Synthesis and spectroscopic studies of novel mononuclear complexes of cyclic and acyclic Schiff-base derivatives of tridentate and tetradentate coordination with some bivalent transition metal ions

Abstract

Eight novel cyclic and acyclic Schiff-base ligands, L¹ = 6-amino-3-methyl-1-phenyl-4-aza-3-hepten-1-one, L² = 3,7-diaza-2,4,8-trimethyl-6-phenylnona-3,7-diene-1,9-diamine, L³ = 4,7-diaza-3,5,8-trimethyl-1,10-diphenyldeca-3,7-diene-1,10-dione, L⁴ = 3,5,10,14-tetramethyl-7,12-diphenyl-1,4,8,11-tetraazacyclotetradeca-4,7,11,14-tetraene, L⁵ = 7-amino-3-methyl-1-phenyl-4-aza-3-hepten-1-one, L⁶ = 4,8-diaza-5-methyl-7-phenylundeca-4,8-diene-1,11-diamine, L⁷ = 4,8-diaza-3,9-dimethyl-1,11-diphenyldideca-1,11-dione and L⁸ = 2,12-dimethyl-4,10-diphenyl-1,5,9,13-tetraazacyclohexadeca-1,4,9,12-tetraene, have been prepared and characterized by elemental analysis, IR, ¹H NMR and mass spectroscopy. Their corresponding Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes (1–15) have been prepared by the reaction of the ligand with the metal sulfate or chloride in a 1:1 molar ratio and characterized by elemental analysis, thermogravimetric analysis (TGA), IR, electronic and magnetic susceptibility measurements. Electronic spectra and magnetic susceptibility measurements of the solid complexes indicate an octahedral geometry around Cu(II), Co(II), Ni(II), Zn(II) and Cd(II) and a square-planar geometry around the Ni(II) complexes of L² and L³. The

ion is coordinated to the central metal(II) ion as a bidentate ligand through two oxygen atoms in all of the complexes except those with Ni(II). The chloride ion is coordinated to the central Ni(II) ion in complexes of L¹. The conductances of the complexes are very low, indicating their nonelectrolytic nature except for the Ni complex of L², whose molar conductance of 192.5 ohm⁻¹ mol⁻¹ cm² indicates an ionic character for [NiL²]Cl₂. The antifungal properties of the ligands and their complexes were investigated.

Keywords:

• Cyclic and acyclic Schiff bases
• Mononuclear metal complexes
• IR and mass spectroscopy of metal complexes