ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The radical anions of alkynes have been first observed by electron spin resonance spectroscopy following alkene anions previously studied. Hexyne radical anions were formed in 1-, 2-, or 3-hexyne/n–hexane mixed crystals irradiated at 4.2 or 77 K. The characters of the anions were as follows; (a) the α-proton hyperfine coupling is very large (∼4.5 mT for the 1-hexyne anion), (b) the β-proton couplings are very small (∼1.0 mT for C–Hβ proton with the conformational angle of 0°), and (c) the radicals show a negative g shift (2.0014). From these observations, it was found that the anions have a nonlinear(bent) molecule structure in the anticonfiguration (trans C–C≡C–C) with the bend angle ∼60°, and that the unpaired electron orbital is approximately composed of the anticombination of the sp2 hybrid orbitals of the C≡C carbon atoms. A discussion based on complete neglect of differential overlap (CNDO) molecular orbital (MO) calculations was given for the observed negative g shift, which was shown to be characteristic of the alkyne anions which have a high-lying unpaired electron orbital and an antibonding 2p–2p π carbon orbital just above it on the upper energy side.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.460659
