Room Temperature Phase Transition and Luminescence Behavior of a Novel Metal-Free Ionic Crystal [C₇H₁₆NO][ClO₄]

Metal-free ionic crystals have attracted tremendous attention for their environmental friendliness, biocompatibility, easy fabrication and structural variability. Herein, a metal-free ionic crystal [C₇H₁₆NO][ClO₄] ([C₇H₁₆NO]=1-methyl-4-piperidinemethanol) with a dielectric transition at room temperature was designed and constructed. Differential scanning calorimetry (DSC) proved that there exists a reversible phase transition near room temperature at 304 K, accompanied with switchable dielectric behaviors between the low and high dielectric states. The single crystal structure show that the mechanism of such structural phase transition mainly results from the dynamic motion of perchlorate anions. The compound is further shown to exhibit remarkable luminescent properties, characterized by a prolonged lifetime of 18.6 ns. This work offers valuable insights into the construction of room temperature phase-transition ionic crystals involved with dielectric switching and blue luminescence properties.