The Chemistry of Dinuclear Silver N-Heterocyclic Carbene Complexes

Dinuclear silver N-heterocyclic carbene (Ag-NHC) complexes are readily accessible either by reacting imidazolium salts (e.g., Cl, Br, PF₆, BPh₄) with Ag₂O or by the direct formation of the carbene from 1,3-disubstituted imidazol-2-ylidenes with a suitable base (e.g., KHMDS) followed by addition of silver salts (e.g., AgPF₆). Many Ag-NHC complexes have shown considerable potential across various fields due to their versatile properties. Notably, the lability of silver-carbene bonds enables efficient ligand transfer to other transition metals, thereby enhancing catalytic, photophysical, antimicrobial, and anticancer activities -key topics discussed in this review. Complexes with square geometries are particularly effective as chemosensors, offering low detection limits, high sensitivity, and selectivity. In antimicrobial and anticancer research, complexes with lipophilic side chains, benzimidazole groups, and silver -silver interactions show encouraging results, in some cases surpassing standard drugs. Despite these advances, their catalytic potential remains underexplored, with current catalysts showing performance similar to mononuclear analogs. Future studies should focus on designing catalysts with cooperating silver centers and incorporating novel functionalities, such as halogenated imidazoles, to improve both biological activity and catalytic efficiency.