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Hydrothermal Synthesis and Comparative Coordination Chemistry of New Rare-Earth V4+ Compounds
文摘
Several new hydrated rare earth vanadates and rare earth oxy-vanadates have been synthesized using hydrothermal techniques and characterized using single crystal and powder X-ray diffraction and infrared and UV鈥搗is absorption spectroscopies. The hydrated rare earth vanadates adopt the space group P21/m with general formula A3VO5(OH)3 (A = Y (1), Dy (2), or La (3)) and contain anionic distorted square pyramidal [VO5]鈭? units and AO7 and AO8 polyhedra. The oxy-vanadates with the general formula A2O(VO4) (A = Y (4), Dy (5; 6), or Yb (7)) form two polymorphs in either P21/c or C2/c space groups and contain anionic tetrahedral [VO4]鈭? units and nonvanadium bonded O2鈥?/sup> anions in distorted [OA4] tetrahedra. In all cases, the vanadium ion is in the tetravalent oxidation state, and its original source was the trace V4+ impurities in YVO4. The observed vanadyl and equatorial vanadium鈥搊xygen bond lengths about the square pyramid in compounds 1鈥?b>3 and the tetrahedral vanadium coordination found in compounds 4鈥?b>7 are unusual for V4+. The electronic and vibrational spectra are also reported and correlated with the appropriate coordination environment.
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