Synthesis, X-ray structure, electrochemical behaviour and fluorescence studies of mononuclear dioxouranium complexes with oxygen donor ligands

摘要

Two phenol-based mononuclear dioxouranium complexes [UO_2(mdbp)_2{OHCH_2CMe_3}] (1) and [UO_2 (bdbp)_2{OCHNMe_2}] (2) (where mdbpH = 4-methyl-2,6-dibenzoylphenol and bdbpH = 4-tert-butyl-2,6-dibenzoylphendol) have been synthesized and characterized by mass spectrometry, IR, NMR and electronic spectroscopy, cyclic voltammetry and single crystal X-ray diffraction studies. In both the complexes the U~(VI) atom has pentagonal bipyramidal geometry with two apical oxo groups, two chelating dibenzoyl phenolate ligands and one unidentate neopentanol or DMF molecule in the equatorial plane. The electrochemical behaviour of the complexes was investigated by cyclic voltammetry in CH_3CN and DMSO. Both complexes exhibited a single quasireversible/irreversible reduction corresponding to the UO_2~(2+)/UO_2~(1+) couple. The potential for 1 in DMSO shifted towards a more positive value by 0.604 V, indicating the exchange of coordinated neopentanol with DMSO. The fluorescence of 1 and 2 was studied by fluorometric method and was compared with that observed for the ligand precursors. The results indicated characteristic charge transfer emissions.