Solid-state NMR techniques have been applied to the structure and dynamic characterisation of a range of phosphorus-containing compounds. Comparisons have been made within several series of compounds as well as studies of individual molecules with interesting NMR properties, whether dynamic, structural or magnetic. Spectral features such as shielding anisotropy, the high sensitivity of phosphorus and its large chemical shift range are extensively utilised in this work. Triple-channel, fluorine-observe and variable-temperature spectrometer facilities at different magnetic field strengths have been explored to give as much complementary information as possible. For both chlorinated and fluorinated diazadiphosphetidines, motional properties have been examined and the indirect spin-spin and dipolar interactions, together with shielding have been studied. Spectra from the NMR-active nuclei in these cyclic dimers have been used to compare effects of differing substituents on NMR properties. The bowl-shaped' molecules, calix[4] resorcinols with phosphorus functionality modifying the upper rim, constitute the other major group of compounds studied. These are of interest in inclusion chemistry. As well as simple one-dimensional NMR characterisation of solid-state calix[4]resorcinol compounds, interesting two-dimensional correlation results have helped with the assignment and conformational conclusions. A qualitative and quantitative study of a co-crystal of triphenylphosphine oxide and phenol was made to establish the nature of the disorder observed, but undefined, in an X-ray structural investigation of the hydrogen-bonded network. Complementary NMR techniques were used to extend the temperature range over which the rate of any motion can be characterised. Bandshape analysis, Tip measurement and selective polarisation inversion experiments have proved to be accurate in different regions of a variable temperature study. Other compounds explored were those which showed interesting solid-state NMR results, for example, the complexities of cross-polarisation dynamics between two abundant spins in inorganic phosphates, and compounds with potential solid-state applications. These include (i) phosphorus-containing compounds with chlorine and fluorinated aromatic substituents and (ii) complexes with transition metals. Comparison with single-crystal and powder X-ray diffraction has also been exploited. In some cases, data have been produced, and in others the applicability of a theoretical approach has led to other conclusions.

No description available.

Following an introduction on calixarene chemistry and their metal-ion complexes including some of their applications, the aims of the work are described. Thus, this thesis concerns an investigation on the solution properties of p-tert-butylcalix(4)arene tetraketone derivatives and their metal-ion complexes. Macrocycles such as 5,11,17,23-tetra-terf-butyl-25,26,27,28-tetra(benzoyl)methoxycalix(4)arene and 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetra(acetoyl)methoxy calix(4) arene are structurally (1H NMR and X-ray crystallography) and thermodynamically (solubility, calorimetry) characterised. The complexing abilities of these ligands for metal cations are investigated by a variety of techniques. To obtain information about the active sites of the ligand in its interaction with metal cations, 1H NMR studies were performed. Conductance and UV spectrophotometric measurements were used to establish the composition of the metal-ion complexes in dipolar aprotic media. Potentiometric and calorimetric measurements were carried out to derive the thermodynamic parameters of complexation of p-tert-butylcalix(4)arene tetramethyl ketone and metal-ions in acetonitrile at 298.15 K. This ligand shows the highest affinity for calcium amongst all the investigated metal cations. The medium effect on the complexation process involving metal cations and calixarene derivatives is quantitatively assessed using as an illustrative example the interaction of p-terf-butylcalix(4)arene tetraphenyl ketone and the sodium cation. Thus, detailed thermodynamics of this system is reported taking into account the solution properties of the reactants and the product in various solvents and in acetonitrile / N,N- dimethylformamide solvent mixtures. In these mixtures a linear relationship is observed between the stability constant and the solvent composition. The strength of complexation decreases from MeCN through the mixtures to pure DMF. However in terms of the enthalpy of complexation, only small variations are found between the values in different mixtures. The complexation and solution data for the reactants and the product are used to calculate the standard co-ordination enthalpies as a means of checking the reliability of the data. Based on stability constant data, two metal-ion complexes were isolated. X-ray diffraction data shows that p-tert-butylcalix(4)arene tetraphenyl ketone hosts the sodium cation in its hydrophilic cavity where it is coordinated by four ethereal oxygen atoms and four carbonyl oxygen atoms. One molecule of acetonitrile is found in the hydrophobic cavity of the ligand with the CH3 end pointing inward. The crystal structure of the cadmium and acetonitrile p-tert-butylcalix(4)arene tetramethyl ketone complex shows that the metal ion is coordinated by four ethereal oxygen atoms of the ligand and only by three carbonyl oxygens. The eight coordination site is provided by the nitrogen atom of the molecule of acetonitrile which is present in the hydrophobic cavity of calixarene derivative with the CN end pointing inward. Conclusions and suggestions for further research in this area are given.

No description available.

