4-bromo, 3,4’-dibromo, 2,4’-dibromo, 3-nitro, 4-dimethylamino, 4-methoxy, 2,6-dimethyl-4’-chloro, 2,6,2’,6’-tetramethyl and 2,2’-ethyleneazobenzene. 2,2’- and 4,4’-azobispyridine were also used along with diphenyltriazine. Six different silver(I) salts were used to make the complexes; they are tetrafluoroborate, hexafluorophosphate, perchlorate, nitrate, triflate and trifluoroacetate. All of the complexes were analysed using X-ray crystallography. In the complexes with azobenzene the anion was the most crucial factor in determining the resulting structure, as five different molecular topologies were seen with each change of anion. The 2-bromoazobenzene containing complexes continue this trend giving similar topologies to the azobenzene containing complexes. Once we come to the 3-bromo and 4-bromoazobenzene, we get a different molecular topology for the hexafluorophosphate containing complexes when compared to the original azobenzene containing complex, but we see a very similar structure for the perchlorate containing complexes. This would suggest that the coordinating anions give more predictable structures than the non-coordinating anions. The trend continues with both the 3,4’-dibromo and 2,4’-dibromoazobenzene complexes with triflate being structurally similar to the previous triflate containing complexes. The trend is reinforced further with 3-nitro and 4-methoxyazobenzene showing similar structures to the previously discussed complexes. The complex containing 4-dimethylaminoazobenzene can be disregarded, as the ligand has become protonated and therefore is unlike all the previously described results. When we come to the sterically hindered ligands 2,6-dimethyl-4’-chloroazobenzene the first three complexes show the same molecular topology of a silver atom bound to two ligands with a coordinating anion, however once we come to a tridentate coordinating anion triflate a 1-D metallopolymer is observed. This breaks the trend, as the structures are similar regardless of the change in anion. A similar effect is seen in 2,6,2’,6’-tetramethylazobenzene with both structures standing alone as no complexes with a similar molecular topology were observed. This effect is again noted in the complexes containing 2,2’-ethyleneazobenzene. The complexes all form a similar structure regardless of the anion used. As expected the 2,2’- and 4,4’-azobispyridine along with diphenyltriazine do not follow the trend observed earlier with the non-sterically hindered ligands as they can coordinate through additional nitrogen atoms in the aromatic ring or in the case of diphenyltriazine an additional nitrogen atom in the triazine group.

The aim of this thesis is to develop novel receptors for the recognition of anions and ion-pairs. The guest binding and sensing properties of the receptors are studied by spectroscopic and electrochemical techniques. The ion-pair receptors described herein incorporate amide or urea functionalities for anion binding and crown ether moieties for alkali metal cation complexation. In addition, many receptors contain redox- and/or photo-active groups capable of sensing guest binding events. Chapter One introduces the field of supramolecular chemistry. A review of synthetic cation, anion and ion-pair receptors reported in the literature is undertaken, and the formation of selfassembled architectures is discussed. Chapter Two details the synthesis and study of a range of new upper-rim functionalised calix[4]arene anion and ion-pair receptors. The anion and ion-pair binding and sensing properties of the receptors are investigated by ¹H NMR spectroscopy, electrochemistry and luminescence spectroscopy. Two ion-pair receptors display a positive cooperative ion-pair effect, whereby the presence of potassium cations causes an enhancement in the strength of anion binding via electrostatic interactions and conformational effects. Chapter Three centres on ion-pair receptors incorporating an azacrown group for alkali metal cation complexation together with amide functionalities for anion binding. Receptors containing either ferrocene or transition metal dithiocarbamate groups are capable of electrochemically and/or optically sensing the binding of anionic guests. Chapter Four describes disulphide-appended receptors designed for self-assembly onto gold surfaces. A ferrocene- and disulphide-appended calix[4]arene receptor incorporating hydrogen bonding moieties forms self-assembled monolayers on gold electrodes which exhibit a surface sensing amplification in the electrochemical recognition of anions. In addition, the assembly of receptors onto gold nanoparticles is explored with the aim of producing UV-VIS spectroscopic sensors for guest binding. Chapter Five reports the experimental procedures and characterisation for all products. The Appendices provide information on experimental techniques, list the crystallographic data and summarise all the receptors studied.

