Synthesis, density functional theory calculations and luminescence of lanthanide complexes with 2,6-bis[(3-methoxybenzylidene)hydrazinocarbonyl] pyridine Schiff base ligand

A pyridine?diacylhydrazone Schiff base ligand, L = 2,6?bis[(3?methoxy benzylidene) hydrazinocarbonyl]pyridine was prepared and characterized by single crystal X?ray diffraction. Lanthanide complexes, Ln?L, {[LnL(NO3)2]NO3.xH2O (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Er)} were prepared and characterized by elemental analysis, molar conductance, thermal analysis (TGA/DTGA), mass spectrometry (MS), Fourier transform infra?red (FT?IR) and nuclear magnetic resonance (NMR) spectroscopy. Ln?L complexes are isostructural with four binding sites provided by two nitro groups along with four coordination sites for L. Density functional theory (DFT) calculations on L and its cationic [LnL(NO3)2]+ complexes were carried out at the B3LYP/ 6?31G(d) level of theory. The FT?IR vibrational wavenumbers were computed and compared with the experimentally values. The luminescence investigations of L and Ln?L indicated that Tb?L and Eu?L complexes showed the characteristic luminescence of Tb(III) and Eu(III) ions. Ln?L complexes show higher antioxidant activity than the parent L ligand.