Zaihui Yang

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.

Synthesis, crystal structure, and DNA-binding studies of different coordinate binuclear silver(I) complexes with benzimidazole open-chain ether ligands

Three new binuclear silver(I) complexes, namely, [Ag2(Meobb)2](pic)2·2H2O (1), [Ag2(Etobb)2(pic)](pic)·(CH3CN) (2) and [Ag2(Bobb)2(pic)2] (3) (Meobb = 1,3-bis(1-methylbenzimidazol-2-yl)-2-oxapropane, Etobb = 1,3-bis(1-ethylbenzimidazol-2-yl)-2-oxapropane, Bobb = 1,3-bis(1-benzylbenzimidazol-2-yl)-2-oxapropane, pic = picrate), have been synthesized and characterized by elemental analyses, IR spectroscopy and X-ray single crystal diffraction. Complex 1 displays an Ag2(Etobb)2 dimeric structure. Each silver(I) ion is coordinated to two nitrogen atoms that adopt a distorted linear configuration. In complex 2, the coordination environment of silver(I) atoms is different. The Ag1 ion is coordinated in a T-shaped tri-coordinated geometry and the Ag2 is best described to be in a distorted tetrahedron. Complex 3 exhibits a discrete di-silver metallacyclic framework. One silver atom (Ag1) is present in a distorted tetrahedral geometry, whereas the other silver atom (Ag2) is five-coordinated with two nitrogen atoms, oxygen atoms and the Ag1 to form a distorted square-based pyramidal configuration. The interactions of the three complexes with calf thymus DNA (CT-DNA) has been investigated by electronic absorption titration, fluorescence spectroscopy and viscosity measurements, and the modes of CT-DNA binding to the complexes have been proposed. Experimental results suggest that the silver(I) complexes bind to DNA in an intercalation mode, and their binding affinity for DNA follows the order 1 > 2 > 3. The DNA-binding studies demonstrate that steric hindrance has a large influence on the binding ability to DNA. The complex that has smaller steric hindrance binds more strongly to DNA.

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.

Manganese(II) and silver(Ι) complexes based on the V-shaped ligand, bis(2-benzimidazolylmethyl)amine: synthesis, crystal structures, DNA-binding properties, and antioxidant activities

Two Mn(II) and Ag(I) complexes, [Mn(IDB)2](pic)2 (pic = picrate) (1) and [Ag2(IDB)2](pic)2 (2) (IDB = bis(2-benzimidazolylmethyl)amine), have been synthesized and characterized by elemental analysis, IR, UV–vis spectral measurements, and X-ray single-crystal diffraction. Single-crystal X-ray diffraction revealed that Mn(II) is six-coordinate by six nitrogens from two IDB as a distorted octahedron, and the Ag(I) complex revealed two Ag(I) ions bonded to two IDB ligands through six nitrogens, resulting in an asymmetric binuclear structure. The complexes can bind to DNA through an intercalative mode, and the affinity for DNA is stronger for the Mn(II) complex than the Ag(I) complex; the Mn(II) complex exhibits excellent antioxidative activity. Graphical Abstract

Synthesis, crystal structures, antioxidant activities, and DNA-binding studies of two silver(I) complexes with 1,3-bis(1-ethylbenzimidazol-2-yl)-2-thiapropane, and α,β-unsaturated carboxylates

Abstract Two new ternary complexes of silver(I) with 1,3-bis(1-ethylbenzimidazol-2-yl)-2-thiapropane (bebt) and two ·α,β-unsaturated carboxylates, [Ag(bebt)(crotonate)] (1) and [Ag(bebt)2](o-coumarate)·CH3CN·2C2H5OH (2), have been synthesized, and characterized by physicochemical and spectroscopic methods. Single-crystal X-ray diffraction revealed that the coordination environment of 1 can be described as trigonal planar, while 2 has a distorted tetrahedral geometry. Experimental studies of the DNA-binding properties indicated that the free ligand and both complexes bind to DNA via intercalation, and the order of the binding affinity is 1 > bebt > 2. Antioxidant activity experiments show that 2 possesses significant antioxidant activity against hydroxyl radicals, with more efficient hydroxy radical scavenging compared with mannitol and vitamin C.

V-shaped ligand 1,3-bis(1-ethylbenzimidazol-2-yl)-2-thiapropane and manganese(II), cobalt(II) and copper(II) complexes: Synthesis, crystal structure, DNA-binding properties and antioxidant activities.

A V-shaped ligand 1,3-bis(1-ethylbenzimidazol-2-yl)-2-thiapropane (bebt) and its transition metal complexes, [Mn(bebt)(pic)2]·CH3OH (pic=picrate) 1, [Co(bebt)2](pic)22 and [Cu(bebt)2](pic)2·2DMF 3, have been synthesized and characterized. The coordinate forms of complexes 1 and 2 are basically alike, which can be described as six-coordinated distorted octahedron. The geometric structure around Cu(II) atom can be described as distorted tetrahedral in complex 3. The DNA-binding properties of the ligand bebt and complexes have been investigated by electronic absorption, fluorescence, and viscosity measurements. The results suggest that bebt and complexes bind to DNA via an intercalative binding mode and the order of the binding affinity is 1<2<3<bebt. The possible relations between the structure and DNA-binding properties are also discussed. Moreover, the complex 3 possess significant antioxidant activity against superoxide and hydroxyl radicals, and the scavenging effects of it are stronger than standard mannitol and vitamin C.

