Synthesis and spectroscopic characterization of gallic acid and some of its azo complexes

A series of gallic acid and azo gallic acid complexes were prepared and characterized by elemental analysis, IR, electronic spectra and magnetic susceptibility. The complexes were of different geometries: Octahedral, Tetrahedral and Square Planar. ESR was studied for copper complexes. All of the prepared complexes were of isotropic nature. The thermal analyses of the complexes were studied by DTA and DSC techniques. The thermodynamic parameters and the thermal transitions, such as glass transitions, crystallization and melting temperatures for some ligands and their complexes were evaluated and discussed. The entropy change values, ΔS#, showed that the transition states are more ordered than the reacting complexes. The biological activities of some ligands and their complexes are tested against Gram positive and Gram negative bacteria. The results showed that some complexes have a well considerable activity against different organisms.

► A series of gallic acid and azo gallic acid complexes were prepared and characterized.
► The complexes were of different geometries: octahedral, tetrahedral and square planar.
► The thermal analyses of the complexes were studied by DTA and DSC techniques.
► The biological activities of some complexes are tested.