Effect of the type of metal on the electrical conductivity and thermal properties of metal complexes: The relation between ionic radius of metal complexes and electrical conductivity

Co(II) complexes (1–4) and Ni(II) complexes (5–8) were prepared and characterized by elemental analyses, IR spectra and thermal analysis data. Thermal decomposition of all complexes was discussed using thermogravimetric analysis. The dielectric properties and alternating current conductivity were investigated in the frequency range 0.1–100 kHz and temperature range 300–660 K. The thermal activation energies of electrical conductivity (ΔE₁ and ΔE₂) values for complexes were calculated and discussed. The values of ΔE₁ and ΔE₂ for complexes (1–8) were found to decrease with increasing the frequency. Ac electrical conductivity (σ_ac) values increases with increasing temperatures and the values of σ_ac for Co(II) complexes are greater than Ni(II) complexes. Co(II) complexes showed a higher conductivity than other Ni(II) complexes due to the higher crystallinity as confirmed by X-ray diffraction analysis.