Synthesis, characterization, and antimicrobial activity of silver carbene complexes derived from 4,5,6,7-tetrachlorobenzimidazole against antibiotic resistant bacteriaElectronic supplementary information (ESI) available. CCDC 845904-845910. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c2dt00055e

Silver N -heterocyclic carbene complexes have been shown to have great potential as antimicrobial agents, affecting a wide spectrum of both Gram-positive and Gram-negative bacteria. A new series of three silver carbene complexes (SCCs) based on 4,5,6,7-tetrachlorobenzimidazole has been synthesized, characterized, and tested against a panel of clinical strains of bacteria. The imidazolium salts and their precursors were characterized by elemental analysis, mass spectrometry, 1 H and 13 C NMR spectroscopy, and single crystal X-ray diffraction. The silver carbene complexes, SCC32 , SCC33 , and SCC34 were characterized by elemental analysis, 1 H and 13 C NMR spectroscopy, and single crystal X-ray diffraction. These complexes proved highly efficacious with minimum inhibitory concentrations (MICs) ranging from 0.25 to 6 μg mL −1 . Overall, the complexes were effective against highly resistant bacteria strains, such as methicillin-resistant Staphylococcus aureus (MRSA), weaponizable bacteria, such as Yersinia pestis , and pathogens found within the lungs of cystic fibrosis patients, such as Pseudomonas aeruginosa, Alcaligenes xylosoxidans , and Burkholderia gladioli . SCC33 and SCC34 also showed clinically relevant activity against a silver-resistant strain of Escherichia coli based on MIC testing. Three silver carbene complexes were synthesized and tested against a panel of clinical strains of bacteria.