Large negative magneto-LC effects induced by racemic dimerization of liquid crystalline nitroxide radicals with a terminal cyano group

This article reports the synthesis and mesomorphism of new nitroxide radical compounds with a terminal cyano group and discusses the magneto-LC effects in the new compounds; one of the new compounds shows the largest decrease of paramagnetic susceptibility at the crystalline-to-liquid crystalline (LC) phase transition (negative magneto-LC effects) in the all-organic LC radicals reported thus far. The origins of the phenomenon are rationalized on the basis of the racemic magnetic dipolar interaction model using electron paramagnetic resonance (EPR) spectroscopy; the temperature dependences of the Lorentzian and Gaussian components of the line widths obtained by fitting EPR spectra with Voigt function provide important insights.