106 research outputs found
Over or Under: Hydride Attack at the Metal versus the Coordinated Nitrosyl Ligand in Ferric Nitrosyl Porphyrins.
Hydride attack at a ferric hemeâNO to give an FeâHNO intermediate is a key step in the global N--âcycle. We demonstrate differential reactivity when six--â and five--âcoordinate ferric heme--âNO models react with hydride. Although FeâHNO formation is thermodynamically favored from this reaction, FeâH formation is kinetically favored for the 5C case
Electrochemical investigation of the kinetics of chloride substitution upon reduction of [Ru(porphyrin)(NO)Cl] complexes in THF.
The electrochemistry of several ruthenium porphyrin nitrosyl chloride complexes [Ru(por)(NO)Cl] have been examined in tetrahydrofuran. The complexes undergo 1-electron irreversible reductions which result in the diffusion-limited substitutions of the chloride ligands for THF. This chloride metathesis is reversible in the presence of added NBu4Cl, and equilibrium constants and rate constants for chloride loss have been estimated. These parameters correlate with the NO stretching frequencies of the parent complexes, with more electron-donating porphyrin ligands favouring chloride loss from the reduced complexes. The [Ru(por)(NO)(THF)] products of the reductions can be detected by IR, EPR and visible spectroscopies. These species undergo three further reductions, with good reversibility at scan rates \u3e0.40 V s-1. The [Ru(por)(NO)(THF)]+/0 couples have also been determined, and the rate constants and equilibrium constants for recombination with chloride have been estimated. One-electron reductions of the [Ru(por)(NO)Cl] complexes result in ~1018 enhancement of the rates of chloride loss
Mild NâO Bond Cleavage Reactions of a Pyramidalized Nitrosyl Ligand Bridging a Dimolybdenum Center
Endomyocardial Fibrosis: Still a Mystery after 60 Years
The pathologist Jack N. P. Davies identified endomyocardial fibrosis in Uganda in 1947. Since that time, reports of this restrictive cardiomyopathy have come from other parts of tropical Africa, South Asia, and South America. In Kampala, the disease accounts for 20% of heart disease patients referred for echocardiography. We conducted a systematic review of research on the epidemiology and etiology of endomyocardial fibrosis. We relied primarily on articles in the MEDLINE database with either âendomyocardial fibrosisâ or âendomyocardial sclerosisâ in the title. The volume of publications on endomyocardial fibrosis has declined since the 1980s. Despite several hypotheses regarding cause, no account of the etiology of this disease has yet fully explained its unique geographical distribution
Why Is the Oxidation State of Iron Crucial for the Activity of Heme-Dependent Aldoxime Dehydratase? A QM/MM Study
(1-Methyl-1H-imidazole-ÎșN3)(1-methyl-2-nitrosobenzene-ÎșN)(5,10,15,20-tetraphenylporphyrinato-Îș4N)iron(II) dichloromethane monosolvate
The solvated title compound, [Fe(C44H28N4)(C4H6N2)(C7H7NO)]·CH2Cl2, is a porphyrin complex containing an octahedrally coordinated FeII atom with 1-methylimidazole [FeâN = 2.0651â
(17)â
Ă
] and o-nitrosotoluene ligands at the axial positions. The o-nitrosotoluene ligand is N-bound to iron(II) [FeâN = 1.8406â
(18)Ă
and FeâNâO = 122.54â
(14)°]. The axial NâFeâN linkage is almost linear, with a bond angle of 177.15â
(7)°. One phenyl group of the porphyrin ligand is disordered over two orientations in a 0.710â
(3):0.290â
(3) ratio. The dichloromethane solvent molecule was severely disordered and its contribution to the scattering was removed with the SQUEEZE routine [van der Sluis & Spek (1990). Acta Cryst. A46, 194â201]
CarbonâNitrogen and NitrogenâNitrogen Bond Formation from Nucleophilic Attack at Coordinated Nitrosyls in Fe and Ru Heme Models
The
conversion of inorganic NO<i><sub>x</sub></i> species
to organo-N compounds is an important component of the global N-cycle.
Reaction of a C-based nucleophile, namely the phenyl anion, with the
ferric heme nitrosyl [(OEP)ÂFeÂ(NO)Â(5-MeIm)]<sup>+</sup> generates a
mixture of the <i>C</i>-nitroso derivative (OEP)ÂFeÂ(PhNO)Â(5-MeIm)
and (OEP)ÂFeÂ(Ph). The related reaction with [(OEP)ÂRuÂ(NO)Â(5-MeIm)]<sup>+</sup> generates the (OEP)ÂRuÂ(PhNO)Â(5-MeIm) product. Reactions with
the N-based nucleophile diethylamide results in the formation of free
diethylnitrosamine, whereas the reaction with azide results in N<sub>2</sub>O formation; these products derive from attack of the nucleophiles
on the bound NO groups. These results provide the first demonstrations
of CâN and NâN bond formation from attack of C-based
and N-based nucleophiles on synthetic ferric-NO hemes
Hydride Attack on a Coordinated Ferric Nitrosyl: Experimental and DFT Evidence for the Formation of a Heme ModelâHNO Derivative
Synthesis, Characterization, and Solid-State Molecular Structures of Nitrosoarene Complexes of Osmium Porphyrins
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