Hydrothermal Synthesis And Structure Of Organically Templated One-Dimensional And Three-Dimensional Iron Fluorophosphate

Abstract

Two new open‐framework iron fluorophosphates, [C4N2H12]0.5[FeF(HPO4)(H2PO4)] (I) [C4N2H12][Fe4F2(H2O)4(PO4)4] · 0.5H2O (II), were synthesized hydrothermally using piperazine as a templating agent. The structures were determined by single‐crystal X‐ray diffraction. Compound I crystallizes in the orthorhombic space group Pbca, a = 7.2126(2) Å, b = 14.2071(4) Å, c = 17.1338(2) Å, Z = 8. The structure is composed of infinite anionic chains of [FeF(HPO4)(H2PO4)]- n built by trans‐fluorine sharing FeF2O4 octahedra. These chains are similar to those found in tancoite‐type minerals. Compound II crystallizes in the monoclinic space group P21/n, a = 9.9045(3) Å, b = 12.3011(3) Å, c = 17.3220(4) Å, β = 103.7010(10)°, Z = 4. The structure of compound II has a three‐dimensional (3D) architecture with an eight‐membered channel along the b axis, in which protonated piperazine molecules reside. The complex framework is built from two types of secondary building unit (SBU): one hexamer [Fe3F2(H2O)2(PO4)3$] (SBU6), and one dimer [FeO4(H2O)2PO4] (SBU2). The vertex sharing between these SBUs create the 3D structure.