On the high-temperature phase transition of a new chlorocadmate() complex incorporating symmetrical CdCl clusters: structural, optical and electrical properties

In the present investigation, a new hybrid crystal, with the formula [(C 4 H 9 ) 4 P] 2 Cd 2 Cl 6 has been synthesized by the slow evaporation method at room temperature. It was characterized by X-ray diffraction (XRD), Hirshfeld surface, differential scanning calorimetry (DSC), optical measurement and complex impedance. Single crystal X-ray diffraction structural analysis revealed that the title compound crystallizes in the triclinic system with space group P 1&cmb.macr; and cell parameters: a = 11.972 (1) Å, b = 15.418 (1) Å, c = 15.426 (2) Å, αa = 68.71 (2) °, β = 73.20 (3) ° and γ = 74.39 (2)°. The Hirshfeld surface analysis was conducted to investigate intermolecular interactions and associated 2D fingerprint plots, revealing quantitatively the relative contribution of these interactions in the crystal cohesion. DSC studies indicated one phase transition at about 348 K. Optical absorption spectra show that the band gap of [(C 4 H 9 ) 4 P] 2 Cd 2 Cl 6 is approximately 2.65 eV. The Nyquist plot showed only one semicircular arc, representing the grain effect in the electrical conduction. The thermal evolution of the conductivity of the grains presents an Arrhenius type behavior, demonstrating that charge carriers have to overcome different energy barriers while conducting and relaxing. Besides, the AC conductivity was analyzed by Jonscher's law and the conduction mechanism is well ensured by the correlated barrier hopping (CBH) model. The detailed mechanism of conductivity before and after the structural phase transition has been analyzed for the hybrid material [(C 4 H 9 ) 4 P] 2 Cd 2 Cl 6 . The optical study of this coordination compound suggests its semiconductor character.