Síntese, caracterização e estudo magnético de redes lantanídeo-orgânicas e complexos contendo o precursor metálico [Cu(bpca)]+ com ligantes N-O doadores

Abstract

In this work, the synthesis, characterization and magnetic studies of ten novel compounds have been described, including their crystal structures elucidated by X-ray diffraction. The first part of this work describes the synthesis and characterization of five novel complexes containing the precursor [Cu(bpca)]+ (where bpca = bis(2-pyridylcarbonyl)-amide), two dinuclear and three mononuclear complexes, which were prepared by a direct addition synthetic route. The structures of the dinuclear compounds {[Cu(bpca)]2(BPP)(NO3)(H2O)}NO37H2O (1) and {[Cu(bpca)]2(pzdc)} (2) (where BPP = 1,3-bis(4-pyridyl)propane and pzdc = 2,5-pyrazinedicarboxilic) show the ligands acting as a bridge connecting the units of [Cu(bpca)]+. The mononuclear compound [Cu(bpca)(mpzc)H2O]3H2O (3) (where mpzc = 5-methyl-2-pyrazinecarboxilic) show the ligand coordinating to copper(II) in a bidentate mode, through the nitrogen atom of pyrazine ring and the carboxylate oxygen, while the others mononuclear complexes [Cu(bpca)(3-Phpr)(H2O)]2H2O (4) and [Cu(bpca)(4,4-dps)]NO3H2O (5) (where 3-HPhpr = 3-phenylpropionic acid and 4,4-dps = di(4-pyridyl) sulfide) the ligands are coordinated to copper(II) in a monodentate mode. Only for 3 a change in copper(II) coordination number was observed, from pentacoordinated to hexacoordinated, with regard to the precursor. The second part of this work describes the synthesis and characterization of five new isostructural metallo-organic frameworks containing the ligand lanthanide ions and the ligand pzdc: {[Nd(pzdc)1.5(H2O)2]4H2O}n (6), {[Pr(pzdc)1.5(H2O)2]4H2O}n (7), {[Eu(pzdc)1.5(H2O)2]4H2O}n (8), {[Er(pzdc)1.5(H2O)2]5H2O}n (9), and {[Ce(pzdc)1.5(H2O)2]4H2O}n (10). The ligand pzdc was produced from the oxidation of the ligand mpzc using hydrothermal condition. Magnetic studies have been made, where a weak magnetic coupling between the spins of the lanthanide ions through a pzdc-bridge has been observed. Compound 6 showed significant interlayer antiferromagnetic interactions, which became evident at low temperatures.