X-ray Structure and Properties of the Ferrous Octaethylporphyrin Nitroxyl Complex

Abstract

Synopsis:The X-ray crystal structure of [Fe(OEP) (NO)]− is reported, along with infrared and NMR spectra. The Fe−N−O bond angle decreased upon reduction and was consistent with those in other {FeNO} 8 complexes. The 1 H NMR spectrum was reported, which was different from those for other S = 0 metalloporphyrin complexes due to the displacement of the Fe atom from the porphyrin plane. This spectrum was consistent with DFT calculations.NOT THE PUBLISHED VERSION; this is the author's final, peer-reviewed manuscript. The published version may be accessed by following the link in the citation at the bottom of the page.Inorganic Chemistry, Vol 55, No. 5 (2016): pg. 2070-2075. DOI. This article is © American Chemical Society and permission has been granted for this version to appear in e-Publications@Marquette. American Chemical Society does not grant permission for this article to be further copied/distributed or hosted elsewhere without the express permission from American Chemical Society. 2 AbstractThe preparation and characterization of the iron octaethylporphyrin nitroxyl ion, [Fe(OEP), is reported. The complex was synthesized by the oneelectron reduction of Fe(OEP)(NO) using anthracenide as the reducing agent. The compound was isolated as the potassium (2.2.2)cryptand salt. The anion was characterized using X-ray analysis with visible and infrared spectroscopy. The spectral features of the iron nitroxyl complex were consistent with previous literature reports. The important structural changes upon reduction were a significant decrease in the Fe-N-O bond angle from 142° to 127° and an increase in the N-O bond length from that in the starting nitrosyl moiety. The porphyrin ring became significantly less planar upon reduction, but the displacement of the iron atom from the 24-atom plane was essentially unchanged. In spite of the attempt to encapsulate the potassium ion with the (2.2.2)cryptand, significant interaction between K + and the oxygen of the nitroxyl were observed, indicating a contact ion pair in the crystal structure. Comparison between the experimental structure and the DFT-calculated parameters were reported. The results are consistent with the Fe-N-O moiety being the site of the reduction, with little evidence for the reduction of the iron itself or the porphyrin ring. The proton NMR spectrum was also obtained, NOT THE PUBLISHED VERSION; this is the author's final, peer-reviewed manuscript. The published version may be accessed by following the link in the citation at the bottom of the page.Inorganic Chemistry, Vol 55, No. 5 (2016): pg. 2070-2075. DOI. This article is © American Chemical Society and permission has been granted for this version to appear in e-Publications@Marquette. American Chemical Society does not grant permission for this article to be further copied/distributed or hosted elsewhere without the express permission from American Chemical Society.3 and the chemical shifts were significantly different from other S = 0 metalloporphyrin complexes. These shifts, though, were consistent wit...

On the Structure of [K(crypt‐222)]+

“…Moreover, coordination of an extra donor to the metal inside [K(crypt‐222)] + would fold back two ‘arms’ of the cryptand, distorting the N–K–N angle from the ideal value of 180° and ultimately destroying the natural 32 point‐group symmetry of the cation . The N–K–N angle distortion varies in a range of 171 – 177° . In 1 , the symmetry of the [K(crypt‐222)] + is not distorted.…”

Insight into Solvent Coordination of an Iron Porphyrin Hydroxylamine Complex from Spectroscopy and DFT Calculations

“…The reduction of Fe(OEP)(NO) in THF occurs in two one‐electron steps with the formation of Fe(OEP)(NO) – and Fe(OEP)(NO) 2– . The spectroscopic properties of Fe(OEP)(NO) – have been obtained as well as an X‐ray structure , . In the presence of weak acids, such as substituted phenols, Fe(OEP)(NO) – can be protonated to form Fe(OEP)(HNO), and be further reduced to Fe(OEP)(NH 2 OH).…”

Structural and Electronic Responses to the Three Redox Levels of Fe(NO)N2S2‐Fe(NO)2

“…While structural parameters of the DNIU are largely unaffected by redox levels, the MNIU readily responds;t he neutral, S = 1 = 2 ,c omplex, 1 0 ,f inds the extra electron density added into the DNIU affects the adjacent MNIU as seen by the decrease its Fe-N-O angle (from 1718 to 1498). [8][9][10][11] Examples are also knownf or non-heme, cyclam-basedm acrocycles and in at etracarbeneb inding scaffold. These features are addressedb yc omputational studies which indicatet hat the MNIU in 1 À À is at riplet-state {Fe(NO)} 8 with strong spin polarization in the more linear FeNO unit.…”

“…[5,6] Nevertheless, the predominant chemicalr elevance of NO in biology stemsf rom varioush emetype {Fe(NO)} 6/7/8 species of distinctive IR and EPR spectral features and solid state metric parameters. [8][9][10][11] Examples are also knownf or non-heme, cyclam-basedm acrocycles and in at etracarbeneb inding scaffold. [8][9][10][11] Examples are also knownf or non-heme, cyclam-basedm acrocycles and in at etracarbeneb inding scaffold.…”