Networks of intermolecular interactions involving nitro groups in the crystals of three polymorphs of 9-aminoacridinium 2,4-dinitrobenzoate • 2,4-dinitrobenzoic acid

We report on the crystal structures of three polymorphs of 9-aminoacridinium 2,4-dinitrobenzoate center dot 2,4-dinitrobenzoic acid (I, II and III). Single-crystal X-ray diffraction measurements show that the title compound forms three polymorphs with the space groups P2(1)/n (I) and P (1) over bar (II and III). The asymmetric units of all the polymorphs consist of 9-aminoacridinium cation, the 2,4-dinitrobenzoate anion and the 2,4-dinitrobenzoic acid molecule. The neutral and ionic forms of 2,4-dinitrobenzoic acid are linked via O-H center dot center dot center dot O hydrogen bonds with a D graph-set motif, forming monoanionic dimers. The amine and carboxylic acid moieties are linked via N-H center dot center dot center dot O, O-H center dot center dot center dot O and C-H center dot center dot center dot O hydrogen bonds. The acridinium skeletons in the crystal packing form it-stacked columns, whereas the monoanionic dimers of 2,4-dinitrobenzoic acid are linked by different types of intermolecular interactions, especially those involving nitro groups. To the best of our knowledge, the crystal structure of 9-aminoacridinium 2,4-dinitrobenzoate center dot 2,4-dinitrobenzoic acid is the first in which the appearance of monoanionic dimers of 2,4-dinitrobenzoic acid has been documented. (c) 2013 Elsevier B.V. All rights reserved.