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

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.