Structural and AC electrical properties study of solid metal urea complexes

Abstract

The complexation of solid urea with (Co[Formula: see text]), (Cu[Formula: see text]) or (Ni[Formula: see text]) ions has been studied by using dielectric spectroscopy technique over a wide frequency range at different temperatures. Samples' structure were investigated by XRD, FTIR and FT-Raman spectroscopy. FTIR and Raman analysis indicated that the urea coordinates with the metal atoms through the same oxygen–metal bond (O–M). Furthermore, XRD analysis showed that the samples have polycrystalline structure with single phase. The permittivity of complexes was found at much higher values than that of the ligand (pure urea), showing structure dependency. Furthermore, two relaxation peaks were observed in the dielectric loss spectra corresponding to the orientation polarization of urea molecule, and some parts of urea molecule may be NH2 groups. Both relaxation peaks correspond to thermally activated because they were shifted to higher frequency with the temperature increase. The peak position for the low frequency relaxation peak was observed at the same relaxation time ([Formula: see text][Formula: see text]s), corresponding to the coordination mode through the same O–M bond. Novelty of this work is the successful finding of the relationship between the crystalline phase, coordination mode and the dynamic molecular behavior of solid urea and its complexes using the dielectric spectroscopy technique.