Bistable
materials with multiphysical channels, such
as optical,
electrical, and magnetic properties, have been paid dramatic attention
due to their alternativity of the signal status in electronic devices.
Herein, three stable supramolecular radicals ([(NH3-TEMPO)(18-crown-6)][XF6] (1, X = P; 2, X = As; 3, X = Sb)) were synthesized and characterized. The former two molecules
present ferroelectric phase transitions around 381.7 and 382.7 K,
respectively, with bistability in dielectric property and second-harmonic
generation (SHG) effect, which are first found in supramolecular radicals.
Their ferroelectric transition and bistable properties are generated
from a net polar crystal structure owing to the static ordered packing
of NH3-TEMPO radical cations in the low-temperature phase
(LTP) to a nonpolar structure owing to a distinctive symmetric scissoring
motion of NH3-TEMPO radical cations between two 18-crown-6
molecules in the high-temperature phase (HTP). Both of them exhibit
paramagnetic properties in HTP and LTP states since no intermolecular
spin–spin interaction occurs due to the long distances among
the radicals in their crystals. These results make us possible to
design bistable optoelectronic radical materials with bistability
in magnetic property in the future.