Magnetically Manipulable Ionic Liquid Crystals Incorporating Neutral Radicals.

Invited for this month's cover are the collaborating groups of Dr. Yoshiaki Uchida from Osaka University, Japan, Prof. Rui Tamura and Prof. Masahito Sugiyama from Kyoto University, Japan and Dr. Dmitrii G. Mazhukin from Novosibirsk State University, Russia. The cover picture depicts a contrast between localized spins and conductive ions in the newly-synthesized ionic liquid crystalline (ILC) nitroxide radicals. The ILC droplet of the new compounds is magnetically manipulable. More information can be found in the Full Paper by Yoshiaki Uchida, Rui Tamura, and co-workers.

Magnetically Manipulable Ionic Liquid Crystals Incorporating Neutral Radical Moiety.

With a view to fabricating a new remote input-output system by applying functional ionic liquid crystalline (ILC) materials, we have developed novel ILC compounds containing a nitroxide radical unit in the organic cations, which show an enantiotropic smectic A (SmA) phase. We have implemented the magnetic manipulation of a droplet of one of the ILC compounds on the basis of the intermolecular magnetic interactions between radical moieties. This ILC monoradical compound shows a 55 % larger increase in paramagnetic susceptibility at the solid-to-LC melting point in the first heating process than the non-ionic LC monoradical compounds. It is most likely owing to the nanosegregation of strongly bonded ionic and non-ionic moieties. The increased molar magnetic susceptibility is preserved not only in the SmA phase but also in the isotropic liquid and solid phases during the first cooling process.

Unique Superparamagnetic-like Behavior Observed in Non-π-delocalized Nitroxide Diradical Compounds Showing Discotic Liquid Crystalline Phase.

A unique superparamagnetic-like behavior and a large "positive magneto-LC effect" were observed in the solid phases and the hexagonal columnar (Colh ) liquid crystalline (LC) phase, respectively, of novel achiral non-π-delocalized nitroxide diradical compounds (R,S)-1, which showed polymorphism in the solid phases (solids I and II). The SQUID magnetization measurement revealed that (1) (R,S)-1 containing a small amount of racemic diastereomers (R*,R*)-1 possessed an unusual and large temperature-independent magnetic susceptibility (χTIM >0) component in the original nanocrystalline solid I that was responsible for the observed superparamagnetic-like behavior under low magnetic fields and did not arise from the contamination by extrinsic magnetic metal or metal ion impurities, besides ordinary temperature-dependent paramagnetic susceptibility (χpara >0) and temperature-independent diamagnetic susceptibility (χdia <0) components, (2) a large increase in molar magnetic susceptibility (χM ) (positive magneto-LC effect) that occurred at the solid I-to-liquid crystal transition upon heating was preserved as an additional χTIM increase in the resulting polymorphic nanocrystalline solid II by cooling, and (3) such unique magnetic phenomena were induced by thermal processing for (R,S)-1 or by adding a small amount of (R*,R*)-1 to (R,S)-1 as the impurity.