Yanhui Zhang

Synthesis, crystal structure, antioxidation and DNA-binding properties of a dinuclear copper(II) complex with bis(N-salicylidene)-3-oxapentane-1,5-diamine

A Schiff base bis(N-salicylidene)-3-oxapentane-1,5-diamine (H2L) and its Cu(II) complex, [Cu2(L)2]∙CHCl3, have been synthesized and characterized by physicochemical and spectroscopic methods. Single-crystal X-ray analysis revealed that the complex is a centrosymmetric binuclear neutral entity, in which Cu(II) is a five-coordinate in a distorted trigonal bipyramidal geometry. The DNA-binding properties of the free ligand and the complex have been investigated by electronic absorption, fluorescence, and viscosity measurements. The results suggest that the H2L and the complex to DNA via the intercalation mode and the binding affinity of the complex were higher than that of the H2L. The intrinsic binding constants Kb of the ligand and the complex are 2.2 × 104 and 2.7 × 104 M−1, respectively. Antioxidant assay in vitro shows the Cu(II) complex possesses significant antioxidant activities and better scavenging activity than the H2L and other antioxidants. Graphical Abstract

Synthesis, structure, antioxidation, and DNA-binding studies of a binuclear ytterbium(III) complex with bis(N-salicylidene)-3-oxapentane-1,5-diamine

A new complex of ytterbium(III) nitrate with bis(N-salicylidene)-3-oxapentane-1,5-diamine (H2L), with the composition Yb2(L)2(NO3)2·2H2O, was synthesized and characterized by physic-chemical and spectroscopic methods. The crystal structure of the ytterbium(III) complex has been determined by single-crystal X-ray diffraction. It reveals a centrosymmetric binuclear neutral entity where Yb(III) metal centers are bridged by two phenoxo oxygen atoms. Electronic absorption titration spectra, ethidium bromide displacement experiments, and viscosity measurements indicate that both the ligand and the Yb(III) complex can bind calf thymus DNA, presumably via a groove binding mechanism. Furthermore, the antioxidant activities of the Yb(III) complex were determined by a superoxide and hydroxyl radical scavenging method in vitro, which indicates that it is a scavenger for OH and O2− radicals.

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⋅6H2O afforded three novel complexes, namely, Sm(L)(NO3)(DMF)(H2O) 1, [Eu(H2L)2(NO3)3]n2 and Tb2(L)2(NO3)23. 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 Eu(3+) 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 Kb of the complexes 1-3 are (1.19±0.112)×10(5), (4.22±0.086)×10(4) and (3.89±0.104)×10(4) M(-)(1) respectively. Moreover, the antioxidant activity experiments show that these compounds also exhibit good antioxidant activities against OH· and O2(-·) in vitro studies.

Gadolinium(III) and dysprosium(III) complexes with a Schiff base bis(N-salicylidene)-3-oxapentane-1,5-diamine: synthesis, characterization, antioxidation, and DNA-binding studies

A pentadentate Schiff base bis(N-salicylidene)-3-oxapentane-1,5-diamine (H2L) and its lanthanide(III) complexes, [GdL(NO3)(DMF)(H2O)] (1) and [Dy2L2(NO3)2]·2H2O (2), have been synthesized and characterized by physical, chemical, and spectroscopic methods. Single crystal X-ray structure reveals that 1 is a discrete mononuclear species with nine-coordinate Gd(III) in a distorted mono-capped square antiprism geometry. Complex 2 is a centrosymmetric binuclear neutral entity, in which Dy(III) is eight-coordinate in a distorted square antiprism. Electronic absorption titration spectra, ethidium bromide competitive experiments, and viscosity measurements indicate that both the ligand and complexes bind calf thymus DNA, presumably via groove binding. Investigations of antioxidant activities show that both complexes have some scavenging effects for hydroxyl and superoxide radicals.

Preparation, structure, DNA-binding properties, and antioxidant activities of a homodinuclear erbium(III) complex with a pentadentate Schiff base ligand

An erbium (III) complex of a pentadentate Schiff base ligand [(NO3)Er(μ-L)2Er(NO3)].2H2O [H2L=bis(N-salicylidene)-3-oxapentane-1,5-diamine] has been synthesised, characterised and its structure confirmed by X-ray crystallography. H2L and the Er(III) complex both bind to DNA via a groove binding mode, and the Er(III) complex binds to DNA more strongly than H2L. The complex shows strong scavenging effects for hydroxyl radicals (OH·) and superoxide radicals (O2-).

V-shaped ligand bis(2-benzimidazolylmethyl)amine containing three copper(II) ternary complexes: synthesis, structure, DNA-binding properties and antioxidant activity

Three copper(II) ternary complexes with the V-shaped ligand bis(2-benzimidazolylmethyl)amine (bba), with composition [Cu(bba)(crotonate)]·ClO4 (1), [Cu(bba)(methacrylate)]·ClO4 (2) and [Cu(bba)(acrylate)(CH3OH)]·NO3·H2O (3), have been synthesized and characterized by elemental analyses, molecular conductivities, IR, UV spectra and X-ray single crystal diffraction. The copper ions in these three complexes have a similar coordination mode, which can be described as a five-coordinated tetragonal pyramid geometry. The interaction of the ligand bba and copper(II) complexes with calf thymus DNA was investigated by electronic absorption, fluorescence spectroscopy and viscosity measurements. The experimental results suggest that the ligand bba and copper(II) complexes bind to DNA in an intercalation mode, and their binding affinity for DNA follows the order 2 > 1 > 3 > bba. The main reason for the DNA-binding behaviors can be attributed to the large coplanar aromatic rings in the V-shaped ligand. Such a trend in the DNA-binding affinities of the bba ligand and copper(II) complexes binding to DNA can be reasonably explained by the change of the electron density, the V-shaped angle (αV) and the value of τ. Moreover, the antioxidant assay in vitro also shows that the copper(II) complexes possess significant antioxidant activities.

