Hydrogen bonds are of great interest in the solid state due to their importance in structural, functional and dynamical properties of chemical systems. Moderate hydrogen bonds have been linked with proton transfer, whereas the short, strong hydrogen bonds enable proton migration. Previous work in our group on relatively simple hydrogen bonded adducts relied on the combination of ab initio computational modelling (molecular dynamics) with variable temperature diffraction results (X-ray and neutron). These demonstrated that the interplay of these techniques was successful in studying the phenomena of proton transfer and migration. The present work follows on from that, and focuses on the effects of temperature and pressure on proton transfer and migration using both experimental and computational methods. The systems studied continue to encapsulate adducts with N…O and O…O hydrogen bonds. The study of the adduct formed between squaric acid and 4,4’-bipyridine was found to exhibit proton transfer associated with a single-crystal to single-crystal phase transition at 450 K that is coupled to a colour change (yellow to red). X-ray and neutron diffraction initially revealed the heavy atom structure and secondly the location of the hydrogen atoms along the moderate N…O hydrogen bond (ca. 2.6 Å). Computational modelling supported this and deduced the reason for the striking colour change. Pressure studies also determined that the adduct underwent two phase-transitions with a similar colour change, indicating that proton transfer is also a factor here, but with powder patterns different from the high temperature form, indicating that further polymorphs for this interesting system must exist. In an attempt to lower the temperature at which proton transfer would occur the base was changed to one of a more basic nature, i.e. co-crystallisation of squaric acid and 2,2’-dimethyl–4,4’-bipyridine was pursued. This lead to the formation of two red crystals that were found to posses the base doubly protonated at all temperatures studied (from 300 K to 100 K). The adduct of N,N-dimethylurea with phosphoric acid was obtained from a systematic study designed to follow the success of a previously reported system that showed proton migration (the adduct of urea and phosphoric acid). The new material was found to crystallise as the 2:1 adduct and maintained the short, strong hydrogen bonds characteristic of the parent structure. As part of the systematic approach undertaken throughout the research presented here, co-crystallisation of a combination of acids and bases were attempted in order to synthesise new materials containing short, strong hydrogen bonds. These yielded the adducts between oxalic acid and 2,2’-dimethyl-4,4’-bipyridine, and oxamic acid and 4,4’-bipyridine. In addition to these adducts some compounds ended up reacting to create new ones, e.g. the fusing of dimethyl urea and squaric acid to give N-(2-hydroxycyclobutene-3,4-dione)-N’,N’-dimethylurea and N-(2- hydroxycyclobutene-3,4-dione)-N,N'-dimethylurea, while a new polymorphs of one of the precursors on its own was also obtained (N,N’-dimethylurea). The resulting co-crystallisations did not all follow the design quite as intended. They did, however, yield interesting new structures, some of which have the potential to be proton migration and transfer systems.

There is a current requirement for technologies that store heat for both domestic and industrial applications. Phase-change materials (PCMs) represent an important class of materials that offer potential for heat storage. Heat-storage systems are required to undergo multiple melt/freeze cycles without any change in melting-crystallisation point and heat output. Salt hydrates are attractive candidates on account of their high energy densities, but there are issues associated with potential crystallisation of lower-hydrates, long-term stability, and reliable nucleation. An extensive review of the PCMs in the literature, combined with an evaluation of commercially available PCMs led to the conclusion that many of the reported PCMs, lack at least one of the key requirements required for use as a heat-storage medium. The focus of this research was therefore to identify and characterise new PCM compositions with tailored properties. New PCM compositions based of sodium acetate trihydrate were developed, which showed improved properties through the use of selective polymers that retard the nucleation of undesirable anhydrous sodium acetate. Furthermore, the mechanism of nucleation of sodium acetate trihydrate by heterogeneous additives has been investigated using variable-temperature powder X-ray diffraction. This study showed that when anhydrous Na2HPO4 was introduced to molten sodium acetate trihydrate at 58°C the hydrogenphosphate salt is present as the dihydrate. On heating to temperatures in the range 75-90°C the dihydrate was observed to dehydrate to form anhydrous Na₂HPO4. This result explains the prior observation that the nucleator is deactivated on heating. The depression of melting point of sodium acetate trihydrate caused by the addition of lithium acetate dihydrate has also been investigated using differential scanning calorimetry and powder X-ray diffraction. It has been possible to tune the melting point of sodium acetate trihydrate thereby modifying its thermal properties. Studies of the nucleation of sodium thiosulfate pentahydrate, a potential PCM, led to the structural characterisation of six new hydrates using single crystal Xray diffraction. All of these hydrates can exist in samples with the pentahydrate composition at temperatures ranging from 20°C to 45°C. These hydrates are: α-Na₂S₂O₃·2H₂O, which formed during the melting of α-Na₂S₂O₃·5H₂O; two new pentahydrates, β-Na₂S₂O₃·5H₂O and γ-Na₂S₂O₃·5H₂O; Na₂S₂O₃·1.33 H₂O, β-Na₂S₂O₃·2H₂O and Na₂S₂O₃·3.67 H₂O, which formed during the melting of β- Na₂S₂O₃·5H₂O. Furthermore, new PCMs in the 75-90°C range were identified. The commercial impact and route to market of several of the PCMs are discussed in the final chapter.

