80137-20-8Relevant articles and documents
One-Electron-Transfer Reaction of the Couple SO2/SO2(1-) in Aqueous Solutions. Pulse Radiolytic and Cyclic Voltammetric Studies
Neta, P.,Huie, Robert E.,Harriman, Anthony
, p. 1606 - 1611 (1987)
Rate constants for one-electron reduction of SO2 by several radicals and for reduction of several compounds by SO2(1-) radicals were determined by pulse radiolysis at pH 1.SO2 is reduced by the (CH3)2COH radicals with k = 2.1E9/M*s and by viologen radicals and certain porphyrin Π-radical anions with k ca. 1E8 - 1E9/M*s.The SO2(1-) radical reduces compounds which have reduction potentials more positive than -0.28 V.The rate constants for these reductions vary from ,1E7 to>1E9/M*s and depend on the redox potentials of the compounds and on other propeties such as charge and self-exchange rate.The reduction potentials for SO2 and for he porphyrins were determined by cyclic voltametry under identical conditions.These production potentials were used along with the rate constants and previously reported self-exchange rates to estimate the self-exchange rate for the couple SO2/SO2(1-) radical in acidic solutions.The calculated values were found to vary over many orders of magnitude, similar to the situation reported before for the O2/O2(1-) couple.
Cobalt(I) porphyrin catalysis of hydrogen production from water
Kellett, Richard M.,Spiro, Thomas G.
, p. 2373 - 2377 (2008/10/08)
Cobalt complexes of three water-soluble porphyrins, meso-tetrakis(N,N,N-trimethylanilinium-4-yl)porphine chloride (CoTMAP), meso-tetrapyrid-4-ylporphine (CoTPyP), and meso-tetrakis(N-methylpyridinium-4-yl)porphine chloride (CoTMPyP), have been examined as catalysts of H2O reduction to H2. They have been shown to catalyze H2 production via controlled-potential electrolysis (-0.95 V vs. SCE at Hg-pool electrode; 0.1 M trifluoroacetic acid) at rates approximately 10-fold greater than background and with nearly 100% current efficiency. Reversible cyclic voltammograms were observed in dry Me2SO, with Co(III)/Co(II) and Co(II)/Co(I) potentials near their expected values. Addition of water (0.5-2%) increased the cathodic peak and decreased the anodic peak at the Co(II)/Co(I) couple, consistent with electrocatalytic H2O reduction. In aqueous buffers, catalytic currents were observed for CoTMPyP, which increased with decreasing pH, but at a rate less than expected, due to porphyrin adsorption. Adsorption was more pronounced for CoTMAP, which showed no catalytic current except at very low pH. The rate of CoITMAP reaction with H2O, however, is extremely fast as shown by spectrophotometry in dry acetonitrile; a lower limit for the Co(I)-H2O reaction rate constant was estimated to be approximately 104 M-1 s-1. Co(I) reactivity and cobalt hydride stability are discussed in comparison with the reactivity and stability of related compounds.
