Crystal structures of the microporous compounds M-6(V2O3)(2)(VO)(2)(PO4)(4)(HyP2-xVxO7) with M=K+, Tl+

Brownish compounds of M-6(V2O3)(2)(VO)(2)(PO4)(4)(HyP(2-x)V(x)O(7)) were pr epared hydrothermally and were found to crystallize in the orthorhombic sym metry (space group Pmn2(1)) with cell parameters a = 13.5043(7) Angstrom, b = 6.9895(2) Angstrom, c = 14.1962(8) Angstrom (K+): a = 13.5372(5), B = 7. 1765(1) Angstrom, c = 14.3812(3) (Tl+). Their structures were solved from s ingle crystal X-ray diffraction down to the reliability factors R-1(Fo) = 0 .048 (K+), 0.042 (Tl+). The three dimensional network consists of infinite [VO3] chains of trans sharing distorted octahedra and dimers [V2O6] built u p from the linkage of square planar pyramids [VO5]. The chains and the dime rs are assembled through PO4 bridges. In addition, disordered and partially substituted (HyP2-xVxO7) groups that run along b ensure the connectivity b etween adjacent [V2O6] units. The resulting host lattice consists of inters ecting tunnels in which the univalent cations are located. (C) 2001 Elsevie r Science Ltd. All rights reserved.