Room‐Temperature Reversible σ‐Dimerization of a Phenalenyl Radical

Abstract

Comprehensive SummaryPhenalenyl derivatives have been of tremendous interest due to their reversible dimerization in response to the external stimuli such as temperature. However, most of PLY derivatives only show the reversibility dependent on temperature. Herein, we report a unique PLY‐based radical anionic salt with reversible σ‐dimerization controlled by solvent rather than temperature. The structure and reversibility of this PLY anion system have been spectroscopically, crystallographically, and theoretically investigated. The molecule exists mainly as the σ‐dimer form of K2[σ‐12] in toluene, while it can be broken into the monomeric radical anion 1•– by re‐dissolving in THF. Moreover, when THF is replaced with toluene, radical 1•– could be σ‐dimerized back again. Theoretical calculations reveal that the potassium ions are necessary for the formation of the σ‐dimer and the solvent polarity controls the σ‐dimerization by regulating the presence of K+.