Hydrothermal synthesis and crystal structure of a novel polymolybdic(VI) acid:: {[H3O]2+[Mo2O4(OH)6]2-}n

A novel supramolecular polymolybdic(VI) acid was unexpectedly synthesized by the reaction of sodium molybdate with 1,2,4,5-benzenetetracarboxylic and trichloroacetic acids in 1:1:1 molar ratio under hydrothermal condition. The crystal belongs to tetragonal with space group P-4/mbm, a = 0.88867(17), b = 0.88867(17), c = 0.55676(15) nm, Z = 3, V = 0.43969(17) nm(3), D-c = 4.486 g/cm(3), mu = 4.365 mm, F(OOO) = 576, R = 0.0273 and wR = 0.0679. In the crystal, the Mo(VI) atoms are six- and five-coordinated in distorted octahedral and trigonal bipyramidal geometries, respectively. Furthermore, these Mo(VI) atoms, bearing different coordinated environments, are bridged by OH groups with disorder 0 atoms to form a two-dimensional framework with pentagonal grids. It is worthy of notice that these adjacent two-dimensional frameworks are extended into a three-dimensional supramolecular array with pentagonal large cavities by Van Der Waals' forces and hydrogen bonding interactions.