Experimental and Computational Studies of the Structures and Energetics of Cyclooctatetraene and Its Derivatives

Abstract

Conformational changes in cyclooctatetraene (COT) and its substituted derivatives have been the subject of considerable interest for several decades.1,2 Relatively little is known, however, about the thermochemical properties of COT and, in particular, its radical and anionic derivatives. We have employed the selected-ion flow tube (SIFT) technique, photoelectron spectroscopy (PES), and molecular orbital (MO) calculations for a comprehensive study of the structures and energetics of C8Hn and C8Hn (n) 6-8). We report the electron affinities, gas-phase acidities, and C-H bond dissociation energies for COT and the related radicals. In addition, we have observed unusual properties for the electronic structure and reactivity of the C8H7 anion, which is shown to have a novel π-electron configuration and which exhibits a rare example of collisioninduced isomerization leading to transannular bond formation. Electron affinities (EA) were determined from SIFT and PES measurements. The EA of COT was obtained from the forward and reverse reaction rate constants for the electron-transfer equilibrium (eq 1). The rate constants were measured separately