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

Abstract

Enrofloxacinium citrate monohydrate (I), C19H23FN3O3+·C6H7O7-·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)Å, b=9.6531(8)Å, c=14.913(1)Å, α=98.813(1)°, β=92.029(1)°, γ=91.013(1)°, Z=2, V=1286.1(2)Å3, S.G. P1¯. The crystal structure determination reveals the importance of inter- and intramolecular interactions in the crystal formation. The EnrH2+andH3Cit- 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 π-stacking interactions are observed between the aromatic cycles of the adjacent cations which are located in an antiparallel style in a layer.