Spectral and thermal properties of complexes of 1,10-phenanthroline and thiocyanate with rare-earth elements

The complexes of rare-earth elements with phenanthroline and thiocyanate have been obtained as monohydrates with a metal to ligand ratio of 1:3. Their colours are those typical for Ln(3+) ions. In these complexes presumably three phenanthroline molecules attach to trivalent rare-earth element ions, two or one thiocyanate groups and one molecule of water are in the inner or outer-sphere of coordination. The complexes decompose in various ways: in three, four or five steps. Ar first, they dehydrate to form anhydrous salts, which, in the succeeding steps of decomposition, gradually lose thiocyanate groups and phenanthroline molecules to form the sulphates of the respective rare-earth elements. All complexes are polycrystalline compounds with various degrees of crystallinity and low symmetry. Their solubility in water at 293 K is in the order of 10(-3) mol/dm(3).