Order–Disorder Transition of Dipolar Rotor in a Crystalline Molecular Gyrotop and Its Optical Change

Successful
control of the orientation of the π-electron systems
in media has been achieved in certain liquid crystals, making them
applicable to devices for optical systems because of the variation
in the optical properties with the orientation of the π-electron
system. However, because of close packing, changing the orientation
of molecules in the crystalline state is usually difficult. A macrocage
molecule with a bridged thiophene rotor was synthesized as a molecular
gyrotop having a dipolar rotor, given that the dipole derived from
the thiophene can rotate even in the crystal. The thermally induced
change in the orientation of the dipolar rotors (thiophene ring) inside
the crystal, i.e., order–disorder transition, and the variation
in the optical properties in the crystalline state were observed.