Synthesis, Characterization and Biological Studies of Nickel ( Ii) and Zinc ( Ii) Complexes with Mono - and Di - Bromo Substituted Schiff Base Ligands

Abstract

Transition metal complexes of nickel(II) and zinc(II) with 5-bromo- N -(8-quinolyl)salicylaldimine (HqsalBr, HL 1 ) and 3,5-dibromo- N -(8-quinolyl)salicylaldimine (HqsalBr 2 , HL 2 ) have been synthesized and successfully characterized using several techniques: IR, 1 H-NMR, mass spectrometry and thermogravimetric analysis (TGA). The molecular structures of nickel(II) and zinc(II) complexes with HL 2 were determined by single crystal X-Ray crystallography. Ligands HL 1 and HL 2 both act as a tridentate ligand and coordinate to metal ion center via deprotonated hydroxyl oxygen atom, nitrogen of azomethine functional group and nitrogen of quinoline substituent. The interaction of these complexes with DNA was investigated using calf thymus DNA (CT-DNA) in which the studies by electronic absorption and luminescence titrations reveal that DNA binding mode of the complexes is intercalation. All the synthesized complexes provide great values of binding constant (K b ) and these results are consistent with the quenching capability defined by quenching constant values (K q ). Amongst the synthesized complexes, zinc(II) with ligand HL 2 complex, [Zn(qsalBr) 2 ], exhibits the most superior ability in the interaction with CT-DNA and the verification mode of binding by the competitive reaction with ethidium bromide (EB) also indicates the strongest intercalation by such complex. Additionally, ligands and complexes were also examined in anti-lung cancer activity against A549 cell line and compared with standard compounds, Etoposide and Cisplatin.