Studies on the manganese and copper complexes derived from chiral Schiff base: synthesis, structure, cytotoxicity and DNA/BSA interaction

Three new manganese and copper complexes, [Mn(ONO-(S)L1)2] (1), [Cu(ONO-(R)L2)]4·2CH3OH (2), and [Mn3(ONO-(S)L3)4(OAc)4(H2O)2] (3), {[H2L1 = (S)-2-phenyl-2-(2-hydroxy-5-chlorobenzylideneamino)ethane-1-ol], H2L2 = (R)-2-(2-hydroxy-5-chlorobenzylideneamino)butane-1-ol] and H2L3 = (S)-2-phenyl-2-(2-hydroxy-3-methoxybenzylideneamino)ethane-1-ol]}, have been synthesized. The crystal structures of 13 were determined through single-crystal X-ray diffraction. The structure of mononuclear 1 shows a six-coordinate octahedral geometry around the manganese ion. Complex 2 is a five-coordinate tetranuclear copper complex with the central Cu atoms adopting distorted square pyramidal geometry. Complex 3 shows a trinuclear structure with the six-coordinate Mn ions surrounded by four L3 ligands and acetate ions. The in vitro cytotoxicity screening revealed that the 1–3 had substantial cytotoxicity against three cancer cell lines (HepG2, MDA-MB-231, and A549), even higher than that of cisplatin. Inspiringly, 2 derived from (R)-Schiff base ligand H2L2 was more potent against MDA-MB-231 cells. Interaction of 13 with calf-thymus DNA (CT-DNA) has been investigated using UV-vis, viscosity and thermal denaturation experiments. It was found that 1 binds with DNA through intercalation while 2 and 3 interact with DNA probably through groove-binding and electrostatic mode. In addition, the capability of the complexes to bind with bovine serum albumin was monitored using some spectral techniques. The metal ions, chiral and nuclearity have significant influences on the properties of the title compounds.