Supramolecular spectroscopic and thermal studies of azodye complexes

• The ligands (HLn) and their Cu(II) complexes were prepared and characterized.
• The molecular and electronic structures of the investigated compounds (HLn) have been discussed.
• ESR calculations support the characterization of the structures of the complexes geometries.
• Thermal data suggested that the ligands are more stable as compared to complexes.
• Different thermodynamic parameters were discussed.

A series of heterocyclic ligand of copper(II) complexes have been synthesized by the reaction of copper(II) acetate with 5-(4′-derivatives phenylazo)-2-thioxothiazolidin-4-one (HLn) yields 1:1 and 1:2 (M:L) complexes depending on the reaction conditions. The elemental analysis, spectral (IR and ESR), conductance, magnetic measurements, and thermogravimetric analysis (TGA) are used to characterize the isolated complexes. It is found that the change of substituent affects the thermal properties of azodye rhodanine derivatives and their Cu(II) complexes. The molecular and electronic structures of the investigated compounds (HLn) were also studied using quantum chemical calculations. According to intramolecular hydrogen bond leads to increasing of the complexes stability. The data revealed that the coordination geometry around Cu(II) in all complexes (1–4) exhibit a trans square planar by NO monobasic bidentate and the two monobasic bidentate in octahedral complexes (5–7). Electronic, magnetic data and ESR spectra proposed the square planar structure for all complexes (1–4) under investigation. The value of covalency factor (β1∗)2 and orbital reduction factor K accounts for the covalent nature of the complexes. The activation thermodynamic parameters, such as activation energy (Ea), enthalpy (ΔH*), entropy (ΔS*), and Gibbs free energy change of the decomposition (ΔG*) are calculated using Coats–Redfern and Horowitz–Metzger methods.

Structures of [Cu(Ln)(OAc)(OH2)]·2H2O (A) and [Cu(Ln)2(OH2)2] (B).Figure optionsDownload as PowerPoint slide