Acta Cryst. (2013). C69, 1537-1540 [ doi:10.1107/S0108270113030801 ]
Abstract: Two products from the proton-transfer reactions of benzene-1,2,4,5-tetracarboxylic acid (pyromellitic acid, PMA) with 2,2'-biimidazole and 4,4'-dimethyl-2,2'-bipyridine, namely 2,2'-biimidazole-3,3'-diium 2,5-dicarboxybenzene-1,4-dicarboxylate, C6H8N42+,C10H4O82-, (I), and 4-methyl-2-(4-methylpyridin-2-yl)pyridinium 2,4,5-tricarboxybenzoate monohydrate, C12H13N2+·C10H5O8-·H2O, (II), have been prepared and their structures determined. Both compounds crystallize in the space group P. The asymmetric unit of (I) is composed of two independent ion pairs. Both the 2,2'-biimidazole-3,3'-diium dication and the PMA2- anion are located on special positions (inversion centres). The protonated 2,2'-biimidazole-3,3'-diium ring H atoms are involved in hydrogen bonding with carboxylate O atoms to form one-dimensional hydrogen-bonded chain structures. Adjacent chains are further linked via carboxyl-carboxyl O-HO hydrogen bonding, resulting in a two-dimensional supramolecular sheet with the R65(34) motif extending in the (11) plane. In (II), classical O-HO hydrogen-bond-linked anion-anion units are extended into a one-dimensional chain running parallel to the  direction, giving an R22(8)R44(30) motif. The chains are connected by water-carboxyl O-HO hydrogen bonds to form a two-dimensional network parallel to the (01) plane. The 4-methyl-2-(4-methylpyridin-2-yl)pyridinium cations lie between the two-dimensional supramolecular layers linked via N-HO hydrogen-bonding interactions.
CCDC references: 787056 and 971187
Formula: C6H8N42+·C10H4O82- and C12H13N2+·C10H5O8-·H2O
Keywords: crystal structure; hydrogen bonding; pyromellitic acid; 2,2'-biimidazole; 4,4'-dimethyl-2,2'-bipyridine.
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