Ion Solvation Equilibria in -Conjugated Reduced Systems

The reduction process of polycycles by alkali metals converts the neutral atoms to anions. The electron transfer is best achieved in ethereal solvents. This enables the stabilization of the metal cation by coordination to the oxygen atoms of the solvent. 

The following observation emphasizes the influence of the temperature on the ion solvation equilibrium. The reduction product of naphthalene 1 with Li metal in 2-methyltetrahydrofuran is temperature dependent [43]. At —120 °C only the radical anion (l ) could be observed by EPR, while at higher temperatures the paramagnetism disappears and the dianion (1 ) is detected. This reaction must be endothermic, it therefore seems that disproportionation is driven by entropy and not by energy, due to the ion pair solvation equilibrium. It is noteworthy that the dianion cannot be observed by NMR spectroscopy due to its special electronic structure [44]. 

---