Thermal, spectroscopic studies and hydrogen bonding in supramolecular assembly of azo rhodanine complexes

• A series of Cu(II) complexes of azo rhodanine derivatives (HLn) were prepared and characterized.
• It is found that the change of substituent affects the thermal properties of Cu(II) complexes.
• The Cu(II) complexes showed antimicrobial activities against S. aureus and P. italicum.
• ESR calculations support the characterization of the structures of the complexes geometries.
• Different thermodynamic parameters were discussed.

A novel series of Cu(II) complexes of azo rhodanine derivatives (HLn) have been prepared and characterized by thermal analysis, spectral studies (IR, mass, UV–Vis, ESR) and magnetic measurements. IR spectra suggest that the HLn acts as a bidentate ligands coordinating via (NN) and deprotonated enolized carbonyl oxygen (–C–O–). ESR spectra of the Cu(II) complexes show dx2−y2 as a ground state, suggesting tetrahedral distorted or square planar geometries around Cu(II) center. The X-ray diffraction (XRD) patterns powder forms of Cu(II) complexes shows many diffraction peaks which indicates the polycrystalline phase. Thermal properties and decomposition kinetics of compounds are investigated. The thermodynamic parameters and evaluation of kinetic parameters (Ea, ΔS∗, ΔH∗ and ΔG∗) of thermal decomposition stages have been evaluated using Coats–Redfern and Horowitz–Metzger methods. Cu(II) complexes are screened for their biological activity against bacterial and fungal species. The Cu(II) complexes showed antimicrobial activities against Staphylococcus aureus and Penicillium italicum.

It was found that the values of Gibbs free energy (ΔG∗) for Cu(II) complexes (1, 3 and 5) increase with increasing Hammett’s substituent coefficients (σR), attributed to the fact that the effective charge experienced by the d-electrons increases due to the electron withdrawing p-substituent NO2 while it decreases by the electron donating character of OCH3.Figure optionsDownload as PowerPoint slide