Complexation of U(VI) with diphenyldithiophosphinic acid: spectroscopy, structure and DFT calculations

The complexation of U(VI) with diphenyldithiophosphinic acid (denoted as HL) in acetonitrile was studied by UV-Vis, FT-IR, crystallography and DFT calculations. UV-Vis absorption spectrophotometry implies that three successive complexes, UO2L+, UO2L2, UO2L3 (-), form in the solution. Significant ligand to metal charge transfer occurs from soft atom S to U(VI) in all the three complexes. A crystal of UO2L2 complex was successfully synthesized from the solution. In the crystal both the two ligands coordinate to U(VI) in bidentate form. DFT calculations confirm the formation of UO2L3 (-) complex and help illustrate the structures of all the U(VI) species in the solution.