Abstract
A series of symmetrically n-alkyl-substituted mono benzimidazolium salts with steady increase in n-alkyl chain length have been prepared by stepwise N-alkylation resulting in salts (1-8). The mono N-heterocyclic carbene (NHC)-Ag(I) complexes (9-16) derived from the respective salts were readily accessible by in situ deprotonation using Ag2O. All the salts and the complexes were characterized using Fourier transform infrared, H-1 NMR, C-13 NMR and elemental analyses. Furthermore, the structures of salts 3 and 7 and complex 16 were elucidated using X-ray crystallography, which established that this mono NHC-Ag(I) complex has a linear biscarbene arrangement (C-2-Ag). The proligands and the respective Ag(I) complexes were studied for their in vitro anticancer potential against human colon cancer cell line (HCT-116) using 5-fluorouracil as a standard. From the IC50 values of all the tested compounds, it can be postulated that there is an influential relationship between the increase in chain length of the wingtip n-alkyl groups and the anticancer potential. The proligands 4-8 and their respective complexes 12-16 with long n-alkyl chain lengths (n = 6-10) showed better IC50 values (0.3-3.9 mu M) than the standard drug with the complexes displaying markedly better antiproliferation activity against HCT-116 cell line than the respective proligands and the standard drug (IC50 = 10.2 mu M).