Hydrothermal synthesis and structural characterization of a gallium pyromellitate Ga(OH)(btec)•0.5H2O, with infinite Ga-(μ2-OH)Ga chains (MIL-61)

A new gallium carboxylate Ga(OH)(btec)center dot 0.5H(2)O (MIL-61) was synthesized under mild hydrothermal conditions (200 degrees C, 24 hours) in the presence of 1,2,4,5-benzenetetracarboxylic (btec) acid and water. The crystal structure, characterized by means of Rietevelt refinement of powder XRD data, consists of trans chains of GaO4(OH)(2) octahedra, connected to each other through a mu(2)-OH group. The three-dimensional framework is built up from these chains linked together via the organic molecules so delimiting the cavities where the water molecules are encapsulated. Analysis by solid state NMR (1 H and C-13) has confirmed the presence within the structure of both water molecules and carboxylate moieties partially deprotonated. The structure of Ga(OH)(btec)center dot 0.5H(2)O corresponds to that of MIL-61 obtained with vanadium replacing gallium. Crystal data for Ga-4(OH)(4)((HO2C)(2)-C6H4-(CO2)(2))(4)center dot 2H(2)O: a = 14.8325(10) angstrom, b = 6.7792(10) angstrom, c = 10.6726(10) angstrom, V 1073.2(2) angstrom(3), Prima (n degrees 62). (c) 2005 Elsevier SAS. All rights reserved.