Cyclooctatetraenes electron affinity

Recently, Cooks and coworkers176 determined the electron affinity (EA) of 1,3,5,7-cyclooctatetraene by using the kinetic method, that is, by performing CID of the cluster anions of the cycloolefin with a number of reference molecules of known EA. The value obtained (EA = 0.58 0.10 eV) was found to be in excellent accordance with that reported previously by Wentworth and Ristau177. 

In the case of the photoelectron spectra of cyclooctatetraene (COT) the ECD and TCT values for the ground-state electron affinity can be used to assign the onset to the formation of a transition state. Thus, the onset occurs at an energy higher than the adiabatic electron affinity. In the case of the photodetachment data for COT the onset occurs between the adiabatic electron affinity and the onset for photoelectron spectroscopy [50]. These will be considered more extensively... 

In the case of tetracyanoquinodimethane, carbon disulfide, nitromethane, and the purines and pyrimidines, two or more negative-ion states have been observed. In some cases the photoelectron spectrum can be assigned to an excited state and reveal an electron affinity lower than adiabatic electron affinity. In the case of cyclooctatetraene the onset in the PES spectrum is higher than adiabatic electron affinity because of the significant change in the geometry of the anion. 

Determination of the Singlet-Singlet and Singlet-Triplet Electronic Spectra, Lowest Ionization Potentials, and Electron Affinity of Cyclooctatetraene. 

The ring inversion presumably involves a planar Dih transition state having alternate single and double bonds, and the bond shift is believed to proceed via a planar Dsh transition state in which all of the C—C bonds become equal in length. The inversion barrier has been measured in the gas phase for cyclooctatetraene via a measurement of the electron affinity of COT and was found to be 12.7 0.5 kcal/mol. ° The bond shift process has a somewhat higher barrier, 14 kcal/mol. The antiaromatic de-stabilization of the Dsh form is then about 2 kcal/mol Theoretical calculations are in good accord with the experimental results. 

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