Howard, C.A.; (2005) Metal-ammonia-fulleride solutions. Doctoral thesis , University of London.

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Abstract

This project is the first concerted effort to study the structure of metal-ammonia- fulleride solutions. These novel solutions contain high concentrations of fulleride anions, C6on" (n = 1 to 5). A detailed understanding of the solubility of fullerenes and their derivatives has long been sought after: something this project addresses. The work focuses on the structure of the solutions using the complementary techniques of wide angle neutron diffraction, Small Angle Neutron Scattering (SANS), and Monte Carlo simulations. A highly developed structure is found over the short and intermediate length scales. The results show concentrated solutions of solvent separated, strongly coordinated, fulleride anions, maintained by an intriguing reorganisation of the ammonia solvent around the anions in solution. In more detail, we find two solvation shells around the C6o anions containing around 45 and -80 ammonia molecules respectively. The ammonia solvent molecules direct one of their hydrogen atoms towards the centre of the Ceo anions, allowing the other two hydrogen atoms to complete hydrogen-bonds within and across the shells. The solvation structure of the cation in solution is found to be very similar to its solvation structure in bulk metal-ammonia solutions. The structure and stability of the solutions is found to be dependent on both anionic charge and cation charge density. The scientific importance of the solutions is demonstrated by the attainment of high quality 13C NMR spectra for the fulleride anions Ceo"" {lcub}n = 1 to 5) for the first time in an identical solvent. Previous limitations of low concentrations, poor quality samples, and restrictions due to the air sensitivity of the anions have been overcome. The data here includes the first l3C NMR spectrum of C6o5". These data reveals that all the carbon atoms have an identical electronic environment in this anion.

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