Two Lanthanide(III) Complexes based on the Schiff Base N,N′-Bis(salicylidene)-1,5-diamino-3-oxapentane: Synthesis, Characterization, DNA-binding Properties, and Antioxidation

The Schiff base N,N'-bis(salicylidene)-1,5-diamino-3-oxapentane (H2L) and its lanthanide(III) complexes, PrL(NO3)(DMF)(H2O) (1) and Ho2L2(NO3)(2)center dot 2H(2)O (2), were synthesized and characterized by physicochemical and spectroscopic methods. Single crystal X-ray structure analysis revealed that complex 1 is a discrete mononuclear species. The Pr-III ion is nine-coordinate, forming a distorted capped square antiprismatic arrangement. Complex 2 is a centrosymmetric di-nuclear neutral entity in which the Ho-III ion is eight-coordinate with distorted square antiprismatic arrangement. The DNA-binding properties of H2L and its Ln(III) complexes were investigated by spectrophotometric methods and viscosity measurements. The results suggest that the ligand H2L and its Ln(III) complexes both connect to DNA in a groove binding mode; the complexes bind more strongly to DNA than the ligand. Moreover, the antioxidant activities of the Ln(III) complexes were in vitro determined by superoxide and hydroxyl radical scavenging methods, which indicate that complexes 1 and 2 have OH center dot and O-2(-center dot) radical scavenging activity.