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The study of the macrocyclic aggregates of iso-tellurazole N-oxide has previously unveiled a wide variety of complexes with transition metal ions. The compound 3-methyl-5-phenyl-1,2-tellurazole-2-oxide and its derivatives bind soft d6, d8 and d10 metal ions exclusively by tellurium. The electron withdrawing ability of the cations strengthen the Te…O chalcogen bonding (ChB) interactions. In this thesis, we investigated the coordination chemistry of iso-tellurazole N-oxide with hard metal ions from elements of groups 1 and 2, as salts with weakly-coordinating anions. X-ray crystallography of the isolated products showed that the oxophilic nature of these cations results in coordination to the oxygen atom. However, formation of Te…O ChBs is not inhibited, in contrast to the cases in which oxygen binds protons or boranes. Novel dodecameric macrocycles were obtained from experiments with Na+ cations. The large supramolecular ring folds onto itself forming a cage-like structure capable of hosting molecules such as dioxane, THF and pyrazine. Their encapsulation is facilitated by the coordination to the metal ion. In the absence of such molecular guests, a tris-tetramer structure was assembled with four sodium ions. Although full refinement of its crystal structure is yet to be completed, the tris-tetramer suggests a mechanism that leads to the formation of the dodecamers. In contrast to Na+, K+ yielded a 1-D coordination polymer of the tetramers. The more oxophilic Mg2+ yielded complexes of macrocyclic hexamers of iso-tellurazole oxides linked by C-Te…O ChBs. Thesis Master of Science (MSc)

Noncovalent interactions have attracted significant attention in the recent decades, both seeking a fundamental understanding and pursuing a wide range of applications. One particular case that has been studied in great detail is halogen bonding (XBs). The use of chalcogen bonding (ChBs) is only beginning to thrive but already has made a mark in the chemical community. In this thesis, we intended to augment the study of ChBs by examining 1,2-chalcogenazole 2-oxides. These N-oxides of C3NCh (Ch = Se, Te) heterocycles spontaneously assemble supramolecular structures through reversible Te…O ChB interactions. In solution, their macrocyclic tetramers and hexamers exist in equilibrium. These rings as well as supramolecular polymers (infinite chains in crystalline phase) have been authenticated by single-crystal X-ray diffraction. Despite the reversibility of the Te…O link, the macrocycles display properties typical of covalent macrocycles, including ability to coordinate metal ions, host small molecules, and form adducts with fullerenes. The compounds are stable to tellurium halogenation and unreactive to Lewis bases. However, they are readily cleaved by Brønsted and Lewis acids. Transformation of the structure of iso-tellurazole N-oxides by formal insertion of an aromatic bridge between the nitrogen and oxygen atoms led to a new family of supramolecular building blocks. A disubstituted benzene bridge yielded three isomers, all of which display signs of aggregation in solution and crystallize in either polymeric or macrocyclic aggregates. Among the latter, the ortho compound assembled a calixarene-like trimer while the para derivative built a macrocyclic tetramer akin to a molecular square. Thesis Doctor of Philosophy (PhD) Supramolecular chemistry is a rapidly growing field of research that uses non-covalent interactions to spontaneously build well-organized structures. Among such interactions, hydrogen bonds are the most investigated and highly utilized in chemical and biological systems such as in DNA self-assembly, protein folding, cellulose, synthetic polymers and more. In recent years, much attention has been given to other non-covalent interactions, in particular bonding interactions that occur between electron-rich centres with electron-poor covalently bonded atoms of elements in groups 14 to 17 on the periodic table. These bonding interactions are named according to the group of the electron-deficient elements such as halogen bonds (XBs, group 17), chalcogen bonds (ChBs, group 16), “tetrel bonds” (group 14) and “pnictogen bonds” (group 15), as alternatives to hydrogen bonding. The purpose of this thesis is to augment our knowledge of ChBs by investigating the supramolecular chemistry of iso-chalcogenazole N-oxides and related compounds. Such molecules spontaneously assemble robust supramolecular structures, like infinite chains (polymers), and macrocyclic tetramers hexamers through Te…O ChB interactions that are strong and yet reversible. The macrocyclic aggregates coordinate to transition metal ions, form adducts with fullerene and host small molecules. The unusual stability of these tellurium-containing supramolecular building blocks, in addition to their strong ChBs, facilitated these investigations. The solubility of these compounds was improved by installing non-polar bulky groups. The macrocyclic cavity can be enlarged by replacing the oxygen atom with phenoxides groups, creating a new family of supramolecular building blocks.

