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)

摘要

The organic inorganic hybrid phase-transition material, (4-nitroanilinium(+)) (18-crown-6) (H2PO4-) (H3PO4)(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 center dot center dot center dot 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. (C) 2018 Elsevier B.V. All rights reserved.