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This thesis describes the synthesis and X-ray crystallographic analysis of a series of supramolecular architectures prepared using seven flexible multimodal ligands with Ag(I), Cu(I), Cd(II), Co(II), Ni(II) and Pd(II) metal salts. Chapter one introduces some examples of fundamental supramolecular systems with particular focus on metallo-supramolecular motifs, specifically coordination polymers. Topological analysis is discussed as a method for the simplified description and comparison of network structures. Chapter two describes the design, synthesis and characterisation of the symmetrical ligands bis(2-pyrazylmethyl)sulfide (psp), bis(4-pyrimidylmethyl)sulfide (msm) and 5,5�-(thiodimethylene)di-pyrazine-2-carboxylic acid methyl ester (csc) as well as the asymmetrical ligands 2-benzylsulfanylmethyl-pyrazine (psb), 2-pyridylsulfanylmethyl-pyrazine (psd), 3-pyridylsulfanylmethyl-pyrazine (psn) and 4-pyridylsulfanylmethyl-pyrazine (psy). Chapter three presents a literature review of ligands related to psp, msm and csc, followed by the synthesis and characterization of thirteen Ag(I), Cd(II), Co(II), Ni(II) and Pd(II) complexes. The X-ray crystal structures of nine of these complexes are reported and compared. The structures were present as either one- or two-dimensional coordination polymers. The {[Ag(psp)](PF₆)}[infinity] and {[Ag₂(psp)(C₆H₆)(CH₃CN)₂](PF₆)₂�CH₃CN}[infinity] structures demonstrated a solvent dependence by forming a 1-D twisted ladder with a [eta]�-bound benzene and a 2-D undulating sheet with a 4.8� topology respectively. Six of the structures {[Cd₂(psp)(CH₃CN)(H₂O)(NO₃)₄]�H₂O}[infinity], {[Co(psp)(CH₃CN)₂](ClO₄)₂}[infinity], {[Ni(psp)(NO₃)₂]}[infinity] and {[Ag(msm)](X)}[infinity] (X = BF₄⁻, ClO₄⁻, PF₆⁻) displayed anion-[pi] interactions between multi-atomic anions and [pi]-acidic ring centres. A novel N[pz]���cent[pz] T-shaped [pi]-[pi] interaction was also identified in the {[Ni(psp)(NO₃)₂]}[infinity] structure. A 2-D sheet with 6� topology was observed in the X-ray structure of {[Ag₂(csc)](NO₃)₂}[infinity]. Following a review of related ligands, chapter four focuses on seven Ag(I), Cd(II), Co(II) and Cu(I) complexes formed using the asymmetric pyrazine-benzene ligand psb. In total six 1-D coordination polymer chains are reported. Two structurally disparate supramolecular isomers were formed in [Ag(psb)NO₃][infinity] and {[Ag₂(psb)₂NO₃]NO₃�H₂O}[infinity]. The compound {[Ag(psb)](BF₄)}[infinity] was similar to the former isomer [Ag(psb)NO₃][infinity]. The structurally similar coordination polymers {[Cd(psb)(H₂O)(NO₃)₂]}[infinity] and {[Co(psb)(H₂O)₃](ClO₄)₂�H₂O}[infinity] formed structures that showed anion-[pi] interactions using coordinated and non-coordinated anions respectively. The [Cu₂(psb)I₂][infinity] chain consisted of ligands linked together by a Cu₄I₄ stepped cubane tetramer. Chapter five presents seventeen Ag(I) and Cu(I) complexes prepared using three asymmetric pyrazine-pyridine ligands psd, psn and psy. A review of asymmetric pyrazine-pyridine ligands is provided. Seventeen X-ray crystal structures are described. Four psd complexes using AgBF₄, AgClO₄, AgNO₃ and AgPF₆ crystallised as discrete dimers with three types of crystal packing and ligand-supported Ag���Ag interactions. The complexes {[Ag₂(psd)₂CF₃SO₃]CF₃SO₃}[infinity] and {Cu₂(psd)I₂}[infinity] were a 1-D X-shaped chain and a 2-D 6� net respectively. The isostructural 2-D sheets in {[Ag(psn)]ClO₄}[infinity] and {[Ag(psn)]PF₆�CH₃CN}[infinity], had 4.8� topologies whereas a thicker sheet was formed in {[Ag₂(psn)₂](BF₄)₂}[infinity] with a complicated (4�.6�.8�)₂(4.6.8)₂ topology. The {[Ag₃(psn)₂](CF₃SO₃)₃�CH₃CN}[infinity] chain polymer displayed three different coordination geometries around the three Ag(I) centres with two ligand-unsupported Ag���Ag interactions. The complex [Cu₂(psn)₂I₂] crystallised as a discrete dimer with a different ligand arrangement than those found in the psd dimers. Six Ag(I) 3-D networks were formed using psy. The complexes {[Ag(psy)]X}[infinity] (X = BF₄, ClO₄, PF₆) formed as isostructural non-interpenetrated (10,3)-d networks. An unprecedented tri-nodal (4.6.8)₂(6.8�)₂(4.6.8�.10)₂ topology was observed in the {[Ag₂(psy)₂](CF₃SO₃)₂}[infinity] structure. The suprarmolecular isomers {[Ag₃(psy)₂(NO₃)₂]NO₃]}[infinity] and {[Ag₃(psy)₂(NO₃)₃]�H₂O}[infinity] formed inclined interpenetrated 6� sheets and a (4�.6)₂(4⁴.6�.8⁸.10) 3-D network respectively. The structures in this chapter showed a general trend of increasing dimensionality when progressing from psd to psn to psy. Chapter six presents a summary of the more significant results and concluding remarks.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--Brigham Young University. Dept. of Chemistry and Biochemistry, 2006. / Includes bibliographical references.

Thesis (Ph. D.)--Auburn University. / Abstract. Vita. Includes bibliographical references.