Spectrophotometric Study of the Complexation of Sulfa Drugs with CU(II) and Coupling Reagents in the Presence of Molybdate Ions

Abstract

In a part of this research, the complexation of sulfamethoxazole (SFMx) with Cu(II) have been studied at different temperatures. The obtained data show that copper(II) and SFMx combine in a molar ratio of 1 : 2 at pH 11.0. The experimental conditions have been optimized. The stoichiometry of Cu(II) – SFMx complexes was estimated by the molar ratio and continuous variation methods and emphasized by the KINFIT program. The values of the thermodynamic parameters for complexation reaction were obtained from the temperature dependence of the stability constants. In addition, the complexation reaction of SFMx and dapsone (DAP) with catechol derivatives and some coupling reagents and molybdate ions have been studied in water in 25°C by a spectrophotometric method based on the formation of a colored product via diazotization of sulfonamides, SFMx and DAP, followed by the complexation with dopamine in the presence of molybdate ions in (1 : 1) H2SO4 medium. Absorbance of the resulting red colored product is measured at 493 nm for pyrocatechol (PCLv) and at 523 nm for dopamine (DPH) in DAPand at 498 and 529 nm in SFMx. Beer’s law range was determined for the obtained complexes. Analytical data for determination of the pure compound are presented together with the application of the proposed method to the analysis of some pharmaceutical formulations.