Syntheses, characterizations, and a preliminary comparative cytotoxicity study of gold(I) and gold(III) complexes bearing benzimidazole- and pyrazole-derived N-heterocyclic carbenes

Abstract

A series of Au(I) and Au(III) mono-, homobis-, and heterobis(carbene) complexes, [AuCl(FPyr)] (2), [Au( iPr 2-bimy) 2]PF 6 (3), [Au(FPyr) 2]PF 6 (4), [Au(FPyr)( iPr 2-bimy)]PF 6 (5), [AuCl 3( iPr 2-bimy)] (6), [AuCl 3(FPyr)] (7), [AuCl 2( iPr 2-bimy) 2]PF 6 (8), [AuCl 2(FPyr) 2]PF 6 (9), and [AuCl 2(FPyr)( iPr 2-bimy)]PF 6 (10), bearing the benzimidazole-derived iPr 2-bimy (1,3-diisopropylbenzimidazolin-2-ylidene) and/or the pyrazole-derived FPyr (1,2,3,4,6,7,8,9-octahydropyridazino[1,2-a]indazolin-11-ylidene) N-heterocyclic carbene (NHC) ligands have been synthesized. Complexes 2-10 have been fully characterized using multinuclei NMR spectroscopy, ESI mass spectrometry, and elemental analysis. X-ray diffraction analyses have been performed on 2, 3, 5, 6, and 8. Together with the previously reported [AuCl( iPr 2-bimy)] (1), the cytotoxic activities of all 10 complexes have been studied in vitro with the NCI-H1666 non-small cell lung cancer cell line. The cationic bis(carbene) complexes 3-5 and 8-10 show better cytotoxicity in comparison to cisplatin. In particular, the heterobis(carbene) complexes 5 and 10 have superior activity, with IC 50 values of around 0.2 μM. © 2012 American Chemical Society.