The development of synthetic routes to thioether macrocycles is reviewed, with emphasis on innovative improvements.

We have investigated the coordination chemistry of the tripodal alcohols H₃thme, H₃tmp, Br-mpH₃, H₄peol and their analogues aepH₂and ampH₂, with a particular focus on Mn. In combination with other bridging/chelating ligands such as carboxylates or β-diketonates a plethora of polymetallic clusters whose topologies are based on shared triangular Mn₃ units have been synthesised. 25 New complexes are reported. These are: a family of seven “rod-like” structures; a family of three “wheel-like” structures; two supertedrahedra; a family of deca- and tetradecametallic “planar discs”; edge-sharing bioctahedra and a bioctahedral polymer.

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No description available.

The potential of two unusual methods of zeolite synthesis has been investigated; firstly the synthesis of zeolites in the form of pseudomorphic aggregates and secondly zeolite synthesis by soxhlet extraction of silica. Pseudomorphic particles of silicalite-1 and ZSM-5 have been synthesised in stirred autoclaves and characterised by a variety of techniques including X-ray powder diffraction, scanning electron microscopy and thermal analysis. Some ZSM-5 samples have been further characterised by N<SUB>2</SUB> sorption, mercury porosimetry and pyridine desorption and have also been tested catalytically, using the isomerisation of a meta-xylene feedstock as the test reaction. Further investigations into pseudomorphic synthesis have included the use of different types of reactor and the way in which this affects the products; and attempts to synthesise a variety of zeolites and silica molecular sieves in pseudomorphic form. Soxhlet extraction of silica was used to enable zeolite synthesis from an essentially monomeric silica source. Investigations into the potential advantages of this synthesis techniques have been carried out in both aqueous and organic-based reaction mixtures.

A novel method for the electrochemical synthesis of titanium nitride thin films and powders has been developed. This involves the anodisation of an oxide-free titanium electrode in a solution of potassium amide in liquid ammonia. The system is inherently free from carbon-, halide- and oxygen-containing contaminants. At -78°C and atmospheric pressure coherent films of titanium nitride are produced, which adhere very well to the substrate. The amount of charge passed may be used to control the thickness of the resulting film. The films have been characterised by electrochemical studies, scanning electron microscopy with energy dispersive x-ray spectroscopy, Raman spectroscopy, magnetic and reflectance measurements, microhardness testing and x-ray photoelectron spectroscopy. A thick-walled pressure cell has been constructed in order to contain liquid ammonia at 25°C at a pressure of 10 bar. Operation under these conditions favours the synthesis of nano-particulate powders. The powders have been characterised by scanning electron microscopy with energy dispersive x-ray spectroscopy, Raman spectroscopy, transmission electron microscopy and electron diffraction. The method has also been extended to the synthesis of molybdenum, tungsten, tantalum, aluminium and iron nitrides. A new route for the electrodeposition of titanium metal has also been designed. The precursor K₃[Ti(SCN)₆] in acetonitrile solution or dissolved in a novel 1-butyl-3-methylimidazolium thiocyanate 'ionic liquid', has been used to deposit titanium on copper or iron under ambient conditions. The films have been characterised by electrochemical studies and SEM-EDXS.

The complexes [OsCl<SUB>6</SUB>-<SUB>n</SUB>PY<SUB>n</SUB>]<SUP>(n-y)</SUP>+ , where n = 0, 1, 2(<i>trans</i>), 2(<i>cis</i>), 3(<i>mer</i>), 4(<i>trans</i>), 5 and 6, and y varies between 2 and 4, have been synthesised <i>via</i> redox induced substitution reactions of [OsCl<SUB>6</SUB>]<SUP>2-</SUP>. The series has been fully characterised using electrochemical and spectroelectrochemical techniques. Several key members namely <i>trans</i>-[TPA] [OsCl<SUB>4</SUB>py<SUB>2</SUB>], <i>cis</i>-[OsCl<SUB>4</SUB>py<SUB>2</SUB>], <i>trans</i>-[OsCl<SUB>2</SUB>py<SUB>4</SUB>] and [Ospy<SUB>6</SUB>]9BF<SUB>4</SUB>]<SUB>2</SUB>, have also been examined by X-ray crystallography. Voltammetric data derived from these complexes has been compared to PROB*LEM/2 values predicted by two recent models. PROB*LEM/2 values for the series [OsCl<SUB>6</SUB>-<SUB>nPYn</SUB>]<SUP>(n-y)</SUP>, where y = 3 and 2, are dependent on n but independent of the isomeric form adopted. However, we propose that PROB*LEM/2 values for the series [OsCl<SUB>6-nPYn</SUB>]<SUP>(n-4</SUP>)<SUP></SUP>+ are dependent not only on n and the isomeric form, but also on the precise coordination mode of the pyridine ligands. As a comparison some members of the series [OsBr<SUB>6-n</SUB>py<SUB>n</SUB>]<SUP>(n-y)</SUP>+ and [OsI<SUB>6-n</SUB>py<SUB>n</SUB>]<SUP>(n-y)</SUP>+ , and complexes [TBA][OsCl<SUB>5</SUB>L], where L = PhCn, 2, 3 and 4-cyanopyridine and 3,4-dicyanopyridine, have also been synthesised and characterised using the methods described above. Kinetic studies on the reduction of [OsCl<SUB>6</SUB>]<SUP>2-</SUP> in the presence of pyridine, dmf and CO suggest Cl<SUP>-</SUP> loss is the rate determining step for this process.

