Mononuclear and polynuclear complexes ligated by an iminodiacetic acid derivative: synthesis, structure, solution studies and magnetic properties

Abstract

Two novel families of coordination polymers, [Ln(bzlida)(Hbzlida)]·H₂O (Ln = La, Nd) and [Ln₂(bzlida)₃]·3H₂O (Ln = Nd, Sm, Eu, Gd) were prepared by hydrothermal reaction of Ln₂O₃ with benzyliminodiacetic acid (H₂bzlida). The conditions of synthesis, in particular the pH value, were selected on the basis of previous speciation studies reported in this work. The first type of complex consists of 1D chains built by a fully deprotonated ligand bridging two lanthanide ions and protonated Hbzlida⁻ ligands connecting three cations. The second type is formed by [Ln₂(bzlida)₃] bimetallic units in which the ligand has a tridentate NOO coordination mode. This is expanded to a 2D network through carboxylate linkers. Under similar synthetic conditions but including copper acetate in the reaction mixture, a new compound was also obtained and characterized: [Cu(bzlida)₂{Er(AcO)(H₂O)₅}₂][Cu(bzlida)₂]·6H₂O (AcO = acetate). This salt is made up of the [Cu(bzlida)₂{Er(AcO)(H₂O)₅}₂]²⁺ heterotrimetallic complex cation containing an acetato bridge, and the [Cu(bzlida)₂]²⁻ anion. The same reaction produces the monomeric [Cu(Hbzlida)₂]·4H₂O whose structure was also elucidated. Magnetic properties of the Gd(III) derivative were studied and analyzed experimentally and theoretically. The results are compared and discussed with respect to those reported in the literature and a magnetostructural correlation is suggested.