Phase transitions, thermal, vibrational (FT-IR and Raman) and optical characterizations, dielectric relaxation and electrical conductivity of a cobalt (II) based hybrid material

Abstract

The combination of various organic molecules and inorganic fragments into a single hybrid crystalline lattice has sparked much attention for the potential physical properties and applications. The present investigation addresses the characterization of a novel crystalized compound, formulated as (C7H11N2)2CoCl4. In order to characterize the various types of intermolecular interactions in the title compound, the interaction variability of the two independent cations and four chloride atoms is checked via Hirshfeld surface analysis. Indeed, phase structures were characterized using thermogravimetric analysis, differential scanning calorimetry, Infrared and Raman data. Furthermore, UV−vis and PL measurements revealed a semiconductor character of the obtained compound. The calculated direct and indirect band gaps (Egd, Egi) were predicted to be 1.45 and 1.56 eV, respectively. In addition, a phase transition was discovered by thermal analysis at 390 K, and comprehensive dielectric research showed a good agreement with thermal data. Impedance spectroscopy measurements were used to study the electrical and dielectric characteristics of the title compound over a wide range of frequencies and temperatures, 40 Hz–10 MHz and 313–483 K, respectively. The Nyquist plot (Z" versus Z′) from the complex impedance spectrum revealed semicircular arcs described by a Cole-Cole model. Using the Z-view software, a series of Nyquist representations were built and fitted to an equivalent circuit that reflected the behavior of this material. The thermal evolution of the conductivity follows an Arrhenius-type behavior. Also, the real and imaginary parts of dielectric permittivity of (C7H11N2)2CoCl4 at different frequencies were discussed. The presence of grain and grain boundaries is confirmed by the modulus investigations. Electric and dielectric analyses highlight the good protonic conduction of this material.