Síntese e caracterização de difenil-4-amina-sulfonatos de cobre (II) e zinco (II) e estudo de suas interações com a polianilina

Abstract

In this work two metal sulfonates were obtained: Copper (II) diphenyl-4-amine-sulfonate hexahydrate, Cu(DAS)2.6H2O, and Zinc (II) diphenyl-4-amine-sulfonate pentahydrate, Zn(DAS)2.5H2O. Both were synthesized from diphenyl-4-amine-sulfonate and barium salts of their ions in the form sulfate. The sulfonates were characterized by the elemental contents CHNS and metals. The IR analysis showed a change of the symmetry the Cu(DAS)2.6H2O in comparison the barium sulfonate motivated by a new alignment of the ligands around the Copper ion and the presence of water. The thermal characterization employed two atmospheres: the synthetic air and N2. TGA/DTGA results for the compound of Copper (II) shows that dehydration took place in two stages, showing the distinct character of the connections of water molecules. Under oxidizing atmosphere was obtained a stable residue (CuO), while, under inert atmosphere was obtained a residue containing carbon and even some sulfur. In the complex of Zinc (II), the dehydration followed in a single stage and the same residue (ZnO) was obtained in the two atmospheres. All the analysis performed allowed us to establish an appropriated formula for the compound, the location of ligand binding sites and the type of coordination assumed by the ligand around the metal ion. The complexes synthesized were then used in the electrochemical synthesis of polyaniline, in the absence and presence of sulfonate, through successive cycles, 1:1 (Aniline: DAS) and in the potential range from -0.1 to 1.5 V. Without sulfonates, the current increased with the number of cycles with no degradation. In the presence of sulfonate (Sodium, Copper and Zinc) the oxidation of the anion DAS took place leading to a decrease in current. The deposits were characterized by IR, showing the presence of sulfonate and the absence of degradation products, such as p-benzoquinone. The micrograph of the deposit polyaniline without sulfonate showed a very porous structure. However, micrographs of polyaniline with sulfonates showed structures more compact, with two-dimensional growth for the Sodium sulfonate, and mixed for Copper (II) and Zinc (II) sulfonates. The morphology of the deposits has contributed directly to the results of the electrochemical impedance spectroscopy, since the deposits containing sulfonate Copper (II) and Zinc (II) showed lower resistance