Au(i)- and Pt(ii)-N-heterocyclic carbene complexes with picoline functionalized benzimidazolin-2-ylidene ligands; synthesis, structures, electrochemistry and cytotoxicity studies

Novel Au(I)-N-heterocyclic carbene complexes, 1-methyl-3-(2-pyridylmethyl)-benzimidazolylidenegold(I)-chloride, 1; 1-benzyl-3-(2-pyridylmethyl)-benzimidazolylidenegold(I)chloride, 2; and Pt(II)-N-heterocyclic carbene complexes 1-methyl-3-(2-pyridylmethyl) benzimidazolylidene platinum(II)chloride, 3; and 1-benzyl-3-(2-pyridylmethyl) benzimidazolylidene platinum-(II)chloride, 4, have been synthesized, based on CN-donor proligands 1-alkyl-3-(2-pyridylmeth-yl)-benzimidazoliumchloride L1 and L2 [alkyl, R = –CH3 = L1; R = –CH2Ph = L2]. All the compounds have been synthesized and characterized by different spectroscopic methods. The Au(I) complexes 1 and 2 have been synthesized by a silver carbene transfer method. The solid-state structures of 1 and 3 have been determined by single crystal X-ray diffraction studies. The square planar Pt(II) complexes 3 and 4 show a reversible Pt(II)/Pt(IV) couple at 0.69 eV and 0.67 eV respectively. Among the complexes 1–4, complexes 1 and 3 have been used for cytotoxicity studies on the cell lines B16F10 (mouse melanoma), HepG2 (human hepatocarcinoma) and HeLa (human cervical carcinoma). IC50 values are compared with cisplatin, among 1 and 3, the Au(I) complex 1 is more effective than Pt(II) complex 3.