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The following thesis discusses the combined use of electron paramagnetic resonance (EPR) spectroscopy, electron nuclear double resonance (ENDOR) spectroscopy and density functional theory (DFT) calculations to investigate a number of transition metal catalyst systems the binding of epoxide molecules by a vanadyl analogue of the catalytically important metallosalen class of compounds the binding of a chiral aryl amine by a copper salen complex and the incorporation of copper(II) ions in aluminophosphate materials. Two classes of epoxide selectivity by a vanadyl salen derivative are presented here, the discrimination of the geometric isomers of 2,3-epoxybutane, cw-2,3-epoxybutane and /ra 5-2,3-epoxybutane by Ar,Ar'-bis(3,5-di-tert-butylsalicylidene)-l,2-diaminocyclohexa- ne-vanadium(IV) oxide ( VO(l) ) 1 and the stereoselectivity of epoxypropane, 1,2- epoxybutane, chloromethyloxirane and fluoromethyloxirane by VO(l) . In both cases it is shown that hydrogen-bonding interactions, including interactions between the epoxide oxygen atom and a hydrogen atom bonded to a stereocentre carbon atom of the complex are important in determining the binding mode, thus implicating the given stereocentre carbon atom in the transfer of chirality. In the geometric isomerism of 2,3-epoxybutane, steric arguments regarding the obstruction caused by the methyl groups made on the basis of the DFT structures explain the selectivity observed in the EPR/ENDOR spectra. In the chiral selectivity of the other epoxides, more complicated reasoning, based on tripodal weak hydrogen-bonding configurations involving the hydrogen atoms of the epoxide ring and the oxygen atoms of the complex ligand is required to fully explain the selectivity observed, with different selectivity effects in the more electronegative halogenated epoxides compared to the alkyl cases. The coordination of methyl benzyl amine to a series of analogues of Cu(l) with various levels of tert-butylation, to model the steric effects in this interaction is studied here using DFT methods to explain the coordination preference for heterochiral pairings observed in the EPR spectra. Reasoning based on the preference of each enantiomer of the MBA to become involved in % - n interaction with alternate benzene rings of the complex, along with a slightly increased crowding of one ring over the other caused by the same hydrogen atom as implicated in determining selectivity in the epoxide study (above), namely the hydrogen atom bonded to one of the stereocentre C atoms, explains the selectivity observed in terms of n n interactions, also identifying the role of the stereocentre C atoms in conferring chirality. In combination, these studies demonstrate the importance of weak interactions, namely hydrogen-bonding andn-n interactions, in determining the binding configurations, and by extension the selectivity of these transition metal complexes. They also describe the nature of the involvement of the stereocentres of the complex in directing that selectivity, delineating a link between the chirality of the complex and that of the bound species in each case. The importance of using both EPR/ENDOR and DFT techniques in such studies, namely of explaining selectivity observed by EPR in terms of ENDOR and DFT derived geometry parameters is further explored in this thesis in the development of genetic algorithm routines to modify DFT-derived structures, by means of the ENDOR spectra simulated with the hyperfine parameters derived from a simple point-dipole model applied to the coordinates. The application of this process to a sample axial system, VO(acac)2, demonstrates the effectiveness of exploiting the complementary nature of the ENDOR and DFT techniques in this manner. Finally, a second copper study is reported here. This example is of a microporous aluminophosphate material, and concerns the incorporation of Cu11 ions into framework vs. extra-framework sites, a subject of some controversy. Here, evidence is presented for the ability of copper to distort the tetrahedral lattice into a distorted octahedral and a square- based pyramidal environment in which one or both of the remaining coordination sites is/are occupied by the templating molecules and water molecules, without rendering the lattice unstable, arguing in favour of framework site incorporation.

Temperature and soil moisture are two of the most important parameters that affect a wide variety of ecological, geochemical, and hydrological processes in the shallow subsurface. By understanding and exploiting the coupled physics of heat transport and water content, temperature can be used as a proxy for soil moisture measurement in variably saturated conditions. This dissertation develops and refines novel temperature-based hydrogeophysical methods while expanding the applicability of heat-tracing to unsaturated conditions. To this end, a comprehensive review of existing research into heat-tracing in the vadose zone is presented. Thermo-hydraulic physics of vadose zone porous media, field-based and numerical methods, thermal regime studies, and both active and passive heat tracing methods are reviewed. Several knowledge gaps and opportunities that exist in its application to unsaturated conditions are identified. Two novel methodologies related to heat-tracing are developed. The first, a matrix method, delineates contrasting subsurface conditions and compares existing saturated zone velocity heat-tracing methods. The method is applied to both coiled fibre-optic distributed temperature sensing (FO-DTS) measurements and finite element (FE) model output. These are used to illustrate the thermal signature of common subsurface conditions as well as to assess the reciprocal relationship between sensor spacing and noise in water flux estimates. Next, a semi-analytical vadose zone heat tracing model and associated methodology, based on the full advection-conduction-dispersion equation coupled with an established empirical thermal conductivity-saturation model, are derived for the calculation of soil moisture profiles. The method exploits measurements of ambient temperature profiles in the subsurface and is shown to predict soil moisture profiles accurately under certain limits on percolation rate or saturation level. Finally, the subsurface thermal regime of an estuarine inter-tidal zone is investigated. In this highly transient and variably saturated zone, analytical heat-tracing methods are not applicable and common electromagnetic probes can fail due to high salinity. Measured FO-DTS temperature profiles and a fully coupled thermo-hydraulic FE model are used to evaluate the relative propagation depths of tidal and diurnal signals and to quantify the importance of variably unsaturated conditions for heat transport.