DFT studies of structure and vibrational frequencies of isotopically substituted diamin uranyl nitrate using relativistic effective core potentials

The infrared and Raman spectra of UO2(NH3)2(NO3)2 with 14NH3/15NH3 isotopic substitution were measured. The structure was optimized and the vibrational spectrum was calculated by DFT (B3LYP/6-31G(d)) methodology using relativistic effective core potential for U atom. The results for force constant and vibrational frequencies support the experimental assignments and the proposed model, mainly in the far-infrared region, where the metal–ligand bond and lattice vibrations are observed. Based on the theoretical findings and the observed spectra a structure of distorted D2h symmetry with the nitrate group acting like bidentate ligands for the UO2(NH3)2(NO3)2 is proposed.