The nonlinear propagation of a visible, continuous wave laser beam was studied in three types of polymer systems that harness photochemical reactions: (i) a photopolymerization to create permanent self-written structures, (ii) a photo-oxidation hosted within a polymer matrix and (iii) a reversible photoisomerization that triggers the contraction of a photoresponsive hydrogel. The process of self-trapping was characterized by monitoring the spatial intensity profiles over time. The mechanism of each material was determined with a series of control experiments in order to confirm the nature of the nonlinear response, including their reversibility and intensity-dependence. These observations led to the study of interactions between self-trapped beams. Two beams under linear conditions will pass through one another, but two beams travelling in a nonlinear medium will interact and influence one another. The interactions of two beams introduced into the aforementioned photochemical systems were investigated and revealed a rich diversity of phenomena including: (i) the attraction between beams, (ii) merging of beams into a single waveguide, (iii) nonlocal attraction between beams, (iv) orbiting of beams, (v) switching of beam positions, and (vi) inhibition of the self-trapping of a neighbouring beam. Each observation is dependent on a detailed understanding of the underlying mechanism of refractive index change. Numerical simulations supplement some of these experiments and provide further evidence for the nonlinear mechanisms. The formation of permanent self-written structures with these nonlinear waves offers the opportunity to create seamless 3D printed materials with prismatic geometries. Several macroscopic objects were constructed using nonlinear waves from incoherent LEDs and amplitude masks. Decomposition of 3D objects into prismatic elements was carried out using an algorithm that breaks an object into individual pieces. Using a multi-step printing process, several prismatic elements can be combined to form a target object. The results of these experimental and theoretical studies improve upon the current understanding of the dynamics of nonlinear light propagation in photochemical systems. These insights may allow us to harness other nonlinear effects and develop new materials for applications such as optical communication, computing and 3D printing. Thesis Doctor of Science (PhD) The nonlinear propagation of a visible, continuous wave laser beam was studied in three types of polymer systems that harness photochemical reactions: (i) a photopolymerization to create permanent self-written structures, (ii) a photo-oxidation hosted within a polymer matrix and (iii) a reversible photoisomerization that triggers the contraction of a photoresponsive hydrogel. Photochemical changes to the material lead to self-induced light-guiding structures that influence the behaviour of light. These self-trapped beams can interact with one another inside of a nonlinear medium, giving rise to a rich diversity of phenomena including: (i) the attraction between beams, (ii) merging of beams into a single waveguide, (iii) nonlocal attraction between beams, (iv) orbiting of beams, (v) switching of beam positions, and (vi) inhibition of the self-trapping of a neighbouring beam. Each observation is dependent on a detailed understanding of the underlying mechanism of refractive index change. Numerical simulations supplement some of these experiments and provide further evidence for the nonlinear mechanisms. The formation of permanent self-written structures with these nonlinear waves offers the opportunity to create seamless 3D printed materials with prismatic geometries. Several macroscopic objects were constructed using nonlinear waves from incoherent LEDs and amplitude masks. Decomposition of 3D objects into prismatic elements was carried out using an algorithm that breaks an object into individual pieces. Using a multi-step printing process, several prismatic elements can be combined to form a target object. The results of these experimental and theoretical studies improve upon the current understanding of the dynamics of nonlinear light propagation in photochemical systems. These insights may allow us to harness other nonlinear effects and develop new materials for applications such as optical communication, computing and 3D printing.

Previous studies of supramolecular association through chalcogen-centred secondary bonding interactions (SBIs) demonstrated the versatility of 1,2,5-telluradiazoles and their annulated congeners, the benzo-2,1,3-telluradiazoles, as supramolecular building blocks. Key to the properties of those compounds is their propensity to undergo auto-association through the [Te-N]2 supramolecular synthon leading to dimers or supramolecular ribbon polymers. Moderate steric repulsion induces structural distortions of [Te-N]2 without dissociation and, in doing so, enables properties of practical interest such as chromotropism and second-order non-linear optical responses. However, moisture sensitivity discourages wide-spread application of these compounds. While being more tolerant of the atmosphere, the analogous selenadiazoles form weaker intermolecular interactions. Using a combined experimental and computational approach, this thesis investigates methods by which the selenium-centred supramolecular interactions can be enhanced and applied in the construction of supramolecular architectures. The quantum mechanical description of the SBIs formed by 1,2,5-chalcogenadiazoles was updated with the application of modern dispersion corrections to relativistic density functional theory calculations (PBE-D3, ZORA). While in all cases the dispersion effect on optimized SBI distances is small (< 0.03 Å), the dispersion corrections to the calculated interaction energy range from 6 to 10 kJ mol-1 and increase with the weight of the chalcogen. The total interaction energy increases faster, however, therefore the relative weight of dispersion for the telluradiazole (10%) is significantly less than for the sulfur analogue (40%). The same dispersion-corrected functional was applied to the identification of the secondary ions observed in the Laser Desorption Ionization mass spectrum of benzotelluradiazoles. The most stable structure of the [2M+H]+ ion was shown to