Super Deuterated Isotope Effect in Phase Transition Materials Based on 2, 6‐Dimethylaniline

Variable‐temperature single‐crystal X‐ray diffraction and differential scanning calorimetry (DSC) showed that the compounds (C 8 O 5 H 12 N) + ⋅ ClO 4 – ⋅ H 2 O ( 1 ) and (C 8 O 5 H 12 N) + ⋅ ClO 4 – ⋅ D 2 O ( 2 ) underwent reversible phase transitions, as confirmed by dielectric measurements also. The two compounds underwent a phase transition from room‐temperature phase with a space group of Iba2 to lower‐temperature phase with a space group of C2/c . Upon cooling, the crystalline sample of 1 showed a main endothermic peak at 213.8 K, and after using deuterium water instead of water that of 2 exhibited a main endothermic peak at 281.7 K. Compound 2 showed a relatively significantly isotope effect ( T iso = 61–68 K). The dielectric isotope effect was ca. 336.6 % [(44.4–10.1)/10.1], whereas its isotope effect Δ T c was 75 K, being in good agreement with the result of DSC measurement.