Advanced analytical techniques were utilized to investigate the intermolecular forces in several nanostructured materials. Techniques including, but not limited to, isothermal titration calorimetry (ITC), variable temperature Fourier transform infrared (FTIR) spectroscopy, and ultraviolet-visible (UV-Vis) thermal curves were used to study the fundamental interactions present in various nanomaterials, and to further probe the influence of these interactions on the overall behavior of the material. The areas of focus included self-assembly of surfactant micelles, polycation complexation of DNA, and temperature-dependent hydrogen bonding in polymeric systems. ITC was successfully used to determine the low critical micelle concentration (CMC) for a novel gemini surfactant with limited water solubility. CMCs were measured at decreasing methanol molar fractions (xMeOH) in water and the resulting linear relationship between CMC and methanol concentration was used to mathematically extrapolate to a predicted CMC at xMeOH = 0. Using this technique, the CMC value for the novel gemini surfactant was predicted to be 0.037 ± 0.004 mM. This extrapolation technique was also validated with surfactant standards. ITC was also used to investigate the binding thermodynamics of polyplex formation with polycations and DNA. The imidazolium-containing and trehalose-based polycations were both found to have endothermic, entropically driven binding with DNA, while the adenine-containing polycation exhibited exothermic DNA binding. In addition, ITC was also used to confirm the stoichiometric binding ratio of linear polyethylenimine and DNA polyplexes as determined by a novel NMR method. Dynamic light scattering (DLS) and zeta potential measurements were also performed to determine the size and surface charge of polyplexes. Circular dichroism (CD) and FTIR spectroscopies provided information regarding the structural changes that may occur in the DNA upon complexation with polymers. UV-Vis thermal curves indicated that polyplexes exhibit a greater thermal stability than DNA by itself. Variable temperature FTIR spectroscopy was used to quantitatively compare the hydrogen bonding behavior of multi-walled carbon nanotube (MWCNT)-polyurethane composites. Spectra were collected from 35 to 185 deg C for samples containing various weight percent loadings of MWCNTs with different hydrogen bonding surface functionalities. Peak fitting analysis was performed in the carbonyl-stretching region for each sample, and the hydrogen-bonding index (Rindex) was reported. Rindex values were used to quantitatively compare all of the composite samples in regards to temperature effects, weight percent loadings of MWCNTs, and the different functionalizations. In general, higher weight percent loadings of the MWCNTs resulted in greater Rindex values and increased hydrogen bond dissociation temperatures. In addition, at 5 and 10 wt% loadings the initial Rindex values displayed a trend that tracked well with the increasing hydrogen bonding capacity of the various surface functionalities. / Ph. D.

