Thiobarbiturate and barbiturate salts of pefloxacin drug: Growth, structure, thermal stability and IR-spectra

Three new salts of pefloxacin (PefH) with thiobarbituric (H₂tba) and barbituric (H₂ba) acids, pefloxacinium 2-thiobarbiturate trihydrate, PefH₂(Htba)·3H₂O (1), pefloxacinium 2-thiobarbiturate, PefH₂(Htba) (2) and bis(pefloxacinium barbiturate) hydrate, (PefH₂)₂(Hba)₂·2.56H₂O (3) are synthesized and structurally characterized by the X-ray single-crystal diffraction. The structures of 1–3 contain intramolecular hydrogen bonds CH⋯F, OH⋯O. Intermolecular hydrogen bonds NH⋯O and OH⋯O form a 2D plane network in 1. In 2 and 3, intermolecular hydrogen bonds NH⋯O form the infinite chains. In 1–3, the Htba⁻ and Hba⁻ ions are connected with PefH₂⁺ only by one intermolecular hydrogen bond NH⋯O. In 2 and 3, two Htba⁻ and Hba⁻ ions are connected by two hydrogen bonds NH⋯O. These pairs form infinite chains. All three structures are stabilized by the π−π interactions of the head-to-tail type between PefH₂⁺ ions. Compounds 2 and 3 are characterized by powder XRD, TG-DSC and FT-IR.