Spectroscopic and density functional theory investigation of novel Schiff base complexes

Novel Schiff base (H2L, 1,2-bis[(2-(2-mercaptophenylimino)methyl)phenoxy] ethane) derived from condensation of bisaldehyde and 2-aminothiophenol was prepared in a molar ratio 1:2. The ligand and its metal complexes are fully characterized with analytical and spectroscopic techniques. The metal complexes with Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Th(IV) have been prepared and characterized by elemental analyses, IR and 1H-NMR spectroscopy, thermal and magnetic measurements. The results suggested that the Schiff base is a bivalent anion with hexadentate OONNSS donors derived from the etheric oxygen (O, O′), azomethine nitrogen (N, N′) and thiophenolic sulphur (S, S′). The formulae of the complexes were found to be [ML]·xH2O (M = Mn(II) (x = 0), Co(II) (x = 1), Ni(II), (x = 1), Cu(II) (x = 2) and Zn(II) (x = 0)) and [ML]·nCl (M = Cr(III) (n = 1), Fe(III) (n = 1) and Th(IV) (n = 2)). The thermogravimetric analysis of the complexes shows metal oxide remaining as the final product at 700–1000 °C. Density functional theory at the B3LYP/6-31G* level of theory was used to investigate molecular geometry, Mulliken atomic charges and energetics. The synclinal-conformer was found to be responsible for complex formation. The calculation showed that ligand has weak field. Structural deformation and the dihedral angles rotation during complexation were investigated. The binding energy of each complex was calculated. The calculated results are in good agreement with experimental data.

New metal complexes of novel Schiff base are prepared and characterized based on elemental analyses, IR, 1H NMR, magnetic moment, molar conductance, and thermal analyses techniques. The complexes are formed in 1:1 [Metal]:[Ligand] ratio, are non-electrolytes except Cr(III), Fe(III) and Th(IV) complexes, are electrolytes, coordinated to the metal ions in a uninegative hexadentate manner with O2N2S2 donor sites of the etheric O, azomethine N and thiophenolic S atoms and have octahedral geometry. Density Functional Theory at the B3LYP/6-31G* level of theory were used to investigate molecular geometry, Mulliken atomic charges and energetic.Optimized geometry of anti-conformers of the ligand in the ground state. Bond lengths are given in angstroms and angles are in degrees. Vector in the middle represent the total dipole moment vector.Figure optionsDownload as PowerPoint slideHighlights
► Metal complexes of the general formula [ML]·xH2O (M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) (x = 0–2)) and [ML]·nCl (M = Cr(III), Fe(III) and Th(IV) (n = 1–2)) are prepared.
► They are characterized with analytical and spectroscopic techniques (elemental analyses, IR, 1H NMR, magnetic moment, molar conductance, and thermal analyses.
► On the basis of spectral studies, an octahedral geometry was assigned for the complexes.
► Density functional theory at the B3LYP/6-31G* level of theory were used to investigate molecular geometry.