Investigating intermolecular interactions motifs in ammonium carboxylate salts

[摘要] ENGLISH ABSTRACT:This thesis reports an in-depth investigation of the intermolecular interaction motifs insecondary, primary and ammonium carboxylate salts. The investigation wasconducted using the Cambridge Structural Database (CSD), together with a systematicsteric-specific experimental study.The tendency in the literature has been to analyse organic salt crystal structures interms of hydrogen bonding patterns, almost ignoring cation-anion interactions. Thisstudy focuses on the cation-anion interactions in secondary, primary and ammoniumcarboxylate salts, which have a direct effect on the formation of specific structuralmotifs. The ideas of ring-stacking and ring-laddering, which arise from the tendencyof cations and anions to arrange themselves so as to maximise electrostaticinteractions, have been applied to ammonium carboxylate salts.An extensive survey of organic ammonium carboxylate salt structures in the CSD hasbeen carried out. The structural motifs in ammonium carboxylates were investigated,and a set of predictive rules for the pattern of intermolecular interactions in these saltswas developed. Using these results, the formation of ring-stacking or ring-laddering inprimary ammonium carboxylate salts can be predicted. The results from the CSDsurvey are discussed in Chapter 3.An experimental study has been carried out, which complements the results obtainedfrom the CSD survey. The experimental study formed 19 novel ammoniumcarboxylate salts, of which 2 formed hydrates and 2 co-crystals of salts. Theexperimental results confirm what was found in the CSD survey, and this is discussedin Chapter 4.This study has found that the principle of ring-stacking and ring-laddering can beapplied in a general form to the crystal structures of organic ammonium carboxylatesalts. The size of the cation and the anion in these salts has a significant effect on theformation of structural motifs in the solid state. Interactions between cation and anionsubstituents also play an important role in the formation of particular structural motifsin ammonium carboxylate salts.

[发布机构] Stellenbosch University