Incorporation of Neptunium(VI) into a Uranyl Selenite

The incorporation of neptunium­(VI) into the layered uranyl selenite Cs­[(UO2)­(HSeO3)­(SeO3)] has yielded the highest level of neptunium uptake in a uranyl compound to date with an average of 12(±3)% substitution of NpVI for UVI. Furthermore, this is the first case in nearly 2 decades of dedicated incorporation studies in which the oxidation state of neptunium has been determined spectroscopically in a doped uranyl compound and also the first time in which neptunium incorporation has resulted in a structural transformation.