Porphyrin-assisted oxidation

Bedioui, F., P. Moisy, J. Devynck, L. Salmon, and C. Bied-Charreton (1989). Poly(pyrrole manganese porphyrin) film electrode as a catalyst in electro-assisted oxidation reactions using molecular-oxygen. Comparison with described homogeneous systems. J. Mol. Catal. 56(1-3), 267-275. 

The cathode photocurrent is in proportion to the number of TCPP layers at least up to 10 cycles. The efficiency is greatly dependent on the kinds of oxide gel. These experimental observations suggest that electron transfer from the electrode to the porphyrin via the oxide gel layer is an essential mechanism of the photocurrent generation. Oxygen molecules as an electron acceptor readily diffuse in the oxide gel films of about 20 nm thickness. The electron transfer from the electrode to the porphyrin is assisted by satisfactory conductivity of the gel layer. The overall photocurrent value is considerably smaller than the conventional wet solar cell [11]. However, modification of the electrode surface by ultrathin oxide gel films will facilitate the design of novel light harvesting devices. 

The process involves deprotonation of the peroxy reagent and proton transfer to assist loss of a poor LG. Consistent with this heterolytic process, the reactivity of Fe porphyrins is found to be retarded by electron-withdrawing substitution when the oxidant is pentafluoroiodosylbenzene, but is accelerated with hydroperoxides [534]. 

Figure 33. Proposed pathway for proton-assisted metal-oxo formation and substrate oxidation by HPX Hangman porphyrins.

Gonsalves, A.M., R.A.W. Johnstone, M.M. Pereira, J. Shaw, and A.J.F. do N. Sobral (1991). Metal-assisted reactions. Part 22. Synthesis of perhalogenated porphyrins and their use as oxidation catalysts. Tetrahedron Lett. 32, 1355-1358. 

The present report deals with an overview on the very recent metal-assisted redox chemistry of /w o-octaalkylporphyrinogen. This investigation has led to the discovery of oxidized forms of porphyrinogen other than porphyrins, the so-called artificial porphyrins . 

Metal-assisted cycloaddition reactions involving meso-perfluoroalkylated porphyrinic templates define a versatile methodology for the syntheses of both cofacial porphyrin structures and facially-functionalized (porphinato)metal species [62], and corresponding compositions that offer new opportunities for development of small molecule redox catalysts [63, 64]. Scheme 21 shows the versatile metal-mediated [2+2+2] cycloaddition step for the isolation of meso-perfluoroalkyl cofacial porphyrins that results in the purified indane complexes in 10-12 % yields. These cofacial complexes are directly applicable to multi-electron redox reactions such as oxygen or nitrogen reduction and even hydrocarbon oxidation. 

Chen J, Wagner P, Tong L, Wallace GG, Officer DL, Swiegers GF (2012) A porphyrin-doped polymer catalyzes selective, light-assisted water oxidation in seawater. Angew Chem Int Ed 51 1907-1910... 

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