Next-generation cobalt hybrid material: structural, luminescence, and dielectric properties for advanced functional applications

Abstract

Significant attention has been devoted to the development of a unique cobalt-based hybrid material with intriguing structural properties. In this study, we successfully synthesized a new hybrid compound via slow evaporation at room temperature. The compound was thoroughly characterized using single-crystal and powder X-ray diffraction (SXRD and PXRD), scanning electron microscopy (SEM), thermal analysis (DSC and TG/DTA), Fourier transform infrared (FT-IR) spectroscopy, and photoluminescence (PL) spectroscopy. X-ray diffraction analysis revealed that the zero-dimensional hybrid compound [(C₆H₅N₂)₂CoCl₄] crystallizes in the tetragonal P4₁ space group, with the unit cell parameters a = b = 6.8311 (3) Å, c = 36.092 (3) Å, α = β = γ = 90°, and Z = 4. The structure is stabilized by an extensive network of hydrogen bonds and π–π interactions, which connect the organic and inorganic components, forming a three-dimensional framework. FT-IR spectroscopy confirmed the presence of all expected vibrational modes. SEM analysis, combined with EDX, verified the presence of all non-hydrogen elements. Thermal analysis showed that the compound is thermally stable up to 380 K. PL spectroscopy demonstrated that the material exhibits blue-green emission, indicative of a charge-transfer process. The AC conductivity behavior was modeled using Jonscher's power law, confirming that the conduction process is thermally activated within the studied frequency range. The temperature dependence of the frequency exponent suggests that both the non-overlapping small polaron tunneling (NSPT) and correlated barrier hopping (CBH) mechanisms contribute to electrical conduction. Impedance spectroscopy of the real part of the dielectric permittivity showed a high dielectric constant at low frequencies, suggesting contributions from space charge accumulation and dipolar orientation. Additionally, the modulus spectra displayed two distinct relaxation peaks, corresponding to the grain and grain boundary effects.