ESR Studies of the Alkali Metal-Acenaphthene Ion Pairs

Abstract

Abstract Ion pairs formed by alkali metals with acenaphthene in ether-type solvents have been investigated by means of electron spin resonance (ESR). The ESR spectra of the ion pairs were found to show phenomena quite analogous to those found by de Boer et al. in the pyracene-alkali ion system; similar two-line-width alternation effects were also observed in the present work. These observations were contrary to the expectations formed by a consideration of the pyracenealkali metal ion pair, where the phenomena have been explained on the basis of the assumption that a potential well exists near the two ethylene bridges. This paper shows that, in the acenaphthene-alkali metal ion pairs, the alkali ion may be situated above the naphthalene skeleton rather than near the ethylene bridge. One of the line-width alternation effects is explained in terms of the exchange reaction between two ion-pair conformations in which the alkali ion is situated above and under the molecular plane respectively, while the other is ascribed to the oscillation of the cation in the potential well above either side of the molecular plane.