Temperature and frequency dependence of dielectric relaxation in a metal–organic perovskite-like framework

Abstract

This study dielectrically analyzed the three-dimensional metal–organic framework complex of imidazolium magnesium formate [(C3N2H5)(Mg(HCOO)3)] (HImMg) to investigate the temperature–frequency dependence of the perovskite-like structure’s dielectric relaxation processes. HImMg was synthesized via solution diffusion at room temperature. The high-temperature phase transition of the HImMg was confirmed at around 178 °C by differential scanning calorimetry and temperature-dependent X-ray powder diffraction. Single-crystal X-ray diffraction revealed a monoclinic structure in the space group P21/n, indicating a centrosymmetric system, with the HIm+ dipole in the cages of the Mg(HCOO)3. The dielectric values were recorded between −50 °C and 200 °C and at radio and microwave frequency ranges between 1 kHz and 1 GHz. Dielectric relaxation was calculated using the Arrhenius and Cole–Cole relationships. Low-temperature activation energies of 0.14, 0.35, and 0.25 eV were connected to the gradual freezing of the imidazolium cations’ reorientation movements. This behavior may demonstrate that the dielectric relaxations of HImMg are caused by the orientational motion of dipolar guest molecules.