Variable Dimensionality, Valence, and Magnetism in Fluoride-Rich Iron Phosphates BaxFex(PO4)Fy (1 ≤ x ≤ 3, 2 ≤ y ≤ 12)

We report the synthesis and characterization of three fluoride-rich barium iron phosphates BaxFex(PO4)Fy (1 ≤ x ≤ 3, 2 ≤ y ≤ 12), which exhibited abundant structural chemistry, exhibiting diverse frameworks and connecting modes between [FeOnF6–n]m– octahedra surrounding Fe2+ or Fe3+ ions. BaFe(PO4)F2 (I) consisted of two-dimensional [Fe(PO4)F2]2– sheets built from linear ∞[Fe2O6F4]10– moieties formed by fluorine corner-sharing FeO4F2 and FeO2F4 octahedra with linking PO4 tetrahedra. Mixed-valence Ba2Fe2(PO4)F6 (II) possessed a three-dimensional framework containing Fe4O6F12 tetramers formed by the edge-sharing oxygen or fluorine atoms of cis-FeF4O2 octahedra. Ba3Fe3(PO4)F12 (III) contained one-dimensional columns of ∞[Fe3(PO4)F12]6– infinite sections built from cis-FeF4O2 and FeF5O octahedra and tetrahedral PO4 linkers. The magnetic characterization of BaxFex(PO4)Fy unveiled diverse magnetism: an S = 5/2 spin chain for (I), a weak ferrimagnet or canted antiferromagnet for (II) thanks to the presence of di...