An electron spin resonance investigation of the 4,5-methylenephenanthrene dianion radical

The e.s.r. spectrum of the 4,5-methylenephenanthrene dianion radical has been studied with particular interest in the variation of the alkali-metal splitting constant with the nature of the solvent, the nature of the counterion, and temperature. The results may be interpreted in terms of interaction of the unpaired electron with one counterion only. The results also indicate that a variety of environments are possible for the counterion in the ‘contact’ ion pair and that in particular cases an equilibrium is also present in which this counterion is in a ‘solvent-separated’ environment. Interaction of the unpaired electron with the second counterion is not observed and is probably due to a solvent separated environment for this counterion.