Infrared studies on Co and Cd complexes of sulfamethoxazole

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 investiga ted. The infrared spectra of the samples were recorded in the range 4000-40 0 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 sulfonami do 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 compoun d, the metal atom coordinates through the sulfonamide and amino nitrogens. The low energy calculations were also carried out by using geometry optimiz ation. It is shown that the proposed structure for the metal complexes of S MX derived from the infrared spectra are consistent with the theoretical re sults. (C) 2001 Elsevier Science B.V. All rights reserved.