Study on synthesis, crystal structure, antioxidant and DNA-binding of mono-, di- and poly-nuclear lanthanides complexes with bis(N-salicylidene)-3-oxapentane-1,5-diamine

A Schiff base ligand bis(N-salicylidene)-3-oxapentane-1,5-diamine H2L have been prepared. Reaction of the shape-specific designed ligand with Ln(NO3)(3)center dot 6H(2)O afforded three novel complexes, namely, Sm(L)(NO3)(DMF)(H2O)1, [Eu(H2L)(2)(NO3)(3)](n)2 and Tb-2(L)(2)(NO3)(2)3. The ligand and complexes were characterized by elemental analysis, UV-Vis, IR, NMR spectroscopy and X-ray crystallography. It is noteworthy that the complexes demonstrate three different types of the structure which changed according to the charge density and acidity of the lanthanide. Complex 1 is a discrete mononuclear species that Sm(III) ion is nine-coordinated in the structure and forming a distorted tricapped trigonal prism geometry. Complex 2 is possessed a 1-D ribbon framework constructed from an extended array of ten-coordinated Eu3+ centers and the Schiff base ligands. Complex 3 is revealed as a centrosymmetric binuclear neutral entity, in which Tb(III) ion is eight-coordinated with the coordination surround of distorted square antiprism geometry. In order to explore the relationship between the structure and biological properties, the DNA-binding properties have been investigated by electronic absorption, fluorescence, and viscosity measurements. The results suggest that the ligand and complexes bind to DNA via groove modes. The intrinsic binding constants K-b of the complexes 1-3 are (1.19 +/- 0.112) x 10(5), (4.22 +/- 0.086) x 10(4) and (3.89 +/- 0.104) x 10(4) M-1 respectively. Moreover, the antioxidant activity experiments show that these compounds also exhibit good antioxidant activities against OH center dot and O-2(-center dot) in vitro studies. (C) 2014 Elsevier B.V. All rights reserved.