Recent Developments in the Antimicrobial Efficacy of Coinage Metal (Cu, Ag, and Au) <i>N</i> ‐Heterocyclic Carbene Complexes

Abstract N ‐heterocyclic carbenes (NHCs) are a class of compounds known for their biological activities which the presence of a therapeutic metal can enhance. The discovery of cisplatin as an effective anticancer metallodrug led to research into other metal‐based drugs, not only for anticancer but other biological applications such as antimicrobial, antirheumatic, and antidiabetic. Since metallic silver has been known to have antimicrobial efficacy, Ag(I)‐NHC complexes have been developed to enhance the therapeutic efficacy of both the metal and the NHC. In this study, we present a current review of the antimicrobial activity of several azolium salts and the corresponding NHC complexes of coinage metals (Ag, Au, and Cu in order of importance). We fully analyzed and discussed the efficacies of the complexes when benchmarked against the salts and commercially available antimicrobial drugs. Also highlighted where available are studies based on structure‐activity relationships, which included variations in the wingtip N ‐substituents of the ligands and changes in the type, number and oxidation state of the metal ions in the complex.