Hydrogen-bonding behaviour of benzene-1,2,4,5-tetracarboxylic acid: supramolecular structures of different dimensionality in the 2:1 adducts formed with 4,4′-bipyridyl and hexamethylenetetramine

Abstract

Co-crystallization of benzene-1,2,4,5-tetracarboxylic acid, C10H6O8, with 4,4′-bipyridyl, C10H8N2, or with hexamethylenetetramine, C6H12N4, from methanol solutions yields in each case a 2:1 salt, [(C10H9N2)+]2·[(C10H4O8)2−] (1) and [(C6H13N4)+]2·[(C10H4O8)2−] (2). In (1) the carboxylate anions lie across centres of inversion, but they contain no intramolecular O—H...O hydrogen bonds: the cations and anions are linked by strong O—H...N and N—H...O hydrogen bonds into a chain-of-rings, and these chains are further linked into a three-dimensional framework structure by means of C—H...O hydrogen bonds and aromatic π...π stacking interactions. Compound (2) contains two independent three-molecule aggregates, comprising a central anion and two cations, linked to the anion by means of short N—H...O hydrogen bonds. One of these aggregates is centrosymmetric, but the other is not, and the two types of anion both form two intramolecular O—H...O hydrogen bonds. The two types of three-molecule aggregate, in which all the anions are virtually parallel, are linked by short C—H...O hydrogen bonds into a molecular staircase.