Application of the dimensional reduction formalism to Pb9-xBax[Li2(P2O7)2(P4O13)2] (x=0, 2, 6, 7): a series of phosphates with two types of isolated polyphosphate groups

A series of phosphates, Pb9-xBax[Li-2(P2O7)(2)(P4O13)(2)] (x = 0, 2, 6, 7), have been synthesized by a high temperature solution method and the crystal structures were determined by single crystal X-ray diffraction. They are isostructural and crystallize in the triclinic space group P (1) over bar. It is interesting that there are two kinds of isolated polyphosphate anionic groups coexisting in the crystal structure, which is rare among phosphates. Their structures exhibit zero-dimensional [Li-2(P2O7)(2)(P4O13)(2)](18-) anionic clusters constructed by the LiO4, P2O7 and P4O13 groups, which are separated by the Pb2+ or Ba2+ cations. The structure of Pb-9[Li-2(P2O7)(2)(P4O13)(2)] could be obtained using Li2O as a dimensional reduction agent to dismantle Pb3P4O13. In addition, the infrared spectra and the UV-Vis-NIR diffuse reflectance spectra, as well as thermal analyses are reported. The first-principles theoretical studies are also carried out to understand the relationship between their electronic structures and linear optical properties.