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Influence of the pH for the CeIV - [AsIIIW9O33]9- association to the formation of hexanuclear cerium(IV) oxo-hydroxo-clusters stabilized by trivacant polyanions.

Abstract

Four hetero-polyoxometalate compounds were obtained in aqueous solution, following the synthetic combination of Na9[B--AsIIIW9O33] with the 4f tetravalent cerium cation, in the presence of formate ligand at different pH values (ranging from 1.5 to 6). Each of these four molecules [{Ce6(µ3 O)4(µ3 OH)4(HCOO)3,5}4(AsIIIW9O33)4]2- compound 1, [(Ce6(µ3 O)4(µ3 OH)4)(H2O)4(AsIIIW9O33)(HCOO)9]6- compound 2, [(Ce6(µ4 O)3(µ3 O)5 (µ2 H2O)3(HCOO)3(AsVW9O34)3]22- compound 3 and [(W4O10){(Ce6(µ3 O)5(µ4¬ O)3(µ2-H2O))(AsVW9O34)3}2]44- compound 4 are constructed around one to four hexanuclear cerium clusters of [Ce6O8] type. For the compounds 1-3, the arsenato-polytungstate POM units and formate ligands are associated and participate in the stabilization of one cerium(IV)-bearing hexanuclear unit in a cyclic motif (1), a monomeric POM species for 2, and a trimeric POM species for 3. However, in the last molecular system (4), only inorganic entities are bonded to the hexameric cerium(IV) clusters. From the structural point of view, compound 4 appears as the association of two compound 3 entities, in which the formate ligands have been replaced by an inorganic tungsten-based sub-unit, coming from the partial decomposition of the {AsIIIW9O33} precursor. The behavior and the association modes of the four molecular species are explained on the basis of the pH variation used for their syntheses. All four compounds have been characterized by single-crystal X-ray diffraction, IR spectroscopy, TGA and SEM/EDX microscopy and ICP analyses. Solution behavior was assessed on compound 3 by using Small Angle X-ray Scattering (SAXS) measurements.

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Publication details

The article was received on 21 Oct 2019, accepted on 27 Nov 2019 and first published on 28 Nov 2019


Article type: Paper
DOI: 10.1039/C9CE01663E
CrystEngComm, 2019, Accepted Manuscript

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    Influence of the pH for the CeIV - [AsIIIW9O33]9- association to the formation of hexanuclear cerium(IV) oxo-hydroxo-clusters stabilized by trivacant polyanions.

    M. Dufaye, S. Duval, G. Stoclet and T. Loiseau, CrystEngComm, 2019, Accepted Manuscript , DOI: 10.1039/C9CE01663E

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