Yes / Diffusion ordered 1H-NMR spectroscopy (DOSY) is a useful, non-destructive technique for analysing polymer hydrodynamic size and intrinsic/solution viscosity. However, to date there has been no investigation of DOSY under variable temperature conditions that allow trends in polymer conformation to be determined. Poly(2-ethyl-2-oxazoline) (P(EtOx)) is a hydrophilic polymer that has the potential to replace poly(ethylene glycol) (PEG) in biomedical applications. Applying DOSY to a series of narrow-distribution P(EtOx) revealed that the apparent hydrodynamic radii scaled with molecular weight as expected. By altering the temperature of the solution the trends in Flory-type exponents were determined, enabling the determination of the power laws related to the coil-globule conformation of linear polymers directly from NMR data. These measurements were complicated by the onset of convection currents at higher temperatures, which impose a limit to the effective measurement range of ca. 10–35 °C. It was revealed that P(EtOx) had a more expanded random coil conformation than PEG, and it trended towards θ conditions at the lower critical solution temperature. In comparison, PEG was approximately in θ-conditions at room-temperature. This shows the use, and limitations of DOSY in polymer conformation analysis, and applies it to P(EtOx), a polymer which has not been analysed in this manner before. / University of Ghent (Grant Number: RM1602-1695)

This dissertation aims to develop, characterize, and fundamentally understand a new class of materials termed "molecular ionic composites" (MICs). MICs show promise as next-generation solid electrolytes for batteries. MICs form when mixing a rigid polyanion with purely ionic fluids, and they behave mechanically as a solid but contain a high density of ions that move nearly as in a neat liquid. Specifically, prototypical MICs are based on solutions of the rigid-rod polyelectrolyte poly(2,2'-disulfonyl-4,4'-benzideneterephthalamide) (PBDT), which forms a double helix, combined with imidazolium-based ionic liquids (ILs). The IL comprises 75-97 wt% of the final solid, even though the Young's modulus can reach ~ 2 GPa at 80 wt% IL. We propose that these properties are driven by a biphasic internal structure in MICs corresponding to IL-rich "puddles" (an interconnected liquid phase) and PBDT-IL associated "bundles" where IL ions form the collective electrostatic associations that cause the MICs to be a solid. Through this dissertation I will discuss a wide variety of MICs that have been created through the use of two different formation processes, the "ingot" method and the "solvent casting" method, which allow for the use of many different ionic fluid sources to further tune MIC properties. The following chapters build to the fundamental knowledge and our current understanding of the wide variety of materials that can be created from PBDT and IL. / Doctor of Philosophy / Battery electrolytes, biosensors, and hydrogels all depend on new materials for next-generation applications. For these new materials to be used characterization on the interactions, morphological restrictions, and/or what unique internal structures used to generate their properties must be performed. Through This analysis using common polymeric characterization techniques these materials can be further optimized. This dissertation highlights a new class of materials termed "molecular ionic composites" (MICs) which are formed from a rigid double helical polymer, poly(2,2'-disulfonyl-4,4'-benzideneterephthalamide) (PBDT), and fluids composed entirely of ions, including ionic liquids (ILs). These composite systems feature a unique combination of properties including high thermal stability, mechanical stability, and excellent ionic conductivity, all of which are highly tunable through the amount of PBDT incorporated or the fluid ion types. Chapters 3, 4, 5, and 6 present fundamental investigations of MICs to determine how tunable they are, the processes by which they form, and the various ways we can fabricate them. Chapter 7 describes the creation of another impressive material formed from PBDT-low-polymer-content hydrogels. These studies are intended to provide deeper understanding of the behaviors of these unique materials and how they may be used in the future.

