Ueber die Ferroverbindungen des Stickoxydes

Manchot, W.; Zechentmayer, K.

doi:10.1002/jlac.19063500307

Cited by 31 publications

(12 citation statements)

References 2 publications

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“…Absorption of nitric oxide by ferrous salt solutions up to a limiting ratio of 1NO: lFe++ is well known (30,31,35,53) and is the basis for the familiar brown-ring test for nitrites and nitrates. The reaction is readily reversed (31, 44), especially by increased temperature, and loss of nitric oxide regenerates ferrous salts unchanged.…”

Section: Compounds Containing Coordinated Nitrosyl Groupsmentioning

confidence: 99%

Inorganic nitrosyl compounds. II. Coordination compounds.

Moeller¹

1946

J. Chem. Educ.

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Section: Compounds Containing Coordinated Nitrosyl Groupsmentioning

confidence: 99%

Inorganic nitrosyl compounds. II. Coordination compounds.

Moeller¹

1946

J. Chem. Educ.

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“…In the absence of L, the reaction product is [Fe II (H 2 O) 5 NO] 2+ , i.e., {Fe−NO}, which can formally be stabilized as either [Fe I (H 2 O) 5 (NO + )] 2+ or [Fe III (H 2 O) 5 (NO - )] 2+ . The reversible reaction of aquated Fe II salts with NO has been the topic of numerous investigations dating back as far as the late 19th century.…”

Section: Introductionmentioning

confidence: 99%

“…The reversible reaction of aquated Fe II salts with NO has been the topic of numerous investigations dating back as far as the late 19th century. Since 1906, the first quantitative investigations dealing with the binding of NO to ferrous complexes, especially from the work by Manchot et al and others, were published . Much work has also been done on the decomposition products of the brown-ring compounds in acidic, neutral, and alkaline solutions, which was reviewed by Tarte .…”

Section: Introductionmentioning

confidence: 99%

Kinetics, Mechanism, and Spectroscopy of the Reversible Binding of Nitric Oxide to Aquated Iron(II). An Undergraduate Text Book Reaction Revisited

et al. 2001

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A detailed kinetic and mechanistic analysis of the classical "brown-ring" reaction of [Fe(H(2)O)(6)](2+) with NO was performed using stopped-flow and laser flash photolysis techniques at ambient and high pressure. The kinetic parameters for the "on" and "off" reactions at 25 degrees C were found to be k(on) = 1.42 x 10(6) M(-1) s(-1), DeltaH(++)(on) = 37.1 +/- 0.5 kJ mol(-1), DeltaS(++)(on) = -3 +/- 2 J K(-1) mol(-1), DeltaV(++)(on) = +6.1 +/- 0.4 cm(3) mol(-1), and k(off) = 3240 +/- 750 s(-1), DeltaH(++)(off) = 48.4 +/- 1.4 kJ mol(-1), DeltaS(++)(off) = -15 +/- 5 J K(-1) mol(-1), DeltaV(++)(off) = +1.3 +/- 0.2 cm(3) mol(-1). These parameters suggest that both reactions follow an interchange dissociative (I(d)) ligand substitution mechanism, which correlates well with the suggested mechanism for the water exchange reaction on [Fe(H(2)O)(6)](2+). In addition, Mössbauer spectroscopy and EPR measurements were performed on the reaction product [Fe(H(2)O)(5)(NO)](2+). The Mössbauer and EPR parameters closely resemble those of the [FeNO](7) units in any of the other well-characterized nitrosyl complexes. It is concluded that its electronic structure is best described by the presence of high-spin Fe(III) antiferromagnetically coupled to NO(-) (S = 1) yielding the observed spin quartet ground state (S = (3)/(2)), i.e., [Fe(III)(H(2)O)(5)(NO(-))](2+), and not [Fe(I)(H(2)O)(5)(NO(+))](2+) as usually quoted in undergraduate text books.

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“…The addition of H 2 SO 4 to a solution containing nitrate ions, in presence of Fe 2+ ions, produces a distinct brown ring at the interface of the two aqueous solutions. The green-brown color of the brown ring is traditionally attributed to the formation of the [Fe(H 2 O) 5 (NO)] 2+ complex [1][2][3], which has a quartet (S=3/2) ground state. This is considered to be a very unstable complex, degraded by light and heat, and also the presence of sulfate ions.…”

Section: Introductionmentioning

confidence: 99%

Hydration dynamics gives the distinctive brown color in the "brown ring" nitrate test

Banerjee

Coates

Odelius

2021

Preprint

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The brown ring test is one of the most popular and visually appealing reagent tests, commonly known to chemistry undergrads and familiar even to school students. The exact composition, mechanism and structure of the complex has been investigated for nearly a century. Recent studies have elucidated its UV-vis, EPR and Mossbauer spectra, mechanistic details and kinetics, followed by crystallization and structure determination in solid state. Nonetheless these studies were unable to address the aspects of solution structure and dynamics of the brown ring complex. We have conducted ab initio molecular dynamics simulations of the classic brown ring complex in aqueous solution. In the process from the simulation trajectory, we have identified that the classically established pseudo-octahedral [Fe(H2O)5(NO)]2+ complex is in chemical equilibrium with the square-pyramidal [Fe(H2O)4(NO)]2+ complex through the exchange of one of the coordinated H2O molecules. The dynamics in aqueous solution between the penta-aqua and tetra-aqua complexes in the brown ring system has to our knowledge never been suggested earlier. Interestingly we find, using ab initio multi-reference quantum chemical methods i.e. CASSCF/NEVPT2 and CASPT2 calculations, that the mixture of these two complexes is what gives the distinctive brown coloration to the brown ring test. We show that its UV-vis spectrum can be theoretically reproduced only by accounting these two species, and not solely the classically established [Fe(H2O)5(NO)]2+ complex. The energetics of the penta-aqua and tetra-aqua complexes is also investigated at the level of multi-reference quantum chemical methods.

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Ueber die Ferroverbindungen des Stickoxydes

Cited by 31 publications

References 2 publications

Inorganic nitrosyl compounds. II. Coordination compounds.

Inorganic nitrosyl compounds. II. Coordination compounds.

Kinetics, Mechanism, and Spectroscopy of the Reversible Binding of Nitric Oxide to Aquated Iron(II). An Undergraduate Text Book Reaction Revisited

Hydration dynamics gives the distinctive brown color in the "brown ring" nitrate test

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