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A model complex of dysprosium, Dy(N2O2C7H11)3 (Dy2) was built by successive capping of the peripheral aromatic ring of a butterfly-shaped dysprosium complex of a schiff base ligand, Dy(N4O5C14H11)3 (Dy1). The structural modifications were carried out in order to investigate the effect of the chemical surroundings like aromaticity on the observation of single-molecule magnet (SMM) behaviour in a lanthanide-based complex (Dy1). Experimental techniques were combined with theoretical tools to investigate the dynamics of magnetic properties of the Dy1 and compared with the theoretical results for Dy2 to gain insight on the contribution of covalency, crystal field effect and the role of aromaticity in stabilizing the excited magnetic levels of a single-molecule magnet. Dy1 showed frequency-dependent slow magnetic relaxation characteristics of a single-molecule magnet with and without applied dc field and a blocking temperature of about 8 K. The obtained results showed that despite f−electrons having weak interactions with ligand field, it is possible to tune the magnetic properties of lanthanide-based complexes using ring currents, control of covalency and peripheral ligand substitution. Furthermore, di-nuclear acetate bridged lanthanide complexes with two different structural motifs, Er1 = [Er(CH3COO)(CH3COO)2(H2O)2]2 · 4H2O and [Ln(CH3COO)(CH3COO)(CH3COO)(H2O)CH3COOH]2 · 2CH3COOH (Ln = Er (Er2), Y0.8Er0.2 (Er3)) were characterised. The solvent effects on the structure, electronic and magnetic properties were studied by experiments and theoretical methods. The tetraacetate-bridged erbium (Er2) showed a shorter intra-molecular Er - Er distance of 3.878 Å compared to the doubly-bridged counterpart (Er1) with Er - Er intra-molecular separation of 4.152 Å. Er2 exhibited weak ferromagnetic ordering at very low temperature in the dc magnetic measurement due to the short proximity of the Er centres. A field-induced slow magnetic relaxation for spin reversal characteristics of single-molecule magnet behaviour with relaxation dynamics dominated by Orbach process was observed for Er2. Er1 showed very fast slow magnetic relaxation dominated by quantum tunnelling of magnetization as evidenced in the Cole-Cole plot and the observed plateau in the susceptibility curve. The role of inter-molecular interactions between Er centres was investigated using yttrium diluted sample (Er3). The enhanced magnetic property of Er2 and Er3 over Er1 is attributed to the structural changes accompanying the choice of synthetic solvents used as well as the stronger interactions between Er and oxygen donor atoms of the acetate/acetic acid over that of water molecule as ligands. The present study presents an interesting result on solvent effects in the design of single-molecule magnets. In addition to the peripheral, aromatic, solvent effect and accompanying lanthanide-lanthanide coupling investigated, the role of hetero-metallic Pd-Ln bonding interaction was investigated using a set of tetranuclear acetate-bridged palladium-lanthanide complexes of the formula [Pd2Ln2(H2O)2(AcO)10] · 2AcOH (AcO = CH3COO- , Ln = Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm and Yb) by theoretical means and compared with experimental results for the lanthanide series to establish an interesting alternating trend in the observation of slow magnetic relaxation between Kramers and non-Kramers ions along the series. The role of axial perturbation, electron-cloud distortion and utility of metal as a ligand to upset the electronic properties of lanthanide complexes and their implication to the observation of slow magnetic relaxation were investigated. Results showed that transition metal-lanthanide bonding interaction presents a unique way to control the ligand field of lanthanide at varying degrees while confirming the role of rigidity in SMM design.