Traditional solution and solid state approaches (Nuclear Magnetic Resonance, X-Ray Crystallography) are methods of choice when analysing both biological and inorganic analytes. However, the characterisation of transient species, often encountered in self-assembling systems, is difficult. Such systems rarely produce crystals of high quality and due to their dynamic nature; their structures are difficult to study with NMR. Hyphenated gas phase methods which rely on mass spectrometry detection offer simultaneous structural analysis and direct stoichiometry measurement. As a consequence, it is possible to investigate specific, non-interacting molecules and molecular complexes in an isolated environment. This thesis focuses on the development and applications of two such methods - ion mobility mass spectrometry (IM-MS) and cold ion spectroscopy. IM-MS measurements yield a so called collisional cross sectional area (CCS). This parameter can be pictured as a rotationally averaged, shadow projection of a molecule structure. When correlated with the ion abundance, a CCS distribution yields intuitively interpretable information about the conformational preferences of an isolated molecule. Although indispensable in describing a "global" geometrical structure, the CCS parameter itself provides a limited insight into the local structural features of the assembly. Ion spectroscopy, both in the UV and IR regions, can provide an extra layer of highly descriptive information. Here, we present several cases where the above techniques have been applied. With the aid of IM-MS, we have analysed the geometry of inorganic supramolecular assemblies, highlighting the stability of particular metal-ligand interactions. Using cold ion spectroscopy, we have assessed the fine structural information of self-assembled oligomers of an amyloidogenic peptide. We correlated spectral features of isolated oligomers to features observed in the mature fibrils; therefore attempting to delineate the events in early stages of amyloidogenic aggregation. A major part of this report focusses on technological aspects of the design and development of a high resolution, variable temperature ion mobility mass spectrometer (VT-IM-MS). The thermal stability of molecules is a vital aspect in industrial process development and formulation science. Solution phase Differential Scanning Calorimetry (DSC) is a widely applied technique, allowing to monitor reversibility of thermally induced conformational transitions, a key aspect in protein folding analysis. The instrument reported here aims to provide parallel information about gaseous ions, with a particular focus on protein ions. Capabilities of the newly built instrument have been tested using small, rigid molecules, a small protein and a large multiprotein complex.

Since the middle of the 20th century, significant interest has evolved from the scientific community towards the polypropionate family of marine natural products. A number of these compounds have been shown to possess significant biological activity, and this property, as well as their structural complexity, has driven numerous efforts towards their synthesis. The first chapter provides an introduction into the world of polypropionates, with a discussion on synthetic studies into a number of members of the tridachiapyrone family. Fundamental synthetic concepts utilised in this thesis towards the preparation of polyketides are also described, with a focus on their application towards the synthesis of 9,10-deoxytridachione, anti tridachiahydropyrone and syn tridachiahydropyrone. Chapter 2 describes the work undertaken towards the total synthesis of 9,10-deoxytridachione. The novel tandem conjugate addition-Dieckmann condensation of complex enones developed previously in the Perkins group was used to generate anti methylated cyclohexenones as key synthetic intermediates. The conversion of the cyclohexenones into the corresponding cyclohexadienes via allylic alcohols was attempted, utilising a Grignard-mediated reaction to achieve the selective 1,2-reduction. Studies into the Grignard-mediated reduction were also undertaken on seven additional cyclohexenones, in order to investigate the utility and scope of the reaction. The extension of the methodology previously developed for the synthesis of cyclohexenones is the subject of Chapter 3. This section describes investigations into the synthesis of stereochemically-diverse cyclohexenones from complex enones. The conjugate addition-Dieckmann condensation strategy was extended successfully towards the synthesis of a syn methylated cyclohexenone, which allowed the synthesis of the proposed true structure of tridachiahydropyrone to be pursued. The methodology developed in Chapter 3 was utilised in Chapter 4 to synthesise a model system of syn tridachiahydropyrone. A comparative analysis of the NMR data of the syn model, an anti model and anti tridachiahydropyrone with the natural product indicated that the true structure of tridachiahydropyrone may indeed have syn stereochemistry. The synthesis of syn tridachiahydropyrone was attempted, and to this end a suitable cyclohexanone was successfully synthesised. However, the subsequent methylation-elimination cascade failed to furnish the desired syn methylated cyclohexenone, producing only an anti methylated cyclohexanone. The stereochemistry of the methylation was deduced using high and low variable temperature NMR coupled with selective irradiation NOESY.

