Composition and stability of lanthanoid complexes in solutions of hydrogen chloride in absolute ethanol

The composition and stability of the complexes of Pr3+, Nd3+, Eu3+, Tb3+, Dy3+, Ho3+ and Er3+ formed in hydrogen chloride solutions in the absolute ethanol are determined. It is found that at HCl concentrations up to 3 M in solutions monochloride complexes LnCl2+ are formed, and at 3-8 M and higher concentrations of HCl hexachloride complexes LnCl63- are formed. The complexes of Pr3+, Nd3+, Ho3+ and Er3+ are studied by the spectrophotometric method using the absorption bands which do not correspond to ''supersensitive'' transitions (SST). In the case of the Eu3+, Tb3+ and Dy3+ complexes the investigation has been carried out using the value of the intensity ratio of two bands of luminescence spectra: one band is corresponding to SST, and the other one is not corresponding to SST or corresponding to magneto-dipole transition. The found values of logarithms of stability constants of the complexes LnCl2+ and LnCl63- are equal to: Pr3+ - (-0.52, -3.87); Nd3+ - (-0.50; -3.59), Eu3+ - (-0.22; -2.69), Tb3+ - (-0.36; -3.20), Dy3+ - (-0.44; -3.34), Ho3+ - (-0.27; -2.95), Er3+ - (-0.39; -2.05)