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 Mn^II and Mn^III porphyrins. However, for oxidation of a Mn^III 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 Mn^IV and Mn^V 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 Mn^V porphyrin was not observed. In CH₂Cl₂ solution, reaction with phenoxathiinylium hexachloroantimonate gave the Mn^III porphyrin π-radical cation whilst reaction with iodosylbenzene resulted in formation of the Mn^IV porphyrin µ-oxo-dimer.