Synthesis, crystal structure, thermal, spectroscopic and theoretical studies of N3O2-donor Schiff base and its complex with CuII ions

Abstract

The new o-hydroxy N3O2-donor Schiff base (H2L) was synthesized and characterized using FITR and UV–Vis spectroscopies, X-ray diffraction analysis, thermogravimetric methods and computational studies. In the solid state intramolecular proton transfer from the phenolic oxygen to the imino nitrogen atom is observed. The resulting compound occurs as a mixture of phenol-imine and zwitterionic forms. The temperature does not affect significantly the shift of equilibrium from the phenol-imine tautomer to the zwitterion form. In solution the H2L exists mainly in the phenol-imine tautomeric form but in more polar solvents stabilization of the more polar keto-amine form is also observed. The reaction of H2L with CuII ion at the stoichiometric metal:ligand 2:1 ratio results in formation of cyclic, tetranuclear complex where the coordination geometry around each metal centres is distorted square pyramid.