Photochemistry of manganese porphyrins. Part 7. Characterisation of manganese porphyrins in organic and aqueous/organic microheterogeneous systems
Abstract
Studies with aqueous and organic solvents and with micelles, membranes, and microemulsions showed that the environment had little effect upon the spectroscopic and chemical properties of MnII and MnIII porphyrins. However, for oxidation of a MnIII porphyrin, the environment makes important contributions towards the ease of oxidation and the nature of the oxidation process. In alkaline aqueous solution, oxidation was facile and resulted in formation of MnIV and MnV porphyrins. Identical, but less efficient, oxidation processes were observed in membranes and positively charged micelles but in both negatively charged micelles and microemulsions oxidation was extremely inefficient and the MnV porphyrin was not observed. In CH2Cl2 solution, reaction with phenoxathiinylium hexachloroantimonate gave the MnIII porphyrin π-radical cation whilst reaction with iodosylbenzene resulted in formation of the MnIV porphyrin µ-oxo-dimer.