Dielectric and charge transport behavior of a thermally stable semicarbazone pyranoquinoline copper complex with structural, morphological, and magnetic characterization

Abstract

This study reports a comprehensive investigation of a newly synthesized semicarbazone-based pyranoquinoline copper complex, Cu(II)–PQMHC, with emphasis on its structural, thermal, magnetic, and dielectric characteristics. The coordination environment of the complex was verified by Fourier transform infrared spectroscopy, confirming the proposed binding mode of the ligand to the Cu(II) center. Morphological analysis using high-resolution transmission electron microscopy revealed nanofibrous features with diameters in the range of 10–50 nm, while field-emission scanning electron microscopy showed the formation of aggregated fibrous networks with characteristic dimensions of approximately 30–150 nm. Thermal behavior examined by thermogravimetric analysis and differential scanning calorimetry demonstrated that the complex remains thermally stable over an extended temperature range. Magnetic measurements indicated an overall weak magnetic response, dominated by the diamagnetic contribution of the organic framework, which limits the direct experimental resolution of the intrinsic paramagnetic behavior of the Cu(II) ions. The dielectric properties and AC conductivity of compressed Cu(II)–PQMHC pellets were evaluated over a wide frequency window (0.1 Hz–20 MHz) and temperature range (303–383 K). The dielectric response exhibits a strong dependence on both frequency and temperature, reflecting polarization and charge-transport processes that are sensitive to external thermal and electrical stimuli. These results provide insight into the structure–property relationships governing the functional response of semicarbazone-based copper complexes.