Metal-free liquid-crystalline (LC) materials consisting of a LC nitroxide radical compound exhibit light-induced reversible switching of the magnetic properties as a new photomagnetic effect. This behavior is based on the abrupt change of magnetic properties at the phase transition directly from a chiral smectic C phase to an isotropic liquid (Iso) phase. The origin of the abrupt change is probably the difference in the inhomogeneity of the intermolecular magnetic interactions between LC and Iso phases. To our knowledge, there are no existing reports on a material showing the reversible and quick phase transitions with the large difference of the inhomogeneity. Here we show a relatively simple way to design a compound to enlarge the difference between LC and Iso phases and to make the response quick and reversible. In addition, the presented analysis method that mines Gaussian components from electron paramagnetic resonance spectra enables us to precisely evaluate magnetic properties in condensed phases.

Large negative magneto-LC effects occur in the LC phase of a racemate of a chiral nitroxide radical with a terminal cyano group.

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