Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2017. / Crystal engineering principles were used to cocrystallize sulfa drugs, sulfapyridine (SFP) and
sulfadiazine (SFD) with aromatic acids and an amine via solution crystallization.
Sulfapyridine formed cocrystals with 3-nitrobenzoic acid (SFP∙3NBA), 5-bromosalicylic acid
(SFP∙5BSA), 4-dimethylaminopyridine (SFP∙4DMAP) and salts with 4-nitrobenzoic acid
[SFP+][4NBA-], 3,5-dinitrosalicylic acid [SFP+][DNSA-] and 3,5-dibromosalicylic acid
[SFP+][DBSA-], while sulfadiazine formed a salt with 3,5-dinitrosalicylic acid [SFD+][DNSA-].
The newly formed complexes were analyzed by differential scanning calorimetry (DSC),
thermogravimetric analysis (TGA), fourier transform infrared spectroscopy (FTIR), single
crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD) and nuclear magnetic
resonance spectroscopy (1H and 13C NMR).
The hydrogen bonding and crystal packing of the new solid forms were analyzed with the
aid of Mercury and CrystalExplorer. The SFP and SFD compounds exhibit tautomerism. In
this work it was investigated how the introduction of coformers with varying acidity
provides the possibility to form a variety of synthons, and therefore disrupt the common
preferred interactions within the sulfonamides. Using selected acids as coformers, the effect
on crystal packing of the coformer’s substituent position was examined by using the isomers
3NBA and 4NBA. 5BSA and DBSA were employed to analyse the effect of the number of
substituents on hydrogen bond formation and crystal packing. In addition, it was
investigated how small structural changes in the pharmaceutical compound influences the
crystal packing by cocrystallising structurally similar SFP and SFD with the same coformer.
Evaluation of the change in coformer acidity was studied by using a pyridine coformer,
4DMAP, and its crystal packing was analyzed and compared to structures formed with
carboxylic acid coformers.
Finally, we examined how inter-conversion of tautomers promotes crystal formation by
conforming to the geometric demands of the different coformers. / National Research Foundation(NRF)
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:cput/oai:localhost:20.500.11838/2680 |
| Date | January 2017 |
| Creators | Shunje, Kelly Nzwanai |
| Contributors | Báthori, Nikoletta B, de Vries, Elise |
| Publisher | Cape Peninsula University of Technology |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | http://creativecommons.org/licenses/by-nc-sa/3.0/za/ |
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