Radical Ions in the Pentalene Series. Part III . Three paramagnetic redox stages of a dicyclopenta[ a,e ]pentalene

Five redox stages have been observed for the recently synthesized 1,3,5,7‐tetra( tert ‐butyl) derivative 1 of the dicyclopenta[ a,e ]pentalene, a novel non‐alternant hydrocarbon: the radical cation \documentclass{article}\pagestyle{empty}\begin{document}$1^{+ \atop \dot{}}$\end{document} , the neutral compound 1 , the radical anion \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document} , the dianion 1 2− , and the radical trianion \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{3\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document} . Information about the the electronic structure of the three paramagnetic stages, \documentclass{article}\pagestyle{empty}\begin{document}$1^{+ \atop \dot{}}$\end{document} , \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document} , and \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{3\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document} is provided by the use of ESR, ENDOR, and TRIPLE resonance spectroscopy. The unpaired electron in the trianion resides mainly on the ‘inner’ butadiene‐π‐system. Whereas in the cation and the anion, it is largely localized on the two ‘outer’ five‐membered rings.