Luminescence studies of uranyl-aliphatic dicarboxylic acid complexes in acetonitrile medium

The uranyl (UO22+)-aliphatic dicarboxylic acid complexes are studied by luminescence and UV-Vis spectroscopy in acetonitrile (MeCN) medium. The ligands used are malonic acid (MA), succinic acid (SA), glutaric acid (GA), adipic acid (AA) and pimelic acid (PA). The complexes of UO22+ with the above ligands showed well resolved luminescence spectra at pH 4.0 with M/L=5. Both luminescence and UV-Vis spectra indicated the formation of 1:2 and 1:3 complexes of UO22+ with MA and GA, AA, PA, respectively. DFT computations indicated the formation of 1:2 chelate complex of UO22+ with MA and two types of 1:3 complexes of UO22+ with SA, GA, AA and PA. Furthermore, the effect of solvent (water and acetonitrile) on the UO22+-ligand complexes has been performed using COSMO model. The present study demonstrates, for the first time, the formation of tris complexes of uranyl with these ligands in acetonitrile medium.