94423-69-5Relevant academic research and scientific papers
Preparation, characterization, and reactions of novel iron(III) porphyrin dication complexes
Tsurumaki, Hiroshi,Watanabe, Yoshihito,Morishima, Isao
, p. 11784 - 11788 (1993)
A dication complex of (meso-tetramesitylporphynato)iron(III) (FeIIITMP) has been prepared by the reaction of FeIIITMP N-oxide with trifluoroacetic acid in toluene at low temperature. The electronic structure of the complex is characterized to be ferric high spin with rhombic symmetry on the basis of iodometric titration and UV-vis, 2H NMR, and EPR spcctroscopies. A value of E/D, which shows rhombicity of the heme environment, was estimated to be 0.29 by EPR measurement. An unusually high E/D value indicates that the symmetry of the ligand field around the iron is rather similar to those of nonheme ferric complexes, and the porphyrin ring could exhibit large nonplanarity. While tetraphenylporphyrin dication complexes of Zn, Mg, and Ni are known to react with methanol to afford the corresponding isoporphyrins, the dication complex of FeIIITMP was found to react with methanol to yield FeIIITMP N-methoxide, possibly due to the sterric barrier of the o-methyl groups of mesitylene. The FeIIITMP dication is not thermally stable and is readily reduced to the FeIIITMP π-cation radical even at -25 °C in toluene. The dication complex of (meso-tetrakis(2,6-dichlorophenyl)porphynato)iron(III) (FeIIITDCPP) was also prepared by the same reaction. The preparation of the dication complex of Fe(III) porphyrin demonstrates possible manipulation of the two-electron-oxidized equivalent in various forms by Fe porphyrin, i.e., the O=Fe(IV) porphyrin π-cation radical, O=Fe(V) porphyrin, Fe(III) porphyrin N-oxide, and the Fe(III) porphyrin dication.
