The crucial role of C-H...O and C=O...pi interactions in the building of three-dimensional structures of dicarboxylic acid-biimidazole compounds.

The supramolecular architectures of three dicarboxylic acid-biimidazole compounds, namely, 2,2'-biimidazolium malonate, C(6)H(8)N(4)(2+).C(3)H(2)O(4)(2-), (I), 2,2'-bi(1H-imidazole) succinic acid, C(6)H(6)N(4).C(4)H(6)O(4), (II), and 2,2'-biimidazolium 2,2'-iminiodiacetate chloride, C(6)H(8)N(4)(2+).C(4)H(6)NO(4)(-).Cl(-), (III), are reported. The crystal structures are assembled by the same process, namely double conventional N-H...O or O-H...N hydrogen bonds link the dicarboxylates and biimidazoles to form tapes, which are stacked in parallel through lone-pair-aromatic interactions between carbonyl O atoms and biimidazole groups and are further linked via weak C-H...O interactions. The C=O...pi interactions involved in stacking the tapes in (II) and the C-H...O interactions involved in linking the tapes in (II) and (III) demonstrate the crucial role of these interactions in the crystal packing. There is crystallographically imposed symmetry in all three structures. In (I), two independent malonate anions have their central C atoms on twofold axes and two biimidazolium dications each lie about independent inversion centres; in (II), the components lie about inversion centres, while in (III), the unique cation lies about an inversion centre and the iminiodiacetate and chloride anions lie across and on a mirror plane, respectively.