Dr John Dennis Project Abstracts
BSc Project Abstracts
Synthesis, purification and spectroscopic characterisation of isomer-pure fullerenes
Fullerene have been synthesised in the range C60-96. As the number of carbon atoms increases, the number of possible structural isomers (same number of atoms, but different arrangements of them) also increases. For example, C60 has only one isomer, but C84 has 24 possible isomers. Despite the huge number of possible isomers, relatively few have actually been purified (about 20). The student will be tasked with using chromatographic separation techniques to purify a fullerene for which no isomers have previously been purified (e.g., C88) from an as-produced mixture of fullerenes (which range from C60 – C96). After which, the student will further purify their sample into its individual isomers. The isomer pure samples will then be characterised by a number of spectroscopic techniques.
Synthesis, purification and spectroscopic characterisation of thermodynamically stable C70 adducts as precursors for targeted drug delivery systems
Unlike C60, where all carbon atom environments are identical, C70 is a fullerene, which is still available in high yields, has several (5) different carbon-atom environments. Hence, unlike C60, the synthetic chemistry of C70 exhibits both chemo- and region-selectivity. The synthetic chemistry of C70 has until recently been kinetically rather than thermodynamically driven (i.e. the products are those that form the fastest rather than those that are the most stable). Indeed the most thermodynamically stable products were never formed. Recently, we have developed high temperature techniques whereby the most stable product is formed. These have the advantage that a thermodynamically stable anchor can be added to C70, which cannot be removed under normal chemical processes. Hence, C70 can be made water soluble (by adding –OH groups) without affecting the anchor. The anchor on the water-soluble fullerene can then be exploited whereby a drug is attached to it. By also adding a specific tissue-targeting group, a local drug-delivery system may be produced. Research in this area is at an early stage, but the student will have the task synthesising and purifying a thermodynamically stable carbonyl (-C=O) adduct of C70 using out new high temperature techniques. The student will then prove that they have produced the adduct by a number of spectroscopic techniques (including Mass, Infra-red (vibrational), and/or 1H and 13C NMR spectroscopy).
MSci Review Project Abstracts
DFT for NMR
Nuclear Magnetic Resonance spectroscopy ("NMR") is the most powerful analytical tool in molecular structure determination. However, in the majority of cases it alone is unable to make a unique identification. Quantum chemical calculations that simulate molecular spectra are hence a useful additional aid in interpretation of NMR spectra. This is because strongly help in discriminating between spectra with same nominal form (i.e., two spectra with the same number of lines with the same distribution of peak intensities will have differing groupings of line/intensity combinations, which the simulated spectra may differentiate). However, the ability of the simulations to aid depends on the method used to perform the calculations (some are better than others). Hybrid Density Functional Theory ("DFT") and Hartree Fock ("HF") methods have proved quite reliable; where he 6- 31G**/B3LYP method is particularly successful. There are however, several other methods which may prove more reliable under certain conditions. Indeed it might be better to choose the simulation method depending on the conditions of the measurements.
During the project, the student will review the literature on quantum-chemical simulations of 13C NMR spectra of fullerenes and fullerene derivatives, together with that on experimental spectra of the same molecules. The student will then compare and contrast the experimental data and the analogous simulated data in order to draw meaningful conclusions on which hybrid HF/DFT methods make the better simulations for each of the different types of fullerene and different types of fullerene derivatives.
MSci Research/Investigative Project Abstracts
Synthesis, purification and spectroscopic characterisation of isomer-pure fullerenes
Fullerene have been synthesised in the range C60-96. As the number of carbon atoms increases, the number of possible structural isomers (same number of atoms, but different arrangements of them) also increases. For example, C60 has only one isomer, but C84 has 24 possible isomers. Despite the huge number of possible isomers, relatively few have actually been purified (about 20). The student will be tasked with using chromatographic separation techniques to purify a fullerene for which no isomers have previously been purified (e.g., C88) from an as-produced mixture of fullerenes (which range from C60 – C96). After which, the student will further purify their sample into its individual isomers. The isomer pure samples will then be characterised by a number of spectroscopic techniques.
Synthesis, purification and spectroscopic characterisation of thermodynamically stable C70 adducts as precursors for targeted drug delivery systems
Unlike C60, where all carbon atom environments are identical, C70 is a fullerene, which is still available in high yields, has several (5) different carbon-atom environments. Hence, unlike C60, the synthetic chemistry of C70 exhibits both chemo- and region-selectivity. The synthetic chemistry of C70 has until recently been kinetically rather than thermodynamically driven (i.e. the products are those that form the fastest rather than those that are the most stable). Indeed the most thermodynamically stable products were never formed. Recently, we have developed high temperature techniques whereby the most stable product is formed. These have the advantage that a thermodynamically stable anchor can be added to C70, which cannot be removed under normal chemical processes. Hence, C70 can be made water soluble (by adding –OH groups) without affecting the anchor. The anchor on the water-soluble fullerene can then be exploited whereby a drug is attached to it. By also adding a specific tissue-targeting group, a local drug-delivery system may be produced. Research in this area is at an early stage, but the student will have the task synthesising and purifying a thermodynamically stable carbonyl (-C=O) adduct of C70 using out new high temperature techniques. The student will then prove that they have produced the adduct by a number of spectroscopic techniques (including Mass, Infra-red (vibrational), and/or 1H and 13C NMR spectroscopy).
