Solvate formation in lutidinium pamoate salts: a systematic study

Abstract

A series of salts, solvates and co-crystals formed by reaction of the isomers of lutidine and picoline with pamoic acid have been prepared and characterised. These reactions were carried out in the solvents DMF and NMP in an attempt to understand the role of the solvent in the structure type observed. A total of 16 new structures are described and compared to the known structures of lutidinium pamoate previously obtained from neat lutidine or from THF. A number of structural features previously observed in these systems reappear in this study, as well as some entirely novel structure types. The solvent does not only fulfill a space-filling role, but rather seems to influence the state of ionisation of the pamoate moiety, which appears to be the major contributor to the crystal structure observed.