SYNTHESIS, CHARACTERIZATION, AND INTERCALATION OF VANADYL PHOSPHATE MODIFIED WITH MANGANESE

A yellow-brown crystalline solid, stable in air and having a variable composition of [Mn(H2O)](x)(VO)(1-x)PO4 . 2H(2)O (O less than or equal to x less than or equal to 0.25), has been prepared by the reaction of solid V2O5 with a boiling aqueous solution of H3PO4 and KMnO4. The elementary cell of this compound is tetragonal (space symmetry group either Win or P4/nmm) with the following parameters for x = 0.25: a = 0.62034 nm, c = 1.3814 nm, V = 0.51359 nm(3), Z = 4, M(r) = 199.44, D-calc = 2.492 g/cm(3), and D-exp = 2.52 g/cm(3). The magnetic behavior of this substance indicates the presence of manganese atoms at the oxidation level of III. The paramagnetic centers formed by the MnIII atoms are not markedly magnetically coupled. The structure of the compound is probably derived from the original layered lattice of vanadyl phosphate hydrate VOPO4 . 2H(2)O by replacement of at most one quarter of the vanadyl groups ((VO)-O-V)(3+) by [Mn-III(H2O)](3+) groups. Upon being heated, the substance forms a monohydrate at first, then the anhydrous salt forms, and finally the water coordinated with manganese atoms escapes. The compound can be intercalated with foreign molecules and ions in the same way as vanadyl phosphate, and the results of intercalation experiments with methanol, ethanol, 1-propanol, 1-butanol, 1-butylamine, 1-octylamine, formic acid, acetic acid, and pyridine, as well as those of oxidation-reduction intercalation with a solution of sodium iodide in acetone, are presented. The experimental conditions of the intercalations are described. The layered complexes formed have been identified by powder X-ray structure analysis, thermogravimetry, differential thermal analysis, and infrared absorption spectroscopy. (C) 1995 Academic Press, Inc.