The influence of crown ethers on cation migration processes. Part 3. The 5,12-dihydrotetracene radical anion with lithium or potassium as counterion

Abstract

The addition of dibenzo-18-crown-6 to a solution of 5,12-dihydrotetracene in tetrahydrofuran has been found to reduce dramatically the rate of cation migration when Li⁺ is the counterion. The resulting e.s.r. spectra, which exhibit linewidth alternation, have been computer-simulated employing modified Bloch equations. The activation energy for this process has been found to be 13.5 kJ mol^–1. Linewidth alternation is also present when K⁺ is the counterion, and is accompanied by a significant change in the various splitting constants as the ‘fast exchange’ region is approached.