Chiral Plastic Crystal of Solid-State Dual Rotators

Phase transition, molecular assembly,dielectric constant,and optical properties of the new chiral plastically crystalline phaseand the chiral glassy phase formed by rod-shaped molecule consistingof adamantane and camphor linked by sulfonamide bond were exhibited. A dual molecular rotor N-adamantyl camphorsulfonamide(ADCS) consisting of adamantane (AD) andcamphor (CA) linked by a sulfonamide (-SO2NH-) bond was designed to form a chiral plastic crystal.Chiral 1S-ADCS and racemic rac-ADCS crystals exhibited a phase transition from thecrystal to the plastic crystal phase upon heating at approximately400 K, as confirmed by optical, structural, and dielectric measurements.In the plastic crystal phase, both the AD and CA units have thermally activated motional freedom and their dynamicsfreeze to form a low-temperature plastic crystal phase rather thana crystal phase. The most stable and metastable ADCS conformationscoexist in the as-grown crystalline phase, and the dynamic behaviorof the plastic crystal phase makes it difficult to recover the initialconformations necessary for the formation of the closest packing structureupon cooling, resulting in a phase transition to the plastic crystallinestate. The as-grown white crystals of both 1S-ADCS and rac-ADCS exhibitedweak luminescence, whereas the phase transition from glass to transparentplastic crystals changed to a non-fluorescent state.