Only within the last decade has supramolecular chemistry begun to adopt the Group 15 elements into its field of research. This dissertation presents a supramolecular approach to the self-assembly and reactivity of Group 15 metalloids, specifically arsenic and antimony, with organothiolate ligands. Investigating the self-assembly of pnictogen-based coordination complexes allows for in-depth characterization of the chemical behavior of arsenic, antimony and other Group 15 elements. Currently, the infiltration of arsenic into global groundwater systems has developed into a worldwide health concern. There are no chelating agents available for public use in the treatment of arsenic poisoning which are capable of binding arsenic (III) in its preferred coordination geometry thereby hindering the selectivity for rapid chelation. Chapter I is a review covering two important characteristics observed in the Group 15 elements: 1) a stabilizing, non-covalent cation-π interaction aiding in the formation of pnictogen-aryl thiolates, and 2) an observed lack of selectivity in environments containing multiple pnictogen ions which enables transmetalation of the complexes to occur or the generation of heterometallic assemblies. Based on the discovery of this new transmetalation reactivity, the remainder of the dissertation explores the effects of external additives during self-assembly in order to understand how they may affect the reactivity of these self-assembled complexes and provide insight into formation mechanisms. Chapter II identifies a catalyst for the acceleration of a slow self-assembly reaction between AsCl3 and a dithiolate ligand to give an As2L3 cryptand. Chapter III examines the oxidation of the arsenic cryptand using iodine, which leads to the self-assembly of a series of differently sized, discrete disulfide-bridged macrocycles. In Chapter IV, the self-assembly of the first trinuclear arsenic- and antimony-based coordination complexes was studied, revealing interesting solvent dependent conformational isomerism in solution. Chapter V applies the pnictogen-enhanced iodine oxidation to the synthesis of known and new cyclophanes using supramolecular chemistry, including the self-assembly and covalent capture of an unprecedented tetrahedral thiacyclophane. Additionally, an unusual trithioorthoformate capped tricyclophane cage was also synthesized and isolated by pnictogen-activated oxidation. Chapter VI includes the conclusion and future directions for the project. This dissertation includes co-authored material and previously published results. / 10000-01-01

New synthetic routes to nitrogen- and phosphorus-containing polymers have been investigated. These routes rely on amine- and phosphine-containing monomers bearing pendant alkyne substituents, and subsequent hydroamination, oxidation, or hydrophosphination polymerization. A series of primary amines of the form H2NC6H2R2C≡CR’ (R = H or iPr; R’ = Ph, SiMe3, nBu, or p-C6H4Me) is reported. These amines are deprotonated with nBuLi to give lithium amides, which react with zirconocene compounds to provide amidozirconium complexes. Characterization is achieved by multinuclear NMR spectroscopy, IR spectroscopy, high-resolution mass spectrometry, elemental analysis, X ray crystallography, and DFT calculations. Three routes were attempted towards nitrogen-containing oligomers: (1) thermolysis of amidozirconium complexes to afford [2+2] cycloaddition polymers; (2) Ti(IV)-catalyzed hydroamination of H2NC6H4C≡CPh; (3) chemical oxidation of H2NC6H4C≡CPh. The latter two strategies resulted in distinct nitrogen-containing oligomers. The oligomer formed by Ti(NR2)4-catalyzed hydroamination (R = Me, Et) contains up to 15 repeat units in the chain, with both imine and enamine moieties, and is capped by a molecule of HNR2 (R = Me or Et) originating from the catalyst. The oligomer formed by chemical oxidation contains up to 9 repeat units in the chain. A series of phosphines of the form X2PC6H2R2C≡CR’ is reported (X = NEt2, Cl, H; R = Me, iPr; R’ = Ph, SiMe3). Characterization is achieved by multinuclear NMR spectroscopy, IR spectroscopy, high-resolution mass spectrometry, elemental analysis, and X-ray crystallography. The primary phosphines, H2PC6H2R2C≡CR’, are relatively “user-friendly” in that they are not particularly malodorous, they are isolated as solids or highly viscous liquids, and they are stable when stored under N2 in the solid state and in solution. The primary phosphine H2PC6H2iPr2C≡CPh serves as a precursor for a zirconium phosphinidene and for the secondary phosphines RP(H)C6H2iPr2C≡CPh (R = CH2iPr, CH2Ph). Hydrophosphination polymerization gives cyclic P(III)-containing oligomers, which are converted to P(V)-based macromolecules by treatment with sulfur. The oligomers contain ca. 5 to 10 repeat units, and heating to 800 °C gives rise to phosphorus-containing ceramics. The mechanism of hydrophosphination is discussed with the use of DFT calculations.

