Three salicylaldehyde derivative Schiff base ZnII complexes: synthesis, DNA binding and hydroxyl radical scavenging capacity

Three new Schiff base ligands N-(3-formyl-5-methylsalicylidene)-2-aminoethanol (H2L1), N-(3-hydroxylmethyl-5-methylsalicylidene)-2-aminoethanol (H3L2), 2,6-bis(o-carboxyphenyliminomethene)-4-methylphenol (H3L3) and their binuclear ZnII complexes [Zn2(HL1)2]Cl2 · 2H2O (ZnHL1), [Zn2(H2L2)2]Cl2 · H2O (ZnH2L2) and [Zn2(HL3)Cl2] · H2O (ZnHL3) were synthesized and characterized by 1H-NMR, elemental analysis, IR and molar conductivity. The results suggest, in every case, two Zn2+ ions were bridged by phenolic OH group oxygen, forming a binuclear complex. The binding properties of these complexes to calf thymus DNA (ct-DNA) were investigated. Absorption and fluorescence spectra are together suggestive that both ZnHL1 and ZnHL3 interact with ct-DNA through intercalative mode, while ZnH2L2 interact with ct-DNA by non-intercalative interaction. Moreover, ZnHL3 can bind to ct-DNA more strongly than ZnHL1. These complexes also exhibited good scavenging activity on the hydroxyl radical (•OH), which are better than those of their corresponding ligands.