Fabrication of blue organic light-emitting diodes from novel uranium complexes: synthesis, characterization, and electroluminescence studies of uranium anthracene-9-carboxylate complexes

In this study, three uranium( vi ) complexes, [UO 2 (C 15 H 9 O 2 ) 2 (CH 3 CH 2 OH) 2 ]·2CH 3 CH 2 OH ( 1 ), [U 2 O 4 (C 15 H 9 O 2 ) 2 (CH 3 O) 2 (CH 3 OH) 2 ]·2CH 3 OH ( 2 ), and [U 2 O 4 (C 15 H 9 O 2 ) 4 (CH 3 OH) 2 ]·2H 2 O ( 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. The optical properties of the prepared complexes are associated with the aromatic ligand resonant system.