HYDROTHERMAL SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF 2 LAYERED MIXED-VALENCE VANADYL PHOSPHATE HYDRATES NA0.50VOPO4.2.0H2O AND K0.50VOPO4.1.5H2O

The single crystals of two mixed-valence vanadium phosphates A0.50VOPO4.xH2O (A = Na, x = 2.0; A = K, x = 1.5) were grown hydrothermally. Their structures were characterized by single-crystal X-ray diffraction and thermogravimetric analysis. For Na0.50VOPO4.2.0H2O, triclinic, P1BAR, a = 6.2851 (7) angstrom, b = 6.284 (1) angstrom, c = 13.262 (2) angstrom, alpha = 80.30 (1)-degrees, beta = 87.434 (9)-degrees, gamma = 89.94 (1)-degrees, V = 515.7 (1) angstrom 3, Z = 4, and R = 0.0351, R(w) = 0.0480 for 2413 unique reflections. For K0.50VOPO4.1.5H2O, triclinic, P1BAR, a = 6.282 (2) angstrom, b = 6.285 (1) angstrom, c = 6.679 (2) angstrom, alpha = 89.11 (2)-degrees, beta = 72.84 (2)-degrees, gamma = 89.98 (2)-degrees, V = 251.9 (1) angstrom 3, Z = 2, and R = 0.0309, R(w) = 0.0369 for 1030 unique reflections. Both structures contain layers of distorted vanadium octahedra and phosphate tetrahedra with the water molecules and alkali-metal cations between the layers. The layer is a 4-connected net in which corner-sharing vanadium and phosphorus polyhedra alternate. These two structures are discussed along with the parent VOPO4.2H2O.