Intermediate species generated from halogenated manganese porphyrins electrochemically and in homogeneous catalysis of alkane oxidation

This paper reports the intermediate species of six different manganese porphyrins of first, second and third generation obtained by electrolysis and homogeneous chemical oxidation catalysis of cyclohexane. In order to understand some of the electrochemical processes and transitions involved, studies focused on coupling techniques involving electro-generated species and UV–vis and EPR spectroscopy methods applied to characterize the species formed in situ. Homogenous catalysis for cyclohexane oxidation showed that Mn-second-generation porphyrins are better catalysts than the other classes, and also have the most catalyst recovery, with lower destruction of the catalyst during the run. For all porphyrins, it was possible to observe various intermediate species such as Mn(II), Mn(IV) and radicals. Only for the third-generation porphyrin was it possible to observe a radical species during electro-reductive procedures with SEC–EPR spectroscopy.