Crystal Structure and Properties of Levofloxacinium 2-Thiobarbiturate Trihydrate

The structure of levofloxacinium 2-thiobarbiturate trihydrate LevoH ₂ ⁺ Htba^–·3H₂O (I) (LevoH is levofloxacin, H₂tba is 2-thiobarbituric acid) is determined (CIF file CCDC No. 1547466); its thermal decomposition and IR spectrum are studied. The crystals of I are triclinic: a = 8.670(1) Å, b = 9.605(1) Å, c = 15.786(2) Å, α = 89.144(5)°, β = 88.279(5)°, γ = 76.068(5)°, V = 1275.4(3) ų, space group P1, Z = 2. The unit cell of I contains two LevoH ₂ ⁺ ions, two Htba^– ions, and six H₂O molecules. The absolute structure of the crystal and the configuration of the chiral center in a levofloxacin molecule S are determined. Experiments for generating the second optical harmonics gave a positive result. Intermolecular hydrogen bonds (HBs) N–H···O and O–H···O in I form a bilayer system along the ab diagonal with hydrophilic moieties within a layer and hydrophobic moieties directed outward. The structure is stabilized by multiple HBs and the π–π interaction between the Htba–and LevoH ₂ ⁺ ions and between the LevoH ₂ ⁺ ions.