feature the [Te-N]2 supramolecular synthon and would be preferred over alternatives held by hydrogen bonding alone, one TeN SBI, a combination of the two or -stacking. The [2M]+ would also feature the [Te-N]2 supramolecular synthon. Shortening of the TeN distances in these ions implies that electron withdrawing groups strengthen the SBIs. The updated computational method was also applied to characterize the bonding in the adducts of a N-heterocyclic carbene with benzo-2,1,3-telluradiazole and 3,4-dicyano-2,1,5-telluradiazole recently prepared by the Zibarev group. The long TeC distances (2.53 and 2.34 Å) correspond to fractional bond orders (9.2 Å) distance between [M(-Cl)2]∞ chains, the manganese derivative is only paramagnetic, not ferromagnetic. Symmetry-broken DFT calculations for small models were unable to quantitatively reproduce the measured couplings (J) but do indicate that the heterocycle acquires significant spin density in the MnII compound enabling paramagnetic coupling through the [Se‑N]2 supramolecular synthon. General methods for the synthesis of N-alkylated selenadiazolium cations were investigated. Methyl, iso-propyl and tert-butyl benzo-2,1,3-selenadiazolium cations were prepared by direct alkylation or cyclo-condensation of the alkyl-phenylenediamine with selenous acid. While the former reaction only proceeds with the primary and tertiary alkyl iodides, the latter is very efficient. Difficulties reported in earlier literature are attributable to the formation of adducts of benzoselenadiazole with its alkylated cations and side reactions initiated by aerobic oxidation of iodide. However, the cations themselves are resilient to oxidation and stable in acidic to neutral aqueous media. X-ray crystallography was used in the identification and characterization of the following compounds: [C6H4N2(R)Se]+X-, (R = CH(CH3)2, C(CH3)3; X = I-, I3-), [C6H4N2(CH3)Se]+I-, and [C6H4N2Se][C6H4N2(CH3)Se]2I2. Formation of SeN SBIs was only observed in the last structure because anion binding to selenium is stronger. The relative strengths of those forces and the structural preferences they enforce were assessed with DFT-D3 calculations supplemented by AIM analyses of the electron density. The methods developed for the preparation of N-alkyl benzoselenadiazolium cations were extended to the syntheses of dications intended for use as building blocks of supramolecular polymers. The structure of several salts was established by single-crystal X-ray diffraction. [H4C6NSeN-CH2-CH2-NSeNC6H4]Cl2 crystallized forming a macrocyclic structure in which two dications are bridged by SeCl SBIs; a third halide anion sits at the centre of the macrocycle. [1,2-(H4C6NSeN)2-C6H10]Cl2 features two selenadiazolium cations bridged by a 1‑(R),2‑(R)‑substituted cyclohexane and short SeCl SBIs. [1,4-(H4C6NSeN-CH2)2-C6H4](BF4)2, featuring a p-xylene bridge, crystallizes in two pseudopolymorphs; with dications in anti or syn conformations making SeF contacts. [H4C6NSeN-CH2-CH2-NSeNC6H4](CF3SO3)2 does dimerize though the [Se-N]2 supramolecular synthon, although SeO interactions with the anions cap the second selenium atom. In contrast, [H4C6NSeN-CH2-CH2-CH2-NSeNC6H4](CF3SO3)2 only displays SeO contacts. An oligonucleotide analogue containing N-substituted selenadiazolium cations was designed to create foldamers with structures controlled by main-group secondary bonding. The target structures take advantage of the methods developed in this thesis for the functionalization of selenadiazoles and is meant to be compatible with automated methods for oligonucleotide synthesis. The proposed synthesis begins with the preparation of 1-(α,β)-O-methyl-2-deoxy-D-ribose, which was chlorinated and treated with phenylenediamine. High-resolution mass spectrometry confirmed the attachment of the diamine to the ribose, however, the yield was too low to continue this synthetic project. A ground-breaking development in the application of secondary bonding in supramolecular chemistry is the discovery of the reversible auto-association of iso-tellurazole N-oxides through TeO SBIs into annular structures. These rings are persistent in solution and behave as actual macrocycles able to complex transition metal ions, form adducts with fullerenes, and host small molecules. Single-crystal X-ray diffraction was critical to the characterization of these structures and required careful disorder modelling for tetrahydrofuran molecules included in a macrocyclic hexamer and the occupational disorder of CH2Cl2 and BF4- anions due to metal depletion in the crystal of a PdII complex. Thesis Doctor of Philosophy (PhD) Supramolecular chemistry is a prominent area of research that pursues the construction of large structures by the spontaneous assembly and organization of molecular building blocks. Its fundamental premise is that the judicious use of intermolecular forces allows the design of a structure and control of its properties. Most of the work in supramolecular chemistry has relied on hydrogen atoms bridging molecules and the bonding of metal ions to atoms rich in electrons. This thesis pursued the use of a different type of intermolecular force, termed “secondary bonding”, which is characteristic of the heaviest elements at the right of the periodic table (the “main-group” of elements). Previous work at McMaster demonstrated that cyclic molecules containing carbon, nitrogen and tellurium were particularly efficient as supramolecular building blocks. However, they are easily degraded by atmospheric water, this fact severely limits practical applications of these compounds. In this thesis, the tellurium atoms are replaced by selenium, a lighter element in the same family. The resulting molecules are more tolerant of atmospheric conditions but form weaker intermolecular links. Through a combination of quantum mechanical, synthetic, spectroscopic and structural studies, it is shown that certain modifications to the molecular structure increase the affinity of the selenium atoms for electrons. In this way, it is possible to strengthen the intermolecular interactions and promote the spontaneous assembly of supramolecular structures. These investigations eminently fall in the category of fundamental research but have broad-reaching implications for practical applications in optical and electronic technologies.

