Hydrocarbon Anions with High Stability. Part 2.1} Structure and Stability of Cyclopentadienide Ions with Condensed Aromatic Rings

The ionization-potential and oxidation-potential values have been examined as stability parameters in the gas and solution phase, respectively, for cyclopentadienide ions with from one to four condensed aromatic rings. They indicate that, without solvation effects, the condensed aromatic rings intrinsically stabilize the cyclopentadienide ion in solution as well as in the gas phase, and that an apparent destabilisation effect by the aromatic rings in solution is most probably ascribed to a decrease in the stabilizing solvation effects due to charge delocalization on the carbanions. Theoretical investigations from governing orbital interactions using the frontier orbital theory demonstrate that the essential stability of the cyclopentadienide ions is dependent on the structure, itself.