Dispersing co-crystals in a polymeric carrier may improve their physicochemical properties such as dissolution rate and solubility. Additionally co-crystal stability may be enhanced. However, such dispersions have been little investigated to date. This study focuses on the feasibility of dispersing co-crystals in a polymeric carrier and theoretical calculations to predict their stability. Acetone/chloroform, ethanol/water, and acetonitrile were used to load and grow co-crystals in a HPMCAS film. Caffeine-malonic acid and ibuprofennicotinamide co-crystals were prepared using solvent evaporation method. The interactions between each of the co-crystals components and their mixtures with the polymer were studied. A solvent evaporation approach was used to incorporate each compound, a mixture, and co-crystals into HPMCAS films. Differential scanning calorimetry data revealed a higher affinity of the polymer to acidic compounds than their basic counterparts as noticed by the depression of the glass transition temperature (Tg). Moreover, the same drug loading produced films with different Tgs when different solvents were used. Solubility parameter values (SP) of the solvents were employed to predict that effect on the depression of polymer Tg with relative success. SP values were more successful in predicting the preferential affinity of two acidic compounds to interact with the polymer. This was confirmed using binary mixtures of naproxen, flurbiprofen, malonic acid, and ibuprofen. On the other hand, dispersing basic compounds such as caffeine or nicotinamide with malonic acid in HPMCAS film revealed the growth of co-crystals. A dissolution study showed that the average release of caffeine from films containing caffeine-malonic acid was not significantly different to that of films containing similar caffeine concentration. The stability of the caffeine-malonic acid co-crystals in HPMC-AS was prolonged to 8 weeks at 95% relative humidity and 45°C. The theory developed in this project, that an acidic drug with a SP value closer to the polymer will dominate the interaction process and prevent the majority of the other material from interacting with the polymer, may have utility in designing co-crystal systems in polymeric vehicles

Energy conversion using renewable biomass has significant environmental impact. To acquire high value products using preliminary processed biomass, considerable amount of upgrading reactions has been conducted in liquid-phase conditions. Addition of solvents could interact with all component within reaction system. In order to influence heterogeneous catalytic reactions, solvents have to affect the kinetically relevant steps such as adsorption, surface reaction, and desorption. The following chapters investigate kinetics and solvent effects for biomass conversion. In Chapter 4, cyclohexene hydrogenation has been carried out over 0.25 wt.% Pd/α-Al2O3 in heptane, methylcyclohexane and decalin with a wide range of reaction conditions, from 30 psi to 600 psi of hydrogen pressure under 40 °C – 100 °C. Those inert solvents demonstrate competitive adsorption with reactants cyclohexene and lead to its decrease in surface coverage. Decalin competes the strongest and results the lowest hydrogenation rate followed by methylcyclohexane and then heptane. Heptane illustrates negligible surface competitive adsorption. Additionally, the non-ideality of reaction mixtures also alters the surface concentration of the solvent molecules compared to the bulk phase. Four kinetic models have been established based on different surface scenarios, and the cyclohexene hydrogenation has been found to be the first hydrogenation as the rate-determining step with cyclohexene and hydrogen absorbed on different Pd sites. Combined with statistical thermodynamic analysis, surface cyclohexene and hydrogen retain a certain amount of entropy based on their degree of freedom(DOF) of translation, rotation and vibration modes. ∆Sads for cyclohexene is -143 ± 19 J/mol·K, which loses around 2/3 of total entropy of its liquid state. Hydrogen losses more entropy upon adsorption and ∆Sads is -108 ± 12 J/mol·K. Meanwhile, heat of adsorption decreases with surface coverage. ∆Hads for cyclohexene on a clean Pd surface is -75 ± 14 kJ/mol, while the ∆Hads for hydrogen is -41 ± 7 kJ/mol. On a fully covered Pd surface, ∆Hads for cyclohexene becomes -53 kJ/mol, while ∆Hads for hydrogen reduces to -33 kJ/mol. In Chapter 5, the protic solvent, water, participates in the kinetically relevant step, surface reaction step, and influences the reaction rate and product distributions. Furfural hydrogenation in cyclohexane and water over 3% Pd/α-Al2O3 presents distinctive reactivity and product distribution. In the presence of water, hydrogenation of the carbonyl group of furfural is favored and therefore furfuryl alcohol is the main product. While the furanyl ring hydrogenation is favored in solvent cyclohexane and the reactivity in cyclohexane is much less. DFT calculations demonstrate that water stabilizes the intermediate and final product significantly by forming hydrogen bonds and provides an alternative hydrogenation pathway through water H-shuttling mechanism. Water-assist hydrogenation decreases the overall energy at the transition state from 46 kJ/mol to -7 kJ/mol. Kinetic studies in water and cyclohexane further unveil that reaction orders with respect of H2 pressure also differ. 