Corannulene radical

Miscellaneous. The photoejection of an electron from the antiaromatic corannulene dianion has been studied by Shenhar et al. Electrostatic repulsion between the corannulene radical-anion and the ejected electron facilitates the dissociation of the cage of the photoproducts initially formed. 

An early electrochemical study of corannulene revealed the presence of two well-defined polarographic waves with half-wave potentials of-1.88 and -2.36 V (r-butylammonium perchlorate in acetonitrile). The first wave represented a reversible, one-electron reduction leading to radical anion formation (emerald green solution) further characterized by UV-VIS and ESR. The second wave was reported to be associated with the formation of a bright red species which is not paramagnetic, but it is not believed to be the dianion, but rather some decay product of it. Treatment of THF solutions of 8 with sodium and potassium metals also led to the formation of the same species. ... 

A similar concave-to-convex arrangement was recently proposed for the adduct of the radical cation dimer of corannulene with neutral corannulene, formed in a gas-phase. Becker, H. Javabery, G. Petrie, S. Cheng, P-C. Schwartz, H. Scott, L. T. Bohme, D. K. J. Am. Chem. Soc. 1993,115, 11636. 

Bowl-shaped carbocations (33) were obtained by alkylation of the parent corannulene. ° The cations were obtained as stable salts and characterized by X-ray analysis. Phenalenyl cations (e.g. (34)) were obtained as air-stable BPh4 salts. Observations made in a selective synthesis of l,2-di(organo)fullerenes led to a mechanism whereby a cationic fullerene intermediate is generated by Cu(ll) oxidation of a fullerene radical (or anion). ... 

Stabilization of neutral radicals is another interesting property of bowl-shaped corannulene. The buckybowl neutral radicals 39 [52] and 40 [79] are stable as solids in air or as solutions in degassed toluene for long periods. Experimental results suggest spin delocalization of the radical species onto the corannulene moiety in 40 is more significant than 39. 

FVP synthesis of benzo[a]corannulene 85 was conducted with benzofluoranthene 84 [115] or [4]helicene precursor 86 [116] (Scheme 24). The former protocol is similar to the synthesis of coraimulene (1) from fluoranthene 10 (Scheme 2). In the reaction with 86, the reaction mechanism should involve a radical cascade... 

The FVP synthesis of acenaphtho[l,2,3-ftcrf]corannulene (109) started with arylethenylcorannulene 108 (Scheme 32) [48]. A reaction mechanism was proposed in which the aryl radical, generated by chlorine atom loss one at a time, first closes a six-membered ring, and subsequently a five-membered ring, to yield 109. 

Scheme 46 presents an unexpected formation of buckybowl 149 from corannulene derivative 148, which was prepared by a protocol similar to Method C in Scheme 5 [25]. Under FVP conditions, 148 underwent cyclization to give hydrocarbon 149 through the formation of three C-C bonds. The key step in the cyclization should be 1,2-shift of the hydrogen atom of the rim radical, generated by the rupture of C—Br bond one at a time, for the formation of five-membered rings.

Janata J, Gendell J, Ling CY, Barth W, Backes L, Mark HB Jr, Lawton RG (1967) Concerning the Anion and Cation Radicals of Corannulene. J Am Chem Soc 89 3056... 

This result immediately raised the question as to whether the employment of dibromomethyl rather than bromomethyl coupling would improve the yields of a nonpyrolytic route to corannulene. To test this possibility we converted tetrame-thylfluoranthene 10 to its octabromo derivative 11 by a standard radical bromina-... 

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