Synthesis and Crystal Structure of a Three-dimensional Mn(Ⅱ) Coordination Polymer with 3-(Pyrazin-2-yloxy)-pyridine and Azide Anion as Mixed Bridge Ligand

A three-dimensional coordination polymer [Mn2（μ1.3-N3）4（μ-PP）2]n （PP = 3-（pyrazin-2-yloxy）-pyridine） has been synthesized with 3-（pyrazin-2-yloxy）-pyridine and azide anion as mixed bridge ligand, and its crystal structure was determined by X-ray crystallography. The crystal data： triclinic system, space group P1, with a = 6.794（4）, b = 9.885（6）, c = 9.947（6） A, α = 64.170（6）, β= 84.190（8）, γ= 85.319（8）°, V = 597.7（6）A^3, Z = 1, C18H14Mn2N18O2, Mr = 624.35, Dc = 1.735 g/cm^3, F（000） = 314 and μ = 1.117 mm^-1. In the crystal, the azide anion acts as a bridge ligand and makes adjacent Mn（Ⅱ） ions connect into a two-dimensional sheet on the ab plane, then 3-（pyrazin-2-yloxy）-pyridine serves as a bidentate bridge ligand to connect neighboring sheets along

High-pressure study on calcium azide(Ca(N_(3))_(2)):Bending of azide ions stabilizes the structure

The high-pressure structure and elastic properties of calcium azide(Ca(N_(3))_(2))were investigated using in-situ highpressure x-ray diffraction and Raman scattering up to 54 GPa and 19 GPa,respectively.The compressibility of Ca(N_(3))_(2)changed as the pressure increased,and no phase transition occurred within the pressure from ambient pressure up to 54 GPa.The measured zero-pressure bulk modulus of Ca(N_(3))_(2)is higher than that of other alkali metal azides,due to differences in the ionic character of their metal-azide bonds.Using CASTEP,all vibration modes of Ca(N_(3))_(2)were accurately identified in the vibrational spectrum at ambient pressure.In the high-pressure vibration study,several external modes(ext.)and internal bending modes(ν_(2))of azide anions(N_(3)^(-))softened up to~7 GPa and then hardened beyond that pressure.This evidence is consistent with the variation observed in the F_(E)–f_(E)data analyzed from the XRD result,where the slope of the curve changes at 7.1 GPa.The main behaviors under pressure are the alternating compression,rotation,and bending of N_(3)^(-)ions.The bending behavior makes the structure of Ca(N_(3))_(2)more stable under pressure.

ELECTROCHEMICAL INVESTIGATION ON CARBON NANOTUBE FILM WITH DIFFERENT PRETREATMENTS

Wide potential windows were found at carbon nanotube film electrodes in neutral solutions after being treated with nitric acid and mixed acid. Electrochemical reversibility was investigated at carbon nanotube films with different pretreatments for ferri/ferrocyanide and quinone /hydroquinone. Carbon nanotube film electrodes presented quasi-reversible electrochemical behavior for both electrolytes. In the range of scan rate, carbon nanotube film electrodes treated with acids showed heterogeneous electron-transfer properties, which was mainly controlled by its electron state density on the surface of the film. On the whole, the carbon nanotube electrode with nitric acid treatment presented the best electrochemical behaviors, so we chose it as an analytical electrode to determine the trace compound in dilute solution. The results demonstrated that this new electrode material exhibits superior performance characteristics for the detection of azide anion.

A New Tetra-nuclear Nd(Ⅲ) Coordination Polymer Based on Linear Azide and Isonicotinate Anions: Synthesis, Thermal Stability and Near-infrared Luminescent Properties

A novel tetra-nuclear Nd(Ⅲ) coordination polymer, Nd4(μ3-OH)4(μ2-H2O)2(C6H4NO2)6(N3)2(H2O)2(1, C6H4N zide anion), was successfully prepared under hydrothermal conditions and fully characterized by C, H and N elemental analysis, IR spectrum, thermal stability and single-crystal X-ray diffraction. It crystallizes in the triclinic system, space group P1, with Z = 1, a = 8.188(3), b = 12.516(5), c = 12.573(5) ?, α = 107.887(1)°, β = 104.681(2)°, γ = 98.086(6)°, V = 1152.2(8) ?3, M3 r = 1533.73, Dc = 2.210 g/cm, λ = 0.71073 ?, μ = 4.524 mm-1, F(000) = 736, R = 0.0332 and wR = 0.0901 for 3954 observed reflections with Ⅰ > 2σ(Ⅰ) and S = 1.071. The molecular structure of polymer 1 is constructed by four Nd3+ cations, four bridging μ3-OH- anions, two bridging μ2-H2 O, six C6 H4 NO2- anions, two linear azide anions and two coordinated water molecules. The structure of polymer 1 can be viewed as a 3-D supra-molecular network constructed by O-H···O and O-H···N hydrogen bonds between the adjacent chains. Moreover, its near-infrared luminescence and luminescence quenching for Cu2+ cation have also been investigated in detail.