Site‐Directed Dimerization of Bowl‐Shaped Radical Anions to Form a σ‐Bonded Dibenzocorannulene Dimer

• Published in: Angewandte Chemie International Edition Vol. 57; no. 21; pp. 6171 - 6175
• Main Authors: Spisak, Sarah N., Zabula, Alexander V., Alkan, Melisa, Filatov, Alexander S., Rogachev, Andrey Yu, Petrukhina, Marina A.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 22.05.2018
• Edition: International ed. in English
• Subjects: Anions; Anions - chemical synthesis; Anions - chemistry; corannulene; Crystallization; Dimerization; Free Radicals - chemical synthesis; Free Radicals - chemistry; Localization; Models, Molecular; Molecular Conformation; Polycyclic Aromatic Hydrocarbons - chemical synthesis; Polycyclic Aromatic Hydrocarbons - chemistry; Radicals; reduction; Single crystals; X-ray diffraction; π-bowls; corannulene; dimerization; radicals; reduction; π-bowls
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201801537

Designed site‐directed dimerization of the monoanion radicals of a π‐bowl in the solid state is reported. Dibenzo[a,g]corannulene (C28H14) was selected based on the asymmetry of the charge/spin localization in the C28H14.− anion. Controlled one‐electron reduction of C28H14 with Cs metal in diglyme resulted in crystallization of a new dimer, [{Cs+(diglyme)}2(C28H14−C28H14)2−] (1), as revealed by single crystal X‐ray diffraction study performed in a broad range of temperatures. The C−C bond length between two C28H14.− bowls (1.560(8) Å) measured at −143 °C does not significantly change upon heating of the crystal to +67 °C. The single σ‐bond character of the C−C linker is confirmed by calculations. The trans‐disposition of two bowls in 1 is observed with the torsion angles around the central C−C bond of 172.3(5)° and 173.5(5)°. A systematic theoretical evaluation of dimerization pathways of C28H14.− radicals confirmed that the trans‐isomer found in 1 is energetically favored. Make it a double: The asymmetry of charge and spin localization in the bowl‐shaped dibenzocorannulene monoanion radical lead to spontaneous σ‐bond formation in the isolated and structurally characterized dimeric anion, (C28H14−C28H14)2−.