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

Journal Article · Thu Nov 14 04:00:00 EST 1991 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100176a082· OSTI ID:7017116

Matsuura, Kaoru; Muto, Hachizo; Nunome, Keichi ^[1]

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1. Government Industrial Research Inst., Nagoya (Japan)

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.

• OSTI ID: 7017116
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 95:23; ISSN 0022-3654; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400600* -- Radiation Chemistry
ALKENES
ANIONS
CATIONS
CHARGED PARTICLES
CRYSTALS
DATA
DEFECTS
ELECTROMAGNETIC RADIATION
ELECTRON SPIN RESONANCE
ELECTRONIC STRUCTURE
EXPERIMENTAL DATA
HYDROCARBONS
HYPERFINE STRUCTURE
INFORMATION
IONIZING RADIATIONS
IONS
MAGNETIC RESONANCE
MOLECULAR ORBITAL METHOD
MOLECULAR STRUCTURE
NUMERICAL DATA
ORGANIC COMPOUNDS
RADIATIONS
RADICALS
RESONANCE
X RADIATION