Synthesis,characterization, crystal structure and oxygen-evolution activity of a manganese(II) complex with 2,4,6-tris (2-pyridyl)-1,3,5-triazine

The title complex [Mn(tptz)(CH₃COO)(OH₂)₂]NO₃ was synthesized through the reaction of tptz (2,4,6-tris(2-pyridyl)-1,3,5-triazine), nitric acid and manganese(II) acetate. The molecular structure was characterized by X-ray diffraction, elemental analysis, electrochemistry, EPR, IR, fluorescence and UV–Vis spectroscopy and its oxygen evolving activity has been studied. X-ray structure analysis shows that each Mn(II) ion is seven coordinated by a bidentate acetate, three nitrogen atoms of tptz and two oxygen atoms from two water ligands, which are coordinated in axial positions. The complex acts as an oxygen evolving complex with oxone (2KHSO₅·KHSO₄·K₂SO₄) as primary oxidant in aqueous solution with a turnover number of 1 (mol of O₂/mol of the complex). Kinetic studies revealed a first-order dependence on the complex and oxidant. The EPR spectrum shows that the mononuclear complex oxidize to a Mn^III,IV₂ di-μ-oxo by oxone.     

α-[Mn(O2CMe)2]: a two-dimensional coordination polymer of the anhydrous manganese acetate polymorphs

Abstract  Two polymorphs of crystalline anhydrous manganese acetate, α-[Mn(O₂CMe)₂] (1) and β-[Mn(O₂CMe)₂] (2), were prepared under temperature-controlled solvothermal dehydration. X-ray single-crystal (and powder) diffractions revealed that compound 1 crystallizes in monoclinic (a = 9.763(4), b = 4.972(2), c = 6.122(3) ?, β = 102.878(5)°, V = 289.7(2) ?³, Z = 4) space group P2/c. Although it was early prepared, its single crystal structure is firstly determined and known as a two-dimensional (2D) layer structure; whereas, compound 2 demonstrates a three-dimensional diamondoid (dia-e) structure that people in its early X-ray single-crystal study was not aware of. Graphical Abstract  Anhydrous α-[Mn(O₂CMe)₂] was discovered in 1967, which two-dimensional layer structure is firstly determined by the X-ray single-crystal analysis. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Evolution of ( La 1 - y Pr y ) 0.7 Ca 0.3 MnO 3 crystal structure with A-cation size, temperature, and oxygen isotope substitution

The atomic structure of ( La _{1 - y} Pr _y ) _0.7 Ca _0.3 MnO ₃ compound with 0.5≤ y ≤1 has been systematically studied by neutron powder diffraction in the temperature range from 15 to 293 K. For composition with y = 0.75, the structural analysis was performed on two samples, one containing the natural mixture of oxygen isotopes and the other one 75% enriched by ¹⁸ O. The room temperature structural characteristics of the series, including cell volume, average Mn-O bond distance, and average Mn-O-Mn bond angle, are the linear functions of the < r _A >. Temperature dependencies of these parameters are quite smooth, except for the point T = T _FM , where a jump like changes occur. The isotope enriched samples have been found identical in crystal and magnetic structure down to the temperature of transition of the sample with ¹⁶ O into the metallic ferromagnetic phase. It confirms that different transport and magnetic properties of the samples with ¹⁶ O and ¹⁸ O at low temperature are driven by the different oxygen atoms dynamics solely. Temperature dependencies of the CO and AFM diffraction peak intensities and of the peak widths for compositions close to the metal-insulator boundary ( y ≈ 0.75) indicate the macroscopically phase separated AFM-dielectric + FM-metallic state below T _FM . Received 28 April 2000     

单晶Ni纳米线阵列的制备与磁性能

采用恒电流沉积方法, 在多孔阳极氧化铝(AAO)模板中制备出了具有单晶结构的Ni纳米线阵列. 采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和X射线衍射(XRD)技术对制备的Ni纳米线阵列的形貌及结构进行了表征. 利用振动样品磁强计(VSM)对单晶Ni纳米线阵列的磁性能进行了研究. 结果表明, 单晶镍纳米线阵列的易磁化方向为纳米线轴向, 并且与多晶纳米线相比显示出了更高的矫顽力. 直径为30 nm的纳米线具有较高的矫顽力(8.236×104 A/m)和较高的剩磁比(Mr＝0.94Ms).