A MIXED-VALENCE VANADIUM PHOSPHATE WITH A TUNNEL STRUCTURE - RB6V6P6O31

A new mixed-valence vanadium phosphate Rb6V6P6O31 has been isolated. Its structure was determined from single-crystal X-ray diffraction data. It crystallizes in the orthorhombic space group Pnma with a = 7.0656(4) Å, b = 13.4988(8) Å, c = 14.4198(9) Å, v = 1375.3(2) Å3, Z = 4, R = 0.049, and Rw = 0.052 for 1058 unique reflections with I > 3σ(I). The three-dimensional framework [V6P6O31]∝ can be described by the assemblage of octahedral [VO3]∝ chains with double chains [V2P2O10]∝ built up from single PO4 tetrahedra and double pyramidal units V2O9. The cohesion of the framework is achieved by P2O7 groups which share their corners with V2O9 units. This host lattice delimits very large tunnels running along b and five-sided tunnels running along a. The rubidium cations are located at the intersection of these tunnels. © 1991.