A Schiff base bis(N-salicylidene)-3-oxapentane-1,5-diamine and its yttrium(III) complex: synthesis, crystal structure, DNA-binding properties, and antioxidant activities

A Schiff base bis(N-salicylidene)-3-oxapentane-1,5-diamine (H2L) and its yttrium(III) (Y(III))complex, Y2L2(NO3)2·2H2O, have been synthesized and characterized by physico-chemical and spectroscopic methods. The crystal structure of the Y(III) complex has been determined by single-crystal X-ray diffraction, revealing a centrosymmetric binuclear neutral entity where Y(III) centers are bridged by two phenoxo oxygens. The DNA-binding properties of the Schiff base H2L and the Y(III) complex were investigated by spectrophotometric methods and viscosity measurements. The results suggest that ligand H2L and Y(III) complex both bind to DNA via groove binding, and the Y(III) complex binds to DNA more strongly than H2L. The antioxidant activity of the Y(III) complex was determined by superoxide and hydroxyl radical-scavenging method in vitro, which indicates that Y(III) complex scavenges OH· and O2 −· radicals.

DNA-binding studies and antioxidant activities of two-, three- and four-coordinate silver(I) complexes containing bis(2-benzimidazolyl)aniline derivatives

Three ligands bis(benzimidazol-2-ylmethyl)aniline (bba), bis(N-methylbenzimidazol-2-ylmethyl)aniline (Mebba), and bis(N-ethylbenzimidazol-2-ylmethyl)aniline (Etbba) have been prepared. Reaction of these shape-specific designed ligands with Ag(pic) (pic = picrate) afforded three novel complexes, namely, [Ag2(bba)2](pic)2·2DMF 1, [Ag(Mebba)2](pic)·Et2O 2 and [Ag(Etbba)(pic)] 3. The ligands and Ag(I) complexes were characterized by elemental analysis, UV-vis, IR, NMR and X-ray crystallography. 1 is a dinuclear metallacycle with 2-fold rotational symmetry in which two syn-conformational bba ligands are connected by two linearly coordinated Ag(I) atoms. 2 consists of a centrosymmetric uninuclear pore canal structure assembled from a Ag(I) ion and two Mebba ligands, resulting in a distorted tetrahedron geometry. The structure of 3 consists of a ligand of Etbba, one picrate anion, and one Ag(I) atom, and the coordination geometry around Ag(I) is best described as Y-shaped. 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 experimental results suggest that Ag(I) complexes bind to DNA in an intercalation mode, and their binding affinity for DNA follows the order 2 > 1 > 3. Moreover, antioxidant activities of the title complexes have been investigated. The result demonstrates that the three Ag(I) complexes have a strong potential to be applied as scavengers to eliminate hydroxyl and superoxide radicals in vitro.

The V-shaped ligand bis(N-allylbenzimidazol-2-ylmethyl)benzylamine and its Ag(I) complex: Synthesis, crystal structure, DNA-binding properties and antioxidation

A novel dinuclear Ag(I) complex of the type, [Ag2L2](pic)2, was synthesized by the reaction of the V-shaped ligand bis(N-allylbenzimidazol-2-ylmethyl)benzylamine (L) with Ag(pic) (pic=picrate). Ligand L and Ag(I) complex were characterized on the basis of elemental analysis, UV-vis, IR, NMR spectroscopy and X-ray crystallography. Single-crystal X-ray revealed that two L coordinated to a central silver(I) cation in a near-linear fashion through their benzimidazol-1-yl nitrogen atoms, and a centrosymmetric dinuclear pore canal structure was constructed in the discrete [Ag2L(2)2](2+) cation. The DNA-binding properties of the free ligand L and Ag(I) complex have been carried out by using electronic absorption, fluorescence, and viscosity measurements. The results support that ligand L and Ag(I) complex both bind to DNA via an intercalative binding mode, and the affinity for DNA is more strongly in case of Ag(I) complex when compared with ligand L. Moreover, Ag(I) complex also exhibited potential antioxidant properties in vitro studies.

Synthesis, crystal structures, electrochemical studies, and antioxidant activities of manganese(II) and copper(II) complexes of bis(N-allylbenzimidazol-2-ylmethyl)aniline

Abstract Bis(N-allylbenzimidazol-2-ylmethyl)aniline (baba) and its transition metal complexes, [Mn(baba)(Cl)2] 1 and [Cu(baba)(Br)2]·DMF 2, have been synthesized and characterized by physico-chemical and spectroscopic methods. The structures of both complexes have been determined by X-ray single-crystal diffraction. The coordination environment of complex 1 can be described as distorted trigonal bipyramidal, while complex 2 has as a distorted square-pyramidal geometry. Cyclic voltammograms of complex 2 indicate an electrochemically irreversible Cu2+/Cu+ couple. In addition, the antioxidant activities of both baba and its complexes were investigated by hydroxyl and superoxide radical scavenging methods in vitro. Both of these complexes exhibit excellent radical scavenging activity.