Spectroscopic Study of the Dimerization Process οf Iron Protoporphyrin IX

K. Dziedzic-Kocurek a, H.J. Byrne b, A. Świderski c and J. Stanek a a Marian Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Kraków, Poland, b Focas Institute, Dublin Institute of Technology, Kevin Street, Dublin 8, Ireland c Department of Biochemistry, Faculty of Horticulture, University of Agriculture in Kraków, al. 29 Listopada 54, 31-425 Kraków, Poland

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The commercial protoporphyrin IX, iron-ferriprotoporphyrin IX-chloride and synthesized iron porphyrin μ-oxo-dimers were examined by UV/vis absorption and fluorescence, Fourier transformed infrared spectroscopy, resonance Raman, X-ray absorption, Mössbauer spectroscopy and SQUID. The evidence of Fe-O-Fe antiferromagnetic coupling concluded from SQUID and Mössbauer in the case of samples containing dimerized forms confirmed the presence of the oxo-bridges. In this paper the results of UV/vis, fluorescence, Fourier transform infrared FTIR and Raman spectroscopies are reported and discussed. The study is based on the comparison of the free-base protoporphyrin IX, Fe-PPIX-Cl and the synthesized dimerized specimen. The vibrational modes in two energy regions i.e. 330-650 cm-1 and 750-900 cm-1, reportedly characteristic of the existence of Fe-O-Fe bridges, are discussed. A significant photoluminescence emission, strongly Stokes shifted from the Soret band, absent in the protoporphyrin IX and the iron-ferriprotoporphyrin IX-chloride, is observed. The strong Stokes shift and the mismatch of the excitation spectrum to the Soret band suggest that is does not have origin in the de-excitation of the porphyrin moiety and that it could have origin in an Fe-O-Fe charge transfer state.

DOI: 10.12693/APhysPolA.115.552 PACS numbers: 36.20.-r, 36.20.Kd, 36.20.Ng