Generation of Large Polynuclear Rare Earth Metal-Containing Organic-Inorganic Polytungstoarsenate Aggregates

Eight members of a new family of polyoxometalate (POM)-ligated organic-inorganic rare earth metal compounds K11LiH21[RE3(H2O)(7){RE2(H2O)(4)As2W19O68(WO2)(2)(C6O7H4)(2)}(3)]center dot nH(2)O (RE = Y (1), Tb (2), Dy (3), Ho (4), Er (5), Tm (6), Yb (7), Lu (8); for compounds 1-6 and 8, n = 46; for compound 7, n = 57; C6H8O7 = citric acid) have been synthesized through conventional aqueous solution by introducing organic ligand citric acid into the arsenotungstates system, which were further characterized by elemental analyses, IR and UV spectroscopy, thermogravimetric analyses, and single-crystal X-ray diffraction. The polyoxoanions [RE3(H2O)(7){RE2(H2O)(4)As2W19O68(WO2)(2)(C6O7H4)(2)}(3)](33-) in compounds 1-8 are composed of three {RE2(H2O)(4)As2W19O68{WO2(C6O7H4)}(2)} subunits linked by another three rare earth ions. What's more, the fluorescence properties of 2 and 3 have also been investigated. Electron paramagnetic resonance (EPR) experiments further demonstrated the result of the interesting photochromic property.