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[Li2(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. 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 [Li2(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 Pb9[Li2(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.