Syntheses, crystal structures and vibrational spectra of KLn(SO4)2·H2O (Ln=La, Nd, Sm, Eu, Gd, Dy)

The potassium lanthanide double sulphates KLn(SO4)2·H2O (Ln=La, Nd, Sm, Eu, Gd, Dy) were obtained by evaporation of aqueous reaction mixtures of rare earth (III) sulphates and potassium thiocyanate at 298 K. X-ray single-crystal investigations show that KLn(SO4)2·H2O (Ln=Nd, Sm, Eu, Gd, Dy) crystallise monoclinically (Ln=Sm: P21/c, Z=4, a=10.047(1), b=8.4555(1), c=10.349(1) Å, wR2=0.060, R1=0.024, 945 reflections, 125 parameters) while KLa(SO4)2·H2O adopts space group P3221 (Z=3, a=7.1490(5), c=13.2439(12) Å, wR2=0.038, R1=0.017, 695 reflections, 65 parameters). The coordination environment of the lanthanide ions in KLn(SO4)2·H2O is different in the case of the Nd/Sm/Gd and the Eu/Dy compounds, respectively. In the first case the Ln atoms are nine-fold coordinated in contrast to the latter where the Ln ions are eight-fold coordinated by oxygen atoms. The vibrational spectra of KLn(SO4)2·H2O and the UV–vis reflection spectra of KEu(SO4)2·H2O and KNd(SO4)2·H2O are also reported.

The lanthanide potassium double sulphates exhibit an unexpected change in the coordination mode by a simple rotation of sulphate tetrahedron 2.Figure optionsDownload as PowerPoint slide