Misplaced Pages

Revision as of 02:41, 11 September 2011

Corannulene

Names
IUPAC name Dibenzofluoranthene
Other names circulene
Identifiers
CAS Number	5821-51-2
3D model (JSmol)	Interactive image Interactive image
ChemSpider	10006487
PubChem CID	11831840
CompTox Dashboard (EPA)	DTXSID80474164
InChI InChI=1S/C20H10/c1-2-12-5-6-14-9-10-15-8-7-13-4-3-11(1)16-17(12)19(14)20(15)18(13)16/h1-10HKey: VXRUJZQPKRBJKH-UHFFFAOYSA-N InChI=1/C20H10/c1-2-12-5-6-14-9-10-15-8-7-13-4-3-11(1)16-17(12)19(14)20(15)18(13)16/h1-10HKey: VXRUJZQPKRBJKH-UHFFFAOYAF
SMILES c16ccc2ccc3ccc5c4c(c1c2c34)c(cc5)cc6 c1cc2ccc3ccc4ccc5ccc1c6c2c3c4c56
Properties
Chemical formula	C20H10
Molar mass	250.29 g/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Y verify (what is  ?) Infobox references

Corannulene is a polycyclic aromatic hydrocarbon with chemical formula C₂₀H₁₀. The molecule consists of a cyclopentane ring fused with 5 benzene rings, so another name for it is circulene. It is of scientific interest because it is a geodesic polyarene and can be considered a fragment of buckminsterfullerene. Due to this connection and also its bowl shape, corannulene is also known as a buckybowl. Corannulene exhibits a bowl-to-bowl inversion with an inversion barrier of 10.2 kcal/mol (42.7 kJ/mol) at −64 °C.

Synthesis

Several synthetic routes exist to corannulene. Flash vacuum pyrolysis techniques generally have lower chemical yields than solution-chemistry syntheses, but offer routes to more derivatives. Corannulane was first isolated in 1966 by multistep organic synthesis. A flash vacuum pyrolysis method followed in 1991. One synthesis based on solution chemistry consists of a nucleophilic displacement–elimination reaction of an octabromide with potassium hydroxide:

The bromine substituents are removed with an excess of n-butyllithium.

Much effort is directed at functionalization of the corannulene ring with novel functional groups such as ethynyl groups, ether groups, thioether groups, platinum function groups, aryl groups, phenalenyl fused and indeno extensions.

Aromaticity

The observed aromaticity for this compound is explained with a so-called annulene-within-an-annulene model. According to this model corannulene is made up of an aromatic 6 electron cyclopentadienyl anion surrounded by an aromatic 14 electron annulenyl cation. This model was suggested by Barth and Lawton in the first synthesis of corannulene in 1966. They also suggested the trivial name 'corannulene', which is derived from the annulene-within-an-annulene model: core + annulene.

However, later theoretical calculations have disputed the validity of this approximation.

Corannulene anions

Corannulene can be reduced up to a tetraanion in a series of one-electron reductions. This has been performed with alkali metals, electrochemically and with bases. The corannulene dianion is antiaromatic and tetraanion is again aromatic. With lithium as reducing agent two tetraanions form a supramolecular dimer with two bowls stacked into each other with 4 lithium ions in between and 2 pairs above and below the stack.. This self-assembly motif was applied in the organization of fullerenes. Penta-substituted fullerenes (with methyl or phenyl groups) charged with five electrons form supramolecular dimers with a complementary corannulene tetraanion bowl, 'stitched' by interstitial lithium cations. In a related system 5 lithium ions are sandwiched between two corannulene bowls

In one cyclopentacorannulene a concave - concave aggregate is observed by NMR spectroscopy with 2 C–Li–C bonds connecting the tetraanions.

Metals tend to bind to the convex face of the annulene. Concave binding has been reported for a cesium / crown ether system

Corannulene radicals

Corannulene-based free radicals have also been synthesised and studied. A semiquinone radical anion obtained by reduction of the diketone by a sodium mirror (see below) has been reported stable in the solid state

.

In this radical anion spin density is delocalized with a significant contribution from the central cyclopentadienyl radical.

Corannulene carbocations

Corannulene can react with electrophiles to form a corannulene carbocation. Reaction with chloromethane and aluminium chloride results in the formation of an AlCl₄ salt with a methyl group situated at the center with the cationic center at the rim. X-ray diffraction analysis shows the that the new carbon-carbon bond is elongated (157 pm)

Bicorannulenyl

Bicorannulenyl is the corannulene dimer, in which two corannulene units are connected through a single bond. The molecule's stereochemistry consists of two chiral elements: the asymmetry of a singly substituted corannulenyl, and the helical twist about the central bond. In the neutral state, bicorannulenyl exists as 12 conformers, which intercovert through multiple bowl-inversions and bond-rotations. When bicorannulenyl is reduced to a dianion with potassium metal, the central bond assumes significant double-bond character. This is due to its orbital structure, which has a LUMO orbital localized on the central bond. When bicorannulenyl is reduced to an octaanion with lithium metal, it self-assembles into supramolecular oligomers. This is based on the "charged polyarene stacking" self-assembly motif.

