Silver complexes with sulfathiazole and sulfamethoxazole: Synthesis, spectroscopic characterization, crystal structure and antibacterial assays

The present work describes the synthesis and spectroscopic characterization of two silver(I) complexes with the sulfonamides sulfathiazole (AgC9H8N3O2S2, Ag-SFT) and sulfamethoxazole (AgC10H10N3O3S, Ag-SFM). Elemental analyses indicate a 1:1 metal/ligand composition for both complexes. Spectroscopic techniques such as 1H, 15N NMR and IR evidence the coordination of both ligands to silver through the nitrogen atom of the sulfonamide group, and also indicate the participation of the 5-membered N-heterocyclic ring in the coordination. The Ag-SFT crystal structure was solved by X-ray powder diffraction and indicates the formation of a dimeric structure with silver bridging between two ligand molecules. Biological studies showed the antibacterial activity of Ag-SFT and Ag-SFM complexes against Gram-positive and Gram-negative bacterial strains, with MIC values ranging from 3.45 to 6.90 mmol L-1 for the sulfathiazole complex and 1.74 to 13.9 mmol L-1 for the sulfamethoxazole complex. The complexes have shown to be more active against Gram-negative bacterial strains.