Iron Nitroxyl porphyrin complexes in aqueous and organic media.

AGOSTINA M. MAZZEO; JUAN PELLEGRINO; CARINA GAVIGLIO; FABIO DOCTOROVICH

(Virtual)

Congreso; 7th Latin American Meeting on Biological Inorganic Chemistry; 2021

Interest in HNO (azanone according to IUPAC; usually nitroxyl) has increased in the last decadedue to its remarkable chemical properties and increasing biological relevance.1 In addition, FeIInitroxyl complexes are important intermediates in NO and nitrite-reducing enzymes in bacteriaand fungi, which catalyze important processes related to the biogeochemical cycle of nitrogen.It has been considered that the protonated adduct is stabilized by amino acids,2 and bulkysubstituents.3 The stability reported for [Fe(CN)5(HNO)]3? 4 led us to consider that factors likeH-bonds with water, could stabilize the Fe-HNO moiety. In this work, the heme water solublenitroxyl complexes [FeII(TPPS)HNO]4? and [FeII(TPPS)NO] 5? were obtained and characterizedby UV-Vis spectroscopy. The pKa was estimated from both spectroscopic and electrochemicalmeasurements. The protonated complex spontaneously reoxidizes to the nitrosyl species withinminutes, much slower than in organic media.5 Kinetic measurements in different conditions,along with other experimental results and DFT calculations support an unimolecularreoxidation mechanism involving an homolytic rupture of the H-NO bond, via a phlorinintermediate also proposed and detected in similar systems. Preliminary results obtained inorganic media with soluble derivatives are also discussed.References:1. Doctorovich, F.; Bikiel, D.; Pellegrino, J.; Suárez, S. A.; Larsen, A.; Marí, M. A. Coord. Chem. Rev.2011, 255, 2764-2784.2. Lin, R.; Farmer, P. J. J. Am. Chem. Soc. 2000, 122, 2393?2394.3. Goodrich, L. E.; Roy, S.; Alp, E. E.; Zhao, J.; Hu, M. Y.; Lehnert, N. Inorg. Chem 20134. Montenegro, A. C.; Amorebieta, V. T.; Slep, L. D.; Martín, D. F.; Roncaroli, F.; Murgida, D. H.; Bari,S. E.; Olabe, J. A. Angew. Chemie Int. Ed. 2009, 48. 4213−4216.5. Pellegrino, J.; Bari, S. E.; Bikiel, D. E.; Doctorovich, F. J. Am. Chem Soc. 2010, 132. 989-9956. Solis, B. H.; Maher, A. G.; Dogutan, D. K.; Nocera, D. G.; Hammes-Schiffer, S. PNAS 2016, 113(3), 485?492