Synthesis, Characterization, and Evaluation of Antibacterial Activity of Ferrocenyl-1,2,3-Triazoles, Triazolium Salts, and Triazolylidene Complexes of Gold(i) and Silver(i)

Abstract

1,2,3-triazoles, the corresponding triazolium salts, and the resulting mesoionic carbenes (MICs) of the 1,2,3-triazol-5-ylidene type are at the forefront of contemporary research. In this contribution, we present a comprehensive study involving eight triazoles, seventeen triazolium salts, two silver(i)- and four gold(i)-MIC complexes. The substituents on the N1-atom of the heterocycles are either ferrocenyl or phenyl and those on the C4-atom bear various alkyl groups. All the compounds were thoroughly characterized by a combination of multinuclear NMR spectroscopy, ESI-MS and in many cases through single crystal X-ray diffraction studies. In the electrochemical analysis, all ferrocenyl-containing compounds display a ferrocenyl-based oxidation step. Additionally, in both the triazolium salts, and the respective metal complexes, a ligand centered reduction step is observed. All the complexes were tested for their antibacterial properties against the Gram-negative bacterial strains Salmonella typhimurium (S. typhimurium) and Escherichia coli (E. coli). Many of the tested compounds display good antibacterial activity against the rather resistant Salmonella strain. To inhibit the growth of E. coli, higher concentrations of the compounds tested were required. A preliminary structure-activity relationship of this set of compounds is also reported.