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

The hydrothermal reaction of PuO2 with CH2(PO3H2)(2) results in the formation of alpha-Pu[CH2(PO3)(2)](H2O), beta-Pu[CH2(PO3)(2)](H2O) (1), gamma-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 R-o = 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.