Synthesis, characterization, and anticancer properties of iminopyridine platinum(II) complexes containing long aliphatic chains‡

A series of iminopyridine ligands were prepared from the condensation reaction of 6-methylpyridine-2-carboxaldehyde and long chain aliphatic primary amines. Square planar platinum(II) complexes were synthesized from the reaction of [PtCl2(η2-coe)]2 (coe = cis-cyclooctene) with two equivalents of ligand. The synthesis of the platinum compounds appears to go through a 5-coordinate trigonal pyramidal species where coe remains coordinated initially but eventually dissociates to afford the 4-coordinate complexes. Ligands and platinum complexes were characterized using multi-nuclear NMR and FT-IR spectroscopies as well as an X-ray diffraction study for the platinum complex derived from n-hexylamine. The cytotoxic properties of the platinum complexes against the ovarian cancer cell line SKOV-3 using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric method were examined. Relative cytotoxicities of the platinum complexes follow a trend of greater potency with increasing chain length against the SKOV-3 cell line, with the longest aliphatic hydrocarbon chain (C16) exhibiting anticancer effects comparable to that of cisplatin.