Transient [8]Annulenyl Carbanion from the Anion Radical of Bromo-[8]annulene

Stevenson, Cheryl D.; Kiesewetter, and Matthew K.; Peters, Steven J.

doi:10.1021/jp036801g

Cited by 5 publications

(8 citation statements)

References 29 publications

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“…The magnetic moments for A and B are directly proportional to their respective g -tensor, which varies with the degree of conjugation, which is coupled to SOC. , Conjugation allows the odd electron to delocalize into the p z orbital of the oxygen atom in B. The effective SOC constants for C and O are 28 and 151 cm –1 , respectively, meaning that μ B > μ A .…”

Section: Resultsmentioning

confidence: 99%

“…Isomer A will escape the magnetar faster (see Figure ) than isomer B because of the more dispersed spin densities on B. The actual spin densities were obtained from B3LYP-6-31G* calculations (see Figure ), which have been found to give accurate spin densities on analogous systems. ,, …”

Section: Resultsmentioning

confidence: 99%

“…The actual spin densities were obtained from B3LYP-6-31G* calculations (see Figure 6), which have been found to give accurate spin densities on analogous systems. 9,19,20 The result is different escape velocities and a spatial separation due to different g-tensors. There exist a multitude of studies of g xx , g yy , and g zz of radical systems involving oxygen atoms, dating back to the 60s to the present, where the rotation of the radicals is analogously restricted.…”

Section: Figure 2 (Left)mentioning

confidence: 99%

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Stern–Gerlach-Type Separations of Structural and Chiral Isomers by Interstellar Magnets

Stevenson

Davis²

2020

ACS Earth Space Chem.

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White dwarfs, with masses just above the Chandrasekhar limit (1.4 solar masses), can violently collapse into small (104 km radius) and very dense (ρ = 1017 kg/m3) magnetars that can produce B-fields up to 1012 Tesla (T) with gradients potentially exceeding one-thousandth of the total field. Such strong gradiated fields pull on paramagnetic molecules with a force proportional to the magnetic moment of the radical (μr) dotted into (dB/dz)ẑ, which falls off by the distance cubed. The magnetic force is sufficiently strong to accelerate radicals to velocities of many thousands of meters per second. Radical magnetic moments are strongly dependent on conjugation (dispersion of spin density). As a result, radical isomers, with different μr values, are separated when in the vicinity of a magnetar. The effect is fundamentally due to the radical’s g-value, which, in turn, is embedded in its magnetic moment. Fundamental mathematical protocols were developed to quantify the degrees of large-B-field-enforced isomeric (including chiral isomers) separations. d and l enantiomers have different g-values because of spin orbit coupling effects mediated by the weak force. The alanine enantiomeric radicals falling into or escaping from a nearby magnetar become physically separated in space by many kilometers and may end up in spatially separated molecular clouds. The chiral excess in the Murchison meteorite, and perhaps on Earth, might be a result of this scenario.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Figure 2 (Left)mentioning

confidence: 99%

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Stern–Gerlach-Type Separations of Structural and Chiral Isomers by Interstellar Magnets

Stevenson

Davis²

2020

ACS Earth Space Chem.

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“…This in turn splits the degeneracy of the two spin states, , by energy of Δ E . In solution or gas phase, where there is rapid molecular rotation, the g -tensor (shown in eq ) collapses to a single value, which is very close to that for a free electron ( g e = 2.0023). However, its exact value is perturbed by the molecular structure , but not by isotopic substitution . Consequently, g is often expressed as g = g e + Δ g .…”

Section: Resultsmentioning

confidence: 99%

“…In solution, radical anion bromide release, analogous to that shown in Figure , and other anion radical breakup reactions are common and can be conveniently studied with EPR spectroscopy . In these cases, an electron is usually transferred from an alkali metal or an electrochemical anode to form the corresponding anion radical (R-Br + K → K + + Br-R · – ).…”

Section: Resultsmentioning

confidence: 99%

Magnetars and Magnetic Separation of Chiral Radicals in Interstellar Space: Homochirality

Stevenson

Davis²

2019

J. Phys. Chem. A

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Pasteur was the first to realize Earth’s homochirality. Consequently, he attempted to design experiments revealing a mechanism that would expose life’s chiral preference. Some of these experiments involved the application of magnetic fields to chemical reactions. His experiments failed, in part, because B-fields are pseudo-vectors and cannot couple preferentially to one handedness. However, extremely large magnetic fields cause the Maxwell equations to break down. This allows the motions of spin and charge densities in paramagnetic anion radicals to produce polarized axial B-fields that can undergo preferential coupling to one handedness. Hence, when a racemic mixture of paramagnetic organic molecules passes by an extremely large external gradated magnetic field, the enantiomers experience different torque forces and acquire different translational directions. B-fields of the required magnitude are unknown on this planet. In fact, they would be lethal, thereby eliminating any chance of Pasteur’s success. On the other hand, Duncan and co-workers have recently discovered and garnered physical understanding of magnetars in interstellar space. Some of these neutron star systems produce B-fields greater than the quantum electrodynamic field strength, which is more than enough to generate the required torque for the interstellar enantiomeric separation. In space, chiralitically enriched materials can be deposited on planetesimals and result in homochiral “islands” on the planets. The formation of magnetars is a consequence of weak force events. We assert that, in interstellar space, a plethora of enantiomerically enriched dust clouds resulted from inter-magnetar-paramagnetic molecule force fields.

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Tris-[8]annulenyl Isocyanurate Trianion Triradical and Hexa-anion from the Alkali Metal Reduction of [8]Annulenyl Isocyanate

Peters

Klen

2015

J. Org. Chem.

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The solution phase alkali metal reduction of [8]annulenyl isocyanate (C8H7NCO) yields an EPR spectrum, which reveals electron couplings to seven protons and only one nitrogen. Although this strongly suggested that the C8H7NCO anion radical was generated, experiments on the oxidized product reveal the actual reduced species to be tris-[8]annulenyl isocyanurate. Unlike the previously studied phenyl isocyanurate anion radical, the unpaired electron(s) is now localized within an [8]annulenyl moiety. Further exposure to metal results in the formation of an equilibrium mixture of trianion triradical and trianion radical species. The cyclotrimerization to form the isocyanurate is proposed to be driven by a reactive C8H7NCO dianion, which is produced from the large equilibrium disproportionation of the anion radical. Exhaustive reduction of the tris-[8]annulenyl isocyanurate with potassium in THF generates the first-ever observed hexa-anion of an isocyanurate. NMR analysis reveals that the polarity of the carbonyl bonds within this hexa-anion is augmented and is caused by the close proximity of K(+) ions, which are tightly ion paired to the three [8]annulenyl dianion rings. These preliminary studies on the reduction of C8H7NCO suggest that polymeric materials (e.g., polyisocyanates) made from this isocyanate might exhibit unique properties.

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Transient [8]Annulenyl Carbanion from the Anion Radical of Bromo-[8]annulene

Cited by 5 publications

References 29 publications

Stern–Gerlach-Type Separations of Structural and Chiral Isomers by Interstellar Magnets

Stern–Gerlach-Type Separations of Structural and Chiral Isomers by Interstellar Magnets

Magnetars and Magnetic Separation of Chiral Radicals in Interstellar Space: Homochirality

Tris-[8]annulenyl Isocyanurate Trianion Triradical and Hexa-anion from the Alkali Metal Reduction of [8]Annulenyl Isocyanate

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