Dong-Dong Li

A novel 1,2,4-triazole-based copper(II) complex: synthesis, characterization, magnetic property and nuclease activity.

A novel binuclear copper(II) complex [Cu(2)L(mu-SO(4))](PF(6))(2) (1) (L=3,5-bis (bis(pyridine-2-ylmethyl)amino)methyl)-4H-1,2,4-triazol-4-amine) has been synthesized and structurally characterized. X-ray structure shows that the two copper(II) atoms are bridged by one bidentate sulfate ion and the 1,2,4-triazole ring of L with Cu1cdots, three dots, centeredCu2 distance of 4.404A. Each copper(II) center has a distorted trigonal-bipyramidal configuration. Variable-temperature magnetic susceptibility studies (2-300K) indicate the existence of weak antiferromagnetic coupling between the copper(II) ions in complex 1. The interaction of complex 1 with calf thymus DNA (CT-DNA) has been studied by UV absorption, fluorescence spectroscopy, circular dichroism spectroscopy, viscosity and cyclic voltammetry. Furthermore, complex 1 was able to promote single and double strand DNA cleavage in both aerobic and anaerobic conditions, the pseudo-Michaelis-Menten kinetic parameters k(cat)=2.58h(-1) and K(m)=1.2x10(-4)M were obtained for 1. The hydrolytic cleavage of DNA by the complex was supported by the evidence from free radical quenching, anaerobic experiment, thiobarbituric acid-reactive substances (TBARS) assay.

A case study of the ZnII-BDC/bpt mixed-ligand system: positional isomeric effect, structural diversification and luminescent properties

To systematically investigate the influence of the positional isomeric ligands on the structures and properties of transition metal complexes, we synthesized eight Zn(II) complexes with three positional isomeric carboxylate ligands (p-BDC, m-BDC and o-BDC) and three positional isomeric dipyridyl bridging ligands (4,4′-bpt, 3,4′-bpt and 3,3′-bpt). {[Zn2(p-BDC)2(4,4′-bpt)2]·H2O·(C2H5OH)}n (1), {[Zn(p-BDC)(3,4′-bpt)2(H2O)2]·2H2O}n (2), {[Zn(p-BDC)(3,3′-bpt)2(H2O)2]·3H2O}n (3), {[Zn2(m-BDC)2(4,4′-bpt)(H2O)3]·H2O}n (4), [Zn(m-BDC)(3,4′-bpt)]n (5), {[Zn(m-BDC)(3,3′-bpt)]·H2O}n (6), [Zn(o-BDC)(4,4′-bpt)]n (7) and [Zn2(o-BDC)2(3,4′-bpt)]n (8) (p-BDC = 1,4-benzenedicarboxylate anion, m-BDC =1,3-benzenedicarboxylate anion, o-BDC = 1,2-benzenedicarboxylate anion, 4,4′-bpt = 1H-3,5-bis(4-pyridyl)-1,2,4-triazole, 3,4′-bpt = 1H-3-(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole and 3,3′-bpt = 1H-3,5-bis(3-pyridyl)-1,2,4-triazole). Structural analysis reveals that the benzenedicarboxylate isomers display versatile coordination modes to manage the Zn(II) ions to form 1D chains (for 2–5, 7 and 8) or 2D layers (for 1 and 6), which are further extended via the isomeric bpt connectors in different directions to give rise to a variety of coordination polymers, such as 1D decorated chain, 1D ladder-like chain, 2D sql layer, 2D bilayer with 82·10 topology, 2D wave-like layer, 3D 2-fold interpenetrating porous pcu net and 3D CsCl net. These results indicate that the nature of isomeric benzenedicarboxylates and bpt ligands has an important effect on the structural topologies of such Zn(II) complexes. Moreover, the luminescent properties of the complexes have been briefly investigated.