<p>  </p> <p>Thermal energy storage (TES) is used to reduce the operating costs of heating, ventilation, and air conditioning (HVAC) systems by shifting loads away from on-peak periods, to reduce the maximum heating or cooling capacity needed from the HVAC system, and to store excess energy generated by on-site solar power. The most commonly-used form of TES is ice storage with air conditioning (A/C) systems in commercial buildings. There has been extensive research into many other forms of TES for use with HVAC systems, both in commercial and residential buildings. However, this research is often limited to use with either heating or cooling systems.</p> <p>Year-round, high-density storage for both heating and cooling would yield significantly larger cost savings than existing TES systems, particularly for residential buildings, where heating loads are often larger than cooling loads. This dissertation examines the feasibility of using metal hydrides for year-round storage, as well as analyzing the potential of variable-temperature energy storage for optimizing system performance beyond allowing for year-round use.</p> <p>Metal hydrides are metals that exothermically absorb and endothermically desorb hydrogen. Since the temperature this reaction occurs at depends on the hydrogen pressure, hydrides can be used for energy storage at varying temperatures. System architecture for using metal hydrides with an HVAC system is developed. A thermodynamic model which combines a dynamic model of the hydride reactors with a static model of the HVAC system is used to calculate operating costs, compared to a conventional HVAC system, for different utility rates and locations. The payback period of the system is unacceptably high, due to the high initial cost of metal hydrides and the operating costs of compressing hydrogen to move it between hydride reactors.</p> <p>In addition to the metal hydride system model, a generalized model of a variable-temperature TES system is used to determine the potential cost savings from dynamically altering the storage temperature to achieve optimal cost savings. Dynamic tuning does result in cost savings but is most effective for storage tank sizes significantly smaller than the optimal tank size. An alternate system design where the storage tank is charged with the outlet flow from the house achieves larger cost savings even for the optimally-sized tanks. Payback periods calculated for optimal sizing show that year-round storage has a lower payback period than separate cold and heat storage if the year-round storage system is not more expensive than two separate storage tanks. </p>

Ce travail est axé vers la compréhension détaillée des propriétés de luminescence de composés de certains métaux lourds. La première partie de ce mémoire décrit la caractérisation spectroscopique d'un radical de type nitronyle nitroxyde, 2-(2-pyridinyl)-4,4,5,5-tétraméthyl-4,5-dihydro-1H-imidazolyl-1-oxyl-3-oxyde, abrégé (NIT2-Py), et de ses complexes avec les cations Tb(III), [Tb(hfac)3NIT2-Py], et Y(III), [Y(hfac)3NIT2-Py]. La variation de la température affecte les spectres de luminescence qui montrent de la structure vibronique résolue. Les maxima de ces transitions vibroniques se rapprochent au fur et à mesure que la température augmente. Ces variations des maxima en fonction de la température ne correspondent pas à des variations de fréquences vibrationnelles et sont de l'ordre de 200 cm-1 entre 80 K et 240 K. La variation de la température n'a pas d'influence significative sur la structure moléculaire, comme atteste la variation mineure des maxima des spectres Raman entre 80 K et 300 K. La comparaison des spectres expérimentaux à des spectres calculés montre que ces variations peuvent être reproduites par l'utilisation d'une combinaison de fréquences vibrationnelles. Le paramètre dont la variation est très significative est la résolution du spectre de luminescence, représentée par la largeur à mi-hauteur des transitions vibroniques qui forment le spectre de luminescence. La deuxième partie de ce mémoire décrit les propriétés de luminescence d'une série de complexes d’or(I). Elles sont comparées aux changements structuraux à pression et température variable. Les interactions aurophiles ont une grande influence sur la luminescence. La variation de la température et de la pression est une approche efficace pour varier la luminescence. Les effets observés dans les spectres d'émission de ces complexes dépendent des changements de structure induits par variation de la température et de la pression. Ces petites variations structurales mènent à des changements importants, à titre d'exemple à un déplacement du maximum de la bande de luminescence de 60 cm-1/ kbar vers les faibles énergies pour un des complexes de l'or(I) étudiés au cours de ce projet. / The overall goal of this work is to contribute to the understanding of luminescence properties of transition metal compounds. The first part of this thesis describes the spectroscopic characterization of a pyridine-substituted nitronyl nitroxyde radical 2-(2-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-3-oxide-1-oxyl abbreviated (NIT2-Py) and its complexes with Tb(III) and Y(III), [Tb(hfac)3NIT2-Py] and [Y(hfac)3NIT2-Py], respectively. Their luminescence spectrum show resolved vibronic structure and variations with temperature The energy difference between vibronic luminescence maxima decreases with increasing temperature. This decrease is on the order of 200 cm-1 between 80 K and 240 K and is not due to decreasing Raman frequencies. The variations of temperature do not have a significant influence on the molecular structures, as illustrated by the very small variation of Raman maxima between 80 K and 300 K. Luminescence spectra were calculated using the time dependent theory of spectroscopy. Calculated luminescence spectra show that the variations with temperature are reproduced by using specific combinations of experimental frequencies and by adjusting the width of the vibronic transitions, determining the resolution of the luminescence spectrum. The second part of the thesis describes the luminescence spectroscopic properties of a series of trimetallic gold(I) complexes at variable temperature and pressure. Aurophilic interactions are very important for these compounds and influence the luminescence spectra. The spectroscopic features are compared to structural changes at variable temperature and pressure. Even small changes in structure lead to significant changes in luminescence, for example a shift of the maximum of the luminescence band by 60 cm-1/ kbar to lower energy for one of the gold(I) complexes studied.

