Solvated Electron Pairing with Earth Alkaline Metals in THF 2Reactivity of the (MgII, es-) Pair with Aromatic and Halogenated Hydrocarbon Compounds

Renou, F.; Pernot, Pascal; Bonin, Julien; Lampre, Isabelle; Mostafavi, Mehran

doi:10.1021/jp034290s

Cited by 17 publications

(29 citation statements)

References 19 publications

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“…The solvated electron constitutes an intriguing phenomenon that has continued to draw attention since its discovery. − Understanding the trends and peculiarities of electron solvation in different solvents is helpful to a variety of fields, including radiation chemistry, energy storage, and organic synthesis. Solvated electrons are particularly interesting in the context of electron-transfer phenomena.…”

Section: Introductionmentioning

confidence: 99%

Electron Solvation in Liquid Ammonia: Lithium, Sodium, Magnesium, and Calcium as Electron Sources

Chaban

Prezhdo

2016

J. Phys. Chem. B

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A free electron in solution, known as a solvated electron, is the smallest possible anion. Alkali and alkaline earth atoms serve as electron donors in solvents that mediate outer-sphere electron transfer. We report herein ab initio molecular dynamics simulations of lithium, sodium, magnesium, and calcium in liquid ammonia at 250 K. By analyzing the electronic properties and the ionic and solvation structures and dynamics, we systematically characterize these metals as electron donors and ammonia molecules as electron acceptors. We show that the solvated metal strongly modifies the properties of its solvation shells and that the observed effect is metal-specific. Specifically, the radius and charge exhibit major impacts. The single solvated electron present in the alkali metal systems is distributed more uniformly among the solvent molecules of each metal's two solvation shells. In contrast, alkaline earth metals favor a less uniform distribution of the electron density. Alkali and alkaline earth atoms are coordinated by four and six NH3 molecules, respectively. The smaller atoms, Li and Mg, are stronger electron donors than Na and Ca. This result is surprising, as smaller atoms in a column of the periodic table have higher ionization potentials. However, it can be explained by stronger electron donor-acceptor interactions between the smaller atoms and the solvent molecules. The structure of the first solvation shell is sharpest for Mg, which has a large charge and a small radius. Solvation is weakest for Na, which has a small charge and a large radius. Weak solvation leads to rapid dynamics, as reflected in the diffusion coefficients of NH3 molecules of the first two solvation shells and the Na atom. The properties of the solvated electrons established in the present study are important for radiation chemistry, synthetic chemistry, condensed-matter charge transfer, and energy sources.

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Section: Introductionmentioning

confidence: 99%

Electron Solvation in Liquid Ammonia: Lithium, Sodium, Magnesium, and Calcium as Electron Sources

Chaban

Prezhdo

2016

J. Phys. Chem. B

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“…Thanks to a new detection setup based on a CCD camera with a high resolution and a global Bayesian data analysis, we were able to distinguish between BrOH •– and Br 2 •– and determine the optical spectrum of the intermediate BrOH •– . Indeed, Bayesian data analysis has been used with success in the past years for the analysis of spectrokinetic data. − It has proved to be an essential tool to tackle parametric identification problems, which are omnipresent in the kinetic modeling of time-resolved spectra. Quantum calculations have also been performed for both species to provide some insights on the electronic transitions responsible of the absorption.…”

Section: Introductionmentioning

confidence: 99%

Oxidation of Bromide Ions by Hydroxyl Radicals: Spectral Characterization of the Intermediate BrOH^•–

et al. 2013

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The reaction of (•)OH with Br(-) has been reinvestigated by picosecond pulse radiolysis combined with streak camera absorption detection and the obtained spectro-kinetics data have been globally analyzed using Bayesian data analysis. For the first time, the absorption spectrum of the intermediate species BrOH(•-) has been determined. This species absorbs in the same spectral domain as Br(2)(•-): the band maximum is roughly at the same wavelength (λ(max) = 352 nm instead of 354 nm) but the extinction coefficient is smaller (ε(max) = 7800 ± 400 dm(3) mol(-1) cm(-1) compared with 9600 ± 300 dm(3) mol(-1) cm(-1)) and the band is broader (88 nm versus 76 nm). Quantum chemical calculations have also been performed and corroborate the experimental results. In contrast to Br(2)(•-), the existence of several water-BrOH(•-) configurations leading to different transition energies may account for the broadening of the absorption spectrum in addition to the higher number of degrees of freedom.

