Transformations of manganese tetrasulphophthalocyanine in oxidative conditions

Impacts of hydroxide and sulphite ions on the oxidative transformations of tetrasulphophthalocyanine of manganese(II) ((MnTSPc)-T-II) in aerated solut ions were investigated with a view to the role of porphin-type catalysts in the autoxidation of sulphur dioxide. Spectrophotometric-kinetic measuremen ts were performed using the stopped-flow technique for fast reactions. Reac tion times ranged from 0.01 s to 72 h at the initial concentrations of a ca talyst and substrates 5 x 10(-6) or 1.0 x 10(-5) M (MnSPc)-S-II, 5.0 x 10(- 4)-5.00 x 10(-3) M Na2SO3 and 2.24 x 10(-4) M O-2. Values of pH were varied from 6.6 to 10.3. The formation of Mn(III)TSPe accompanying the dissolutio n of (MnTSPc)-T-II in water, followed by the dimerization to a mu-oxo-dimer in the presence of OH- and/or SO32- and the degradation of TSPc structure (catalyst ageing) in the presence of SO, autoxidation transients were obser ved. (C) 1998 Elsevier Science Ltd. All rights reserved.