Electron spin resonance studies on the interactions between radical ion pairs and macrocyclic polyethers. Part 2. Intramolecular cation exchange in metal ketyl ion pairs

Abstract

The effect of complexation by the polyether dibenzo-18-crown-6 of radical ion pairs from dicarbonyl derivatives has been studied by electron resonance spectroscopy. In the case of the potassium and lithium salts only small variations have been observed both in the hyperfine splitting constants and in the rate of intramolecular migration of the counterion from one carbonyl group to the other. Drastic changes, mainly in the migration rate, were however observed for the sodium salts. From a complete lineshape analysis of the e.s.r. spectra at several temperatures, the effect of complexation on the activation parameters for the intramolecular exchange was determined. In the light of these results we postulate, for the crown complexes of carbonyl derivatives, a structure more realistic than that proposed in our previous paper.