Fluorescent and Ultraviolet—Visible Spectroscopy Studies on the Antioxidation and DNA Binding Properties of Binuclear Tb(III) Complexes

Tb(III) complexes were prepared from Tb(NO₃)₃·6H₂O and four Schiffbase ligands derived from 8-hydroxyquinoline-2-carboxaldehyde with aroylhydrazines. X-ray crystal and other structural analyses indicate that Tb(III) and every ligand can form a binuclear Tb(III) complex with 1:1 metal-to-ligand stoichiometry and nine-coordination at the Tb(III) center. Viscosity titration experiments and fluorescent and ultraviolet-visible (UV-Vis) spectroscopy results indicate that all the Tb(III) complexes can bind to Calf thymus DNA through intercalation with the binding constants at the order of magnitude of 10⁶–10⁷ M^__1, and they may be used as potential anticancer drugs, but complexes containing active phenolic hydroxy groups may have stronger antitumor activities. Antioxidation results indicate that all the Tb(III) complexes have strong abilities of scavenging hydroxyl radicals and superoxide radicals, but complexes containing active phenolic hydroxy groups show stronger scavenging effects on hydroxyl radicals and complexes containing N-heteroaromatic substituent show stronger scavenging effects on superoxide radicals. However, Tb(III) emission with these systems is not observed, for these ligands rather are quenchers and unable to sensitize this metal ion.