Comparisons of Pu(IV) and Ce(IV) Diphosphonates

The hydrothermal reaction of PuO2 with CH2(PO3H2)2 results in the formation of α-Pu[CH2(PO3)2](H2O), β-Pu[CH2(PO3)2](H2O) (1), γ-Pu[CH2(PO3)2](H2O) (2), and Pu[CH2(PO3)2](H2O)·H2O (3) as crystalline compounds with blue, green, red, and very pale peach coloration, respectively. In all cases single crystal X-ray diffraction studies reveals Pu4+ coordinated by [CH2(PO3)2]4− and water to yield PuO7 units. The methylenediphosphonate anions bridge between these units to yield three-dimensional networks. Bond-valence parameters of Ro = 2.068 and b = 0.385 have been derived for Pu4+ using a combination of the data reported in this work with that available in crystallographic databases. UV−vis−NIR spectroscopic measurements demonstrate that despite the dramatic color differences all of the compounds contain Pu4+, and that subtle changes in the visible region of the spectra account for different colors.

二氧化钚（PuO₂）与亚甲基二膦酸（CH₂(PO₃H₂)₂）发生水热反应，分别生成α-Pu[CH₂(PO₃)₂](H₂O)、β-Pu[CH₂(PO₃)₂](H₂O)（1号样品）、γ-Pu[CH₂(PO₃)₂](H₂O)（2号样品）以及Pu[CH₂(PO₃)₂](H₂O)·H₂O（3号样品）四种晶态化合物，其颜色依次为蓝色、绿色、红色与极浅桃色。
所有样品均通过单晶X射线衍射（Single Crystal X-ray Diffraction）表征，结果显示四价钚离子（Pu⁴⁺）与亚甲基二膦酸根阴离子（[CH₂(PO₃)₂]⁴⁻）及水分子配位，形成PuO₇配位单元。亚甲基二膦酸根阴离子在上述配位单元间发挥桥联作用，进而构筑出三维网络结构。
结合本文实验数据与晶体学数据库公开的相关数据，我们推导得到了四价钚离子的键价参数：Ro=2.068，b=0.385。
紫外-可见-近红外（UV-vis-NIR）光谱测试结果表明，尽管四种化合物的颜色差异显著，但其中均含有四价钚离子；光谱可见光区域的细微变化正是导致其颜色各异的原因。