Synthesis, structures and antimicrobial activity of novel NHC∗- and Ph3P-Ag(I)-Benzoate derivatives

Abstract

The rising threat of Antimicrobial Resistance (AMR) requires a novel approach to the treatment of infectious diseases. Covalently bonded silver, which has known antibacterial and antifungal properties and multiple mechanisms of action, may provide a treatment strategy when used alone or in combination with already known antimicrobial compounds. Here we describe the synthesis of eight novel silver(I) complexes, which were screened for in vitro activity against two pathogenic bacterial strains, Methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli), and against two pathogenic fungal strains, Candida albicans and Candida parapsilosis. Complexes 5–8 were synthesized by reacting triphenylphosphine in relative equivalents with the relevant silver benzoates (1, 2 &4), whilst complexes 9–12 were synthesized by generation of a free carbene NHC∗ (1,3-dibenzyl-4,5-diphenyl-imidazol-2-ylidene) and reacting this with the silver benzoates 1–4, under Schlenk conditions. Complexes 9–12 showed the strongest antimicrobial activity, resulting in 50% inhibition of growth against MRSA and C. parapsilosis at concentrations of 12.5 and 3.25 µg/mL, respectively.