Pressure Effects on Emim[FeCl₄], a Magnetic Ionic Liquid with Three-Dimensional Magnetic Ordering

Abstract

We report a combined study using magnetization and Raman spectroscopy on the magnetic ionic liquid 1-ethyl-3-methylimidazolium tetrachloroferrate, Emim[FeCl4]. This material shows a long-range antiferromagnetic ordering below the Néel temperature T(N) ≈ 3.8 K. The effects of pressure on the magnetic properties have been studied using a miniature piston-cylinder CuBe pressure cell. This three-dimensional ordering is strongly influenced when hydrostatic pressure is applied. It is observed that low applied pressure is enough to modify the magnetic interactions, inducing a transition from antiferromagnetic to ferrimagnetic ordering. Raman spectroscopy measurements reveal important information about the existence of isolated [FeCl4](-) anions and the absence of dimeric [Fe2Cl7](-) units in the liquid and solid states. These features seem to suggest that the superexchange pathways responsible for the appearance of magnetic ordering are mediated through Fe-Cl-Cl-Fe. Furthermore, the liquid-solid phase transition exhibits a magnetic hysteresis near room temperature, which can be tuned by weak pressures.

1-Ethyl-2,3-dimethylimidazolium paramagnetic ionic liquids with 3D magnetic ordering in its solid state: synthesis, structure and magneto-structural correlations

“…For Edimim[FeCl 4 ] they also lie antiparallel to each other along the c axis, while they are stacked identically one above the other in the a direction. 39 Fig. In the case of [Edimim] + units, the imidazole ring is aromatic and planar with all the rened values for the C-C and C-N bond lengths laying in the expected range of other imidazolium compounds.…”

“…The measured frequencies and their corresponding assignment in terms of the involved vibrational modes of the molecular ions are summarized in Table 4. 39,60 Variable temperature magnetic susceptibility measurements of the presented compounds were carried out on powdered samples in the 2-300 K temperature range. 6, black) belonging to the symmetry point group T d of the [FeCl 4 ] À iron complex.…”

“…32,33 Many groups have focused their studies on the dipole-dipole, and hydrogen bonds within the crystal and molecular structures of these ILs 34 in order to improve the understanding of these forces, aim at a ne tailoring of their technological applications. 39 The learning of magneto-structural correlations in ILs based on tetrahaloferrate anion and imidazolium cation need a comprehensive understanding through a systematic investigation of a wide variety of compounds by changing the cationic and anionic structures. In addition, if these non-bonding contacts are strong, interesting collective electrical and magnetic phenomena can arise, such as ferroelectricity in the bis(imidazolium) pentachloroantimonate(III), (C 3 N 2 H 5 ) 2 SbCl 5 , or a threedimensional (3D) magnetic ordering in ILs based on tetrahaloferrate ions.…”

Thermochromism and switchable paramagnetism of cobalt(ii) in thiocyanate ionic liquids

“…7,8 Other MIL systems have since been widely investigated. 1,[9][10][11][12] While ionic liquid systems with thermochromism related to changes in coordination of the metal centre have previously been reported, this has either been in the presence of additives or molecular solvents, or the magnetic properties were not investigated. [13][14][15][16][17] Here, we report on solutions of cobalt(II)isothiocyanate in thiocyanate ILs that show reversible switching of the cobalt(II) speciation from tetrahedral [Co(NCS)4] 2at room temperature to octahedral [Co(NCS)6] 4at temperatures around 233 K. These temperature-dependent changes in the co-ordination environment are accompanied by reversible changes in colour (blue to red) and by significant changes of the effective magnetic moment of these fluids.…”

High-pressure phase behavior of the room temperature ionic liquid 1-ethyl-3-methylimidazolium nitrate

“…So far, few studies have been conducted to understand the behavior of [emim]-based RTILs at high pressure [9,[11][12][13][14]. For example, Su et al [11] investigated the solid to liquid phase transition of 1-ethyl-3-methylimidazolium hexafluorophosphate ([emim][PF 6 ]) up to~1 GPa by high pressure differential thermal analysis and found that another crystalline phase exists between solid and liquid [emim][PF 6 ].…”