EXAFS on some uranium coordination compounds in solid state and in solutions

Structures of uranium compounds in solution have been deduced from EXAFS analysis (Extended X-Ray Absorption Fine Structure). Model compounds with structures were first examined in the solid state to determine atomic phase shifts for U-O, U-Cl, U-N pairs, which are needed to quantitatively interpret spectra and to test their transferability. The uranyl ion in dilute aqueous solution is surrounded by five water molecules at 2,45 A in its equatorial plane when dissolved as a perchlorate, nitrate, or acetate salt; in contrast, it remains bonded to the azide ions in a 0,4 M solution of tetraethylamonnium uranyl triazide. Uranium IV is coordinated by nine oxygen atoms at 2.42 A in aqueous 5x10-2 solution