Infrared studies on Co and Cd complexes of sulfamethoxazole

doi:10.1016/S1386-1425(00)00419-4

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy

Volume 57, Issue 5, April 2001, Pages 1031-1036

https://doi.org/10.1016/S1386-1425(00)00419-4 Get rights and content

Abstract

In this study, the new Co and Cd complexes of sulfamethoxazole (SMX) (drug substance) [4-amino-N-(5-methyl-3-isoxazolyl) benzenesulfonamide] have been prepared for the first time and their infrared spectra have been investigated. The infrared spectra of the samples were recorded in the range 4000–400 cm⁻¹ and their fundamental vibrational wave numbers were obtained. The vibrational assignments were determined by using the group frequency tables and compared with the wave numbers of SMX found in the literature. The SMX wave numbers observed in the infrared spectra of the metal complexes were compared with those of free SMX. Investigations of the infrared spectra of the metal complexes indicated the vibrations due to the amino and sulfonamido groups are shifted with respect to the free molecule in line with their coordination to the metal. In the cadmium complex, the active binding sites of SMX are the sulfonamide nitrogen and sulfonic oxygen; in cobalt compound, the metal atom coordinates through the sulfonamide and amino nitrogens. The low energy calculations were also carried out by using geometry optimization. It is shown that the proposed structure for the metal complexes of SMX derived from the infrared spectra are consistent with the theoretical results.

Introduction

Metal binding substances, many of which function by chelation, form a class of substances which have furnished many useful drugs and other substances of value in selective toxicity. Sulfonamides have been extensively used in medicine for their antibacterial properties. The combined antibacterial activity of sulfonamides and antimicrobial activity of heavy metals with a view to establish the relationship and importance of metal–drug interactions have been investigated [1], [2], [3], [4], [5]. The metal chelates of sulfa drugs have been found to be more bacteriostatic than the drugs themselves [6], [7]. Sulfamethoxazole (SMX) is used as an agent to treat urinary tract infections. The synthesis and characterization of some first row transition metal complexes of SMX have been reported by Kanagaraj and Rao [8]. In their spectroscopic studies on SMX and its complexes, only the group frequencies have been given in the region 4000–1000 cm⁻¹. In this study, we reported the new sulfamethoxazole complexes of Co and Cd and investigated the coordination behaviour of the drug by using IR spectra in the range 4000–400 cm⁻¹. We gave interpretations of all the vibrational modes of SMX molecule. In addition, the low energy calculations were also carried out by using geometry optimization.

Section snippets

Materials and methods

The compounds were prepared in the following manner: Sulfamethoxazole (2 mmol) was dissolved in hot water. Then dilute sodium hydroxide solution was added with constant stirring. The ligand solution (pH=8–10) was mixed with an aqueous solution of the metal acetate (1 mmol) under continuous stirring. The compounds, which precipitated, were filtered, washed with distilled water and dried at room temperature for a few days.

Chemical analyses of C, H, N were determined using an elemental analyzer.

Results and discussion

As far as we know, only one vibrational and structural study has been reported for the metal complexes of SMX (Scheme 1). The infrared spectra of some complexes of SMX had been reported in the range 4000–1000 cm⁻¹ by Kanagaraj and Rao [8]. They mentioned that SMX acts as a bidendate ligand, binding the metal ion through deprotonated sulfonamide nitrogen and sulfonyl oxygen in the case of Cr, Mn and Ni complexes or isoxazole ring nitrogen and deprotonated sulfonamide nitrogens in the case of Cu

Acknowledgements

The authors wish to acknowledge the support of Hacettepe University Research Fund (Project No: 97.01.602.003).

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