Coordination and Valence of Europium in the Heteropolyanion [EuP5W30O110]12-

Abstract

The synthesis and characterization of the Eu-encrypted heteropolyanion [ E U P~W~O O I 1 0 1 '~-are presented. X-ray absorption near-edge structure experiments were used to determine that Eu is trivalent in the anion. Optical spectra confirm this finding. The unusual cyclic voltammogram obtained for the Eu heteropolyanion is discussed in terms of the stability of Eu" under reducing conditions. Time delayed optical fluorescence data are only consistent with two structurally inequivalent Eu ions, both inside the heteropoly cavity. Lifetime measurements of the 5Do state indicate that the two structurally different Eu sites are not occupied in the same anion. In addition, from complementary measurements on samples made in D20, it is determined that there are three waters coordinated to Eu in one site and only two waters coordinated to Eu in the second site. 31P NMR and cyclic voltammetry data, obtained from samples with either one or two sites occupied, are indistinguishable. Possible models to explain the presence of two sites are discussed.

EPR Study of Gadolinium(III) Complexes with Heteropolyanions: [Gd(SiW11O39)2]13-and [GdP5W30O110]12-

“…[5,16], and 3 inner sphere H2O's in the case of europium-encrypted Preyssler anion, both in aqueous solution and the solid [4,5]. In the case of the gadolinium-encrypted complex the Gd3+ ion is unsymmetrically encapsulated with two bounded (probably linearly) water molecules and most likely the third water molecule is not directly encrypted [4,5].…”

“…The gadolinium-encrypted heteropolyanion [G dΡ5W30O110]12-was prepared from the parent Preyssler anion according to the previously described method [1,4,5]. Substitution of Na+ by Gd3+ was made according to the reaction The gadοliniumsandwiched complex [Gd(SiW11 O39)2H3-was obtained from the ligand K8[SiW11O39] .…”

Synthesis and Spectroscopic Study of Europium(III) in Heteropolyanion [EuP5W30O110]12-

“…It is difficult to explain the presence of three water molecules in the cylindrical cavity of the heteropolyanion since its diameter is too small (4 Å) to fit the Εu(Ill) ion with coordinated water molecules [4]. It is most likely that the Eu(III) ion is not symmetrically encrypted but near to the end of the anion cylinder, and so that sofiaie of the water is not directly encrypted.…”

“…The significance and wide interest of lanthan ide-encrypted Preyssler anions (and also [ΝaSb9W21O86] 18-heteropolyanion) concerns their potential antyviral activity and applications in catalysis [2][3][4][5]. The [ΝaΡ5W30O110]14-anion consists of five PW6O22 units (derived from the Keggin anion [PW12O40] 3-) arranged in a crown to form a cylindrical cavity.…”

“…In our study the Preyssler heteropolyanion [ΝaΡ5W30O110] 14-and its euro pium-encrylted heteropolyanion [EuP5W30O110]122-were synthesized according to modified by us previouSly described methodS [1,2,4]. We propose a new spectrophotometric procedure of tungSten determination based on previously described for W determination in nuclear materials and steels [7].…”