Synthesis, experimental and theoretical characterization of N,N′-dipyridoxyl (1,4-butanediamine) Schiff-base ligand and its Cu(II) complex

A new N,N′-dipyridoxyl(1,4-butanediamine) [=H2BS] Schiff-base ligand and its Cu(II) salen complex, [Cu(BS)(H2O)(CH3OH)], were synthesized and characterized by IR, UV–vis, 1H NMR, mass spectrometry and elemental analysis. Also, full optimization of the geometries, 1H NMR chemical shifts (for the H2BS) and vibrational frequencies were calculated by using density functional theory (DFT) method. Structure of the H2BS ligand is not planar, i.e. two pyridine rings are not in the same plane. In the structure of the Cu complex, the Schiff-base ligand acts as a dianionic tetradentate ligand in N, N, O−, O− manner. The coordinating atoms of BS2− occupy equatorial positions of the octahedral complex, where the H2O and CH3OH ligands locate at axial positions. The calculated results are in good agreement with the experimental data, confirming the suitability of the proposed and optimized structures for the H2BS ligand and its Cu complex.