The potentiometric determination of stability constants of sulfite and cobalt(II) in ionic strength 2.0 M (NaClO4). Use of the matrix method

Cavalheiro, Éder Tadeu Gomes; Plepis, Ana Maria de Guzzi; Chierice, Gilberto Orivaldo; Neves, E. F. A.

doi:10.1016/s0277-5387(00)86541-9

Cited by 7 publications

(3 citation statements)

References 4 publications

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“…Similarly, as the Co II (SO 3 2Ϫ ) complex 37 is fairly stable, it is quite possible the formation of Ni II G 4 (SO 3 2Ϫ ). However, the complexity of the system does not allow a definite assigment of the species involved.…”

Section: Spectrophotometricmentioning

confidence: 99%

Sulfite induced autoxidation of Ni(ii) and Co(ii) tetraglycine complexes. Spectrophotometric and rotating ring-disc voltammetric studies

et al. 2004

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The oxidation of Ni(II) and Co(II) tetraglycine complexes in borate buffer aqueous solution, by dissolved oxygen, is strongly accelerated by sulfite. The formation of Ni(III) and Co(III) complexes with maximum absorbances at 327 and 265 nm, respectively, was followed by spectrophotometric measurements. Ni(III) formation was also characterized by voltammetry at low temperatures, whose anodic and cathodic components were observed in the recorded voltammograms. Spectra and rotating ring-disc voltammograms, recorded at various rotation speed values, showed that the Ni(III) species decomposes. The electrochemical process related to the couple Co(II)/Co(III), in a medium containing tetraglycine, was not reversible. In both Ni(II) and Co(II) complexes the metal ion oxidation in the presence of oxygen and sulfite involves the reduction of some initial Ni(III) or Co(III) by sulfite to produce the SO(3).- radical, which rapidly reacts with dissolved oxygen to produce SO(5).-, which then oxidizes Ni(II) or Co(II).

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Section: Spectrophotometricmentioning

confidence: 99%

Sulfite induced autoxidation of Ni(ii) and Co(ii) tetraglycine complexes. Spectrophotometric and rotating ring-disc voltammetric studies

et al. 2004

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“…Accordingly, literature shows that Co II SO 3 2-is fairly stable. 39 In the Scheme 1 (proposed for the sulfite induced autoxidation of Ni II G n ), additional steps must be considered in the initiation process for Co III G n generation, with formation of dimeric complexes with oxygen adduct and peroxo bridges.…”

Section: G Nmentioning

confidence: 99%

Autoxidation of Ni(II) and Co(II) tetra, penta and hexaglycine complexes accelerated by oxy sulfur radicals

Carvalho

Alipázaga

Lowinsohn

et al. 2006

J. Braz. Chem. Soc.

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A autoxidação dos complexos de Ni(II) e Co(II) com tetra, penta e hexaglicina, em meio de tampão borato, é acelerada por espécies de enxofre(IV) (H 2 SO 3 , HSO 3 -and SO 3 2-). A formação dos complexos de Ni(III) e Co(III) foi acompanhada espectrofotometricamente em 325 e 265 nm, respectivamente. Técnicas eletroquímicas também foram empregadas para caracterizar a geração destes complexos. A velocidade da reação de autoxidação aumenta com a concentração de S(IV) e é máxima em pH ≅ 8,5. O processo é autocatalítico com Ni(III) ou Co(III) atuando como iniciadores, formados pela oxidação espontânea de Ni(II) ou Co(II) pelo oxigênio molecular. A dependência da constante de velocidade de pseudo-primeira ordem com a concentração de sulfito evidenciou possíveis reações paralelas com formação de um complexo com ligantes mistos antes da etapa da oxidação.The autoxidation of Ni(II) and Co(II) complexes with tetra, penta and hexaglycine, in borate medium, is accelerated by sulfur(IV) species (H 2 SO 3 , HSO 3 -and SO 3 2-). The formation of Ni(III) and Co(III) complexes was followed spectrophotometrically at 325 and 265 nm, respectively. Electrochemical techniques were also employed to characterize the generation of these complexes. The autoxidation rate increases with S(IV) concentration and is maximum at pH ≅ 8.5. The process is autocatalytic with Ni(III) or Co(III) acting as initiators, formed by spontaneous oxidation by oxygen. The dependence of the pseudo first order rate constant with sulfite concentration showed evidences of back or parallel reactions with formation of mixed ligand complex prior to the oxidation step.

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“…The pH values of these buffers were measured with a glass electrode calibrated with solutions of ionic strength 0.50 mol dm -3 (NaClO 4 ), hydrogen ion concentration 1.00 x 10 -2 and 1.00 x 10 -4 mol dm -3 (HClO 4 ), corresponding to pH 2.00 and 4.00, respectively 27 .…”

Section: Buffer Solutionsmentioning

confidence: 99%

Solution and solid state thermal stability of morpholinedithiocarbamates

Antunes¹,

Breviglieri²,

Chierice³

et al. 2001

J. Braz. Chem. Soc.

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Estudos termogravimétricos e calorimétricos diferenciais de morfolinoditiocarbamatos de NH 4 + , Mn 2+ , Co 2+ , Ni 2+ e Cu 2+ foram realizados em atmosferas de ar e nitrogênio, para avaliar a influência da presença do oxigênio como heteroátomo no anel da amina na decomposição térmica. Produtos de decomposicão térmica foram caracterizados através de difratogramas de raios X, sendo predominantemente formados por sulfetos metálicos, sob atmosfera dinâmica de nitrogênio e óxidos metálicos, sob ar. Usando espectrofotometria, também foram determinados o pKa = 3,56 para o ácido morfolinoditiocarbâmico em força iônica 0,50 mol dm -3 (NaClO 4 ) à 25,0 °C e parâmetros cinéticos de decomposição em diferentes valores de pH (k lim = 0,14 ± 0,04 s -1 e t ½ lim = 5,3 ± 1,2 s).Thermogravimetric and differential scanning calorimetric investigation of the thermal behavior of NH 4 + , Mn 2+ , Co 2+ , Ni 2+ e Cu 2+ morpholinedithiocarbamates were performed under nitrogen and air atmospheres in order to investigate the effect, in the thermal decomposition, of the presence of an oxygen as the heteroatom in the amine ring. Decomposition products were identified by their X-ray diffraction patterns. Metal sulfites and oxides were the major residues under nitrogen and air atmospheres, respectively. Spectrophotometric measurements were used to estimate the pKa =3.56 for the morpholinedithiocarbamic acid at 0.50 mol dm -3 ionic strength (NaClO 4 ) at 25.0 °C and kinetic parameters of decomposition at different pH values (k lim = 0.14 ± 0.04 s -1 e t ½ lim = 5.3 ± 1.2 s).

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The potentiometric determination of stability constants of sulfite and cobalt(II) in ionic strength 2.0 M (NaClO4). Use of the matrix method

Cited by 7 publications

References 4 publications

Sulfite induced autoxidation of Ni(ii) and Co(ii) tetraglycine complexes. Spectrophotometric and rotating ring-disc voltammetric studies

Sulfite induced autoxidation of Ni(ii) and Co(ii) tetraglycine complexes. Spectrophotometric and rotating ring-disc voltammetric studies

Autoxidation of Ni(II) and Co(II) tetra, penta and hexaglycine complexes accelerated by oxy sulfur radicals

Solution and solid state thermal stability of morpholinedithiocarbamates

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