Synthesis, fluorescent studies, antioxidative and α-amylase inhibitory activity evaluation of some lanthanide(III) complexes

Abstract

A novel heterocyclic ligand, viz. 1,2-dihydro-1,5-dimethyl-4-[[1-2- -oxo-2H-1-benzopyran-3-yl)ethylidene]amino]-2-phenyl-3H-pyrazol-3-one, was prepared by condensing 3-acetylcoumarin with 4-aminoantipyrine. This ligand is versatile in forming complexes with lanthanum(III), praseodymium(III), samarium(III), gadolinium(III) and dysprosium(III) ions. The ligand and the metal complexes were characterized through various physicochemical and spectral studies. The spectral studies revealed that the ligand is coordinated to the metal ion in a bidentate fashion, through the azomethine nitrogen and the oxygen atom of the pyrazolone ring. The powder XRD patterns of ligand and the dysprosium(III) complex were studied. The photoluminescent properties of ligand and metal complexes were evaluated and the relative quantum yields were determined. It was observed that in all cases the metal ions enhanced the luminescence intensity. The α-amylase inhibitory activity of the ligand and the metal complexes was evaluated using the method of Apostolidis. The metal complexes exhibited increased activity compared to the ligand. The antioxidant property was also examined using the DPPH assay and the metal complexes were found to be more potent antioxidants than the ligand.

Keywords

• 3-acetylcoumarin
• lanthanides
• luminescence
• DPPH assay
• Schiff base
• rare earths