Molecular Networks Created by Charge-Assisted Hydrogen Bonding in Carboxylate Salts of a Bis(amidine)

Amidines can be protonated by carboxylic acids to give amidinium carboxylates, and the ions can associate by forming multiple charge-assisted hydrogen bonds according to reliable motifs. Extended hydrogen-bonded networks can be constructed by treating suitable bis(amidines) with acids containing multiple carboxyl groups. To further explore the potential of this strategy, we have determined the structures of salts produced by treating 2,2′-bi-2-imidazoline, a cyclic bis(amidine), with oxalic, fumaric, terephthalic, and trimesic acids. The structures of the salts proved to incorporate features resulting predictably from the geometry of the ions and their ability to engage in charge-assisted hydrogen bonds.