Synthesis, spectroscopic characterization, DFT studies and antibacterial assays of a novel silver(I) complex with the anti-inflammatory nimesulide

A novel silver(I) complex with nimesulide (NMS) of composition AgC13H11N2O5S was synthesized and characterized by chemical and spectroscopic measurements, density functional theory (DFT) studies and biological assays. Infrared (IR), ESI-QTOF-mass spectrometric (MS) analyses and 1H, 13C and [1H–15N] nuclear magnetic resonance (NMR) studies indicate that NMS acts as a bidentate ligand, being coordinated to Ag(I) through the nitrogen and one of the oxygen atoms of the sulphonamide group. The proposed structure based on the experimental data was confirmed as a minimum of the potential energy surface (PES) with the calculation of the hessians, showing no imaginary frequencies. Also, the theoretical IR spectra of the free ligand and of the silver(I) complex (Ag–NMS) are in a good agreement with the experimental data. Theoretical Time-Dependent DFT (TD-DFT) studies confirmed that the observed transitions in the UV–Vis spectra of the NMS and Ag–NMS are due to π–π∗ transitions. The antibacterial activity of Ag–NMS was evaluated by an antibiogram assay, using the disk diffusion method. The complex showed an effective antibacterial activity against Staphylococcus aureus (Gram-positive), and Escherichia coli and Pseudomonas aeruginosa (Gram-negative) pathogenic bacterial cells.

Optimized structure of the silver(I)–nimesuldie complex: Silver (gray), carbon (dark gray), nitrogen (blue), oxygen (red) and hydrogen (white).Figure optionsDownload as PowerPoint slideHighlights
► A novel silver(I) complex with nimesulide.
► IR, UV–Vis and NMR data permitted proposing coordination through the N, O atoms of nimesulide to Ag.
► ESI-QTOF-MS confirmed the proposed composition of the complex.
► DFT studies supported the proposed N, O coordination of the ligand to Ag(I).
► The compound shows antibacterial activities against Gram-negative and -positive bacterial strains.