Reaction of nitrogen dioxide with iron tetraphenylporphyrinate nitro complex containing the trans-1-methylimidazole ligand

Electron and IR spectroscopy, as well as the data on the isotopic analog ¹⁵NO₂, were used for the studies of the reaction of nitrogen dioxide (NO₂) with thin layers of the six-coordinated Fe^III-porphyrin nitro complex with trans-1-methylimidazole ligand Fe(TPP)(1-MeIm)(NO₂) (TPP is the meso-tetraphenylporphyrinate dianion), which is a heme-modelling system. It was shown that, like in the case of the five-coordinated nitrite complex, additional portions of NO₂ promote the nitrite-to-nitrate transformation, accompanied by the evolution of NO. The reaction leads to the formation in the layer of five- and six-coordinated Fe-porphyrin nitrate complexes and a small amount of imidazole complexes Fe^III(TPP)(1-MeIm)₂ with the outersphere nitrate anion. The latter complex became predominate after treatment of this layer with additional portion of 1-methylimidazole.