Investigations in molecular structure: from scattering to molecular complexes of brominated compounds

The main focuses of this research were to examine the capabilities of solution techniques to attempt to monitor the nucleation process in crystallisation, and to investigate structural outcomes of crystallisation processes, with reference to polymorphism and intermolecular interactions. To achieve this, work on the investigation of nucleation and early-stage crystallisation was carried out at the Department of Pharmaceutical Sciences at the University of Strathclyde and also at the central synchrotron facility of Station 2.1 at the SRS Daresbury. Small angle X-ray scattering (SAXS) was carried out on solutions of methyl-4-hydroxybenzoate (pMHB) and 2-bromobenzoic acid. These studies were carried out after developing solution methods to enable us to determine the point at which crystals emerged from solution. This was achieved using Focussed Beam Reflectance Measurements. Structural studies were also carried out on pMHB to examine its polymorphic behaviour and crystal structures were solved at various temperatures from 100K to 300K. The crystal structure of methyl-2,5- dibromobenzoate was also solved at 100K after discovering it sublimes at room temperature. This structure could only be solved from a twinned crystal and indicated the appearance of interesting halogen interactions occurring. Structural studies have also been carried out using the bromanilic acid molecule as a focus to generate a number of co-crystal complexes to examine their halogen bonding capability and to determine any structural significances in their formation. Co-crystal complexes of bromanilic acid and a variety of molecules were made in 1:1 and 1:2 ratios to see if any additional halogen interactions could be observed or induced, in addition to the expected hydrogen-binding interactions. The co-crystals included a range of picolines and lutidines as well as bromo-substituted pyridines to attempt to induce halogen interactions. This generated a number of new compounds whose structures were determined using single crystal X-ray diffraction and the interactions were monitored to observed whether any defined patterns with regards to the tendency of bromanilic acid co-crystallisations to produce predictable patterns of intermolecular interactions could be determined.

Level dc:type.qualificationlevel

PhD

Grantor dc:publisher.institution

University of Glasgow

Year dc:date.issued

2010

Author dc:creator

• O'Neill, Andrew

• QD Chemistry

Language dc:language

en