Substituted tren-capped porphyrins: probing the influence of copper in synthetic models of cytochrome c oxidase

Abstract

Tris(2-aminoethylamine) (tren)-capped porphyrins bearing electron donating or withdrawing groups on the amino functions of their tripod have been synthesised and the catalytic activity of each complex was carefully studied both as the iron and the iron-copper complexes: only one of our iron-copper complexes was shown to be active and selective towards the reduction of dioxygen to water.

Cobalt(IV) corroles as catalysts for the electroreduction of O2: Reactions of heterobimetallic dyads containing a face-to-face linked Fe(III) or Mn(III) porphyrin

“…The results of our studies indicate that O 2 is initially reduced by the cobalt(III) corrole unit of the complexes. Although the second metal (Fe or Mn) of the (PCY)MClCoCl systems has some influence on the potential where O 2 is reduced, these systems are no more effective towards O 2 catalysis than the monocobalt derivatives (PCY)H 2 Co, indicating that a bimetallic system is not indispensable for the four-electron reduction of oxygen as previously observed for monomeric iron porphyrins [1,6,9,10,12]. However, the introduction of a second cobalt atom into (PCY)H 2 Co produces Co-Co catalysts with significantly higher selectivities toward the four-electron reduction of O 2 than the (PCY)MClCoCl systems.…”

“…Indeed, in the respiratory chain, cytochrome c oxidase enzymes which consist of a bimetallic complex of heme a and Cu (Fea 3 -Cu B ) catalyze the reduction of dioxygen to water by the soluble electron carrier, cytochrome c [8]. A number of biomimetic synthetic analogs have been prepared and successfully applied to mimic the coordination environment of the Fe/Cu core as well as the catalytic function of the four electron reduction of dioxygen [1,[9][10][11][12][13].…”

The Biologically Relevant Coordination Chemistry of Iron and Nitric Oxide: Electronic Structure and Reactivity

“…Several synthetic model complexes have been developed to mimic the c NOR active site. Some of the first mimics for c NORs were model complexes that were originally designed for heme-copper oxidases, and the Cu was subsequently replaced by a non-heme Fe center. ,,− The first heme/non-heme diiron dinitrosyl complex was synthesized by Karlin and coworkers, using a TPP 2– derivative for the heme, with a covalently-linked TMPA (tris­(methylpyridyl)­amine) ligand to mimic the Fe B site (see Figure , left) . While this complex was able to generate a diferrous dinitrosyl complex, it was not able to catalyze the reduction of NO to N 2 O .…”

Tripodal and/or picket porphyrins to mimic the cytochrome c oxidase activity

“…Along with degradation of the catalytic efficiency, observed by multiple scanning [19], the wave shifts to more negative potentials and the reduction current decreases; this is attributed to a diminution of the surface concentration of the catalyst. The FeCu nitro-derivative complex 17FeCu does not exhibit catalytic activity (Fig.…”

“…In the third series of copper TREN-capped iron porphyrins, the difference between the compounds comes from the formal alkylation of porphyrin 4 (Scheme 1) by different benzyl residues [18,19]. The binding of the Cu(I) center to the oxygen/iron porphyrin complex should be influenced by the coordination sphere of the metal.…”