A new pathway of preparation and refined structure of (NH4)2[FeCl5(H2O)]

Abstract

The title compound, (NH 4 ) 2 [FeCl 5 H 2 O] has been prepared by reaction between iron(III) chloride and ammonium chloride which was formed by hydrolysis of isonicotinamide or thionicotinamide in ethanol. The characterization was based on elemental analysis and infrared spectra. The crystal structure of the title compound has been refi ned by single crystal X-ray diffraction method at 293 K. Crystals are orthorhombic, Pnma, with unit cell parameters: a = 13.760(1) Å, b = 9.960(1) Å, c = 7.060(1) Å, Z = 4 and R = 3.5 %. The iron(III) atom in [FeCl 5 2-ion is approximately octahedrally coordinated by fi ve Cl atoms and one O atom of H 2 O molecule. This distortion is caused by the extensively hydrogen-bonded lattice. Structural parameters and IR spectra of similar compounds are compared and discussed.

High-Field Magnetoelectric and Spin-Phonon Coupling in Multiferroic (NH4)2[FeCl5·(H2O)]

“…The crystal structure of (NH 4 ) 2 [FeCl 5 ·(H 2 O)] below the order–disorder transition has been challenging to resolve. ,, Even so, we can assess the possibility of monoclinic domain formation. Naturally, monoclinic domains should have the same c axis but different a and b axes.…”

“…(NH 4 ) 2 [FeCl 5 ·(H 2 O)] is well-studied in the infrared, although previous investigations focus primarily on vibrational motions of water-coordinated aquo complexes en masse and how the pattern varies with counterion substitution (K + , Rb + , NH 4 + ). − For the most part, prior efforts address the behavior of the fundamental excitations of the lattice above 350 cm –1 . − Our interests are different and instead concentrate on the development of magnetoelectricity and the behavior of the lattice across the sequence of temperature- and field-driven transitions. Furthermore, we focus primarily on the low-frequency vibrational modes (Figure a).…”

Thermodynamic properties of the new multiferroic material (NH4)2[FeCl5(H2O)]

“…After considering all this information, we suspect that the structural changes of (NH 4 ) 2 [FeCl 5 (H 2 O)] at T HT probably only affect the hydrogen atoms of the crystal structure. Consequently, the room-temperature crystal structure [19,20] can still serve as a good approximation at lower temperatures, at least concerning the positions of the non-hydrogen atoms. Because our data do not indicate a lowering of the orthorhombic symmetry to the monoclinic (or even triclinic) system, the (NH 4 ) 2 [FeCl 5 (H 2 O)] crystals will be described as being orthorhombic also below T HT in the following, although this assumption should be treated with some caution.…”

Thermodynamic properties of the new multiferroic material (NH$_4$)$_2$[FeCl$_5$(H$_2$O)]

“…Considering all this information, we suspect that the structural changes of (NH 4 ) 2 [FeCl 5 (H 2 O)] at T HT probably only affect the hydrogen atoms of the crystal structure. Consequently, the room-temperature crystal structure [19,20] still can serve as a good approximation at lower temperatures, at least concerning the positions of the non-hydrogen atoms. Because our data do not indicate a lowering of the orthorhombic symmetry to the monoclinic (or even triclinic) system, the (NH 4 ) 2 [FeCl 5 (H 2 O)] crystals will be described as being orthorhombic also below T HT in the following, although this assumption should be treated with some caution.…”

“…Besides ionic bonds between the structural building blocks, there is a pronounced Hbonding (via O-H-Cl) between neighbouring [FeCl 5 (H 2 O)] 2− octahedra along the b axis, which further stabilizes the crystal structure. These H-bonded octahedra form zig-zag chains along b and along these chains the Fe-O bonds of adjacent octahedra are oriented mutually antiparallel to each other [18][19][20].…”