ABSTRACT
To improve our understanding of the chemistry of actinide complexes and to spur their development in the field of actinide markers, two new uranium complexes were synthesized using 8-hydroxyquinoline and 5,7-dichloro-8-hydroxyquinoline. The prepared complexes were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, ultraviolet-visible spectroscopy, elemental analysis, and single-crystal X-ray diffraction. The impact of the electron-withdrawing group of the ligand on the photoluminescence spectra of the complexes in solution and in the solid state was scrutinized. The bandgap of the complexes was calculated using the density functional theory (DFT) method to investigate the effects of the electron-withdrawing groups on energy levels. The synthesized uranium complexes demonstrated appropriate levels of the lowest unoccupied molecular orbital energy, leading to favorable dye stability. The prepared uranium complexes showed blue fluorescent emission, and the sample with the most intense fluorescence was used to construct bluish-green organic light-emitting diodes using simple solution processing fabrication methods. Absorbance spectra, emission spectra, DFT-calculated energy levels, and comparisons of the fabricated organic light-emitting diodes indicated that the electron-withdrawing group was a key factor in photoluminescence behavior.
ABSTRACT
In this study, three uranium(vi) complexes, [UO2(C15H9O2)2(CH3CH2OH)2]·2CH3CH2OH (1), [U2O4(C15H9O2)2(CH3O)2(CH3OH)2]·2CH3OH (2), and [U2O4(C15H9O2)4(CH3OH)2]·2H2O (3), were prepared by reacting anthracene-9-carboxylic acid with uranyl acetate dihydrate using various ligand to uranyl acetate ratios in different solvents. The infrared and UV-Vis spectra along with elemental and thermal analyses showed the formation of mono- and dinuclear anthracene-9-carboxylate complexes of uranium. A 1 to 3 molar ratio of uranyl acetate to anthracene-9-carboxylic acid in ethanol resulted in the formation of the mononuclear complex 1, whereas a 1 to 2 and 1 to 3 molar ratio of uranyl acetate to anthracene-9-carboxylic acid in methanol produced the dinuclear complexes 2 and 3, respectively. Single-crystal structure determinations of 1, 2 and 3 revealed hexagonal bipyramidal geometries for the mononuclear uranium complex of 1 and a pentagonal geometry for the dinuclear uranium complexes of 2 and 3. The single-crystal structures of complexes 2 and 3 showed π-π interactions in contrast to complex 1. The strong π-π interactions in complex 2 and 3 lead to an enhanced photoluminescence intensity in comparison with 1 without π-π interaction. The optical properties of the prepared complexes are associated with the ligand-induced resonant system. The fluorescent uranium complex 1 that showed a blue emission upon excitation at 270 nm was used for the fabrication of a blue organic light-emitting diode (BOLED), an industrially important OLED, using a simple solution-process fabrication method.
