Synthesis, Experimental and Theoretical Studies on N,N′-Dipyridoxyl(4-Chloro-1,2-Phenylenediamine) Tetradentate Ligand and Its Copper(II) Complex

Abstract

In this work, N,N′-dipyridoxyl(4-chloro-1,2-phenylenediamine) [=H₂L] Schiff base and its Cu(II) complex [Cu(L)] are newly synthesized and characterized by IR, NMR, and mass spectroscopies as well as the elemental analysis. In addition to experimental characterizations, their structural parameters, tautomerism of the H₂L, assignment of their IR vibrational bands and NMR chemical shifts together with the natural bond orbital (NBO) analysis are calculated at the density functional theory (DFT) level. The geometry of free H₂L Schiff base is not planar, but each of the three aromatic rings lies in a separate plane. However, the [Cu(L)] complex has a square-planar geometry. The dianionic L²⁻ species acts as a tetradentate ligand in the N,N,O^-,O^- manner. In the structure of the square complex, two phenolic oxygen atoms and two azomethine nitrogen atoms occupy four coordination positions. High-energy gaps approve the stability of two investigated compounds. The DFT-computed values are in good agreement with the experimental ones, confirming the suitability of the optimized geometries for H₂L Schiff base and its [Cu(L)] complex.