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Title: An exploration of polymorphism in molecular compounds using high pressure
Author: Fabbiani, Francesca P. A.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2005
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A novel technique for the study of organic compounds under high pressure has been developed. This involves recrystallisation from solution under high-pressure conditions. Crystals grown using this technique have been characterised in situ by single-crystal X-ray diffraction. This novel high-pressure crystallisation technique has been demonstrated to be successful by growth of a single crystal of a new high-pressure polymorph of the polycyclic aromatic compound phenanthrene, from a dichloromethane solution at 0.6 GPa. A new polymorph of pyrene is also reported at 0.5 GPa. Structural analysis of the new high-pressure polymorphs of these two compounds shows that intermolecular interactions are substantially different from those found in the ambient-pressure structures and do not fit a previously established packing model. Recrystallisation of naphthalene in the 0.2-0.6 GPa pressure range did not result in the formation of a new polymorph, and its crystal structure is reported to be stable to compression to 2.1 GPa. A new monoclinic polymorph of acetamide has been prepared and structurally characterised from an aqueous solution at 0.8 GPa. The first 1:1 solvate of paracetamol with methanol has been crystallised from a methanolic solution at 0.6 GPa. The hydrogen-bonding pattern in this new structure has been compared and contrasted with patterns found in other solvates and polymorphs of paracetamol. It has been demonstrated how the systematic variation of pressure in combination with ambient-pressure polymorph screening can be used not only to identify rapidly all of the known polymorphs of the nootropic drug piracetam, but also to identify and characterise new polymorphs and hydrates.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available