Effect of Ionothermal Conditions on the Crystallization of Organically Templated Uranyl Sulfate Compounds

Seven novel uranyl sulfate compounds were crystallized by ionothermal synthesis methods through systematic changes in experimental conditions. The parameters explored were temperature, soak time, cooling rate, and reactants, including uranium(VI) salt, a uranium(VI) concentration in the ionic liquid, and the pH by cosolvent addition. The ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate (EMIm-EtSO4) was used in each experiment. Although the seven uranyl sulfate compounds all contained the EMIm organic cation of the ionic liquid, the different synthetic conditions produced varying uranyl coordination environments that resulted in discrete crystal structures. The impact of the ionothermal synthetic conditions on the resulting crystal structures is discussed.