Synthesis, characterization, and biological activity of some lanthanide complexes with (E)-N'-(3,5-di-tert-butyl-2-hydroxybenzylidene) picolinohydrazide: Solid-state molecular structure of [DyL(NO3)DMF]2

A series of lanthanide(III) complexes containing Schiff base ligand, [NEt3](2)[Ln(2)(L)(2)(NO3)(4)]center dot xH(2)O {Ln, x: La,1; Pr, 2, Nd, 1; Sm, 1; Eu, 1; Gd, 1; Tb, 2; Dy, 2; and Er, 4; H2L: (E)-N'-(3,5-di-tert-butyl-2-hydroxybenzylidene) picolinohydrazide Schiff Base Ligand}, have been synthesized by reaction of H2L with Ln(NO3)(3)center dot xH(2)O salts {Ln, x: La, 6; Pr, 6; Nd, 6; Sm, 6; Eu, 5; Gd, 6; Tb, 5; Dy, 6; Er, 5} in the presence of Et3N. The structures of these compounds have been characterized by elemental analysis, thermal gravimetric, molar conductivity, and different spectral analysis techniques (IR, UV-vis, 1 H, and 13 CNMR ). Each unit of the anionic part comprises one Ln(3+) ion, one bi-basic L2- ligand, and two bidentate nitrate NO3- groups. Each Ln(3+) ion is coordinated by one pyridyl N atom, two alkoxido O atoms, one azomethine N atom, and one phenolate O atom. The lanthanide centers in the dinuclear core are bridged by two alkoxide groups from two ligands. The molar conductivity results have indicated that each of these complexes is a 2:1 electrolyte. Dy_L complex obtained from a mixture of MeCN/ DMF solution has also been structurally characterized via X-ray diffractometry. The solid-state structure of the Dy_L complex revealed that the asymmetric unit of Dy_L is formulated from Dy3+ ion, one L2- ligand, one bidentate nitrate NO3- group, and one coordinated DMF molecule. The results of antioxidant activities have shown that all investigated complexes are more efficient in quenching DPPH center dot than the free H2L. Antibacterial activities have also been investigated against some Gram-negative bacteria and Gram-positive bacteria. The MIC values have reflected that all complexes have moderate antibacterial activity against the examined Gramnegative bacteria. On the contrary, they are inactive against the examined Gram-positive bacteria.