Diefenbach Kariem, Lin Jian, Cross Justin N, Dalal Naresh S, Shatruk Michael, Albrecht-Schmitt Thomas E
Department of Chemistry and Biochemistry, Florida State University , 95 Chieftan Way, 310 DLC, Tallahassee, Florida 32306, United States.
Inorg Chem. 2014 Jul 21;53(14):7154-9. doi: 10.1021/ic500181t. Epub 2014 Jun 25.
Two new neptunium selenites with different oxidation states of the metal centers, Np(IV)(SeO3)2 and Np(VI)O2(SeO3), have been synthesized under mild hydrothermal conditions at 200 °C from the reactions of NpO2 and SeO2. Np(SeO3)2 crystallizes as brown prisms (space group P21/n, a = 7.0089(5) Å, b = 10.5827(8) Å, c = 7.3316(5) Å, β = 106.953(1)°); whereas NpO2(SeO3) crystals are garnet-colored with an acicular habit (space group P21/m, a = 4.2501(3) Å, b = 9.2223(7) Å, c = 5.3840(4) Å, β = 90.043(2)°). Single-crystal X-ray diffraction studies reveal that the structure of Np(SeO3)2 features a three-dimensional (3D) framework consisting of edge-sharing NpO8 units that form chains that are linked via SeO3 units to create a 3D framework. NpO2(SeO3) possesses a lamellar structure in which each layer is composed of NpO8 hexagonal bipyramids bridged via SeO3(2-) anions. Bond-valence sum calculations and UV-vis-NIR absorption spectra support the assignment of tetravalent and hexavalent states of neptunium in Np(SeO3)2 and NpO2(SeO3), respectively. Magnetic susceptibility data for Np(SeO3)2 deviates substantially from typical Curie-Weiss behavior, which can be explained by large temperature-independent paramagnetic (TIP) effects. The Np(IV) selenite shows weak ferromagnetic ordering at 3.1(1) K with no detectable hysteresis, suggesting soft ferromagnetic behavior.
在200℃温和水热条件下，通过NpO₂与SeO₂反应合成了两种具有不同金属中心氧化态的新型亚硒酸镎，即Np(IV)(SeO₃)₂和Np(VI)O₂(SeO₃)。Np(SeO₃)₂结晶为棕色棱柱体（空间群P21/n，a = 7.0089(5) Å，b = 10.5827(8) Å，c = 7.3316(5) Å，β = 106.953(1)°）；而NpO₂(SeO₃)晶体为石榴石色，呈针状习性（空间群P21/m，a = 4.2501(3) Å，b = 9.2223(7) Å，c = 5.3840(4) Å，β = 90.043(2)°）。单晶X射线衍射研究表明，Np(SeO₃)₂的结构具有三维（3D）框架，由边共享的NpO₈单元组成链状结构，这些链通过SeO₃单元连接形成3D框架。NpO₂(SeO₃)具有层状结构，其中每层由通过SeO₃(2-)阴离子桥联的NpO₈六角双锥体组成。键价和计算以及紫外-可见-近红外吸收光谱分别支持了Np(SeO₃)₂和NpO₂(SeO₃)中镎的四价和六价态归属。Np(SeO₃)₂的磁化率数据与典型的居里-外斯行为有很大偏差，这可以用大的与温度无关的顺磁（TIP）效应来解释。亚硒酸Np(IV)在3.1(1) K时显示出弱铁磁有序，没有可检测到的磁滞现象，表明其具有软铁磁行为。
