A Supramolecular Cytochrome P450 Mimic

Abstract

An amphiphilic rhodium(iii) complex has been incorporated in closed bilayers of surfactants with positive, zwitterionic, or negative charges. In the presence of formate this rhodium complex efficiently catalyzes the reduction of a variety of electron carriers and manganese(iii) porphyrins. The charge of the surfactant head groups determines the acidity of the reduced Rh III hydride complex and the rate of reduction, which increases on going from negatively to positively charged surfactants. A manganese(iii) porphyrin, incorporated in the bilayers together with the Rh complex, can be used as an artificial cytochrome P450-type epoxidation catalyst. The relative concentrations of Mn II and Mn III porphyrin depend on the reduction and reoxidation rates, and an oscillating reaction is observed at a Rh complex/Mn porphyrin ratio of 10. A variety of substrates are epoxidized by reductive activation of O 2 by this model system with turnover numbers of the same order of magnitude as those of the enzyme system. The charge on the surfactant has a dramatic effect on the catalytic epoxidation activity of the model system. Aggregates of positively charged surfactant molecules do not display catalytic activity in this reaction, probably because the protons required for cleavage of the oxygen ± oxygen bond are repelled at the aggregate surface.

Self‐Assembled Nanoreactors

“…This was explained by the fact that the concentration of protons in the DODAC systems was too low to allow the formation of the catalytically active Mn(V) oxo species. 170 Under very specific conditions (temperature, concentration of reagents), the enzyme mimetic system displayed an unprecedented oscillatory behavior. Under the chosen circumstances and at a precise ratio of [Rh]/[Mn] ) 10 after an induction period of 30 min, the Mn(II) species was formed, which was oxidized back to the Mn(III) by the O 2 present in the medium.…”

Platinum(ii) complexes bearing 1,1′-bis(diphenylphosphino)ferrocene as building blocks for functionalized redox active porphyrins

“…2 Porphyrins bearing suitable substituent groups can be embedded in micellar phases or in liposomes 3 achieving stability, orientation and rigidity usually required to exert specific functions. 4, 5 A variety of micelles, 6 fibers 7,8 and vesicles 9,10 has been directly prepared starting from specifically synthesized amphiphilic porphyrins. Recently, mesoscopic structured porphyrin rings have been reported through simple solvent evaporation, as a result of the interplay between wettability of the substrate, evaporation and hydrodynamics of the solution.…”

Bio-inspired electron-delivering system for reductive activation of dioxygen at metal centres towards artificial flavoenzymes

“…Nolte and co-workers have incorporated hydrophobic manganese porphyrins into vesicles in which electrons were provided by the oxidation of either hydrogen with colloidal Platinum 8 or formate at rhodium complexes 9 10 . Other systems also used manganese porphyrins in combination with either nicotinamide and benzoic anhydride 11 , or pyruvate oxidase and flavin cofactors 12 .…”