Electron Attachment and Detachment:  Cyclooctatetraene

Abstract

Electron attachment and detachment rate constants were measured for 1,3,5,7-cyclooctatetraene (COT) in a He/Ar buffer gas over the temperature range 295−365 K. A flowing afterglow Langmuir probe apparatus was used for this work. Within experimental uncertainty, the electron attachment rate coefficient is independent of temperature in this range, at a value of 3.5 ± 1.0 ×10-9 cm3 s-1. The electron detachment rate is negligible at room temperature, but climbs to 995 s-1 at 365 K. The attachment/detachment equilibrium constant implies that the electron affinity of COT is 0.57 ± 0.03 eV, in agreement with other studies using different methods. A vertical detachment transition from the planar anion leaves COT in a planar transition state for ring inversion. G2(MP2) and density functional calculations were carried out for COT neutral, anion, dianion, and the ring inversion transition state. The G2(MP2) ring inversion barrier height compares well with the experimental result from NMR studies.