Thermal Behaviour of Some New Polyoxometalate Complexes of Ciprofloxacin with Keggin-type Heteropoly Acids

Abstract

Abstract: Four polyoxometalate complexes, (CPFX·HCl)₃H₄SiW₁₂O₄₀, (CPFX·HCl)₃H₃PW₁₂O₄₀, (CPFX·HCl)₃H₃PMo₁₂O₄₀ and (CPFX·HCl)₄H₄SiMo₁₂O₄₀, were prepared from ciprofloxacin hydrochloride(CPFX·HCl) reacting with H_nXM₁₂O₄₀·nH₂O(X=P,Si; M=W,Mo) in an aqueous solution, and characterized by elemental analysis, IR spectrometry and TG-DTA. The IR spectrum confirms the presence of Keggin-type anions of heteropoly acids and the characteristic functional groups of ciprofloxacin. The TG/DTA curves show that their thermal decomposition is a multi-step process including simultaneous collapse of the Keggin-type structure. At first, these compounds had a mass loss of water molecules, then several other mass losses occurred due to the decomposition of ciprofloxacin hydrochloride and its fragments with the degradation of Keggin anions. The end product of decomposition is the mixture of WO₃(or MoO₃) and SiO₂(or P₂O₅), identified by X-ray diffraction and IR spectroscopy. The possible thermal decomposition mechanisms of these complexes are proposed. This study exemplified that the thermal stability of the complexes containing tungsten is much better than that of the complexes containing molybdenum.

Key words: Thermal decomposition, Polyoxometalate complexes, Keggin-type heteropoly acids, Ciprofloxacin hydrochloride, TG/DTA

WANG Dun-jia, FANG Zheng-dong, HAN De-yan. Thermal Behaviour of Some New Polyoxometalate Complexes of Ciprofloxacin with Keggin-type Heteropoly Acids[J]. Chemical Research in Chinese Universities, 2005, 21(3): 258-263.

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