Switchable dielectric phase transition originating from disorder–order transformation and distortion in {[(C4H4N2)Co(H2O)4]SO4·2H2O}n

Abstract

A novel 1D organic–inorganic hybrid phase transition material {[(C₄H₄N₂)Co(H₂O)₄]SO₄·2H₂O}_n (1) was prepared and characterized. Differential scanning calorimetry indicated that 1 underwent a reversible phase transition at 181.3 K. Single crystal X-ray diffraction analysis revealed transition from a room temperature phase with the space group C2/c to a low temperature phase with the space group P2₁/c. The SO₄²⁻ anions, located in the free cavities formed by vertically staggered [(C₄H₄N₂)Co(H₂O)₄]_n²⁺ chains, are dynamically disordered in the room temperature phase. The disorder–order transition of SO₄²⁻ anions and the distortion of [(C₄H₄N₂)Co(H₂O)₄]²⁺ chains with the decrease of temperature synergistically drove the phase transition. The step-like dielectric anomaly makes 1 a promising switchable dielectric material.