Cocrystals and Salts of Pyridine-3,5-bis(1-methyl-benzimidazole-2-yl) with Pyromellitic Acid: Aromatic Guest Inclusion and Separation via Benzimidazole–Carboxylic Acid Heterosynthon

Abstract

An arc-shaped molecule pyridine-3,5-bis(1-methyl-benzimidazole-2-yl) was shown to form cocrystals and salts with pyromellitic acid (H4PMA) which are sustained by COOH···Nbim/COO–···Hbim heterosynthons. The reaction between these two components in the presence of large aromatic guest molecules resulted in the crystals of salts with aromatic inclusion, while the absence of guests resulted in the H2O and EtOH solvates of cocrystals. The crystal structures of salts exhibited isostructurality with the inclusion of aromatics such as pyrene, perylene, phenanthrene, and 9-anthraldehyde. The crystal structures of solvates were found to differ significantly despite having similar composition. In all these structures the −COOH functional group has exhibited significant preference to interact with the benzimidazole moiety over the pyridine moiety. The aromatic guest inclusion was found to occur via cation···π interactions between the protonated benzimidazole and π-cloud of guest molecules. The competitive experiments on guest inclusion reveal that the two-component host system exhibits selective inclusion of perylene or 9-anthraldehyde over other aromatics such as pyrene or phenanthrene.