Enrofloxacinium citrate monohydrate: Preparation, crystal structure, thermal stability and IR-characterization

Enrofloxacinium citrate monohydrate (I), C19H23FN3O3+center dot C6H2O7-center dot H2O, [C19H22FN3O3 - enrofloxacin, EnrH] has been crystallized from the mutual solution of citric acid and enrofloxacin in ambient conditions. The colorless crystals have been investigated using X-ray single crystal and powder techniques, and characterized by differential scanning calorimetry, thermogravimetry and infrared spectroscopy. The obtained compound can be considered as a salt with enrofloxacinium in the role of a cation and citrate as an anion. The ions ratio equals to 1:1. The compound crystallizes in the triclinic lattice with a = 9.0489(8) angstrom, b = 9.6531(8) angstrom, c = 14.913(1) angstrom, alpha = 98.813(1)degrees, beta = 92.029(1)degrees, gamma = 91.013(1)degrees, Z = 2, V = 1286.1(2) angstrom(3), S.G. P (1) over bar. The crystal structure determination reveals the importance of inter- and intramolecular interactions in the crystal formation. The EnrH(2)(+) and H(3)Cit(-) molecular ions are packed in alternating layers with water molecules inserted into the citrate layers. A citrate ion in the layer is linked via H-bondings with two adjacent ones and three water molecules. Enrofloxacinium cations are packaged by means of a benched mode and every cation is linked by three intermolecular thymus type H-bondings with nitrogens of adjacent cations and by two links with the oxygen of the citrate ions. The infrared spectra gave the evidence of H-bonding formation in the obtained salt. The pi-stacking interactions are observed between the aromatic cycles of the adjacent cations which are located in an antiparallel style in a layer. (C) 2012 Elsevier B.V. All rights reserved.