Periodic Trends within Actinyl(VI) Nitrates and Their Structures, Vibrational Spectra, and Electronic Properties
Matthieu Autillo, Richard E. Wilson, Monica Vasiliu, Gabriel F. de Melo, David A. Dixon
Abstract
A series of actinyl(VI) nitrate salts of the form MAnO2(NO3)3, where M = NH4+ K+, Rb+, Cs+, and Me4N+ and AnO22+ = U, Np, Pu, and AnO2(NO3)2(H2O)2·H2O, and the uranyl tetranitrates M2UO2(NO3)4 have been synthesized from aqueous solution and their structures determined using single-crystal X-ray diffraction. Together, these complexes represent an isostructural series of actinide complexes among the salts crystallized with the same charge-compensating cation and have been studied using vibrational spectroscopy including Raman and Fourier-transform infrared. Periodic trends in both the structural properties of these complexes and their vibrational spectra are presented and discussed, in particular the invariant nature of the O≡An≡O asymmetric stretching frequencies observed across the actinyl series. Electronic structure calculations were performed at a variety of levels of theory to aid in the interpretation of the vibrational data and to correlate trends in the data with the underlying electronic properties of these molecules.