0.8th order has been found when using water, which indicates the second hydrogenation step is the rate-determining step. 0.3th order in cyclohexane manifests the first hydrogenation step is the rate-determining step. The kinetic results are consistent with DFT calculations. When water shuttles the surface H proton to the oxygen of the carbonyl group through the H-bonding networks, the energy at the transition state for this step decreases from 46 kJ/mol to -16 kJ/mol, making the second hydrogenation of the carbon the rate-determining step. In Chapter 6, water serves as a solvent and the critical reactant that converts surface species to desired products. Aqueous phase reforming (APR) of ethanol over various Pt and Ru catalysts have been carried out in ethanol water mixture. Upon adsorption, ethanol decomposes by sequential dehydrogenation starting from Cα followed by dehydrogenation on Cβ until surface ketene CH2CO species are achieved. The C-C cleavage happens afterwards and surface CO species then react with water to produce more H2 and CO2 through the water-gas-shift (WGS) reaction. The presence of water drives the equilibrium of WGS reaction and removes the surface CO species. Therefore, negligible amount of CO has been detected in products. Serious Ru catalysts with different particle sizes have also been explored. Ru tends to favor the C-C cleavage compared to Pt. However, smaller Ru particles present strong adsorption of surface CO species and cause site poisoning. Larger Ru particles greatly favors the methanation reaction that consumes H2 in the product and CO, CO2 to form CH4. To optimize the catalyst, achieve desired product H2 and inhibit CH4 production, bimetallic Ru-Pt catalysts have been investigated. The co-impregnated 1%Ru-2%Pt/TiO2 displays the synergistic performance, with increased reaction rate for H2 production but lower rate for CH4.

Allostery is an intrinsic property of all globular proteins which governs the structural conformation of proteins to control their binding activity. The affiliation between supramolecular chemistry and host-guest complexity in Nature has inspired the development of artificial receptors to mimic enzymatic functions or emulate the complex binding behaviour, thus offering a better understanding of Nature’s host-guest cooperativity. As part of this work, bis-isophthalamide-crown-6 was synthesised as an ion-pair host. This host is a tetratopic ion-pairing host capable of simultaneous binding to two cations and two anions. The novel host was then used to study important aspects of cooperativity and allostery involving up to four different guest species. The structure and conformational changes due to allosteric effects upon binding to two cations was confirmed using single crystal X-ray analysis of the free host and the 1:2 host:calcium cation complex. In order to determine the complex binding cooperativity towards two cations and two anions, the 1H NMR binding data in four different solvent environments was systematically compared with several possible binding models, focusing on four different variants of the 1:2 binding model. The results demonstrate all three facets of cooperative binding; and most interestingly, the presence of calcium cation co-bound to the host allosterically switches “on” the binding of chloride anion in a competitive protic solvent system. Additional computational studies using DFT on the ion-pair host predicted the possible binding conformation for different host-guest complexes with calcium and chloride ions. The computed binding energies from this theoretical study were in good agreement with the experimental results in the cooperativity for both homotropic and heterotropic binding. In summary, using a combination of detailed structural analysis, binding studies and computational chemistry, this work has highlighted the intricate structural reorganisation within fairly simple small host molecules that accompany the cooperative and allosteric binding of multiple guests. The insight into the complexity of cooperative interactions revealed in this work on the multitopic ion-pair host, should provide a better understanding into cooperativity in natural systems, and can be used to design better cooperative supramolecular systems for information transfer and catalysis.

This study looked at effects of organic solvents dimethylsulfoxide, dimethylformamide and acetone at 0.01%, 0.05% and 0.1% concentration on germination and seedling development wetland plants. Even at 0.01% level, all solvents affected some aspect of seed germination or seedling growth. Acetone at 0.01% was least toxic. Root morphological characteristics were most sensitive compared to shoot morphological characteristics. This study also looked at bioconcentration patterns of antimicrobial compounds triclosan, triclocarban and methyl-triclosan in wetland plants exposed to Denton Municipal Waste Water Treatment Plant effluent. Bioconcentration patterns of antimicrobial compounds varied among species within groups as well as within organs of species. The highest triclocarban, triclosan and methyltriclosan concentration were in shoot of N. guadalupensis, root of N. lutea and in shoots of P. nodous respectively.