New synthetic routes to nitrogen- and phosphorus-containing polymers have been investigated. These routes rely on amine- and phosphine-containing monomers bearing pendant alkyne substituents, and subsequent hydroamination, oxidation, or hydrophosphination polymerization. A series of primary amines of the form H2NC6H2R2C≡CR’ (R = H or iPr; R’ = Ph, SiMe3, nBu, or p-C6H4Me) is reported. These amines are deprotonated with nBuLi to give lithium amides, which react with zirconocene compounds to provide amidozirconium complexes. Characterization is achieved by multinuclear NMR spectroscopy, IR spectroscopy, high-resolution mass spectrometry, elemental analysis, X ray crystallography, and DFT calculations. Three routes were attempted towards nitrogen-containing oligomers: (1) thermolysis of amidozirconium complexes to afford [2+2] cycloaddition polymers; (2) Ti(IV)-catalyzed hydroamination of H2NC6H4C≡CPh; (3) chemical oxidation of H2NC6H4C≡CPh. The latter two strategies resulted in distinct nitrogen-containing oligomers. The oligomer formed by Ti(NR2)4-catalyzed hydroamination (R = Me, Et) contains up to 15 repeat units in the chain, with both imine and enamine moieties, and is capped by a molecule of HNR2 (R = Me or Et) originating from the catalyst. The oligomer formed by chemical oxidation contains up to 9 repeat units in the chain. A series of phosphines of the form X2PC6H2R2C≡CR’ is reported (X = NEt2, Cl, H; R = Me, iPr; R’ = Ph, SiMe3). Characterization is achieved by multinuclear NMR spectroscopy, IR spectroscopy, high-resolution mass spectrometry, elemental analysis, and X-ray crystallography. The primary phosphines, H2PC6H2R2C≡CR’, are relatively “user-friendly” in that they are not particularly malodorous, they are isolated as solids or highly viscous liquids, and they are stable when stored under N2 in the solid state and in solution. The primary phosphine H2PC6H2iPr2C≡CPh serves as a precursor for a zirconium phosphinidene and for the secondary phosphines RP(H)C6H2iPr2C≡CPh (R = CH2iPr, CH2Ph). Hydrophosphination polymerization gives cyclic P(III)-containing oligomers, which are converted to P(V)-based macromolecules by treatment with sulfur. The oligomers contain ca. 5 to 10 repeat units, and heating to 800 °C gives rise to phosphorus-containing ceramics. The mechanism of hydrophosphination is discussed with the use of DFT calculations.

La conversion thermoélectrique a suscité un regain d'intérêt en raison des possibilités d'augmenter l'efficacité tout en exploitant les effets de taille. Par exemple, les nanofils montrent théoriquement une augmentation des facteurs de puissance ainsi qu'une réduction du transport des phonons en raison d'effets de confinement et/ou de taille. Dans ce contexte, le diamètre des nanofils devient un paramètre crucial à prendre en compte pour obtenir des rendements thermoélectriques élevés. Une approche habituelle consiste à réduire la conductivité thermique phononique dans les nanofils en améliorant la diffusion sur les surfaces tout en réduisant les diamètres.Dans ce travail, la caractérisation thermique d'une forêt dense de nanofils de silicium, germanium, silicium-germanium et alliage Bi2Te3 est réalisée par une méthode 3-omega très sensible. Ces forêts de nanofils pour le silicium, le germanium et les alliages silicium-germanium ont été fabriqués selon une technique "bottom-up" suivant le mécanisme Vapeur-Liquide-Solide en dépôt chimique en phase vapeur. La croissance assistée par matrice et la croissance par catalyseurs en or des nanofils à diamètres contrôlés ont été réalisés à l'aide d'alumine nanoporeuse comme matrice. Les nanofils sont fabriqués selon la géométrie interne des nanopores, dans ce cas le profil de surface des nanofils peut être modifié en fonction de la géométrie des nanopores. Profitant de ce fait, la croissance à haute densité de nanofils modulés en diamètre a également été démontrée, où l'amplitude et la période de modulation peuvent être facilement contrôlées pendant la fabrication des matrices. Même en modulant les diamètres pendant la croissance, les nanofils ont été structurellement caractérisés comme étant monocristallins par microscopie électronique à transmission et analyse par diffraction des rayons X.La caractérisation thermique de ces nanofils a révélé une forte diminution de la conductivité thermique en fonction du diamètre, dont la réduction était principalement liée à une forte diffusion par les surfaces. La contribution du libre parcours moyen à la conductivité thermique observée dans ces matériaux "bulk" varie beaucoup, Bi2Te3 ayant une distribution en libre parcours moyen (0,1 nm à 15 nm) très faible par rapport aux autres matériaux. Même alors, des conductivités thermiques réduites (~40%) ont été observées dans ces alliages attribuées à la diffusion par les surfaces et par les impuretés. D'autre part, le silicium et le germanium ont une conductivité thermique plus élevée avec une plus grande distribution de libre parcours moyen. Dans ces nanofils, une réduction significative (facteur 10 à 15 ) a été observée avec une forte dépendance avec la taille des