Aqueous coordination chemistry and photochemistry of uranium(VI)

We have been exploring aqueous coordination chemistry of uranium(VI) by combining different spectroscopic techniques and computational chemistry, i.e. EXAFS and FTIR spectroscopy and DFT calculations. In uranyl(VI) sulfate system we found sulfate may bound to uranium in both unidentate and bidentate modes.
Whether ligand bind to uranium in unidentate or bidentate might seem to be irrelevant. However the EXAFS and DFT study on uranyl(VI) oxalate system proved that this is entirely not the case and the mode of ligand coordination plays decisive role to the photoreactivity of uranyl(VI) oxalate. Only the uranyl(VI) oxalate having unidentate coordination was found to be photoreactive. The result is consistent with recent UV-Vis absorption spectroscopic study by Görller-Walrand and Servaes.
The validity of the use of DFT on uranium complexes is often disputed. Sophisticated theory such as CASPT2 is proved to be requisite for getting accurate excitation energies of uranyl(VI) complexes. However, DFT calculations were also proved to provide accurate geometries as long as the ground states and the lowest lying triplet states are concerned. Photoluminescence characters of uranium(VI) were also found to be well reproduced by cost-effective DFT calculations.