Ag(I)-N-heterocyclic carbene complexes of N-allyl substituted imidazol-2-ylidenes with ortho-, meta- and para-xylyl spacers: Synthesis, crystal structures and in vitro anticancer studies

A series of N-allyl substituted xylyl-linked imidazolium salts (7-10) and their respective Ag(I)-N-heterocyclic carbene (NHC) complexes (11-14) have been synthesized and characterized by a number of spectral and analytical techniques. Molecular structure of complexes 13 and 14 were established by single-crystal X-ray diffraction method. The in vitro anticancer activity of all imidazolium salts and their Ag(I)-carbene complexes were investigated using human colorectal (HCT 116) cancer cell lines. Imidazolium salts displayed no activity for HCT 116 cell lines, except for 9; yielding IC50 value of 15.9 mu M. Ag(I)-carbene complexes 12-14 showed exceptionally good activity (0.9-1.3 mu M) against tested cancer cell lines. Furthermore, complex 11 displayed relatively good anticancer activity with IC50 value of 5.2 mu M, which is almost equal to standard used. (C) 2012 Elsevier B.V. All rights reserved.