AUTHOR=Goerigk Felix Christian , Locke Ralf Jules Christian , Schleid Thomas 

TITLE=Synthesis under high pressure: crystal structure and properties of cubic Dy36O11F50[AsO3]12 ∙ H2O

JOURNAL=Frontiers in Chemistry

VOLUME=12

YEAR=2024

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2024.1354690

DOI=10.3389/fchem.2024.1354690

ISSN=2296-2646

ABSTRACT=<p>The multi-anionic compound with the composition Dy<sub>36</sub>O<sub>11</sub>F<sub>50</sub>[AsO<sub>3</sub>]<sub>12</sub> ∙ H<sub>2</sub>O, which can be described in the non-centrosymmetric cubic space group <italic>F</italic><inline-formula id="inf1"><mml:math id="m1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mn>4</mml:mn><mml:mo>¯</mml:mo></mml:mover><mml:mn>3</mml:mn></mml:mrow></mml:math></inline-formula><italic>c</italic>, already shows an unusually large unit cell with an axis of <italic>a</italic> = 2587.59(14) pm. Its crystal structure exhibits isolated ψ<sup>1</sup>-tetrahedral [AsO<sub>3</sub>]<sup>3–</sup> anions, but both the coordination numbers and the linking schemes of the Dy<sup>3+</sup>-centered polyhedra differ significantly from the mostly layered structures described so far in literature. (Dy1)<sup>3+</sup> is sevenfold coordinated by oxygen atoms and F<sup>−</sup> anions, forming a capped trigonal prism [(Dy1)O<sub>4.333</sub>F<sub>2.667</sub>]<sup>8.333–</sup>, and the remaining two cations (Dy2)<sup>3+</sup> and (Dy3)<sup>3+</sup> both reside in an eightfold coordination of anions. In both cases they form slightly distorted square antiprisms, which have the compositions of [(Dy2)O<sub>3.667</sub>F<sub>4.333</sub>]<sup>8.667–</sup> and [(Dy3)O<sub>4.667</sub>F<sub>3.333</sub>]<sup>9.667–</sup>, respectively. Some of the oxygen atoms are not part of ψ<sup>1</sup>-[AsO<sub>3</sub>]<sup>3–</sup> tetrahedra, but occur as O<sup>2–</sup> anions and one of these even shares a common crystallographic position with fluoride (F<sup>−</sup>). It is also worth mentioning that the single crystals were obtained as comparatively large cubes with an edge length of several 100 µm providing very good data with regard to single-crystal X-ray diffraction. To verify the simultaneous presence of oxygen and fluorine, electron-beam microprobe analysis was carried out, and a single-crystal Raman spectrum ruled out the presence of hydroxide anions or protonated [AsO<sub>3</sub>]<sup>3–</sup> groups, but proved the interstitial crystal-water molecules, which could not be determined precisely by the crystal-structure refinement.</p>