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Accueil du site > Production scientifique > IR Signature of NO Binding to a Ferrous Heme Center

IR Signature of NO Binding to a Ferrous Heme Center

Date de publication: 11 juillet 2013

F. Lanucara, D. Scuderi, B. Chiavarino, S. Fornarini, P. Maitre, M. E. Crestoni
J. Phys. Chem. Lett. 4 (15) 2414-2417 (2013). DOI

Travail réalisé sur le site de l’Université Paris Sud.

Abstract

The bare, five-coordinate iron(II) heme nitrosyl complex [Fe(II)hemeH(NO)]+, namely, an iron(II) complex of the dianion of protoporphyrin IX holding a proton on one vinyl group, has been obtained in the gas phase, trapped in the cell of a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer, and assayed by IR multiple photon dissociation (IRMPD) spectroscopy in the 950–1950 cm–1 fingerprint range. The observed ν(NO) signature at 1720 cm–1, displaying sensitivity to NO isotope labeling, is significantly lower than the corresponding vibrational frequencies of ferric heme NO adducts, and suggests high π* electron density at the ferrous nitrosyl group. Quantum chemical calculations, which allow a complete assignment of the vibrational transitions, support a doublet spin electronic configuration, a bent geometry of the Fe–N–O unit, and a cis-conformation of the peripheral propionyl groups for this five-coordinate ferrous heme nitrosyl complex.