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Title: Role of defects in radiation chemistry of crystalline organic materials. 3. Geometrical and electronic structures of alkene radical anion and cation in alkene/n-alkane mixed crystals as studied by ESR spectroscopy

Abstract

An ESR study has been made in order to elucidate the electronic structures of alkene radical anions and cations, the former radicals being first detected in the hexene/n-hexene mixed crystals irradiated at 4.2 K along with the cation. The present work extended to the hexene and butene isomers has resulted in evidence that both anions with vinylene and vinylidene groups have pyramidal structures with {sigma}-character, which differ from the planar or twisted structures of corresponding cations. The proton hyperfine couplings of their anions were only about one-third as large as those for the cations: {vert bar}A{vert bar}(two {alpha}-H) = {vert bar}0.45, 0.1, {minus}0.25{vert bar} mT; a (two pairs of {beta}-H) = 1.38 and 0.56 mT for the 3-hexene anion, and a(two {alpha}-H) = 1.3 mT and a(two pairs of {beta}-H) = 4.6 and 2.9 mT for the cation. The differences in the geometrical structures and in the sizes of the proton couplings of the anion and cation radicals were discussed on the basis of a simple molecular orbital calculation. It has been found that the anion is stabilized by admixing {vert bar}2s;C> atomic orbitals (AO) with a lower core integral than {vert bar}2p;C> AO to the unpaired electron orbital andmore » that the small {beta}-proton couplings mainly originate from low extent of hyperconjugation due to a wide energy separation of C{double bond}C {pi}-antibonding and C-H pseudo-{pi}-bonding orbitals.« less

Authors:
; ;  [1]
  1. (Government Industrial Research Inst., Nagoya (Japan))
Publication Date:
OSTI Identifier:
7017116
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry; (United States); Journal Volume: 95:23
Country of Publication:
United States
Language:
English
Subject:
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY; ALKENES; ELECTRON SPIN RESONANCE; RADICALS; ELECTRONIC STRUCTURE; MOLECULAR STRUCTURE; ANIONS; CATIONS; CRYSTALS; DEFECTS; EXPERIMENTAL DATA; HYPERFINE STRUCTURE; MOLECULAR ORBITAL METHOD; X RADIATION; CHARGED PARTICLES; DATA; ELECTROMAGNETIC RADIATION; HYDROCARBONS; INFORMATION; IONIZING RADIATIONS; IONS; MAGNETIC RESONANCE; NUMERICAL DATA; ORGANIC COMPOUNDS; RADIATIONS; RESONANCE; 400600* - Radiation Chemistry

Citation Formats

Matsuura, Kaoru, Muto, Hachizo, and Nunome, Keichi. Role of defects in radiation chemistry of crystalline organic materials. 3. Geometrical and electronic structures of alkene radical anion and cation in alkene/n-alkane mixed crystals as studied by ESR spectroscopy. United States: N. p., 1991. Web. doi:10.1021/j100176a082.
Matsuura, Kaoru, Muto, Hachizo, & Nunome, Keichi. Role of defects in radiation chemistry of crystalline organic materials. 3. Geometrical and electronic structures of alkene radical anion and cation in alkene/n-alkane mixed crystals as studied by ESR spectroscopy. United States. doi:10.1021/j100176a082.
Matsuura, Kaoru, Muto, Hachizo, and Nunome, Keichi. Thu . "Role of defects in radiation chemistry of crystalline organic materials. 3. Geometrical and electronic structures of alkene radical anion and cation in alkene/n-alkane mixed crystals as studied by ESR spectroscopy". United States. doi:10.1021/j100176a082.
@article{osti_7017116,
title = {Role of defects in radiation chemistry of crystalline organic materials. 3. Geometrical and electronic structures of alkene radical anion and cation in alkene/n-alkane mixed crystals as studied by ESR spectroscopy},
author = {Matsuura, Kaoru and Muto, Hachizo and Nunome, Keichi},
abstractNote = {An ESR study has been made in order to elucidate the electronic structures of alkene radical anions and cations, the former radicals being first detected in the hexene/n-hexene mixed crystals irradiated at 4.2 K along with the cation. The present work extended to the hexene and butene isomers has resulted in evidence that both anions with vinylene and vinylidene groups have pyramidal structures with {sigma}-character, which differ from the planar or twisted structures of corresponding cations. The proton hyperfine couplings of their anions were only about one-third as large as those for the cations: {vert bar}A{vert bar}(two {alpha}-H) = {vert bar}0.45, 0.1, {minus}0.25{vert bar} mT; a (two pairs of {beta}-H) = 1.38 and 0.56 mT for the 3-hexene anion, and a(two {alpha}-H) = 1.3 mT and a(two pairs of {beta}-H) = 4.6 and 2.9 mT for the cation. The differences in the geometrical structures and in the sizes of the proton couplings of the anion and cation radicals were discussed on the basis of a simple molecular orbital calculation. It has been found that the anion is stabilized by admixing {vert bar}2s;C> atomic orbitals (AO) with a lower core integral than {vert bar}2p;C> AO to the unpaired electron orbital and that the small {beta}-proton couplings mainly originate from low extent of hyperconjugation due to a wide energy separation of C{double bond}C {pi}-antibonding and C-H pseudo-{pi}-bonding orbitals.},
doi = {10.1021/j100176a082},
journal = {Journal of Physical Chemistry; (United States)},
number = ,
volume = 95:23,
place = {United States},
year = {Thu Nov 14 00:00:00 EST 1991},
month = {Thu Nov 14 00:00:00 EST 1991}
}