Cation‐Directed Dimeric versus Tetrameric Assemblies of Lanthanide‐Stabilized Dilacunary Keggin Tungstogermanates. Issue 38 (5th August 2014)

• Record Type: Journal Article
• Authors: Artetxe, Beñat; Reinoso, Santiago; San Felices, Leire; Lezama, Luis; Gutiérrez‐Zorrilla, Juan M.; García, José A.; Galán‐Mascarós, José Ramón; Haider, Ali; Kortz, Ulrich; Vicent, Cristian
• Is Part Of: Chemistry. Volume 20:Issue 38(2014)
• Page Start: 12144
• Page End: 12156
• Publication Date: 2014-08-05
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201403028
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Reaction of mid‐ to late lanthanide ions with GeO<sub>2</sub> and Na<sub>2</sub>WO<sub>4</sub> in NaOAc buffer results in a library of [Ln<sub>2</sub>(GeW<sub>10</sub>O<sub>38</sub>)]<sup>6−</sup> clusters (<bold>Ln<sub>2</sub></bold>), which consist of dilacunary Keggin fragments stabilized by the insertion of 4f atoms in the vacant sites and show the ability to undergo cation‐directed self‐assembly processes. In the presence of Na<sup>+</sup>, two β‐<bold>Ln<sub>2</sub></bold> subunits assemble by means of Ln‐O(WO<sub>5</sub>)‐Ln bridges to form the chiral [Ln<sub>4</sub>(H<sub>2</sub>O)<sub>6</sub>(β‐GeW<sub>10</sub>O<sub>38</sub>)<sub>2</sub>]<sup>12−</sup> dimeric anions (ββ‐<bold>Ln<sub>4</sub></bold>, Ln=Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu). When Cs<sup>+</sup> is present, two <bold>Ln<sub>4</sub></bold>‐like dimers further assemble into the [{Ln<sub>4</sub>(H<sub>2</sub>O)<sub>5</sub>(GeW<sub>10</sub>O<sub>38</sub>)<sub>2</sub>}<sub>2</sub>]<sup>24−</sup> species (<bold>Ln<sub>8</sub></bold>, Ln=Ho, Er, Tm, Yb, Lu). Two types of tetramers coexist in the solid state: One shows a full ββ‐<bold>Ln<sub>8</sub></bold> architecture, whereas the other one is a mixed αβ‐<bold>Ln<sub>8</sub></bold> assembly in which each β‐subunit is linked to its corresponding α‐<bold>Ln<sub>2</sub></bold> derivative. Regardless of differences in isomeric forms and the relative arrangement of <bold>Ln<sub>2</sub></bold> subunits, all anions display virtually identical {Ln<sub>4</sub>} cores as a common structural feature. A combination of ESI mass spectrometry and <sup>183</sup>W NMR spectroscopy experiments indicates that <bold>Ln<sub>8</sub></bold> tetramers fragment into <bold>Ln<sub>4</sub></bold> dimers upon dissolution, which undergo partial dissociation into <bold>Ln<sub>2</sub></bold> monomers and slow dimer/monomer equilibration. This is most likely followed by β‐to‐α isomerization of <bold>Ln<sub>2</sub></bold> clusters with consequent reassembly, as indicated by isolation of three additional αα‐<bold>Ln<sub>4</sub></bold> derivatives. Magnetic and photoluminescence properties in the <bold>Na</bold>‐ββ‐<bold>Ln<sub>4</sub></bold> series are also discussed.</p> </abstract>