Room-Temperature Reversible σ-Dimerization of a Phenalenyl Radical

Phenalenyl 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 sigma-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 sigma-dimer form of K-2[sigma-1(2)] 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 sigma-dimerized back again. Theoretical calculations reveal that the potassium ions are necessary for the formation of the sigma-dimer and the solvent polarity controls the sigma-dimerization by regulating the presence of K+. [GRAPHICS] .

Automated summary

Phenalenyl derivatives have attracted much attention due to their reversible sigma-dimerization controlled by solvent instead of temperature. The structure and reversibility of this system have been investigated spectroscopically, crystallographically, and theoretically.