Cold stress induces apoptosis in a multidrug resistant leukaemic cell line by a caspases-dependent mechanism

Abstract

Novel conformationally rigid half-sandwich organoruthenium(II) complexes ([(η6-p-cymene)Ru(η1-S-TSC1)Cl2], (1); [(η6-p-cymene)Ru(η1-S-TSC2)Cl2], (2) and [(η6-p-cymene)Ru(η2-N,S-TSC3)Cl]Cl, (3) have been synthesized from the reaction of [{(η6-p-cymene)RuCl}2(μ-Cl)2] with the respective thiosemicarbazones TSC1 (2-acetyl-5-chloro-thiophene thiosemicarbazone), TSC2 (2-acetyl-5-methyl-thiophene thiosemicarbazone) and TSC3 (3-thiophene aldehyde thiosemicarbazone) in a 1: 2 M ratio in methanol and all of the complexes have been characterized by elemental analysis, UV–Vis, FT-IR and 1H NMR spectroscopy. The crystal structures of TSC1, TSC2 and [(η6-p-cymene)Ru(η1-S-TSC2)Cl2], (2) have been determined by X-ray crystallography revealing that TSC1 and TSC2, crystallized in the monoclinic space group P21/c and complex (2) show a distorted octahedral geometry around the ruthenium centre. The mononuclear complex adopts a typical three legged piano-stool geometry (a description commonly used for half–sandwich compounds) with the metal centre coordinated by two chlorides and a TSC ligand. The coordination geometry around RuII atom is distorted octahedron with three sites occupied by the p-cymene ligand (with an ƞ6 coordination mode) while the remaining three sites occupied by the S atom of the TSC ligand and two Cl atoms. The spectroscopic studies showed that TSC1and TSC2 are coordinated to the central metal as a monodentate ligand coordinating via the thiocarbonyl sulfur atom (CS) in complexes (1) and (2), whereas TSC3 is coordinated to ruthenium as a bidentate ligand through azomethine nitrogen (CN) and sulfur atom in complex (3).