Photoconductive Bent-Core Liquid Crystalline Radicals with a Paramagnetic Polar Switchable Phase
A series of self-organizing bent-core derivatives 1[12,n], containing a highly π-delocalized stable radical as the central angular structural element, is described. The planarity of the open-shell core permits efficient π–π stacking, which results in the formation of B2 and soft crystalline phases above 100 oC. Optical, XRD and dielectric analyses of 1[12,12] indicate that the ground state of the observed B2 phase is polar antiferroelectric of type SmCAPA exhibiting tristable electro-optical switching. SQUID and EPR measurements revealed strong antiferromagnetic spin-spin exchange interactions below the isotropic phase, which have been estimated at θ = –46 cm-1 with the Curie-Weiss law. Transient photoconductivity was observed in the B2 phase with the hole carrier mobility μh of 1.4 × 10-4 cm2V-1s-1.