Water soluble iron-nitroxyl porphyrin complex: stability studies

AGOSTINA M. MAZZEO; JUAN PELLEGRINO; FABIO DOCTOROVICH

Querétaro

Congreso; 5th Latin American Meeting on Biological Inorganic Chemistry; 2016

HNO and iron-nitroxyl complexes ({FeNO}8) hold remarkable chemical properties and biological relevance.1 It has been considered that the protonated adduct is stabilized by amino acids,2 and bulky substituents.3 The stability reported for [Fe(CN)5(HNO)]3? 4 led us to consider that factors like H-bonds with water, could stabilize the Fe-HNO moiety.The {FeNO}8 adduct of the water-soluble porphyrin TPPS was obtained from FeIIITPPS and characterized by UV-Vis spectroscopy. The product reoxidizes to the {FeNO}7 species within minutes, much slower than in organic media.5 Many hypotheses regarding the nature of this decomposition were considered, including the presence of adventitious oxygen and the identity of the reducing agent and its byproducts. Figure 1. Reoxidation of [FeII(TPPS)HNO]4?.pH, ionic strength and excess dithionite and NO effects were studied in order to determine the cause. Our conclusion is that a bimolecular reaction of [FeII(TPPS)HNO]4? takes place to give [FeII(TPPS)NO]4? and H2. Perspectives include improving our platform and experimental conditions in order to be able to further characterize this elusive species and study its reactions with biological substrates. REFERENCES1.Doctorovich, F. Coord. Chem. Rev. 2011, 255, 2764-2784.2.Lin, R. J. Am. Chem. Soc. 2000, 122, 2393?2394.3.Goodrich, Inorg. Chem 20134.Montenegro, A. Angew. Chemie Int. Ed. 2009, 48. 4213−4216. 5.Pellegrino, J. J. Am. Chem Soc. 2010, 132. 989-995