Syntheses, Characterization, and DNA Binding Studies of a Series of Copper(II), Nickel(II), Platinum(II) and Zinc(II) Complexes Derived from Schiff Base Ligands

Three series of metal salophen complexes derived from Zn2+, Cu2+, Pt2+ and Ni2+ have been synthesized and their interaction with quadruplex DNA has been evaluated. The compounds differ on the number of ethyl piperidine substituents. They have been characterized by H-1 NMR, IR and UV-visible spectroscopies and by HR-mass spectrometry. Their luminescent properties have been also evaluated and we can observe that, as expected, Zn2+ and Pt2+ complexes are those displaying more interesting luminescence with an emission band red-shifted with respect to the corresponding uncoordinated ligand. DNA interactions with G4 and duplex DNA were evaluated by FRET melting assays (for the Zn2+, Cu2+ and Ni2+ complexes) and by emission titrations (for one Pt2+ complex) which indicated that the disubstituted compounds 2-Ni and 2-Pt are the only ones that display good affinity for G4 DNA structures.