Synthesis, structure, and DNA binding of three reduced amino-acid Schiff-base zinc(II), nickel(II), and cadmium(II) complexes

Three new reduced amino-acid Schiff-base complexes, [Zn(HL)2] · H2O (1), [Ni(HL)2] · H2O (2), and [Cd(HL)2] · H2O (3), where H2L is a reduced Schiff base derived from condensation of N-(2-hydroxybenzaldehyde) and L-histidine, have been synthesized and characterized by elemental analysis, UV-Vis absorption spectra and single crystal X-ray diffraction. Complexes 1–3 are isostructural. All metal centers are six-coordinate with O2N4 donor sets in slightly distorted octahedra. Unlike its Schiff-base counterpart, the deprotonated monoanionic ligand HL− has a more flexible backbone and two HL− are tridentate to one metal. Moreover, the binding interactions of these complexes with calf thymus DNA (CT-DNA) have been investigated by UV-Vis spectra and fluorescence quenching, which show that the complexes bind in an intercalative mode.

Pillared cobalt–organic framework with an unprecedented (3,4,6)-connected architecture showing the coexistence of spin canting and long-range magnetic ordering

A novel (3,4,6)-connected 3D porous cobalt–organic framework formulated as {[Co2(Hbidc)2(bpt)2]·7H2O}n (1) (H3bidc = 1H-benzimidazole-5,6-dicarboxylic acid, bpt = 1H-3,5-bis(4-pyridyl)-1,2,4- triazole) has been hydrothermally synthesized and characterized by X-ray diffraction analysis. Compound 1, having a Co-Hbidc layer structure in which the layers are pillared by the bpt spacers in a 3D architecture, exhibits the coexistence of spin-canted weak ferromagnetism with TN = 10 K and long-range magnetic ordering.

Oxidative DNA cleavage by Cu(II) complexes of 1,10-phenanthroline-5,6-dione

A dimeric dichloro-bridged copper(II) complex [Cu2(pdon)2Cl4] · 2DMF (1) and two mononuclear copper(II) complexes [Cu(pdon)(DMSO)Cl2] · DMSO · H2O (2) and [Cu(pdon)3] · (ClO4)2 · 2.25CH3CN · 6H2O (3) (pdon = 1,10-phenanthroline-5,6-dione) have been synthesized and characterized. Variable-temperature magnetic susceptibility studies indicate the existence of weak anti-ferromagnetic coupling in the binuclear complex. The interaction of these complexes with CT-DNA (calf thymus DNA) has been studied using absorption and emission spectral methods. The apparent binding constants (K app) for 1, 2 and 3 are 5.20 × 105, 2.68 × 105 and 7.05 × 105 M−1, respectively, showing moderate intercalative binding modes. All of these complexes cleave plasmid DNA to nicked DNA in a sequential manner as the concentration or reaction time is increased. The cleavage mechanism between the complex and plasmid DNA is likely to involve singlet oxygen 1O2 and •OH as reactive oxygen species.

Synthesis, crystal structure and magnetic properties of an oxamato-bridged heterobinuclear NiIICuII complex [Ni(cyclam)Cu(opba)]2·3DMSO

An oxamato-bridged heterobinuclear NiIICuII complex [Ni(cyclam)Cu(opba)]2 · 3DMSO (1) has been synthesized, characterized by elemental analysis, infrared spectra and magnetic susceptibility, where cyclam is 1, 4, 8, 11-tetraazacyclotetradecane and opba is o-phenylenebis(oxamato). The complex crystallizes in the triclinic system, space group P 1 with a = 12.006(3) Å, b = 12.783(3) Å, c = 20.977(5) Å, α = 76.634(4)°, β = 75.172(4)°, γ = 80.818(4)° and Z = 2. According to X-ray crystallographic studies, the four-coordinate copper(II) atom is a slightly distorted planar geometry and is linked to nickel(II) through the exo-cis oxygen atoms of [Cu(opba)]2−; the six-coordinate nickel(II) center lies in a highly distorted octahedral environment. Magnetic susceptibility measurements of the complex in the temperature range 2–300 K indicate that the heterobinuclear NiIICuII units are coupled antiferromagnetically with J = −57.38 cm−1, g Ni = 2.25 and g Cu = 2.02.