Novel europium(III), terbium(III), and gadolinium(III) Schiff base complexes: Synthesis, structural, photoluminescence, antimicrobial, antioxidant, and molecular docking studies

Abstract

Three lanthanide (III) complexes, L-Eu, L-Tb, and L-Gd, were synthesized using a Schiff base ligand (H₂L) composed of (2,2′-(thiophene-2,5-diylbis(methaneylyl-idene))bis(azaneylyl-idene))diphenol. Complexes with the generic formula LnL(Cl)(H₂O)·xH₂O, where L is the ligand, was studied using elemental analysis, spectrum analysis (IR, mass- UV–Vis), and molar conductivity. Next, the photoluminescence characteristics of the lanthanide complexes were investigated. An assessment was conducted to ascertain the antioxidant activity of the synthetic compounds compared with that of the stable free radical DPPH. The antibacterial activity of the Schiff base metal complexes was assessed against a strain of yeast as well as against a number of Gram-positive and Gram-negative bacteria. Computational studies were also performed to elucidate the mechanisms of the antimicrobial and antioxidant effects. In molecular docking, 1LL9, 6J2O, 3JPU, 2MBR, and 1HD2 crystal structures were determined as targets and the docking score values of H₂L, L-Tb, L-Gd, and L-Eu compounds for these targets were calculated.