Synthetic, characterization and cytotoxic studies of ruthenium complexes with Schiff bases encompassing biologically relevant moieties

Abstract

This research study describes the formation and characterization of novel paramagnetic ruthenium complexes, cis-Cl, trans-P-[RuIIICl2(carboim)(PPh3)2] with bidentate chelating carbohydrazide Schiff bases (carboim = bpc for 1, ttc for 2 and tpc for 3). These metal complexes were synthesized by the equimolar coordination reactions of trans-[RuCl2(PPh3)2] with N-[1,3-benzothiazole-2-ylmethylidene]pyridine-2-carbohydrazide (Hbpc), N-((uracil-5-yl)methylene)thiophene-2-carbohydrazide (Httc) and N-[(uracil-5-yl)methylidene]pyridine-2-carbohydrazide (Htpc), respectively. Physicochemical techniques including nuclear magnetic resonance-, electron-spin resonance- and infrared spectroscopy, UV–Vis spectrophotometry, voltammetry as well as molar conductivity measurements provided definitive determinations of the respective ruthenium compounds’ structures. The DPPH and NO radical scavenging capabilities of 1–3 and two previously reported ruthenium(II) complexes, trans-[RuCl(PPh3)2(Htdp)] (H2tdp = 5-((thiophen-3-yl)methyleneamino)-6-amino-1,3-dimethyluracil) (4) and [RuCl(PPh3)(H3ucp)] (H4ucp = 2,6-bis-((6-amino-1,3-dimethyluracilimino)methylene)pyridine) (5), were investigated. The calf-thymus DNA binding capabilities of 1–5 were explored using electronic spectroscopy and gel electrophoresis. In vitro anticancer studies showed that 1 and 2 were not active in the range tested, while 3–5 were toxic to HCC70 breast carcinoma cells, with 4 showing promising IC50 at 3.4 µM.