Ce travail est axé vers la compréhension détaillée des propriétés de luminescence de composés de certains métaux lourds. La première partie de ce mémoire décrit la caractérisation spectroscopique d'un radical de type nitronyle nitroxyde, 2-(2-pyridinyl)-4,4,5,5-tétraméthyl-4,5-dihydro-1H-imidazolyl-1-oxyl-3-oxyde, abrégé (NIT2-Py), et de ses complexes avec les cations Tb(III), [Tb(hfac)3NIT2-Py], et Y(III), [Y(hfac)3NIT2-Py]. La variation de la température affecte les spectres de luminescence qui montrent de la structure vibronique résolue. Les maxima de ces transitions vibroniques se rapprochent au fur et à mesure que la température augmente. Ces variations des maxima en fonction de la température ne correspondent pas à des variations de fréquences vibrationnelles et sont de l'ordre de 200 cm-1 entre 80 K et 240 K. La variation de la température n'a pas d'influence significative sur la structure moléculaire, comme atteste la variation mineure des maxima des spectres Raman entre 80 K et 300 K. La comparaison des spectres expérimentaux à des spectres calculés montre que ces variations peuvent être reproduites par l'utilisation d'une combinaison de fréquences vibrationnelles. Le paramètre dont la variation est très significative est la résolution du spectre de luminescence, représentée par la largeur à mi-hauteur des transitions vibroniques qui forment le spectre de luminescence. La deuxième partie de ce mémoire décrit les propriétés de luminescence d'une série de complexes d’or(I). Elles sont comparées aux changements structuraux à pression et température variable. Les interactions aurophiles ont une grande influence sur la luminescence. La variation de la température et de la pression est une approche efficace pour varier la luminescence. Les effets observés dans les spectres d'émission de ces complexes dépendent des changements de structure induits par variation de la température et de la pression. Ces petites variations structurales mènent à des changements importants, à titre d'exemple à un déplacement du maximum de la bande de luminescence de 60 cm-1/ kbar vers les faibles énergies pour un des complexes de l'or(I) étudiés au cours de ce projet. / The overall goal of this work is to contribute to the understanding of luminescence properties of transition metal compounds. The first part of this thesis describes the spectroscopic characterization of a pyridine-substituted nitronyl nitroxyde radical 2-(2-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-3-oxide-1-oxyl abbreviated (NIT2-Py) and its complexes with Tb(III) and Y(III), [Tb(hfac)3NIT2-Py] and [Y(hfac)3NIT2-Py], respectively. Their luminescence spectrum show resolved vibronic structure and variations with temperature The energy difference between vibronic luminescence maxima decreases with increasing temperature. This decrease is on the order of 200 cm-1 between 80 K and 240 K and is not due to decreasing Raman frequencies. The variations of temperature do not have a significant influence on the molecular structures, as illustrated by the very small variation of Raman maxima between 80 K and 300 K. Luminescence spectra were calculated using the time dependent theory of spectroscopy. Calculated luminescence spectra show that the variations with temperature are reproduced by using specific combinations of experimental frequencies and by adjusting the width of the vibronic transitions, determining the resolution of the luminescence spectrum. The second part of the thesis describes the luminescence spectroscopic properties of a series of trimetallic gold(I) complexes at variable temperature and pressure. Aurophilic interactions are very important for these compounds and influence the luminescence spectra. The spectroscopic features are compared to structural changes at variable temperature and pressure. Even small changes in structure lead to significant changes in luminescence, for example a shift of the maximum of the luminescence band by 60 cm-1/ kbar to lower energy for one of the gold(I) complexes studied.