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“…The authors suggested that such species have a reducing power so high that they would be better viewed as Mg 2+ -solvated electron pairs. [126] The polynuclear hydrocarbons that we studied, from tetracene (E ½ = -1.34 V vs. NHE, dioxane/water) to pyrene (E ½ = -1.95 V vs. NHE, MeCN) yielded the corresponding radical-anion intermediates (ESR) and possibly the dianions. [151] The driving force for the dianion formation would be the high binding energy of Mg 2+ with dianions compared with radical anions.…”

Section: Resultsmentioning

confidence: 98%

“…[124,125] Pulse radiolysis studies confirm the very high reducing power of Mg + species; thus, the electron transfer corresponding to the propagation step of the chain in Scheme 1 should be rapid. [126] This addition of radicals to the metal surface is also reminiscent of the early Kharasch and Reinmuth's suggestion: "surface adherent radicals, at least in part" should be involved in the formation of organomagnesium halides. [122] This series of facts, added to the previously discussed analogical features of the S RN 1 and Grignard reagent formation mechanisms, led us to propose an extension of the generalised Scheme 1 to the formation of Grignard reagents.…”

Section: Introductionmentioning

confidence: 93%

About the Inhibition of Grignard Reagent Formation by p‐Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the S_RN1 Mechanism

et al. 2010

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Both SRN1‐type reactions and Grignard reagent formation are inhibited by trace amounts (with respect to the halide) of p‐dinitrobenzene (DNB) and other oxidising agents such as CuCl2 or dioxygen. Both are believed to be triggered by an electron‐transfer step. In this report we examine the patterns of reactivity shared by these two types of reaction. Although the two reactions display an amazing number of similarities, the chain character of the Grignard reaction mechanism has been rejected by major contributors to this field. We have performed new experiments to explore the inhibiting effect associated with the addition of trace amounts of p‐dinitrobenzene during Grignard reagent formation. This inhibition involves very reactive nanoparticles of magnesium prepared by metal vapour synthesis. The magnesium slurries studied, in the absence of p‐dinitrobenzene, display no induction period at all. If the p‐dinitrobenzene is added to the solution containing magnesium slurries 25 min before adding the organic halide (here bromobenzene), the reaction is neatly inhibited but, if one waits long enough, the Grignard reagent is nevertheless formed. If, however, the same trace amounts of p‐dinitrobenzene are diluted in the organic halide and this mixture is added to the magnesium slurries, the inhibiting effect is far less pronounced. The addition of the nBu4NBr salt drastically diminishes the inhibiting power of DNB. These observations, in addition to the ESR study of radical anions formed in THF by the reaction of magnesium nanoparticles and DNB with various polyaromatics, suggest a mechanism for the observed inhibitions that involves a series of reversible adsorptions of the present species. This adsorption would depend on both thermodynamic and kinetic factors. Thermodynamics would favour the adsorption of DNB radical anions but C–X bond cleavage of the less strongly adsorbed aromatic radical anions would provide a kinetic driving force for displacing the equilibria in the direction of Grignard reagent formation. Salt effects could operate by displacing the equilibrium – adsorbed DNB radical anion or dianion versus solvated radical anion (with the counterion nBu4N+) – to the right, accelerating therefore the liberation of active sites on the magnesium surface. It appears that the inhibiting effect of the same compound finds its origin in two different molecular series of events in SRN1 and in Grignard reagent formation. The heterogeneous character of the Grignard reagent makes it possible to envision the possibility of active sites even on nanoparticles, whereas the inhibition of the SRN1 mechanism by DNB occurs in homogeneous solution.

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Solvated Electron Pairing with Earth Alkaline Metals in THF 2Reactivity of the (Mg^II, e_s^-) Pair with Aromatic and Halogenated Hydrocarbon Compounds

Cited by 17 publications

References 19 publications

Electron Solvation in Liquid Ammonia: Lithium, Sodium, Magnesium, and Calcium as Electron Sources

Electron Solvation in Liquid Ammonia: Lithium, Sodium, Magnesium, and Calcium as Electron Sources

Oxidation of Bromide Ions by Hydroxyl Radicals: Spectral Characterization of the Intermediate BrOH^•–

About the Inhibition of Grignard Reagent Formation by p‐Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the S_RN1 Mechanism

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Solvated Electron Pairing with Earth Alkaline Metals in THF 2Reactivity of the (MgII, es-) Pair with Aromatic and Halogenated Hydrocarbon Compounds

Cited by 17 publications

References 19 publications

Electron Solvation in Liquid Ammonia: Lithium, Sodium, Magnesium, and Calcium as Electron Sources

Electron Solvation in Liquid Ammonia: Lithium, Sodium, Magnesium, and Calcium as Electron Sources

Oxidation of Bromide Ions by Hydroxyl Radicals: Spectral Characterization of the Intermediate BrOH•–

About the Inhibition of Grignard Reagent Formation by p‐Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the SRN1 Mechanism

Contact Info

Product

Resources

About

Solvated Electron Pairing with Earth Alkaline Metals in THF 2Reactivity of the (Mg^II, e_s^-) Pair with Aromatic and Halogenated Hydrocarbon Compounds

Oxidation of Bromide Ions by Hydroxyl Radicals: Spectral Characterization of the Intermediate BrOH^•–

About the Inhibition of Grignard Reagent Formation by p‐Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the S_RN1 Mechanism