The growth of crystals of the high T c oxide superconductors has been hampe red by the complexities of the materials and their phase diagrams.The most common crys tal growth technique adopted for these oxides is the ...The growth of crystals of the high T c oxide superconductors has been hampe red by the complexities of the materials and their phase diagrams.The most common crys tal growth technique adopted for these oxides is the “flux”method,where the st arting materials are solved in a melt,which is usually formed by excess CuO and BaO or a KCl/NaCl mixture.The crystals are produced by slow cooling of the heate d solvent.This method,however,suffers from several disadvantages: (1) the crystals are contaminated with the crucible material, (2) the crystals are difficult to remove from the crucible, (3) the crystals contain flux inclusions.展开更多
We study some approximation properties of Lagrange interpolation polynomial based on the zeros of （1-x^2）cosnarccosx. By using a decomposition for f（x） ∈ C^τC^τ＋1 we obtain an estimate of ‖f（x） -Ln＋2（f, ...We study some approximation properties of Lagrange interpolation polynomial based on the zeros of （1-x^2）cosnarccosx. By using a decomposition for f（x） ∈ C^τC^τ＋1 we obtain an estimate of ‖f（x） -Ln＋2（f, x）‖ which reflects the influence of the position of the x＇s and ω（f^（r＋1）,δ）j,j = 0, 1,... , s,on the error of approximation.展开更多
The title compounds（PySe）2 1（HPySe=2-pyridineselenol N-oxide,（PySe）2= bis（2-pyridine-N-oxide） diselenide） and Bi2（PySe）6 2 were prepared by the reaction of 2-bromine-N-oxide with NaHSe and Bi（NO3）3·5H...The title compounds（PySe）2 1（HPySe=2-pyridineselenol N-oxide,（PySe）2= bis（2-pyridine-N-oxide） diselenide） and Bi2（PySe）6 2 were prepared by the reaction of 2-bromine-N-oxide with NaHSe and Bi（NO3）3·5H2O with HPySe,and the crystal structure of 2 was studied.Compound 2 crystallizes in the monoclinic space group P21/n with a=9.840（2）,b=10.204（2）,c=18.395（2）,β=102.926（2）°,V=1800.0（5）3,Dc=2.2687 g/cm3,Z=2,the final R=0.0319 and wR=0.0646.The Bi atoms are coordinated by four selenium and four oxygen atoms from four PySe ligands to form a slightly distorted four-column geometry.展开更多
Hydrogen evolution reaction is a critical reaction in water splitting for hydrogen production.However,developing effective and stable non‐noble‐metal electrocatalysts which work well at high current densities demand...Hydrogen evolution reaction is a critical reaction in water splitting for hydrogen production.However,developing effective and stable non‐noble‐metal electrocatalysts which work well at high current densities demanded by industry still remain great challenge.Herein,taking advantage of the highly tunable metal‐organic framework(MOF)templates,nitrogen doped binary transition metal phosphides electrocatalysts(N‐CoP_(x)/Ni_(2)P)with three‐dimensional(3D)conductive network structure were successfully synthesized.The 3D open porous channels could expose more catalytically active sites;nitrogen doping and the synergistic effect between CoP and Ni_(2)P can increase the electron density of Co atoms at active sites,further optimizing the Gibbs free energy of hydrogen(ΔGH*)and water(ΔG_(H_(2)O*)).As a result,the obtained N‐CoP_(x)/Ni_(2)P catalyst exhibits extraordinary electrocatalytic activity in a wide pH range.Especially,it requires an extremely low overpotential of 152 mV to deliver a high current density of 650 mA cm^(–2) in alkaline media.This work may shed some light on the rational design of cheap electrocatalysts and electrode materials that work well at high current densities.展开更多
The title compound, N-（2-（1,3,4-oxadiazol-2-yl）phenyl）-2,3-dimethylaniline, was synthesized and studied by single-crystal X-ray diffraction method. The structure of the product was confirmed by IR, ^1H- and ^13C-N...The title compound, N-（2-（1,3,4-oxadiazol-2-yl）phenyl）-2,3-dimethylaniline, was synthesized and studied by single-crystal X-ray diffraction method. The structure of the product was confirmed by IR, ^1H- and ^13C-NMR spectroscopy, elemental analysis and mass spectrometry. These experimental studies were supported by theoretical optimizations.展开更多
A new compound N-naphthyl-2-deoxy-α-D-ribopyranosylamine was synthesized and structurally determined. It crystallizes in the orthorhombic system, space group P212121 with a = 8.361（2）, b = 12.432（3）, c = 12.791（...A new compound N-naphthyl-2-deoxy-α-D-ribopyranosylamine was synthesized and structurally determined. It crystallizes in the orthorhombic system, space group P212121 with a = 8.361（2）, b = 12.432（3）, c = 12.791（4） A^°, Z= 4, V= 1329.6（6） A^°^3, Dc= 1.295 g/cm^3, F（000） = 552, Cl5H17NO3 and Mr= 259.30. All the active hydrogen atoms are involved in the formation of hydrogen bonds in the molecule.展开更多
By employing functional ligand 3,6-bis（3,5-dimethyl-lH-pyrazol-4-yl）-9-methyl- 9H-carbazole, a novel luminescent Ni complex has been obtained. Its structure was characterized by single-crystal X-ray diffraction anal...By employing functional ligand 3,6-bis（3,5-dimethyl-lH-pyrazol-4-yl）-9-methyl- 9H-carbazole, a novel luminescent Ni complex has been obtained. Its structure was characterized by single-crystal X-ray diffraction analysis. Crystal data： monoclinic, space group P2/c, a = 13.4224（18）, b = 13.759（2）, c = 8.0633（17）/~, fl = 96.448（3）~, C23H23NsNi（NO3）2, M,. = 552.19, V = 1479.7（4） A3, Z = 2, Dc = 1.239 g/cm3,/ffMoKa） = 0.700 mm-1, F（000） = 572, the final R = 0.0566 and wR = 0.1336 for 1638 observed reflections with I 〉 2a（/）. X-ray analysis indicates that each metal center coordinates with two N and two H atoms in tetrahedral interaction geometry. Weak interaction between Ni and N atom of pyrazole ligand and agostic bond （Ni...H-N interaction） play important roles in the formation of the 2-dimension framework. Significantly, this framework could pack into a tubular channel with NO3 anions trapped inside.展开更多
文摘The growth of crystals of the high T c oxide superconductors has been hampe red by the complexities of the materials and their phase diagrams.The most common crys tal growth technique adopted for these oxides is the “flux”method,where the st arting materials are solved in a melt,which is usually formed by excess CuO and BaO or a KCl/NaCl mixture.The crystals are produced by slow cooling of the heate d solvent.This method,however,suffers from several disadvantages: (1) the crystals are contaminated with the crucible material, (2) the crystals are difficult to remove from the crucible, (3) the crystals contain flux inclusions.
