Synthesis, crystallographic studies, high resolution mass spectrometric analyses and antibacterial assays of silver(I) complexes with sulfisoxazole and sulfadimethoxine

Abstract

The present work describes the synthesis, structural characterization and antibacterial assays of two silver(I) complexes with the sulfa drugs sulfisoxazole (SIZH) and sulfadimethoxine (SDMXH). Chemical analyses and high resolution mass spectrometric studies led to 1:1 metal/ligand compositions, suggesting the minimal formulas AgC11H12O3N3S·H2O for Ag–SIZ and AgC12H13O4N4S for Ag–SDMX. Infrared and solution state NMR spectroscopic measurements indicated ligand coordination to Ag(I) by the nitrogen atoms of the SO2N and NH2 groups in Ag–SIZ, whereas for Ag–SDMX the coordination of the ligand to Ag(I) occurs by the SO2N group and one of the nitrogen atoms of the pyrimidine ring. The proposed coordination modes were confirmed by X-ray diffraction studies and showed the formation of dimeric structures in both cases. The Ag–SDMX complex shows the classical bridging mode of coordination, in which the silver ions bridge between the nitrogen atom of the sulfonamide group of one ligand and the nitrogen atom of the pyrimidine ring of the second ligand, while for the Ag–SIZ complex coordination occurs by the nitrogen atoms of the NH2 and SO2N groups. Antibacterial assays indicated that Ag–SIZ and Ag–SDMX complexes are effective against Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus) bacterial strains, being the Ag–SDMX complex more active than the Ag–SIZ one. These results are an indicative that the ligand structures and dissimilar coordination modes of the sulfonamides may be associated to the antibacterial activities of the complexes.