Linewidth alternation in the electron spin resonance spectrum of the fluorene radical anion in the presence of dibenzo crown ethers

Abstract

Two dibenzo crown ethers have been found to decompose slowly when in contact with alkali metals in tetrahydrofuran. Decomposition of these dibenzo crown ethers also occurs when they are brought into contact with a solution of the fluorene radical anion. The addition of the crown ethers to a solution of the radical anion has a dramatic effect upon the e.s.r. spectrum. This effect has been intepreted in terms of linewidth alternation. An interamolecular migration of the crown ether–alkali metal cation complex from one side of the radical anion plane to the other is proposed. It has been possible to examine the slow exchange region of the spectrum in the Li⁺–dibenzo-18-crown-6–fluorene radical anion system. A surprising observation is that these results indicate the complexation of Li⁺ by dibenzo-18-crown-6.