A large variety of post-translational modifications can exist on the N-terminal tails of histone proteins H2A, H2B, H3 and H4. These have been of great interest as they have increasingly been shown to influence fundamental biological processes and human disease. Studying these modifications provides insight into their physiological functions and enables the search for potent small molecule inhibitors. In this thesis, new fluorescence-based supramolecular tools were developed and used to a) measure the binding of covalently modified peptide tails to a collection of synthetic receptors in neutral aqueous solution and b) monitor an enzyme that installs a post-translational modification (PTM) in real-time. Two different approaches were used to detect binding in these systems. The first was the optimization of a competitive dye-displacement method that relies on the ability of the cationic dye lucigenin. The second was the synthesis of novel conjugates that consist of calixarenes covalently appended with multiple different fluorescent dyes. / Graduate / 0487 / 0490 / 0491

The first part of this thesis reports the synthesis of five calixarene molecules and their incorporation into ISEs as thallium(I) selective ionophores for use in clinical and environmental analysis. Four calix[4]arene molecules were successfully synthesized. Two were isolated in the cone conformation with iso-propyl groups attached to the lower rim. The other two were in the 1,3-alternate conformation with allyl groups attached to the phenolic oxygen. The final calixarene synthesized was a calix[6]arene that was partially substituted with iso-propyl groups on the lower rim. The parallel orientation of the aromatic rings was confirmed using single crystal X-ray structure determination. Nuclear Magnetic Resonance (NMR) complexation studies were conducted on the four calix[4]arene derivatives and showed that thallium binds within the aromatic cavity, and that the complexation/decomplexation kinetics and molecule flexibility are affected by the incorporated ion and the attached groups on the calixarene. Once the binding characteristics of the synthesized calixarenes had been examined they were then incorporated into plasticized PVC together with an ion-exchanger to make ISEs capable of determining thallium activities in solutions. Three calixarenes were successfully incorporated into the membranes and produced Nernstian responses over the concentration range 10-2-10-6 M TlNO3. The lower detection limit of the above electrodes lies in the micro-molar range, which is a common characteristic of the experimental setup used. Since the electrodes behaved ideally with respect to thallium(I), it was then decided to test the complex formation constants and selectivities of the three ionophores. / The complex formation constant (Log βILn) of two of the calixarene derivatives with thallium(I) were determined to be 6.44 and 5.85 respectively, through the use of the sandwich membrane technique. The selectivities were measured with a new protocol, whereby the electrode had not previously come into contact with the primary ion. This helps to remove ion fluxes of the primary ion and subsequent biased selectivity coefficient of highly discriminated ions. The three ionophores showed excellent selectivity against Zn2+, Ca2+, Ba2+, Cu2+, Cd2+ and Al3+, and moderate selectivity against Pb2+, Li+, Na+, H+, K+, NH4+ and Cs+. Silver was the only common high interferent in all three ionophores tested. As the detection limits of current thallium(I) ISEs in the literature would be insufficient in practical samples, attempts were made to lower the detection limits of the above ISEs with the application of relatively new experimental techniques. The lower detection limit of the three ISEs was successfully lowered by an order of magnitude from the original values through the use of an EDTA-buffered inner filling solution. The lowest achieved detection limit was obtained with the iso-propyl functionalized calix[4]arene, which reached a value of 8.32 nM (IUPAC definition). / The second part of the thesis investigated the incorporation of one of the calixarenes into a solid-contact ISE (SC-ISEs), which are seen as the future in this field due to their potential for miniaturisation and use in lab-on-a-chip applications. Four different solid-contact designs were tested to evaluate which was the best to pursue for future testing. The chosen calixarene was successfully incorporated into all four designs with Nernstian responses recorded in each case. The best response was recorded for an electrode which had a solid gold substrate, poly(3-octylthiophene) (POT) intermediate layer and a methyl methacrylate/decyl methacrylate (MMA-DMA) co-polymer membrane. This electrode exhibited a slope of 58.4 mV decade-1 and a lower detection limit of 30.2 nM. The other three solid-contact electrodes, which consisted of a graphite contact, a plasticised PVC membrane on a gold substrate, and a plasticized PVC membrane on a gold substrate with a polypyrrole intermediate layer, exhibited detection limits that were inferior to the MMA-DMA/POT SC-ISE. Further tests were used to assess one of the main problems associated with SC-ISEs, being the presence of water layers of droplets between the membrane and the solid substrate. Potential tests, electrochemical impedance spectroscopy, small angle neutron scattering and the electrode’s reactivity to changes in the concentration of dissolved oxygen were used to study water uptake and the concomitant formation of water layers in solid-contact ISEs. Water was confirmed at the surface of the membrane that consisted only of the membrane and gold substrate, but was not confirmed for the other three electrode designs.

