Siberian Federal University

Ciprofloxacinium malonate dihydrate (I) , C 17 H 19 FN 3 O 3 ∙C 3 H 3 O 4 ∙H 2 O, (C 17 H 18 FN 3 O 3 – ciprofloxacin, CfH; C 3 H 4 O 4 − malonic acid) has been crystallized from the mutual solution of malonic acid and ciprofloxacin in ambient conditions. It has improved aqueous solubility against the ciprofloxacin. The colourless crystals have been investigated using X-ray single crystal and powder techniques, and characterized by differential scanning calorimetry and thermogravimetry. The obtained compound can be considered as a salt with ciprofloxacinium in the role of a cation and malonate as an anion. The compound is crystallized in the triclinic lattice with a = 7.283(2), b = 10.090(3), c = 15.104(5)Å, α = 102.711(4), β = 103.328(4), γ = 94.261(4)°, Z = 2, V = 1044.5(6)Å , S.G. P 1 . The crystal structure determination reveals the importance of inter-and intramolecular interactions in the crystal formation. Thermal behavior and solubility of I provided complementary evidences of salt formation.