Tautomerization Reaction, Experimental and Theoretical Characterizations of the N,N′-Dipyridoxyl(4-Methyl-1,2-Phenylenediamine) Schiff Base and its Cu(II) Complex

Abstract

Herein, the tetradentate N,N′-dipyridoxyl(4-methyl-1,2-phenylenediamine) [=H²L] Schiff base and its Cu(II) salen complex [Cu(L)] are newly synthesized and characterized by IR, NMR and mass spectroscopies together with the elemental analysis. In addition, their geometrical parameters, assignment of their IR bands and NMR chemical shifts of the Schiff base are calculated using density functional theory (DFT) methods. Natural bond orbital analyses were performed at the same computational level, too. In the optimized geometry of the free ligand the aromatic rings are not in the same plane. The structure of the complex is more planar, where the dianionic Schiff-base acts as a tetradentate ligand in the N,N,O^–,O^–manner. Two phenolic oxygen atoms and two azomethine nitrogen atoms occupy four coordination positions of the square complex. The DFT-calculated results are in good agreement with the experimental values, confirming the suitability of the optimized geometries for the Schiff base and its Cu(II) complex.