<b>Synthesis and characterization of a heptadentate (N₄O₃) Schiff base ligand and associated La(III), Sm(III) and Gd(III) complexes, and a theoretical study</b>

A new symmetrical potentially heptadentate (N4O3) Schiff base ligand {N[CH2CH2CH2N=CH(2-OH-5-BrC6H3)]3} (H3L6) and associated neutral Gd(III), La(III) and Sm(III) complexes, were synthesized. The new compounds were characterized by IR spectroscopy, elemental analysis and mass spectrometry in all cases and in the case of ligand also with NMR spectroscopy. The relative capability of H3L6 to encapsulate a lanthanide ion, herein La(III), has been theoretically studied by ab initio restricted Hartree-Fock (RHF) and DFT (B3LYP) methods. The calculation confirmed that the H3L6 ligand can effectively encapsulate a lanthanide ion and enforce a seven-coordinate geometry