57Fe isotope-enriched iron phthalocyanine has been synthesized and studied by the Mössbauer spectroscopic method. The samples were investigated in the temperature range 100–350 K. Some peculiarities in atomic and molecular electronic structure fluctuations were observed. The intermediate Fe oxidation states are observed and it has been found that the rate of charge redistribution is temperature-dependent. The correlation between the temperature behavior of the isomeric shift and quadrupole splitting has been demonstrated. At elevated temperatures above 300 K, the Fe2+ oxidation number is quasistable. The alteration of Fe oxidation number is associated with fluctuations of electron charges, and the electron-accepting and electron-donating properties of surrounding ligands. The energy barriers separating Fe oxidation states have been determined. The possibility of modeling Mössbauer spectra of electron-transfer systems has been shown.
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