Chromene-based Schiff base ligand: DNA interaction studies and characterization of tetranuclear zinc, nickel and iron complexes

Three tetranuclear clusters, Zn(II), Ni(II) and Fe(III), have been prepared using a new chromene-based Schiff base ligand (H 2 L) derived from the condensation of 2-aminophenol and 5-hydroxy-2,2-dimethyl-2H-chromene-6-carbaldehyde. The structures of the tetranuclear clusters were determined by single crystal X-ray diffraction and mass spectrometric analyses. The crystallographic data indicates that the Zn and Ni clusters have similar structures [M 4 L 4 (THF) 2 ] and contain a defective dicubane core, with each ligand coordinated to one metal ion through three donor atoms. The iron complex was obtained as a tetranuclear star shaped cluster [Fe 4 L 6 ], consisting of a central Fe(III) ion coordinated to six oxygen atoms, with three Fe(III) ions forming the corners of an equilateral triangle. The metal-mediated DNA cleavage ability of the free ligand, H 2 L, was determined using pBR322 plasmid DNA in the presence of Fe, Co, Ni, Cu, Zn and Cd acetate salts. H 2 L in combination with the Cu(II) salt resulted in significant DNA cleavage. The interaction of the ligand with DNA was investigated by UV–Vis titrations and molecular docking studies, which indicated favorable docking in the minor groove of DNA.