Autillo, Matthieu; Wilson, Richard
The synthesis of a series of molecular actinyl(VI), namely, uranium(VI), neptunium(VI), and plutonium-(VI), hydroxo-bridged dimers is reported. These complexes were isolated from an aqueous nitrate solution by titration with tetramethylammonium hydroxide. The solid-state structures were determined using single-crystal X-ray diffraction, revealing molecular complexes with the formula [Me4N](2)[(AnO(2))(2)(mu(2)-OH)(2)(NO3)(4)], where An = U-VI, Np-VI, and Pu-VI. Spectroscopic data-UV-vis near-IR absorption, IR, and Raman-were collected on the solutions and solid-state complexes where available and compared to those of the aqueous solutions from which the crystals formed. These data provide structural evidence for higher-order polynuclear complexes of actinyl(VI) complexes upon a pH increase in the aqueous solution, confirming earlier thermodynamic models.