This thesis describes the synthesis and characterisation of phosphonium aryloxides, amides and phosphides. These compounds have been formed via the deprotonation of organic acids [of the type ROH, and R(_2)X, where X = NH, PH, R = aryl group] by basic phosphonium ylidic species [R(_3)PX, X = CH(_2,) C(Me)H, C(Ph)H, NH] in mixtures of hydrocarbon (toluene) and/or polar (acetonitrile, thf) solvents. All of these compounds contain both acidic CHs and 'naked' anions which promote extensive hydrogen bonding. Chapter 1 provides an outline of the fields of ylidic chemistry and hydrogen bonding. In Chapter 2, general experimental methods are described. Chapter 3 records all experimental results pertaining to this work. Here preparation of starting materials is documented, followed by an account of the synthesis and characterisation of twenty-three compounds. For all compounds melting point measurements, (^1)H NMR, (^31)P NMR, infrared spectra, and elemental analysis are recorded. Discussion of these results is documented in Chapters 4 to 7. Where possible, solid-state structures for compounds obtained by single crystal X-ray diffraction (nineteen structures) and single crystal neutron diffraction (two structures) are included. Chapter 4 discusses simple phosphonium aryloxide salts, while Chapter 5 is concerned with related phosphonium amides and phosphides. Chapter 6 deals with an extension of this work involving multifiinctional organic acids. Finally, Chapter 7 discusses unexpected results resulting from the work described in Chapter 6.

This thesis presents investigations related to interactions of chelating ligands (macrocyclic and acyclic) with neutral and ionic species in solution. Following a brief introduction on coordination chemistry, each topic is presented separately in three chapters. In Chapter I, thermodynamic studies on drug cyclodextrin interactions in water and in chloroform at 298.15 K are discussed in relation to the effect of the macrocycle on the transfer of N1-substituted sulphonamides from water to chloroform. It is concluded that the transfer of the drug in this solvent system is thermodynamically more favoured in the absence than in the presence of cyclodextrin. Chapter II concerns thermodynamic aspects on calixarenes and their ester derivatives. As far as calixarenes are concerned, thermodynamic parameters of complexation of tert-butylamine and p-tert-butylcalix[4]arene in benzonitrile suggest that two processes are involved; the formation of the adduct followed by that of an endo-calix complex. The interaction of alkyl-p-tert-butylcalix[4]arene tetraethanoates with alkali-metal cations in acetonitrile and in benzonitrile at 298.15 K was studied by titration calorimetry. The limitation of this technique to derive stability constant data for highly stable complexes led to the development of a double competitive potentiometric method. Thermodynamic data are discussed in terms of the solvation of host, guest and resulting complex in these solvents. Chapter III discusses synthesis, characterisation and acid-base properties of ethylenedinitrilo-N,N1-diacetic-N,N1-bis(1-phenylethylacetamido) acid (edtamba) and ethylenedinitrilo-N,N1-diacetic-N,N'bis(pyridylacetamidoacetamioe)acid (edtapa) This is followed by the thermodynamics of complexation of these ligands with metal cations (Pb(II), Cd(II), Cu(II), Ni(II), Zn(II) and Co(II) in water at 298.15 K. These results show that unlike EDTA, edtamba and edtapa do not interact selectively with these cations as a result of a remarkable enthalpy-entropy compensation effect. Computer programs written during the course of these investigations are appended.

Following an overview in the field of calixarene chemistry given in the introduction, this thesis reports, i) The synthesis of p-text-butylcalix[4]arene tetraacetamides, thiophosphates and derivatives containing mixed functional groups and the characterisation by IR, NMR and microanalysis. ii) The solution thermodynamic of p-tert-butylcalix[4]arene tetradiisopropylacetamide and the transfer thermodynamics of this ligand from acetonitrile to various solvents. iii) Spectrophotometric, potentiometric and calorimetric studies on the interaction of p-tert-butylcalix[4]arene tetraacetamides and metal cations in butan-l-ol and in water saturated butan-l-ol at 298.15 K. Metal-ion complexes of p-tert-butylcalix[4]arene tetradiisopropylacetamide were isolated and characterised by IR, NMR and spectroscopy and microanalysis. In butan-l-ol, the selectivity of this ligand for metal cations follows the sequence Na+ > Cd2+ > Pb2+ > Zn2+ > Ag+. However, this sequence is altered in the water saturated solvent to an extent that the strong complexation observed for this ligand and zinc(II) in butan-l-ol is non-existent in the water saturated solvent. Using complexation data in conjunction with solution data of the host, the guest and the resulting complex, enthalpies of coordination (referred to the process which reactants and the product in the solid state) were calculated. iv) Extraction experiments in the water-butan-l-ol solvent system at 298.15 K in the presence of p-tert-butylcalix[4]arene tetradiisopropylacetamide were performed. The higher extraction of lead(II) relative to other metal cations from the aqueous solution to the organic phase in the presence of the ligand at low hydrogen-ion concentration is demonstrated. The extraction of radioactive lead(II) by the same ligand was investigated as a function of i) the pH of the aqueous phase ii) the ligand concentration in the organic phase. vi) A new polymeric material was obtained by attaching the ligand to the polymer. Final conclusions are drawn and suggestions for further work in this area are given.

No description available.