Synthesis and crystal structure of a new copper(II) complex with N,N′-(4,4′-bithiazole-2,2′-diyl)diacetimidamide as ligand: Molecular docking, DNA-binding and cytotoxicity activity studies

A new mononuclear copper(II) complex with formula of [Cu2H(DABTA)2](pic)⋅6H2O, where H2DABTA and pic− stand for N,N′-(4,4′-bithiazole-2,2′-diyl)diacetimidamide and picrate ion, respectively, has been synthesized and characterized by elemental analysis, molar conductivity measurement, IR and electronic spectra studies, and single-crystal X-ray diffraction. The crystal structure reveals that the copper(II) ion has a {CuN4} square-planar coordination environment. The solvent water molecules form a column parallel to c axis by hydrogen bonds. Then the mononuclear copper complexes link to the water columns to make a three-dimensional hydrogen bonding grid with the cavities filled by pic− anions. Besides, there are offset π–π stacking interactions between thiazole rings in the supramolecular system. The interactions between the copper(II) complex and herring sperm DNA (HS-DNA) have been investigated by using electronic absorption titration, fluorescence titration and viscometry. The molecular docking of the complex with the self-complementary DNA duplex of sequence d(ACCGACGTCGGT)2 demonstrates that the complex is stabilized by additional electrostatic and hydrogen bonding interaction with the DNA. The copper(II) complex exhibits potent anticancer activities against human hepatocellular carcinoma cell SMMC-7721 and human lung adenocarcinoma cell A549.