In this thesis two experimental antiferromagnets with the particularly interesting lattice resembling the kagomé basket-weaving pattern, are studied. The kagomé topology frustrates the <i>classical </i>antiferromagnetic Néel state, the commonly encountered magnetic groundstate in transition-metal compounds. Extensive theoretical work has shown that in particular the <i>S</i> = 1/2 kagomé antiferromagnet should not show any symmetry-breaking transition to a classical long-range-ordered state. Hence, experimental realisations of this system should in theory allow a unique insight into properties of the symmetrical quantum-mechanical magnetic groundstate. Recently a viable experimental realisation of the <i>S</i> = 1/2 kagomé antiferromagnet has been discovered, the <i>x</i> = 1 phase of zinc-paratacamite Zn_xCu_(4-x)(OH)₆Cl₂. Here samples of stoichiometry 0.15 ≤ <i>x</i> ≤ 1 were synthesised and characterised. Using muon-spin relaxation spectroscopy on these samples, it was found that for <i>x</i> &gt; 0.6 the spins do not freeze, even at 50 mK. From neutron powder diffraction for <i>x</i> = 1 and heat capacity measurements on zinc paratacamite with 0.5 ≤ <i>x</i> ≤ 1, it was found that ~6% antisite disorder is present in the <i>x </i>= 1 phase, and that samples with Zn stoichiometry 0.8 ≤ <i>x</i> ≤ 1 model the <i>S</i> = 1/2 kagomé antiferromagnet equally well. No quantum critical phase transition to a quantum spin liquid is found. Instead, the groundstate of this model system is magnetic even for <i>x</i> > 0,8. The field dependence of the heat capacity provides additional evidence that the total magnetic quantum number <i>S</i>_totis not a conserved quantity, despite the fact that no symmetry breaking transition occurs in the magnetic degrees of freedom. In a polarised X-ray spectroscopy experiment on synthesised single crystals of the classical (<i>S</i> = 5/2) kagomé antiferromagnet iron jarosite KFe₃ (SO₄)₂(OH)₆, it is shown that the Fe³⁺ ion with a ⁶<i>S</i> free-ion configuration can acquire a large orbital angular momentum in the solid state. The high-resolution spectra are reproduced in excellent detail.

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The work within this thesis is concerned with several different magnetic systems all involving materials that are rich in sulphur and are thus predicted to have strong magnetic coupling through these sulphur atoms. Firstly, a range of molecular salt materials of [dithiazolyl]_x[M(dithiolene)₂] were synthesised and their magnetic behaviour analysed. Dithiolene complex salts of [BDTA]⁺ [2]-[6] were found to have a mainly mixed anion-cation stacked structural motif and show a number of interesting magnetic properties, such as an almost perfect one dimensional antiferromagnetic chain system ([BDTA]₂[Cu(mnt)₂ [2], as well as the conducting charge transfer salt [BDTA][Ni(dmit)₂]₂ [3] that is the first example of the [BDTA]⁺ cation behaving as an open shell cation. The [BDTA]₂[Fe(tdas)₂Cl] salt [5] has the first mixed stacking structural motif of this anion (as it usually dimerises) and this material was found to be paramagnetic. The paramagnetic radical dithiazolyl cation [BBDTA]⁺ was also co-precipitated with dithiolene complexes to create magnetic salts [11]-[15]. These all showed mixed magnetic effects with some unusual magnetic interactions occurring. [BDTA]⁺ was also co-crystallised with MC1₄^2- anions to form molecular materials containing two dimensional magnetic structure with a square lattice magnetic pathway. This magnetic mechanism provides ideal materials for the study of ground state quantum magnetic effects that are thought to be related to the fundamental mechanism of superconductivity. This work also contains the study of the non interacting magnetic molecular thiophosphine complexes of the form [M((SPR¹R²)₂N)₂] (M = Mn, Co, Ni, R¹ = R² = Ph, ⁱPr and R¹=Ph and R²=ⁱPr) which behave as simple paramagnets ([16]-[24]). All M = Mn and Co complexes were found to be simple paramagnetic materials with a strong ligand field splitting.