基金Supported by the National Nature Science Foundation.
文摘We study some approximation properties of Lagrange interpolation polynomial based on the zeros of （1-x^2）cosnarccosx. By using a decomposition for f（x） ∈ C^τC^τ＋1 we obtain an estimate of ‖f（x） -Ln＋2（f, x）‖ which reflects the influence of the position of the x＇s and ω（f^（r＋1）,δ）j,j = 0, 1,... , s,on the error of approximation.
基金supported by the Natural Science Foundation of Xuzhou city government (Nos XJ07069 and XJ08069)
文摘The title compounds（PySe）2 1（HPySe=2-pyridineselenol N-oxide,（PySe）2= bis（2-pyridine-N-oxide） diselenide） and Bi2（PySe）6 2 were prepared by the reaction of 2-bromine-N-oxide with NaHSe and Bi（NO3）3·5H2O with HPySe,and the crystal structure of 2 was studied.Compound 2 crystallizes in the monoclinic space group P21/n with a=9.840（2）,b=10.204（2）,c=18.395（2）,β=102.926（2）°,V=1800.0（5）3,Dc=2.2687 g/cm3,Z=2,the final R=0.0319 and wR=0.0646.The Bi atoms are coordinated by four selenium and four oxygen atoms from four PySe ligands to form a slightly distorted four-column geometry.
文摘Hydrogen evolution reaction is a critical reaction in water splitting for hydrogen production.However,developing effective and stable non‐noble‐metal electrocatalysts which work well at high current densities demanded by industry still remain great challenge.Herein,taking advantage of the highly tunable metal‐organic framework(MOF)templates,nitrogen doped binary transition metal phosphides electrocatalysts(N‐CoP_(x)/Ni_(2)P)with three‐dimensional(3D)conductive network structure were successfully synthesized.The 3D open porous channels could expose more catalytically active sites;nitrogen doping and the synergistic effect between CoP and Ni_(2)P can increase the electron density of Co atoms at active sites,further optimizing the Gibbs free energy of hydrogen(ΔGH*)and water(ΔG_(H_(2)O*)).As a result,the obtained N‐CoP_(x)/Ni_(2)P catalyst exhibits extraordinary electrocatalytic activity in a wide pH range.Especially,it requires an extremely low overpotential of 152 mV to deliver a high current density of 650 mA cm^(–2) in alkaline media.This work may shed some light on the rational design of cheap electrocatalysts and electrode materials that work well at high current densities.
基金supported by Urmia Branch,Islamic Azad University
文摘The title compound, N-（2-（1,3,4-oxadiazol-2-yl）phenyl）-2,3-dimethylaniline, was synthesized and studied by single-crystal X-ray diffraction method. The structure of the product was confirmed by IR, ^1H- and ^13C-NMR spectroscopy, elemental analysis and mass spectrometry. These experimental studies were supported by theoretical optimizations.
基金supported by the National Natural Science Foundation of China (No. 20132020)
文摘A new compound N-naphthyl-2-deoxy-α-D-ribopyranosylamine was synthesized and structurally determined. It crystallizes in the orthorhombic system, space group P212121 with a = 8.361（2）, b = 12.432（3）, c = 12.791（4） A^°, Z= 4, V= 1329.6（6） A^°^3, Dc= 1.295 g/cm^3, F（000） = 552, Cl5H17NO3 and Mr= 259.30. All the active hydrogen atoms are involved in the formation of hydrogen bonds in the molecule.
基金supported by the Natural Science Foundation of Zhejiang Province(Y5080308)
文摘By employing functional ligand 3,6-bis（3,5-dimethyl-lH-pyrazol-4-yl）-9-methyl- 9H-carbazole, a novel luminescent Ni complex has been obtained. Its structure was characterized by single-crystal X-ray diffraction analysis. Crystal data： monoclinic, space group P2/c, a = 13.4224（18）, b = 13.759（2）, c = 8.0633（17）/~, fl = 96.448（3）~, C23H23NsNi（NO3）2, M,. = 552.19, V = 1479.7（4） A3, Z = 2, Dc = 1.239 g/cm3,/ffMoKa） = 0.700 mm-1, F（000） = 572, the final R = 0.0566 and wR = 0.1336 for 1638 observed reflections with I 〉 2a（/）. X-ray analysis indicates that each metal center coordinates with two N and two H atoms in tetrahedral interaction geometry. Weak interaction between Ni and N atom of pyrazole ligand and agostic bond （Ni...H-N interaction） play important roles in the formation of the 2-dimension framework. Significantly, this framework could pack into a tubular channel with NO3 anions trapped inside.
