Synthesis and properties of lanthanide(III) complexes with 4-hydroxy-3,5-dimethoxybenzoic acid

Complexes of yttrium(III) and lanthanides(III) with 4-hydroxy-3,5-dimethoxybenzoic (syringic) acid were obtained as solids with metal to ligand mole ratio of 1: 3. The compounds were characterized by elemental analysis, IR spectroscopy, X-ray diffraction patterns, solubility, and thermal studies. The complexes are sparingly soluble in water and stable at room temperature. Compounds of light lanthanides (from La to Nd) are hydrated and they crystallize in a triclinic system. When heated, they lose water molecules in one step and in the next step they decompose to oxides. Complexes of yttrium and other lanthanides are anhydrous and crystallize in a monoclinic system. They are stable up to 300°C and then decompose to oxides. As the coordination number of lanthanide ions is usually equal to 9 or 8, one can suppose that hydroxy or methoxy groups take part in the coordination of these metal ions.