Three novel 1-aryl-1-(3-butenyl)germacyclopent-3-enes (26a, 26b and 26c) were synthesized and their photochemistry in hexane solution was studied by steady state and laser flash photolysis (LFP) methods. Steady state photolysis of 1-(3-butenyl)-3,4-dimethyl-1-phenylgermacyclopent-3- ene (26a) was found to proceed cleanly to afford the corresponding germylene derived product along with 2,3-dimethyl-1,3-butadiene (DMB) in the presence of acetic acid, methanol and isoprene, suggesting that free (3-butenyl)phenylgermylene (GeBuPh) is the primary photochemically generated species. However, we were unable to detect the germylene by laser flash photolysis with this compound, due to rapid “self –quenching” of the germylene by the precursor. The direct detection of the germylene in solution by laser flash photolysis requires the use of a more strongly absorbing derivative. Indeed, 3-butenylphenylgermylene (GeBuPh) was successfully detected directly by laser flash photolysis of 1-(3-butenyl)-3-methyl-1,4-diphenylgermacyclopent-3-ene (26b) in hexane solution, where it exhibits a UV-Vis absorption band centered at λmax= 490 nm and decays with second order kinetics on the microsecond timescale. In the absence of reactive substrates the decay of GeBuPh is accompanied by the growth of a second transient absorption, assigned to Ge2Bu2Ph2 (34) λmax = 420 nm; the assignment is based on a comparison to the laser flash photolysis of 1,3-dimethyl-1,4- diphenylgermacyclopent-3-ene (26d). Rate constants have been determined for reaction iv of the germylene with selected germylene substrates in order to evaluate the effects of intramolecular π-complexation on its reactivity. The results indicate that GeBuPh exhibits similar reactivity to GeMePh under otherwise identical experimental conditions, and thus show no significant indication of intramolecular π-complexation. With this in mind we have synthesized and studied 1-(3-butenyl)-3-methyl-4- phenyl-1-[3,5-bis(trifluoromethyl)phenyl]germacyclopent-3-ene (26c), which was designed to produce a more strongly electrophilic Ge(II) center in the corresponding germylene. The germylene 46 is detectable as a weakly absorbing transient species with λmax = 490 nm by laser flash photolysis of 26c in hexane solution. Generation of germylene 46 in the presence of THF leads to the formation of the corresponding Lewis acid base complex 48 at λmax = 330 nm. The reactivity of germylene 46 with selected substrates such as AcOH, THF and isoprene has been examined and the results compared to analogous data for the parent germylene GeBuPh. The forward rate constant for germylene 46 with acetic acid is slightly higher than that for GeBuPh, and no evidence for intramolecular complexation with the remote C=C bond could be obtained. Master of Science (MSc)

The goal of this research project is to synthesize, characterize, and examine the properties of a material that undergoes a decrease in refractive index upon exposure to light. It is anticipated that such photoresponses could elicit previously unknown nonlinear phenomena including self-trapped black beams. An appropriate material for these investigations would be a polymer cross-linked by photocleavable groups causing a Δn < 0. Organo-ditellurides, molecules that contain a Te-Te bond, would be appropriate for the crosslinks as their σ*Te-Te ← nTe transition usually absorbs light between 400 and 500 nm, and can lead to photodissociation of the chalcogen-chalcogen bond. Initial attempts to directly functionalize a polymer (polystyrene) resulted in intractable solids. A more promising approach relies on the preparation of cross-linking agents followed by co-polymerization. Despite literature claims, to date, there is no structurally authenticated photoresponsive molecule that simultaneously contains vinyl (CH=CH) and telluride (-Te-) functional groups. The work in this thesis has yielded what would be the first example, in addition to a crystal structure obtained by X-ray diffraction, the compound has been characterized by multinuclear NMR (1H, 13C, 125Te) and vibrational spectroscopy with the support of DFT calculations. Master of Science (MSc)