Characterization of precipitates from the reactions between [Al13O4(OH)24(H2O)12]7+ polycations and [Mo7O24]6- polyoxometalate anions

The reactions between polycation [Al13O4(OH)(24)(H2O)(12)](7+) and polyoxometalate [Mo7O24](6-) in aqueous solutions produced precipitates composed of [Al13O4(OH)(24)(H2O)(12)](7+) [Mo7O24](6-) and [Al(OH)(6)Mo6O18](3-) ions. Infrared and solid state Al-27-NMR spectroscopic data identified the individual polyions in these precipitates. The compositions of the precipitates, derived from the integrated intensity ratio of the Al-27-NMR peaks for the [Al13O4(OH)(24)(H2O)(12)](7+) and [Al(OH)(6)Mo6O18](3-) and the Al/Mo ratios from ICP elemental analysis data, in addition to the charge balance considerations, reflect the composition of the reacting solutions. Depending on the composition, the [Al13O4(OH)(24)(H2O)(12)](7+) inside the precipitates can undergo oligomerization or polymerization reactions upon aging in contact with the mother liquor over a week, as evidenced by the solid-state Al-27-NMR data. (C) 2002 Elsevier Science B.V. All rights reserved.