From Paramagnetic to Superparamagnetic Ionic Liquid/Poly(ionic liquid): The Effect of π–π Stacking Interaction

Abstract

Magnetic ionic liquids (MILs) and poly­(magnetic ionic liquids) (PMILs) with FeCl4 – as anions usually show weak magnetism, such as paramagnetism or antiferromagnetism, at room temperature. Inspired by the natural inorganic ferromagnet with ordered crystal structures, a soft superparamagnetic ionic liquid (TMBBDI­[FeCl4]) and corresponding poly­(ionic liquid) (PTMBBDI­[FeCl4]) were prepared by introducing π–π stacking biphenyl groups into the organic cations. Both of the compounds exhibited superparamagnetism from 100 to 300 K, while a ferromagnetic hysteresis loop was found at 300 K. Ferromagnetic interactions were observed from zero field cooling and field cooling studies for both TMBBDI­[FeCl4] and PTMBBDI­[FeCl4]. However, the MIL and PMIL without π–π stacking interaction were paramagnetic without ferromagnetic interaction. The superparamagnetism of the TMBBDI­[FeCl4] and PTMBBDI­[FeCl4] was ascribed to the π–π stacking interactions between biphenyl groups, which not only shortened the Fe–Fe distance to the ferromagnetic interaction range but also increased the order degree of the molecules.

Coordination Flexibility Aided CO2‐specific Gating in an Iron Isonicotinate MOF

“…To confirm the spin state of the Fe and Mn centers and see if there is any effect of JT‐ distortion, we performed the magnetic measurements for Mn(4‐PyC) 2 and Fe(4‐PyC) 2 ⋅ (OH). The magnetic measurements show that Mn(4‐PyC) 2 is paramagnetic, whereas Fe(4‐PyC) 2 ⋅ (OH) is super‐paramagnetic [37] . To further analyze the magnetic behaviour of Mn vs. Fe PyC phases, we fitted the 1/χ vs. T plot of the MnPyC to a Curie‐Weiss model.…”

All-Organic Polymer Dielectrics Containing Sulfonyl Dipolar Groups and π–π Stacking Interaction in Side-Chain Architectures

“…45 Recently, Yu et al have applied this idea to synthesize magnetic ionic liquid/poly(ionic liquid), where the introduction of π−π stacking biphenyl groups into organic cations shortened the Fe−Fe distance to the ferromagnetic interaction range, resulting in the transition from paramagnetic to superparamagnetic. 46 Moreover, the π−π stacking interaction offers exciting opportunities to improve the dielectric properties of polymers by constructing unique nanostructures. For example, Xie et al have synthesized a series of functional block copolymers containing polyacetylene.…”

“…The π–π stacking interaction has been a powerful means to design advanced function materials not only due to the outstanding photoelectric properties originating from conjugated effect but also the strong unidirectional stacking tendency to facilitate the self-assembly of molecules . Recently, Yu et al have applied this idea to synthesize magnetic ionic liquid/poly­(ionic liquid), where the introduction of π–π stacking biphenyl groups into organic cations shortened the Fe–Fe distance to the ferromagnetic interaction range, resulting in the transition from paramagnetic to superparamagnetic . Moreover, the π–π stacking interaction offers exciting opportunities to improve the dielectric properties of polymers by constructing unique nanostructures.…”

Pyrene-Enhanced Ferromagnetic Interaction in a FeCl4–-Based Poly(ionic liquid)s Organic Magnet

“…The results demonstrate that the π–π stacking interaction is in favor of the ferromagnetic interaction for the FeCl 4 – -based organic magnet. Unfortunately, although superparamagnetism is observed in the MIL and MPIL with a biphenyl linker, ferromagnetism is doubted, as the zero-field cooling and field cooling (ZFC–FC) curves are not split at low temperature …”