ABSTRACT
Keywords: porphyrins, complexes, hydrogen peroxide, disproportionation reaction, catalysis, mechanism, catalase models
Studies of chelate complexes of copper as catalysts of the hydrogen peroxide decomposition reaction [1] showed the common factors for individual reaction mechanisms to be
coordination of peroxide particles on the metal atom and availability of two free coordination sites for the catalytic action of copper(II) compound to be realized. Copper(II) porphyrins (CuP), as polychelate macrocyclic complexes, are of interest in both aspects. First, they contain a coordinatively unsaturated copper atom of the 3d9 electron configuration in the environment of the cyclic aromatic ligand; this copper atom forms direct N→Cu dative π-bonds along with coordination σ-interaction. A similar π-interaction is also possible in the case of addition of axial ligands containing unshared electron pairs. Second, CuP satisfy the requirement of the two-side access of reagents to the coordination core. Prospectivity of using metalloporphyrins with a two-charge metal cation (MP) for catalyzing the disproportionation reaction of hydrogen peroxide is evident at present [2, 3]. However, the required coordinative unsaturation of metal in metalloporphyrins is the greater, the higher the formal charge of the metal atom is [4, 5]. For this reason, studies of acidoporphyrin metal complexes of the oxidation degree greater than two (X)n-2MP is also rather promising. A suitable model in the given case are manganese(III) porphyrins. Thus, in [3], monomeric and covalently bound dimeric manganese porphyrinates were found to exhibit a catalase activity in the presence of the basic nitrogen of imidazole under conditions of phase-transfer catalysis.
