Steric structure and thermodynamic aspects of the complexes of dysprosium(iii) with aminobenzoic acids in aqueous solutions

Abstract

Steric structures of dysprosium(III) aminobenzoate complexes with the 1∶1 and 1∶2 molar ratio in aqueous solutions were determined on the basis of pH-metric and paramagnetic birefringence data. An increase in conjugation observed for the series of the acids,viz., benzoic,meta-, ortho-, andpara-aminobenzoic acids, results in the increased stability of the complexes with the 1∶1 and 1∶2 composition. In the case ofpara-aminobenzoic acid, the polyhedra [DyL(H2O)6]2+ and [DyL2(H2O)4]+ are cubes with the ligands coordinated to one and two edges, respectively. In the case ofmeta-aminobenzoic acid, the polyhedra [DyL(H2O)6]2+ and [DyL2(H2O)4]+ are a dodecahedron with the ligand coordinated to one edge and a square anti-prism with the ligands coordinated to two edges, respectively. In the case ofortho-aminobenzoic acid, both the 1∶1 and 1∶2 complexes have structures that are intermediate between the structures ofmeta- andpara-aminobenzoic acids.