nanofils.Alors que les effets de taille réduisent la conductivité thermique par une meilleure diffusion sur les surfaces, le dopage de ces nanofils peut ajouter un mécanisme de diffusion par différence de masse à des échelles de longueur atomique. La dépendance en température de la conductivité thermique a été déterminée pour les nanofils dopés de silicium afin d'observer une réduction de la conductivité thermique à une valeur de 4,6 W.m-1K-1 dans des nanofils de silicium fortement dopés avec un diamètre de 38 nm. En tenant compte de la conductivité électrique et du coefficient Seebeck calculé, on a observé un ZT de 0,5. Avec l'augmentation significative de l'efficacité du silicium en tant que matériau thermoélectrique, une application pratique réelle sur les appareils n'est pas loin de la réalité. / Thermoelectric conversion has gained renewed interest based on the possibilities of increasing the efficiencies while exploiting the size effects. For instance, nanowires theoretically show increased power factors along with reduced phonon transport owing to confinement and/or size effects. In this context, the diameter of the nanowires becomes a crucial parameter to address in order to obtain high thermoelectric efficiencies. A usual approach is directed towards reducing the phononic thermal conductivity in nanowires by achieving enhanced boundary scattering while reducing diameters.In this work, thermal characterisation of a dense forest of silicon, germanium, silicon-germanium and Bi2Te3 alloy nanowires is done through a sensitive 3ω method. These forest of nanowires for silicon, germanium and silicon-germanium alloy were grown through bottom-up technique following the Vapour-Liquid-Solid mechanism in Chemical vapour deposition. The template-assisted and gold catalyst growth of nanowires with controlled diameters was achieved with the aid of tuneable nanoporous alumina as templates. The nanowires are grown following the internal geometry of the nanopores, in such a case the surface profile of the nanowires can be modified according to the fabricated geometry of nanopores. Benefiting from this fact, high-density growth of diameter-modulated nanowires was also demonstrated, where the amplitude and the period of modulation can be easily tuned during the fabrication of the templates. Even while modulating the diameters during growth, the nanowires were structurally characterised to be monocrystalline through transmission electron microscopy and X-ray diffraction analysis.The thermal characterisation of these nanowires revealed a strong diameter dependent decrease in the thermal conductivity, where the reduction was predominantly linked to strong boundary scattering. The mean free path contribution to the thermal conductivity observed in the bulk of fabricated nanowire materials vary a lot, where Bi2Te3 has strikingly low mean free path distribution (0.1 nm to 15 nm) as compared to the other materials. Even then, reduced thermal conductivities (~40%) were observed in these alloys attributed to boundary and impurity scattering. On the other hand, silicon and germanium have higher thermal conductivity with a larger mean free path distribution. In these nanowires, a significant reduction (10-15 times) was observed with a strong dependence on the size of the nanowires.While size effects reduce the thermal conductivity by enhanced boundary scattering, doping these nanowires can incorporate mass-difference scattering at atomic length scales. The temperature dependence of thermal conductivity was determined for doped nanowires of silicon to observe a reduction in thermal conductivity to a value of 4.6 W.m-1K-1 in highly n-doped silicon nanowires with 38 nm diameter. Taking into account the electrical conductivity and calculated Seebeck coefficient, a ZT of 0.5 was observed. With these significant increase in the efficiency of silicon as a thermoelectric material, a real practical application to devices is not far from reality.

Electrostatic interactions such as halogen bonding and pnictogen bonding interactions have gained a lot of interest in the field of crystal engineering and pharmaceutical science. In the first part of this thesis, we expand our knowledge on anion coordinated halogen bonded cocrystals by looking at a series of cocrystals made from 3-iodoethynyl pyridine and 3-iodoethynylbenzoic acid. We utilize the power of mechanochemistry to create the new cocrystals made with phosphonium salts and use multinuclear solid-state nuclear magnetic resonance spectroscopy and X-ray diffraction and characterize them. We found that mechanochemistry is a fast and powerful tool to explore and synthesize new halogen bonded cocrystals and ³¹P solid-state NMR is a rapid way to identify the formation of a cocrystal. In the second part, we look at the versatility of the pnictogen atom, specifically antimony, as a pnictogen bond donor and a halogen bond acceptor. We evaluate these electrostatic interactions with nuclear quadrupolar resonance and found that nuclear quadrupole resonance is a strong spectroscopy tool to probe these types of electrostatic interactions.