On the redox reactions of radicals with Al III(phthalocyaninate) pendants covalently bonded to poly(ethyleneamide). Mechanistic alterations when radicals are formed inside pockets of micelle-like polymer aggregates

Abstract

The mechanisms of the redox reactions between a polymer containing Al(III) sulfonated phthalocyanine pendants, (Al III( ⌊NHS(O 2)trspc) 2-) 2, and radicals have been investigated in this work. Pulse radiolysis and photochemical methods were used for these studies. Oxidizing radicals, OH •, HCO 3 •, (CH 3) 2COHCH 2 •, and N 3 •, as well as reducing radicals, e aq -, CO 2 •-, and (CH 3) 2C •OH, respectively accept or donate one electron forming pendent phthalocyanine radicals, Al III( ⌊NHS(O 2)trspc •) - or 3-. The kinetics of the redox processes is consistent with a mechanism where the pendants react with radicals formed inside aggregates of five to six polymer strands. Electron donating radicals, that is, CO 2 •- and (CH 3) 2C •OH, produce one-electron reduced phthalocyanine pendants that, even though they were stable under anaerobic conditions, donated charge to a Pt catalyst. While the polymer was regenerated in the Pt catalyzed processes, 2-propanol and CO 2 were respectively reduced to propane and CO. The reaction of SO 3 •- radicals with the polymer stood in contrast with the reactions of the radicals mentioned above. A first step of the mechanism, the coordination of the SO 3 •- radical to the Al(III), was subsequently followed by the formation of a SO 3 •--phthalocyanine ligand adduct. The decay of the SO 3 •--phthalocyanine ligand adduct in a ∼10 2 ms time domain regenerates the polymer, and it was attributed to the dimerization/disproportionation of SO 3 •- radicals escaping from the aggregates of polymer.