Spectroscopic Study of the Dimerization Process οf Iron Protoporphyrin IX

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Acta Physica Polonica A, ISSN: 0587-4246, Vol: 115, Issue: 2, Page: 552-555

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Dziedzic-Kocurek, K.; Byrne, Hugh; Swiderski, A.; Stanek, J.
Institute of Physics, Polish Academy of Sciences; Dublin Institute of Technology
Physics and Astronomy; spectroscopy; fourier transformed infrared spectrosopcy; resonance Raman; X-ray absorption.; Biological and Chemical Physics; Physics
article description
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 cmand 750-900 cm, 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.