Complexes of light lanthanides with 2,3-dimethoxybenzoic acid

Abstract

The complexes of light lanthanides with 2,3-dimethoxybenzoic acid of the formula: Ln(C9H9O4)3, where Ln = La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III) and Gd(III) have been synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric studies, as well as X-ray and magnetic measurements. The complexes have colours typical for Ln3+ ions (La, Ce, Eu, Gd-white, Sm-cream, Pr-green, Nd-violet). The carboxylate group in these complexes is a bidentate, chelating ligand or a tridentate chelating and bridging one. They are crystalline compounds characterized by low symmetry. On heating in air to 1173 K, the 2,3-dimethoxybenzoates of the light lanthanides decompose in various ways. The complexes of Ce(III), Pr(III), Sm(III), Eu(III) and Gd(III) decompose directly to oxides of the respective metals while those of La(III) and Nd(III) via the intermediate formation of La2O2CO3 and Nd2O2CO3. The solubilities of the 2,3-dimethoxybenzoates of the light lanthanides in water at 293Kare in the orders of 10-3-10-2 mol dm-3. The magnetic moments were determined in the range 4.2-298 K and the complexes are found to obey the Curie-Weiss law.