IR-spectral study of solid state complexes of lanthanum with mono- and bis-(2-ethylhexyl) phosphoric acids

IR-spectra of the solid state lanthanum complexes with mono- and bis-(2- ethylhexyl) phosphoric acids (H2B, resp. HA) are studied. It is confirmed that La coordinates HA as LaO6-octahedra, connected through -La-O-P-O-La-bridging bonds. The so fixed polynucleous chains form the crystal structure of the complex. The obtained IR-spectral data as well as the results of the X-ray powder diffraction analysis show that La forms shorter polymeric chains than the other rare earth complexes of the same type. Certain methods for the synthesis of the solid state complexes of La with H2B (studied for the first time) are considered. It is shown that the structure of La-HB-complexes is consituted also by LaO6-octahedra, resp. -La-O-P-O-La-polymeric chains. However they are binded through crosswise PO-H...O(H)-P hydrogen bonds, owing to the non-deprotonized hydroxo-group presented in the complex. The so formed supramolecular structure has to be more disordered than the one in the case of the complexes with HA. This determines the amorphous (nanocrystalline) state of the H2B-complexes and, probably, their abiliity to coordinate water as well.