Supramolecular approaches to cryorelaxors for biological NMR studies

• Main Author: Cuda, Francesco
• Other Authors: Grossel, Martin
• Published: University of Southampton 2010
• Subjects: 547.6; QD Chemistry
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.523555

The work reported in this thesis concerns the development of Cryorelaxors having potential applications in very low temperature NMR studies of biological materials. Two approaches have been explored, namely calixarene host-guest complexes incorporating rotationally labile methyl groups, and endohedral fullerene complexes. The first chapter provides an overview of the background of the project and of potential approaches to the problem of low temperature relaxation agents, particularly those based on supramolecular systems. The next chapter describes the preparation, characterization, and studies of the behaviour of calixarene complexes incorporating potentially freely rotating guests. Ten calixarene complexes have been prepared and characterised by X-ray structural studies and their relaxation behaviour has been investigated using a variety of techniques including MAS and Field Cycling NMR experiments and Inelastic Neutron Scattering spectroscopy. Crystallographically disordered methyl-group environments have been identified in a number of cases and their proton spin-lattice relaxation behaviour has been shown to be strongly dependent on the thermal history of the sample. NMR studies of samples of partially deuterated calixarene complexes reveal a systematic reduction in T1 at low temperatures with higher levels of deuteration of the system studied, the p-iso-propylcalix[4]arene (2:1) p-xylene complex has been shown to have the best relaxation properties. Synthetic strategies towards calixarene and fullerenes complexes bearing active biological anchors are also discussed. The third chapter describes an investigation of the Komatsu route to the endohedral fullerene complex H2@C60 and the structural characterization of one of the key intermediates in this process. The fourth chapter give a brief overview the results obtained and the final chapter details of the experimental work undertaken. Appendices are also included containing full details of the X-ray structural studies and mathematical models