Supramolecular structures of four isomorphous anilinium 2-carboxy-4-nitrobenzoate salts: 4-X-C6H4NH 3+· C8H4NO6 - (X = H, Cl, Br and I)

Abstract

Anilinium 2-carboxy-4-nitrobenzoate, C6H8N +·C8H4NO6- , (I), 4-chloroanilinium 2-carboxy-4-nitrobenzoate, C6H7ClN +-C8H4NO6-, (II), 4-bromoanilinium 2-carboxy-4-nitrobenzoate, C6H7BrN +·C8H4NO6-, (III), and 4-iodoanilinium 2-carboxy-4-nitrobenzoate, C6H 7IN+·C8H4NO6-, (IV), are approximately isostructural. In each compound, the ions are linked into complex sheets by a combination of O-H⋯O and N-H⋯O hydrogen bonds. Within the sheets, two distinct one-dimensional substructures can be identified, viz. a chain of edge-fused R33(13) rings and a double helix of simple C22(9) chains. In (I) and (IV), the sheets are linked by a C-H⋯Onitro hydrogen bond and a two-centre C-I⋯Onitro interaction, respectively, but the corresponding C-Cl⋯O and C-Br⋯O contact distances in (II) and (III) are not significantly shorter than the sum of the van der Waals radii. © 2005 International Union of Crystallography.