Evidence for the equilibration of resonance-stabilized carbocations, carbanions, and radicals by single electron transfer in solution

When THF solutions of the tetrafluoroborate salt of malachite green cation (I) and the sodium salt of the trityl anion (II) are mixed (in the presence of an equivalent amount of 18-crown-6 to prevent ion pairing) electron transfer from anion (II) to cation (I) is observed by disappearance of the 790 nm absorbance of the carbanion (II), correlated with development of an increasing ESR absorption ofthe corresponding radical (IV).