Syntheses, crystal structures, and DNA-binding properties of two nickel(II) complexes with 1,3-bis(benzimidazol-2-yl)-2-oxapropane derivatives

Abstract [Ni(obb)(DMF)2(H2O)]·(Pic)2·0.5DMF (1) and [Ni(Etobb)2]·(Pic)2·2DMF (2) (obb = 1,3-bis(benzimidazol-2-yl)-2-oxapropane, Etobb = 1,3-bis(1-ethylbenzimidazol-2-yl)-2-oxapropane, Pic = picrate) have been synthesized and characterized by physicochemical and spectroscopic methods. The structures of both complexes have been determined by X-ray single-crystal diffraction. The coordination geometries of 1 and 2 can be described as distorted octahedra. The interaction of the nickel(II) complexes with calf thymus DNA was investigated by electronic absorption, fluorescence spectroscopy, and viscosity measurements. The experimental results suggest that 1 and 2 bind to DNA in an intercalation mode, and their binding affinity for DNA follows the order 1 > 2. DNA-binding behaviors can be attributed to the large coplanar aromatic rings in the V-shaped ligand and steric hindrance.

Three- and four-coordinate Ag(I) complexes of crotonate and bis(benzimidazole)-2-oxapropane ligands: syntheses, crystal structures, DNA-binding studies and antioxidant activities

Abstract Two V-shaped ligands, namely 1,3-bis(1-ethylbenzimidazol-2-yl)-2-oxapropane (etobb) and 1,3-bis(1-benzylbenzimidazol-2-yl)-2-oxapropane (bobb), have been prepared. Reaction of these ligands with AgNO3 and sodium crotonate under in the dark afforded the complexes, [Ag(etobb)2](crotonate)·C2H5OH·2(CH3CN)·2(H2O) 1 and [Ag(crotonate)(bobb)] 2. Both complexes have been characterized by physicochemical and spectroscopic methods and also by X-ray single-crystal diffraction. The coordination environment of complex 1 can be described as distorted tetrahedral, while complex 2 has as a trigonal planar geometry. The DNA-binding properties of these complexes have been investigated by fluorescence, electronic absorption and viscosity measurements. The experimental results suggest that they bind to DNA by an intercalation mode. Complex 2 also exhibits excellent hydroxyl radical scavenging activity.

Syntheses, crystal structures, electrochemical studies, and antioxidant activities of zinc(II) and copper(II) complexes with bis(2-benzimidazolyl) aniline derivatives

Two ligands, bis(benzimidazol-2-ylmethyl) aniline (bba) and bis(N-methyl-benzimidazol-2-ylmethyl) aniline (Mebba), and their transition metal complexes [Zn(bba)(Br)2]·2DMF (1) and [Cu(Mebba)(Br)2]·2DMF (2) have been synthesized and characterized by elemental analyses, molar conductivities, UV–vis spectra, IR spectra, NMR spectroscopy, and X-ray crystallography. The structure around Zn(II) can be described as distorted tetrahedral. Complex 2 can be described as distorted trigonal bipyramidal. Cyclic voltammograms of 2 indicate a quasireversible Cu2+/Cu+ couple. Additionally, the antioxidant activities of the free ligands and their complexes were determined by the superoxide and hydroxyl radical scavenging methods in vitro. Complexes 1 and 2 possess potent hydroxyl radical scavenging activity and better than standard antioxidants such as vitamin C and mannitol. Complex 2 possesses excellent superoxide radical activity.

Synthesis, crystal structures, and DNA-binding studies of two silver(I) complexes with 1,3-bis(1-ethylbenzimidazol-2-yl)-2-thiapropane

Abstract Two new silver(I) complexes, [Ag(bebt)(methacrylate)] (1) and [Ag2(bebt)2](pic)2 (2) (bebt = 1,3-bis(1-ethylbenzimidazol-2-yl)-2-thiapropane, pic = picrate), have been synthesized and characterized by physico-chemical and spectroscopic methods. Single-crystal X-ray diffraction revealed that the structure of 1 was four-coordinate in a distorted tetrahedral geometry, while in 2, it may be described as a 2 + 1 coordinated silver(I) compound with a nearly linear N–Ag–N backbone and a weak Ag–S interaction. Two ligands are arranged in a face-to-face syn conformation to coordinate to two Ag(I) ions from opposite directions in 2, generating a U-type double layer structure around the metal ions. Experimental studies of the DNA-binding properties indicated that free bebt and both complexes bind to DNA via intercalation, and the order of the binding affinity is 2 > 1 > bebt.