Synthesis, crystal structure, NMR study and AC conductivity of [(C₃H₇)₄N]₂Cd₂ClF₅ compound

Abstract

The [(C₃H₇)₄N]₂Cd₂ClF₅ compound was crystallized in the triclinic system with space group P1. The crystal structure consists of organic–inorganic layers, stacked along $[0\bar{1}1]$ direction. The organic part consists of two cations types. The inorganic layer is made up of Cd₂ClF₅ dimmers composed of two in-equivalent irregular tetrahedra sharing one edge (Cl–F). The MAS NMR spectra showed two, three and five isotropic resonances relative to ¹¹¹Cd, ¹³C and ¹⁹F nuclei, respectively. DSC measurement disclosed a phase transition at around 380 K. The impedance spectroscopy and AC electrical conductivity measurements of our compound were taken from 209 Hz to 5 MHz over the temperature range of 350–381 K. Nyquist plots (Z″ vs Z′) show semicircle arcs at different temperatures, and an electrical equivalent circuit has been proposed to explain the impedance results. The circuits consist of the parallel combination of bulk resistance (R), capacitance (C) and fractal capacitance (CPE). The conductivity σ _p follows the Arrhenius relation. The near value of activation energies obtained from the conductivity data and circuit equivalent confirms that the transport is through hopping mechanism. The analysis of the experimental data shows that the reorientation motion of [N(C₃H₇)₄]⁺ cations and/or [Cd₂ClF₅]²⁻ anions is probably responsible for the observed conductivity.