Spectral and thermal characterization of 5-chloro-2-methoxybenzoates of light lanthanides

5-Chloro-2-methoxybenzoates of light lanthanides were obtained as penta- or monohydrates with a metal to ligand ratio of 1:3 and general formula Ln(C8 N6ClO3). nH(2)O where n = 5 for Ln = La, Ce, Pr, Nd and n = 1 for Ln = Sm, Eu, Gd. They have colours characteristic for Ln(3+) ions. The complexes wer e characterized by elemental analysis, IR and FIR spectra, thermogravimetri c studies, X-ray diffraction and magnetic measurements. The carboxylate gro up appears to be a symmetrical, bidentate, chelating ligand. All complexes are polycrystalline compounds. Their thermal stabilities were determined in air and in nitrogen atmospheres. When heated they dehydrate to form anhydr ous salts which next in air are decomposed to the oxides of the respective metals whereas in nitrogen to the mixtures of carbon and oxides or carbon a nd oxychlorides of respective metals. The complexes are more stable in air than in nitrogen. The solubility of light lanthanide 5-chloro-2-methoxybenz oates in water at 293 K is of the order of 10(-3) mol/dm(3). Some of the ph ysico-chemical properties of 5-chloro-2-methoxybenzoates of light lanthanid es were compared with those of 2-methoxybenzoates. The influence of the sub stituent position in benzene ring on the thermal stability of complexes and their solubility in water is observed. The magnetic moments of the complexes were determined over the range 77-298 K. They obey the Curie-Weiss law. The values of mu(eff) calculated for all compounds (except that for europium) are close to those obtained for Ln(3) by Hund and Van Vleck. The results show that there is no influence of the ligand field on the 4f electrons of lanthanide ions in the polycrystalline compounds and probably 4f electrons do not take part in the formation of M -O bonding.