Vibrational spectroscopy and structural analysis of uranium complexes

On the basis of experimental and theoretical studies of vibbrational spectra for halides, sulfates, phosphates, uranyl oxalates (and uranium) as well as for more complicated complex systems, reliable spectroscopic criteria have been established for estimation of their structural features by more simple and accessible (than direcrt) methods. Due to coordination to a central ion of U6(U4) ligands a geometry variation specific for each method of addition occurs and concomitant redistribution of the force interaction in the mentioned system as well, which direcrly affects the variation of their frequency characteristics and vibration modes. On this ground stable indications of particular types of coordination for mono- and polyatomic groups (including bridge-type, characteristic of polymetric structures) are pointed out in the IR absorption and Raman spectra. In the investigated structures the predominant effect of coordination on the spectralproperties of complexes, as compared with othe factors (for example, outer-sphere binding) is established. The presence of water molecules in an interlayer spase does not tell essentially on the state of polyatomic ligands with all donor atoms bound with the uranium central atom (particularly, in binary uranyl phosphates). In the presence of free oxygen atoms the H2O effect can lead only to some shift of the maxima of separate bands and their additional weak splitting (in uranyl sulfates)