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

Abstract

[II] have been chosen for EPR study. This study is a continuation of our recent investigation related to solid gadolinium complexes: β-diketonates and aminopolycarboxylates. The EPR spectra of the Gd-polyoxometalates studied provide much better resolution than those recently studied. The spectra of Gd-polyoxometalates containing 1.7 to 2.5% of Gd(HI) do not require an additional computer processinng for correct interpretation. It is on tle contrary to the β-diketonates and polyamieocarboxylates (witl the content of Gd(III) 22-33%) for which the use of the RKU computer program (based on Fourier transform) was necessary in .order to enhance the spectra resolution thus improving their correct interpretation. Tle EPR spectra obtained for the compounds Ι and II markedly differ from the U-spectrum characteristic of Gd(HI) in glasses. Taking into account the spin-Hamiltonian calculations the existence of Gd(III) ion in two different surroundings: in a strong crystal freld of rhombic symmetry and in a weak crystal field, is observed. The differences observed between the case I and II seem to be related to a various hydration degree.

Synthesis and spectroscopic characterisation of chosen heteropolyanions and their Ln(III) complexes containing tetrabutylammonium counter ion

“…These splittings can be attributed to two different coordination sites of tungsten and phosphorus atoms in the polyhedron. The same trend was observed earlier in the case of the europium ion in complex with Preyssler anion [11,13,32]. Similar band splittings were also indicated in IR [14] (Fig.…”

“…Potassium salts of the POMs studied were synthetised and characterised as published earlier [12][13][14][15][16][17][18] according to procedures described in [19][20][21][22][23][24]. The tetrabutylammonium salts (NBu 4 POM) were obtained using the modified procedure [25] developed by Finke and co-workers [26].…”

“…In our previous study the POM anions and its europium complexes were prepared and spectroscopically (UV-Vis, FTIR, EPR and luminescence spectroscopy) characterised in solid (as potassium salt and in xerogel matrix) and in aqueous media [12][13][14][15][16][17][18]. Therefore, it is great interest to know, what occurs if the POMs anion has transferred to non-aqueous media.…”

Polyoxo Anions: Synthesis and Structure

“…[147][148][149][150][151][152] Spectroscopic, luminescence, and ESR studies have been reported for some of the lanthanide-encrypted anions. [153][154][155][156][157][158] All the anions show reversible tungsten-reduction processes, and there is some evidence to suggest that divalent europium is generated in partially reduced [Eu(H 2 O)P 5 W 30 O 110 ] nÀ . 159 Proton exchange on the internal water molecule has been traced by NMR measurements.…”

Spectroscopic Studies of Polyoxometalates and their Complexes with Lanthanide(III) Ions in Solution

“…It was found three water molecules in the inner sphere of Eu(III) in the europium-encapsulated complex in aqueous solution and in the solid state. The gadolinium-encrypted Preyssler anion [GdΡ5W30O110]12-, and gadolinium sandwiched (between the defect site of two ligands) complex, such as [Gd(SiW11O39)2] 122-, we selected for EPR study [39].…”