Bis(1-methylimidazole)iron(II) Complexes of Porphyrins Substituted with Highly Electron-Withdrawing CF3 Groups: Electronic Spectra with Split Q-Bands and MCD Spectra with Unusual Features

The bis(1-methylimidazole)iron(II) complexes of porphyrins substituted with one, two, or four CF3 groups at pyrrole β-positions of a porphyrin have been studied by electronic absorption and magnetic circular dichroism (MCD) spectroscopies. The splittings of Q-bands observed in the electronic spectra of the complexes may arise from asymmetrical electronic effects of the highly electron-withdrawing CF3 group on the porphyrin periphery. The ratio of absorption intensity (ε(α)/(ε(β)) decreased with an increase of the number of CF3 group, suggesting the decrease of a splitting in HOMOs. The MCD spectra of the bis(1-methylimidazole)iron(II) porphyrin complexes were markedly sensitive to the porphyrin peripheral substituents. The MCD spectra in Soret region successively changed in shape with the number of CF3 group on porphyrin periphery and consequently were apparently inverted in sign, which can be explained by the shift of maximal wavelength accompanied by a change in intensity.