Lattice solvent and crystal phase effects on the vibrational spectra of UO2Cl4(2-).

We present the structural and spectroscopic characterization of six uranyl tetrachloride compounds along with a quantified analysis showing the influence of both the crystallographic phase and the lattice solvent upon the vibrational properties of the uranyl moiety. From the uranyl symmetric and asymmetric stretching frequencies we use a valence bond potential model to calculate the stretching and interaction force constants of the uranyl moiety in each compound. Quantifying these second-sphere influences provides insight into the vibrational properties, and indirectly the electronic structure, of the uranyl ion in its ground state. These data provide a better guide for assessing the validity of future comparisons with respect to bond strength, length, and electronic properties among series of actinyl compounds where non-actinide variables may be at play.