Crystal structure of 1-(3-chlorophenyl)piperazin-1-ium picrate–picric acid (2/1)

Abstract

The title salt {systematic name: bis[1-(3-chlorophenyl)piperazinium 2,4,6-trinitrophenolate]–picric acid (2/1)}, 2C10H14ClN2+·2C6H5N3O7−·C6H6N3O7, crystallized with two independent 1-(3-chlorophenyl)piperazinium cations, two picrate anions and a picric acid molecule in the asymmetric unit. The six-membered piperazine ring in each cation adopts a slightly distorted chair conformation and contains a protonated N atom. In the picric acid molecule, the mean planes of the nitro groups in the ortho-, meta-, and para-positions are twisted from the benzene ring by 31.5 (3), 7.7 (1), and 3.8 (2)°, respectively. In the anions, the dihedral angles between the benzene ring and the ortho-, meta-, and para-nitro groups are 36.7 (1), 5.0 (6), 4.8 (2)°, and 34.4 (9), 15.3 (8), 4.5 (1)°, respectively. The nitro group in one anion is disordered and was modeled with two sites for one O atom with an occupancy ratio of 0.627 (7):0.373 (7). In the crystal, the picric acid molecule interacts with the picrate anion through a trifurcated O—H...O four-centre hydrogen bond involving an intramolecular O—H...O hydrogen bond and a weak C—H...O interaction. Weak intermolecular C—H...O interactions are responsible for the formation of cation–anion–cation trimers resulting in a chain along [010]. In addition, weak C—H...Cl and weak π–π interactions [centroid–centroid distances of 3.532 (3), 3.756 (4) and 3.705 (3) Å] are observed and contribute to the stability of the crystal packing.

Keywords

• crystal structure
• piperazin-1-ium
• picrate
• picric acid
• salt