Synthesis of symmetric N,O-donor ligands derived from pyridoxal (vitamin B6): DFT studies and structural features of their binuclear chelate complexes with the oxofilic uranyl and vanadyl(V) cations

The synthesis and the structural characterization of symmetric dimers containing uranium and vanadium atoms provide an outstanding opportunity for the study of hydrogen bonding in supramolecular architectures and unusual interactions. On the search of ligands able to coordinate itself to two metal ions simultaneously, we have synthesized the Schiff bases bis((3-hydroxy-5-(hydroxymethyl)-2-methylpyridin-4-yl)methylene) oxalohydrazide (H6Pyr2oxdihyd) and bis((3-hydroxy-5-(hydroxymethyl)-2-methylpyridin-4-yl)methylene) succinohydrazide (H10pyr2sucdihyd), efficient symmetric ligands with an inversion center, obtained through the reaction of pyridoxine/pyridoxal hydrochloride with oxalyl dihydrazide and succinic dihydrazide. Their reactions and the products obtained with the oxofilic uranyl(VI) and vanadyl(V) cations were discussed, as well as computational methods were used as complementary tools in the study of intra and intermolecular bonds.