E.s.r. study of ion pairs involving the pyrene anion

Abstract

An e.s.r. study of the ion pair formation between pyrene and alkali metals in various ether solvents has been carried out. Depending on the nature of the solvent and the alkali metal ion, various types of species are observed. Loose ion pairs or free ions were observed in dimethoxyethane (DME) and tetrahydrofuran (THF) with lithium, sodium and potassium at all temperatures. Thermodynamic data for the dissociation of ion pairs into free ions were obtained for the systems K + MTHF (methyltetrahydrofuran), Cs + THF, and Li + DEE (diethyl ether). Line broadening effects gave additional kinetic data on the interconversion between tight and loose ion pairs in the Li + DEE system. The experimental data taken with considerations of cation spin density proton splittings and solvating power of the solvents have led to a consistent although speculative model of the ion pair structures formed.