Dioxouranium complexes with pentadentate s-triazine Schiff base ligands: Synthesis, crystal structure and optical properties

Using the reactions of 2,4-dihydrazino-(R)-s-triazine (R – methoxy (DHMT)) with salicylaldehyde and o-vanillin ligands 2,4-Bis(2-hydroxybenzylidenehydrazino)-6-methoxy-s-triazin (L1) and 2,4-Bis(2-hydroxy-3-methoxybenzylidenehydrazino)-6-methoxy-s-triazin (L2) were obtained. Using the reaction of 2,4-dihydrazino-(R)-s-triazine (R – amino (DHAT)) with o-vanillin ligand 2,4-Bis(2-hydroxy-3-methoxybenzylidenehydrazino)-6-amino-s-triazine (L3) was obtained. By the reactions of the prepared ligands, derivatives of hydrazo-s  -triazine, with uranyl acetate or nitrate, three new complexes were prepared. X-ray diffraction shows that the UO22+ ion is in a pentagonal bipyramidal coordination environment. Two oxygen atoms of the UO22+ ion occupy the axial positions and three atoms of nitrogen and two atoms of oxygen construct the equatorial plane. The uranyl(VI) complexes were characterized by single-crystal X-ray diffraction, UV–vis, fluorescence and IR spectroscopy. Thermal stabilities of the complexes were investigated using thermogravimetric analysis.

Graphical abstractThree new mononuclear uranyl complexes have been synthesized using three new Schiff-base ligands based on s-triazine derivative. Crystal structures show pentagonal bipyramidal geometry around uranium atom with the 3-aza and 2-oxo coordinating sites of the ligand.Figure optionsDownload full-size imageDownload as PowerPoint slide