gyong Chen

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

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.

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.

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.

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.

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.

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.

Two 1,8-naphthalimide-based proton-receptor fluorescent probes for pH determination

Two newly synthesised 1,8-naphthalimide-based proton-receptor fluorescent probes N-allyl-4-(4’-N,N-diethylpropionamide-acetamido-piperazinyl)-1,8-naphthalimide I and N-(N,N-dibenzylpro- pionamide-acetamido)-4-allyl-1-piperazinyl-1,8-naphthalimide II were synthesised to monitor the change in pH in such a way that the presence of protons can increase the fluorescence intensity of these compounds. Unlike most of the other pH-sensitive probes reported, the probes possess the obvious advantage of being able to detect stronger acids at pH ≈ 2 and a combination of the two probes could detect a wider pH scale from 1.98 to 6.59; this should be very useful for monitoring the pH of the environment.

1,8-Naphthalimide derivative-based turn-off fluorescent probe for the detection of picrate in organic aqueous media

Abstract The synthesis of a simple fluorescent naphthalimide-based receptor N-allyl-4-iminodi(N-butylacetamide)-1,8-naphthalimide 3 was carried out as a selective picrate (Pic–) anion probe, and the detecting behavior of this probe was studied by fluorescence spectroscopy. In DMF solution, the interaction of compound 3 with different anions, including Pic–, F–, Cl–, Br–, I–, OH–, Ac–, NO3–, ClO4–, SCN–, SO32–, SO42–, H2PO4–, and HPO42–, revealed significant fluorescence quenching only with the Pic– anion. By adding the picrate anions, green-yellow fluorescence emission quenches, which is easily observed by naked eyes under a 365 nm UV light irradiation. This phenomenon is essential for producing a highly selective and sensitive fluorescent probe for picrate anions. The probe can be applied to the quantification of Pic– with a linear range covering from 4.97 × 10–6 to 6.82 × 10–5 m and a detection limit of 5.8 × 10–7 m. Most importantly, probe 3 has a high selectivity for picrate over competitive anions and picrate-containing analytes, which meet the selective requirements for practical application. Thus, the present results would be inspiring findings in the future design of reaction-based fluorescent turn-off probes for the environmentally relevant picrate probe.