Synthesis, crystal structures, DNA binding, and cytotoxicity activities of two copper(II) complexes based on unsymmetrical tripodal ligands

[Cu(L1)Cl-2].3H(2)O (1) and [Cu(L2)Cl].2H(2)O (2) based on new unsymmetrical tripodal ligands (L1={(N-methyl-imidazolylmethyl)[N-methyl-N-(N-methyl-imidazolylmethyl)imidazolylmethyl]amino}ethanesulfonic acid, L2=[bis(2-pyridylmethyl)amino]ethanesulfonic acid) have been synthesized and characterized by elemental analysis, IR, and single-crystal X-ray diffraction. In the discrete mononuclear structures of 1 and 2, copper is five-coordinate in a distorted trigonal bipyramidal structure. Interaction of the complexes with CT-DNA was investigated by UV-vis spectra, fluorescence spectra, and viscosity; the data reveal that 1 and 2 bind to CT-DNA by partial intercalation. Gel electrophoresis assays demonstrate that these two complexes display efficient oxidative cleavage of supercoiled DNA in the presence of H2O2, and MTT assays indicated that both 1 and 2 showed significant cytotoxicity toward human hepatoma cell HepG-2.