Compostos de coordenação com um ligante do tipo oxamato derivado do ácido 4-aminobenzóico: Síntese, Caracterização e estudo das propriedades ópticas e magnéticas

Abstract

In this work, we present the syntheses, characterizations, and studies of the optical and magnetic properties of various novel coordination compounds. We obtained supramolecular systems based on complexes with the ligand Sodium 4- (carboxylatoformamido)benzoate (Na2Hpcpa) and the heavy metal ions Cd2+ and Pb2+, as well as a series of isostructural complexes containing the rare earth metal ions Y3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, and Yb3+. The studies of the optical properties of the Cd2+ and Pb2+ compounds show a shift in the emission band position towards white light when compared to the matrix's emission. The Eu3+ and Tb3+ compounds exhibit red and green emissions, respectively, with high thermal stability over the entire temperature range studied, between 16 and 300 K. The external quantum yield for the Tb3+ compound was considerably improved compared to compounds containing oxamate-type ligands reported in the literature, indicating that the ligand Hpcpa2- may be an efficient sensitizer for energy transfer through the so-called antenna effect to Tb3+ ions. Magnetic properties studies of the Eu3+, Gd3+ , Tb3+, and Er3+ compounds were conducted, and ac susceptibility measurements reveal that the Gd3+, Tb3+, and Er3+ compounds exhibit slow relaxation of magnetization induced by the magnetic field, thus representing new examples of field-induced single-molecule magnets (SMMs). Despite the Y3+, Eu3+, Ho3+, Er3+, and Yb3+ compounds not having well-defined single-crystal X-ray diffraction structures, other structural characterizations indicate that all rare earth Ln3+ compounds obtained in this work are isostructural to the Eu3+, Gd3+, and Tb3+ compounds with defined structures. Therefore, among the compounds obtained in this work, the Tb3+ compound can be classified as multifunctional with possible dual technological applications, optical and magnetic.