An experimental and theoretical investigation of lanthanide complexes [Ln = Nd, Yb, Eu, Dy and tb] with 4-((2-hydroxy-naphthalen-1-yl)methylene amino)benzenesulfonamide ligand

Abstract

Reaction of lanthanide(III) salts with N, O donors 4-((2-hydroxynaphthalen-1-yl) methyleneamino)benzenesulfonamide (L) Schiff base ligand afforded five new mononuclear lanthanide complexes of type [Ln(NO3)2(L)(H2O)2](H2O)x {where Ln = Nd (1), x = 2, Yb (2), x = 1, Eu (3), x = 2, Dy (4), x = 1, Tb (5), x = 2}. These newly synthesized complexes were characterized by elemental analysis, molar conductance, FT-IR, UV–Vis spectroscopy and mass spectrometry. The thermal behavior of complexes was studied by TGA technique. The computational calculations using density functional theory (DFT) of ligand and their lanthanide complexes were performed to obtain optimized molecular geometry, the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) and other parameters. The fluorescence studies reveal that emission spectra of lanthanide complexes show the characteristic luminescence due to lanthanide ions which indicates that Schiff base ligand can sensitize the Ln(III) ions. The Schiff base and their lanthanide complexes were screened for their in vitro antibacterial studies against Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 29213), Klebsiella pneumoniae (BAA 1705), Acinetobacterr baumannii (BAA 1605) and Pseudomonas aeruginosa (ATCC 27853). The results exhibit that the antibacterial activity of Ln(III) complexes was greater than the free Schiff base ligand.