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    STUDIA PHYSICA - Issue no. SPECIAL ISSUE / 2001  
         
  Article:   COORDINATION OF URANIUM(IV) IONS TO MONOLACUNAR AND TRILACUNAR KEGGIN-TYPE HETEROPOLYOXOMETALATES. SPECTROSCOPIC AND MAGNETIC INVESTIGATION.

Authors:  L. DAVID, O. COZAR, D. RUSU.
 
       
         
  Abstract:  Eight complexes with different numbers of uranium ions K12[U(BW11O39H)2]23H2O, K19[U2KAs4W40O140]42H2O, Nam[(UO)3(H2O)6(XW9O34)2]nH2O (X = P, m = 12, n = 21; X = Si, m = 14, n = 19; X = Ge, m = 14, n = 17) and Nam[U3(XW9O33)2]nH2O (X = As, m = 6, n = 15; X = Bi, m = 6, n = 18; X = Sb, m = 6, n = 16) have been investigated by spectroscopic (IR, UV-VIS, ESR) and magnetic susceptibility methods. In all complexes the UIV ions are coordinated by eight oxygen atoms in a cvasicubic local environment. The ground state of the 3H4 multiplet is 1 for the complex with one UIV ion, but 5 for that with two uranium ions. Uranium(IV) complexation intensifies the charge transfer in the tricentric WOb,cW bonds. In the complexes with two and three uranium ions, the actinides are antiferromagneticaly coupled.  
         
     
         
         
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