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Spectroscopic investigation of silver complexes with halogen substituted pyridines

Microbial resistance to antibiotics has become a worldwide concern. Recently, silver(I) compounds have attracted attention as potential antimicrobial agents.1, 2 Combining of silver salts with organic ligands may result in obtaining complexes with broader spectra of activity. We have synthesized a series of 1:2 complexes of silver(I) nitrate with 2- and 3-halopyridine, [Ag(NO3)(Xpy)2], X = Cl, Br, I, in order to investigate the potential biological activity and put some more insight in structure-function relationship as to their solid state structure as well as through characterization the species that exist in solution. We have chosen NO3− anion because it is well known that in metal complexes it could act as a counterion or a ligand and could assist in metallophilic interactions. All compounds were analysed by NMR in solutions and in the solid state and FT-IR and MS. The X-ray crystal structure was also determined (Fig. 1.). Solid state NMR parameters were used as a reference for solution study results. Starting from the experimental geometries, we performed quantum-mechanical calculations of complexes at different DFT levels of theory and compared data with spectroscopic results. Preliminary antimicrobial activities of the complexes against two Gram-negative strains: M. catarrhalis ATCC 23246 and E. coli AcrAB- were evaluated.

silver(I) ; halogen pyridine ; solution and solid state NMR ; antibacterial acitivity ; crystal structure

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