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

Abstract

Organic magnets are promising in quantum computers, spintronic devices, and information storages for their excellent processing and smart design abilities, resulting from the organic part. However, the organic part shields the magnetic centers to weaken the magnetic interaction. In this work, π–π stacking planar pyrene groups are introduced into cations of a magnetic ionic liquid (NBPBI­[FeCl4]) and poly­(ionic liquid) (PNBPBI­[FeCl4]) with FeCl4 – as the anions. By introducing pyrene groups, the shortest distance between neighboring magnetic units is within 4 Å. The ferromagnetic interactions in NBPBI­[FeCl4] and PNBPBI­[FeCl4] are enhanced by the π–π stacking pyrene groups. Moreover, the corresponding organic magnets are soft ferromagnets, as phase transition from paramagnetism to ferromagnetism is observed from zero field cooling and field cooling tests at the low temperature. This is a new strategy for designing a ferromagnetic organic magnet.

Magnetic Poly(ionic liquid)s: Bottlebrush versus Linear Structures

“…The distance is further shortened to ca. 4.0 Å by introducing planar pyrene groups with much stronger π–π stacking interaction . In this case, the Fe­(III)–Fe­(III) distance is similar to the ferromagnetic spin-coupling distance of the magnetic centers in inorganic magnets; the monomer and polymer are ferromagnetic as a result .…”

“…4.0 Å by introducing planar pyrene groups with much stronger π–π stacking interaction . In this case, the Fe­(III)–Fe­(III) distance is similar to the ferromagnetic spin-coupling distance of the magnetic centers in inorganic magnets; the monomer and polymer are ferromagnetic as a result . By introduction of organic groups with strong π–π stacking interaction, the Fe­(III)–Fe­(III) distance is shortened to that preferred by ferromagnetic spin coupling; thus, the MILs and MPILs show a magnetic phase transition.…”

“…However, the MILs and MPILs are usually paramagnetic, which is too weak to use in electromagnetic devices. In our group, we have studied the structure and magnetic property relationship to improve the magnetic properties. ,− ,, The quaternary ammonium polymers with high-spin FeCl 4 – as anions are prepared by living ring-opening metathesis polymerization (ROMP), reversible addition–fragmentation transfer polymerization (RAFT), and the postmodification method . Magnetic homopolymers and block copolymers are prepared by this method .…”

Self-assembly induced ferromagnetic interaction in magnetic polymers with terphenyl linkers

“…− as a single spin carrier. [25][26][27][28][29] The polymers are usually paramagnetic due to their random distribution and the long distance between FeCl 4 − centres. By introducing π-π stacking biphenyl and pyrene groups into the monomers and polymers, the molecules were closely packed to shorten the distance between FeCl 4 − centres to within 4 Å, and ferromagnetic spin coupling was observed as a result.…”

Self-Assembly of a C16M[Mn] Magnetic Surfactant in Water

“…In our group, the magnetic ionic liquid monomers and polymers with π−π stacking interactions formed ordered structures, and the resultant monomers and polymers are superparamagnetic or ferromagnetic. 37,38 Ordered structures are very important for improving the magnetic property of magnetic ionic liquids.…”