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    STUDIA PHYSICA - Issue no. 2 / 2008  
         
  Article:   SPECTROSCOPIC INVESTIGATION OF SOME UO22+ POLYOXOMETALATE COMPLEXES.

Authors:  N.L. MOGONEA, I. HAUER, D. COZMA, I.B. COZAR, A. MARCU, L. DAVID. 		 
       
         
  Abstract:  The Na10[(UO2)2(H2O)2X2W20O70]∙nH2O heteropolyoxometalates (1: X =SbIII, n = 28; 2: X =BiIII, n = 34) were synthesized and investigated by thermal analysis, FT-IR and UV-Vis spectroscopy in order to determine the coordination, the ordering of cation electronic levels and his local symmetry. By comparing FT-IR spectra of the uranyl complexes with the corresponding ligand (L1= Na12[Sb2W22O74(OH)2] and L2= Na12[Bi2W22O74(OH)2]) the coordination UO22 ions to the POM lacunars unities have been estimated. The UV electronic spectra of the UO22 -POM complexes are similar to the ones of the ligands L1 and L2. Each spectrum presents two bands assigned to the charge transfer from the ligand to the metal pπ→dπ transitions in W=O bonds and dπ–pπ–dπ electronic transitions between the W-Ob-W bonds energy levels.
   The spectroscopic investigations of Na10[(UO2)2(H2O)2X2W20O70], X = SbIII (1), BiIII (2) complexes indicate a sandwich-type structure formed by two B-β-XW9O33 fragments binding by two uranyl ions and two WO2 units.

Keywords: Thermal analysis, FT-IR and UV-vis spectroscopy, Chemical complexes. 		 
         
     
         
         
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