The interaction of emeraldine base polyaniline (EB) with Cu(II), Fe(III), and Zn(II) in 1-methyl-2-pyrrolidinone (NMP) solution was monitored using electronic UV−vis−NIR, resonance Raman, and electron paramagnetic resonance (EPR) spectroscopies. The films prepared from these solutions were also spectroscopically characterized. It was demonstrated that the nature of the products (semiquinone and quinone segments) formed from the interaction of EB and metal ions is strongly dependent on the nature of the cation, the metal/EB molar ratio, and the concentration of the components. The presence of semiquinone segments (radical cation) in EB solutions with Cu(II) and Fe(III) was undoubtedly confirmed by the observation of an electronic absorption band at ca. 900 nm, a characteristic Raman band at ca. 1330 cm-1 (νC - N •+ ), and also an EPR signal at g = 2.006. The influences of metal/EB molar ratio and metal ion concentration on the formed species were investigated in Cu(II) and Fe(III) solutions, and it was verified that diluted solutions favor the formation of oxidized segments (pernigraniline) instead of doped ones (emeraldine salt). No matter the nature of metal ion solutions, all the polymeric films show a spectroscopic behavior of ES (doped polymer) according to electronic and Raman spectroscopic data.

No abstract

No abstract

Factorial design analysis was applied to the study of the catalytic activity of diimine copper(II) complexes, in the decomposition of hydrogen peroxide. The studied complexes show a tridentate imine ligand (apip), derived from 2-acetylpyridine and 2-(2-aminoethyl)pyridine, and a hydroxo or an imidazole group at the fourth coordination site of the copper ion. The factorial design models for both [Cu(apip)imH] 2ϩ and [Cu(apip)OH] ϩ were similar. Increasing the peroxide concentration from 3.2 ϫ 10 Ϫ3 to 8.1 ϫ 10 Ϫ3 mol L Ϫ1 resulted in increased oxygen formation. Increasing the pH from 7 to 11 also increased oxygen formation and had an effect about twice as large as the peroxide one. Both complexes also had an important interaction effect between peroxide concentration and pH. However, increasing the catalyst concentration led to a decrease in total oxygen formation. The obtained results were corroborated by further data, achieved by using the usual univariate method, and helped to elucidate equilibrium steps occurring in the studied systems. In very alkaline solutions, the studied [Cu(apip)imH] 2ϩ complex can form the corresponding dinuclear species, [Cu 2 (apip) 2 im] 3ϩ . While the mononuclear complex proved to be an efficient catalyst in hydrogen peroxide decomposition, the corresponding dinuclear compound seemed to be able to coordinate with the dioxygen molecule, inhibiting its observed release.

No abstract