A Carboxylate-Bridged Non-Heme Diiron Dinitrosyl Complex

Feig, Andrew L.; Bautista, Maria T.; Lippard, Stephen J.

doi:10.1021/ic960552b

Cited by 139 publications

(205 citation statements)

References 38 publications

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“…These ν(NO) values are consistent with earlier reports 11,12 and with the S = 3/2 {FeNO} 7 description of non-heme [FeNO] units. 14 As reported previously, 1a is composed of two {FeNO} 7 units, which have identical coordination environments and exhibit the same set of vibrational frequencies.…”

supporting

confidence: 92%

“…Nearly identical ν(FeNO) frequencies are observed in the RR spectrum of 2a , which is consistent with the structural similarity of these [FeNO] units observed by crystallography. 11,12 Additional vibrations in the low-frequency region of the RR spectrum of 2a cannot be assigned with certainty at this time, but these modes do not shift with NO labeling or with the addition of 20% D 2 O to the acetonitrile solutions and are therefore unrelated to the nitrosyl or hydroxy ligands.…”

mentioning

confidence: 83%

“…It also revealed 1a to be stable in an acetonitrile solution for over a day at room temperature. 11 A mixed-valent diiron–mononitrosyl complex, [Fe 2 ( N -Et-HPTB)(OH)(NO)(DMF) 2 ](BF 4 ) 3 ( 2a ), with the N -Et-HPTB ligand was also isolated. 12 Recently, an iron–nitrosyl dimer, [Fe 2 (BPMP)(OPr)(NO) 2 ](BPh 4 ) 2 ( 3a , BPMP = 2,6-bis[(bis(2-pyridylmethyl)amino)methyl]-4-methylphenolate), was structurally characterized and shown to produce N 2 O upon either chemical or electrochemical reduction.…”

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confidence: 99%

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Light-Induced N₂O Production from a Non-heme Iron–Nitrosyl Dimer

et al. 2014

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Two non-heme iron–nitrosyl species, [Fe2(N-Et-HPTB)(O2CPh)(NO)2](BF4)2 (1a) and [Fe2(N-Et-HPTB)(DMF)2(NO)(OH)](BF4)3 (2a), are characterized by FTIR and resonance Raman spectroscopy. Binding of NO is reversible in both complexes, which are prone to NO photolysis under visible light illumination. Photoproduction of N2O occurs in high yield for 1a but not 2a. Low-temperature FTIR photolysis experiments with 1a in acetonitrile do not reveal any intermediate species, but in THF at room temperature, a new {FeNO}7 species quickly forms under illumination and exhibits a ν(NO) vibration indicative of nitroxyl-like character. This metastable species reacts further under illumination to produce N2O. A reaction mechanism is proposed, and implications for NO reduction in flavodiiron proteins are discussed.

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confidence: 92%

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confidence: 83%

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confidence: 99%

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Light-Induced N₂O Production from a Non-heme Iron–Nitrosyl Dimer

et al. 2014

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“…The only reasonably close structurally characterized mimic of the diiron-dinitrosyl coordination spheres in deflavo-FDP(NO) 2 is Fe 2 (NO) 2 (Et-HPTB)(O 2 CPh)(BF 4 ) 2 , where two equivalent S = 3/2 {FeNO} 7 centers are in distorted octahedral coordination geometries with three N ligands and two O ligands from bridging μ-alkoxo and μ-carboxylate ligands. The crystalline complex has FeNO angles of 167 ± 1°, and a single ν(NO) band at 1785 cm −1 24 . Both the FeNO angle and NO stretching frequency are at the higher end of the range observed for S = 3/2 {FeNO} 7 units.…”

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confidence: 99%

Vibrational Analysis of Mononitrosyl Complexes in Hemerythrin and Flavodiiron Proteins: Relevance to Detoxifying NO Reductase

et al. 2012

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Flavodiiron proteins (FDPs) play important roles in the microbial nitrosative stress response in low-oxygen environments by reductively scavenging nitric oxide (NO). Recently, we showed that FMN-free diferrous FDP from Thermotoga maritima exposed to 1 equiv NO forms a stable diiron-mononitrosyl complex (deflavo-FDP(NO)) that can react further with NO to form N2O [Hayashi, T.; Caranto, J. D.; Wampler, D. A.; Kurtz, D. M., Jr.; Moënne-Loccoz, P. Biochemistry 2010, 49, 7040–7049]. Here we report resonance Raman and low-temperature photolysis FTIR data that better define the structure of this diiron-mononitrosyl complex. We first validate this approach using the stable diiron-mononitrosyl complex of hemerythrin, Hr(NO), for which we observe a ν(NO) at 1658 cm−1, the lowest ν(NO) ever reported for a nonheme {FeNO}7 species. Both deflavo-FDP(NO) and the mononitrosyl adduct of the flavinated FPD (FDP(NO)) show ν(NO) at 1681 cm−1, which is also unusually low. These results indicate that, in Hr(NO) and FDP(NO), the coordinated NO is exceptionally electron rich, more closely approaching the Fe(III)(NO−) resonance structure. In the case of Hr(NO), this polarization may be promoted by steric enforcement of an unusually small FeNO angle, while in FDP(NO), the Fe(III)(NO−) structure may be due to a semi-bridging electrostatic interaction with the second Fe(II) ion. In Hr(NO), accessibility and steric constraints prevent further reaction of the diiron-mononitrosyl complex with NO, whereas in FDP(NO) the increased nucleophilicity of the nitrosyl group may promote attack by a second NO to produce N2O. This latter scenario is supported by theoretical modeling [Blomberg, L. M.; Blomberg, M. R.; Siegbahn, P. E. J. Biol. Inorg. Chem. 2007, 12, 79–89]. Published vibrational data on bioengineered models of denitrifying heme-nonheme NO reductases[Hayashi, T.; Miner, K. D.; Yeung, N.; Lin, Y.-W.; Lu, Y.; Moënne-Loccoz, P. Biochemistry 2011, 50, 5939–5947] support a similar mode of activation of a heme {FeNO}7 species by the nearby nonheme Fe(II).

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“…Similar attempts to form an N-N bond between two nitrosyl ligands in a dinuclear iron complex have failed. In this case, warming of the dinitrosyl iron complex led to NO ligand dissociation (Scheme 9) [23].…”

Section: N-n Coupling On Transition Metal Complexes and Elimination Ofmentioning

confidence: 99%