Two caesium vanadium hydrogenphosphates with tunnelled structures: Cs(2)V(2)O(3)(PO(4))(HPO(4)) and Cs(2)[(VO)(3)(HPO(4))(4)(H(2)O)].H(2)O.

Dicaesium divanadium trioxide phosphate hydrogenphosphate, Cs(2)V(2)O(3)(PO(4))(HPO(4)), (I), and dicaesium tris[oxidovanadate(IV)] hydrogenphosphate dihydrate, Cs(2)[(VO)(3)(HPO(4))(4)(H(2)O)].H(2)O, (II), crystallize in the monoclinic system with all atoms in general positions. The structures of the two compounds are built up from VO(6) octahedra and PO(4) tetrahedra. In (I), infinite chains of corner-sharing VO(6) octahedra are connected to V(2)O(10) dimers by phosphate and hydrogenphosphate groups, while in (II) three vanadium octahedra share vertices leading to V(3)O(15)(H(2)O) trimers separated by hydrogenphosphate groups. Both structures show three-dimensional frameworks with tunnels in which Cs(+) cations are located.