Applications

The corannulene group is used in host-guest chemistry with interactions based on pi stacking , notably with fullerenes (the buckycatcher) but also with nitrobenzene

With long aliphatic side chains corannulenes are reported forming a thermotropic hexagonal columnar liquid crystalline mesophase. Corannulenes have also been used as the core group in a dendrimer or as coordinating ligand to metals. Corannulenes with ethynyl groups are investigated for their potential use as blue emitters.

In space

Efforts to detect corannulene in space have thus far failed.

See also

• Coronene
• Helicene

References

1. Template:Cite DOI
2. ^ Template:Cite DOI
3. ^ Template:Cite DOI
4. Template:Cite DOI
5. Template:Cite DOI
6. Template:Cite DOI
7. ^ Template:Cite DOI
8. Template:Cite DOI
9. Template:Cite DOI
10. Template:Cite DOI
11. ^ Template:Cite DOI
12. Template:Cite DOI
13. Template:Cite DOI
14. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1016/0166-1280(94)03961-J, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1016/0166-1280(94)03961-J instead.
15. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1021/jp8038779, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1021/jp8038779 instead.
16. Template:Cite DOI
17. Template:Cite DOI
18. A Main Group Metal Sandwich: Five Lithium Cations Jammed Between Two Corannulene Tetraanion Decks Zabula, et al. Science 19 August 2011: 1008-1011. doi:10.1126/science.1208686
19. Template:Cite DOI
20. Spisak, S. N., Zabula, A. V., Filatov, A. S., Rogachev, A. Y. and Petrukhina, M. A. (2011), Selective Endo and Exo Binding of Alkali Metals to Corannulene. Angewandte Chemie International Edition, 50: 8090–8094. doi:10.1002/anie.201103028
21. The First Bowl-Shaped Stable Neutral Radical with a Corannulene System:  Synthesis and Characterization of the Electronic Structure Yasushi Morita, Shinsuke Nishida, Tadahiro Kobayashi, Kozo Fukui, Kazunobu Sato, Daisuke Shiomi, Takeji Takui, Kazuhiro Nakasuji Organic Letters 2004 6 (9), 1397-1400 doi:10.1021/ol0497786
22. Template:Cite DOI
23. Template:Cite DOI
24. Ueda, A., Ogasawara, K., Nishida, S., Ise, T., Yoshino, T., Nakazawa, S., Sato, K., Takui, T., Nakasuji, K. and Morita, Y. (2010), A Bowl-Shaped ortho-Semiquinone Radical Anion: Quantitative Evaluation of the Dynamic Behavior of Structural and Electronic Features. Angewandte Chemie International Edition, 49: 6333–6337. doi:10.1002/anie.201002626
25. Zabula, A. V., Spisak, S. N., Filatov, A. S., Rogachev, A. Y. and Petrukhina, M. A. (2011), A Strain-Releasing Trap for Highly Reactive Electrophiles: Structural Characterization of Bowl-Shaped Arenium Carbocations. Angewandte Chemie International Edition, 50: 2971–2974. doi:10.1002/anie.201007762
26. Template:Cite DOI
27. Eisenberg, D., Quimby, J. M., Jackson, E. A., Scott, L. T. and Shenhar, R. (2010), The Bicorannulenyl Dianion: A Charged Overcrowded Ethylene. Angewandte Chemie International Edition, 49: 7538–7542. doi:10.1002/anie.201002515
28. Eisenberg, D., Quimby, J. M., Jackson, E. A., Scott, L. T. and Shenhar, R. (2010), Highly Charged Supramolecular Oligomers Based on the Dimerization of Corannulene Tetraanion. Chemical Communications, 46: 9010–9012. doi:10.1039/c0cc03965a
29. Template:Cite DOI
30. Template:Cite DOI
31. Template:Cite DOI
32. Template:Cite DOI
33. Hexahapto Metal Coordination to Curved Polyaromatic Hydrocarbon Surfaces: The First Transition Metal Corannulene Complex T. Jon Seiders, Kim K. Baldridge, Joseph M. O'Connor, and Jay S. Siegel J. Am. Chem. Soc., 1997, 119 (20), pp 4781–4782 doi:10.1021/ja964380t
34. d8 Rhodium and Iridium Complexes of Corannulene Jay S. Siegel, Kim K. Baldridge, Anthony Linden, and Reto Dorta J. Am. Chem. Soc., 2006, 128 (33), pp 10644–10645 doi:10.1021/ja062110x
35. Template:Cite DOI
36. Template:Cite DOI
37. Template:Cite DOI
38. Template:Cite DOI
39. Bandera, D., Baldridge, K. K., Linden, A., Dorta, R. and Siegel, J. S. (2011), Stereoselective Coordination of C5-Symmetric Corannulene Derivatives with an Enantiomerically Pure Metal Complex. Angewandte Chemie International Edition, 50: 865–867. doi: 10.1002/anie.201006877
40. Template:Cite DOI
41. Template:Cite DOI

• Geodesic polyarenes
• Polycyclic aromatic hydrocarbons