Silver(I)-N-heterocyclic carbene complexes of bis-imidazol-2-ylidenes having different aromatic-spacers: synthesis, crystal structure, and in vitro antimicrobial and anticancer studies

A series of Ag(I) complexes (6, 7, 8, 9) derived from imidazol-2-ylidenes was synthesized by reacting Ag2O with an o-, m-, p-xylyl or 1,3,5-triazine-linked imidazolium salts (1, 2, 3, 4) and then characterizing these using various spectro-analytical techniques. Additionally, triazine-linked bis-imidazolium salt 5 was characterized using the single-crystal X-ray diffraction method. Complexes 6-9 were formed from the N-heterocyclic carbene ligand precursors 1-3 as PF6- salts in good yields. Conversely, salt 5 does not form Ag(I) complex even under various reaction conditions. Using ampicillin as a standard, complexes 6-9 were tested against bacteria strains Escherichia coli and Staphylococcus aureus as Gram-negative and Gram-positive bacteria, respectively, showing potent antimicrobial activities against the tested bacteria even at minimum inhibition concentration and bacterial concentration levels. Furthermore, the potential anticancer activities of the reported complexes were evaluated against the human colorectal cancer (HCT 116) cell lines, using 5-fluorouracil as a standard drug. The highest anticancer activities were observed for complex 8 with an IC50 value of 3.4 m, whereas the lowest was observed for complex 9 with an IC50 value of 18.1 m. Copyright (c) 2013 John Wiley & Sons, Ltd.