Ion-molecule reactions of primary radical cations in the liquid-phase radiolysis of n-alkanes: An EPR study

Belevskii, V. N.; Belopushkin, S. I.

doi:10.1007/s10733-005-0001-x

Cited by 6 publications

(8 citation statements)

References 25 publications

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“…While it is conceivable that a single C−H cleavage might initiate a branching chain reaction in which one radical leads to formation of multiple radicals, reactions of this type are rare . A previous study of radicals formed by electron impact on n -alkanes concluded that the radicals that were observed were those formed by the initial impact process, with little or no subsequent chemistry. , Alkene (olefin) polymerization reactions are widely known to be simple chain reactions in which the number of radicals is constant, and only one polymer molecule is formed for each initiation event . Thus, this process cannot easily account for the large number of small reaction products detected in solution.…”

Section: Discussionmentioning

confidence: 99%

Photochemical Functionalization of Hydrogen-Terminated Diamond Surfaces: A Structural and Mechanistic Study

et al. 2005

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Hydrogen-terminated diamond surfaces can be covalently modified with molecules bearing a terminal vinyl (C=C) group via a photochemical process using sub-band-gap light at 254 nm. We have investigated the photochemical modification of hydrogen-terminated surfaces of nanocrystalline and single-crystal diamond (111) to help understand the structure of the films and the underlying mechanism of photochemical functionalization. A comparison of the rates of photochemical modification of single-crystal diamond and nanocrystalline diamond films shows no significant difference in reactivity, demonstrating that the modification process is not controlled by grain boundaries or other structures unique to polycrystalline films. We find that both single-crystal and polycrystalline hydrogen-terminated diamond samples exhibit negative electron affinity and are functionalized at comparable rates, while oxidized surfaces with positive electron affinity undergo no detectable reaction. Gas chromatography-mass spectrometry (GC-MS) analysis shows the formation of new chemical products in the liquid phase that are formed only when the alkenes are illuminated in direct contact with H-terminated diamond, while control experiments with other surfaces and in the dark show no reaction. Our results show that the functionalization is a surface-mediated photochemical reaction and suggest that modification is initiated by the photoejection of electrons from the diamond surfaces into the liquid phase.

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Section: Discussionmentioning

confidence: 99%

Photochemical Functionalization of Hydrogen-Terminated Diamond Surfaces: A Structural and Mechanistic Study

et al. 2005

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“…The planar structure, which could result from complete averaging due to rapid inversion between the boat and chair conformations, as suggested by Belevskii et al, 32 was calculated to be unstable and is actually a saddle point. Moreover, hfs splitting constants calculated for the planar structure are too large (4.55 mT).…”

Section: B 14-dioxanementioning

confidence: 90%

“…Symons and Wren 4 have suggested that the 1,4-dioxane radical cation exists in the boat conformation, having an intramolecular s bond between two oxygen atoms, with unpaired electron confined into the s*(O-O) orbital and this concept was adopted also by Bonazzola et al 6 Glidewell 31 has investigated both chair and boat conformations of the 1,4-dioxane radical cation quantum chemically at UHF/MNDO level and did not make any definitive decision regarding both conformers, though the chair structure was found to be slightly more stable. Belevskii et al 32 have suggested that the observed similarity of the coupling of all eight protons can be explained by rapid inversion between the boat and chair conformations, leading to a nearly planar structure.…”

Section: B 14-dioxanementioning

confidence: 99%

Radical cations of tetrahydropyran and 1,4-dioxane revisited: quantum chemical calculations and low-temperature EPR results

Naumov

Janovský

Knolle

et al. 2003

Phys. Chem. Chem. Phys.

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“…It is known that the efficiency of electron capture for the used concentrations of acceptor (10 -4 M) is about 10%. The remaining primary pairs “electron/solvent radical cation” recombine to form electronically excited molecules of cyclohexane that are prone to decay forming neutral alkyl radicals. − An irradiated alkane solution thus always contains a certain stationary concentration of alkyl radicals. It can be thought that our compound in its initial neutral state can trap these radicals to form the observed product, which is thus formed outside the radical pair.…”

Section: Resultsmentioning

confidence: 99%

Difficulties in Building Radiation-Generated Three-Spin Systems Using Spin-Labeled Luminophores

Matveeva¹,

Sviridenko²,

Korolev³

et al. 2007

J. Phys. Chem. A

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Aromatic compounds are well-known acceptors of primary radical ions that are formed under high-energy irradiation of nonpolar systems. Thus formed radical ion pairs recombine and produce magnetosensitive fluorescence, which helps study the short-lived radical ions. It was initially suggested that a simple introduction of a spin label into the original arene would allow an easy transition from two-spin to three-spin systems, retaining the experimental techniques available for radical pairs. However, it turned out that spin-labeled arenes often do not produce magnetosensitive fluorescence in the conditions of a conventional radiochemical experiment. To understand the effect of the introduced spin label, we synthesized a series of compounds with the general structure "stable 3-imidazoline radical-two-carbon bridge-naphthalene" as well as their diamagnetic analogues. By use of this set of acceptors, we determined the processes that ruin the observed signal and established their connection with the chemical structure of the compound. We found that the compounds with flexible (saturated) two-carbon bridges between the luminophore and the stable radical moieties exist in solution in folded conformation, which leads to suppression of luminescence from naphthalene due to efficient through-space exchange quenching of the excited state by the radical. Increasing the rigidity of the bridge by introducing the double bond drastically increases the reactivity of the extended pi-system. In these compounds, the energy released upon recombination is spent in radiationless processes of chemical transformations both at the stage of the radical ion and at the stage of the electronically excited molecule.

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Ion-molecule reactions of primary radical cations in the liquid-phase radiolysis of n-alkanes: An EPR study

Cited by 6 publications

References 25 publications

Photochemical Functionalization of Hydrogen-Terminated Diamond Surfaces: A Structural and Mechanistic Study

Photochemical Functionalization of Hydrogen-Terminated Diamond Surfaces: A Structural and Mechanistic Study

Radical cations of tetrahydropyran and 1,4-dioxane revisited: quantum chemical calculations and low-temperature EPR results

Difficulties in Building Radiation-Generated Three-Spin Systems Using Spin-Labeled Luminophores

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