Open-Framework Iron Fluoride Phosphates Based on Chain, Trinuclear, and Tetranuclear Chain Fe^III Building Units: Crystal Structures and Magnetic Properties

Abstract

We report the synthesis and characterization of a series of new open-framework iron fluoride-fluorophosphates based on linear, trinuclear, and tetranuclear chain FeIII building units. KFe2(PO3F)2F3 (I) consists of {Fe2(O3F)2F2}10– zigzag chains interconnected by P­(O/F)4 tetrahedra forming a three-dimensional (3D) open framework. K2Fe­(PO2.5F1.5)2F2 (II) is built up by {Fe­(PO2.5F1.5)2F2}2– chains separated by K+ cation layers. The framework for K3Fe3(PO4)­(PO3F)2F5 (III) contains two-dimensional {Fe3O4F4(PO3F)2}2– sheets, which are built from trimeric Fe-octahedra insulated by PO3F tetrahedra. The macroanionic framework of K3Fe4(PO4)2F9 (IV) comprises linear {Fe4O8F9}10– chains consisting of tetranuclear magnetic clusters of [Fe4O8F9] 10– formed via corner-sharing fluorine atoms decorated with PO4 groups. The magnetic characterization of three iron fluorophosphates reveals diversified magnetism: S = 5/2 spin chains for I, antiferromagnetically coupled triangular Fe units for III, and coupled tetrahedral S = 5/2 spin chains for IV. IV shows strong geometric frustration thanks to its spin motifs of corner-shared tetrahedral clusters.

Structure and magnetic properties of an amine-templated one-dimensional cobalt-fluoro-sulfate containing Co4F4 cubane and hydrogen evolution reaction (HER) performance of its derived carbon-wrapped CoSe2 nanorods

“…[8][9][10] Like other oxyanion-based frameworks (silicate, phosphate, sulfate, and selenates), metal-sulfate frameworks limit magnetic exchange interactions among paramagnetic metals except for structures where single vertices of the sulfate tetrahedra are shared with multiple metal octahedra. [11][12][13] Interestingly, multiple exchange pathways are introduced into the structures by integrating fluoride into the sulfate frameworks because of the multiple bridging abilities of fluorine, like μ 2 -F and μ 3 -F. [14][15][16][17][18] It is well known that such linkages are responsible for direct-exchange interactions leading to the observation of long-range ferromagnetic ordering. Besides the fascinating structural features of these materials, the availability of secondary organic ligands or organic templating agents/counterbalancing extra-framework organic components with uniform distribution of metal sites motivated researchers to use them as templating agents to derive crystalline framework-derived materials such as framework-derived oxides, sulfides, phosphides, selenides etc.…”