Anisotropic dielectric phase transition triggered by pendulum-like motion coupled with proton transfer in a layered hybrid crystalline material (4-nitroanilinium+) (18-crown-6) (H2PO4−) (H3PO4)2

Abstract The organic–inorganic hybrid phase-transition material, (4-nitroanilinium + ) (18-crown-6) (H 2 PO 4 − ) (H 3 PO 4 ) 2 ( 1 ), was successfully synthesized. The organic (4-nitroanilinium) (18-crown-6) + supramolecular cation layer and inorganic phosphate anion layer were arranged alternately. Differential scanning calorimetry (DSC), temperature-dependent dielectric measurements, and variable-temperature single-crystal X-ray diffraction analysis confirmed the reversible isostructural phase transition of 1 with the same space group P bca at 225 K, wherein the synergistic effect between the pendulum-like motion of organic cations and the proton transfer in the O H⋯O hydrogen bonding of inorganic anions was mainly responsible for the phase-transition behavior of 1 . The most striking dielectric property was the remarkable anisotropy along various crystallographic axes. A potential-energy calculation further supported the possibility of dynamic motion of cations in the crystal.