Magnetic circular dichroism of iron porphyrin

Magnetic circular dichroism of iron porphyrin aqueous solutions was studied using a photometric ellipsometer with photoelastic modulator of light polarization in the spectral range 350-750 nm in magnetic fields up to 350 mT. Buffered aqueous solutions of iron porphyrin with pH-values equal to 1.7, 3.6 and 6.8 and concentration 0.1-1.0 mM were prepared by dissolving Fe(III) meso-tetra(4- sulfonatophenyl)porphine chloride. The spectra of magnetic circular dichroism were observed in the region of Soret band (390-420 nm) and Q-bands (500-700 nm). The lineshape analysis of magnetic circular dichroism spectra has shown that A-terms were dominant though a significant overlap masked the fine structure of the Q-bands. The magnetic circular dichroism signal was of order 1x10-2 cm-1/T in a linear approximation with respect to magnetic field. The data indicated that complete lifting of the degeneracy of the states involved in the corresponding optical transitions did not occurred in magnetic fields used. The model of the ground and excited states in iron porphyrin was discussed.