Corannulene

Source: Wikipedia, the free encyclopedia.
Corannulene
Names
IUPAC name
Dibenzo[ghi,mno]fluoranthene[1]
Other names
[5]circulene
Identifiers
3D model (
JSmol
)
ChemSpider
UNII
  • 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/h1-10H checkY
    Key: VXRUJZQPKRBJKH-UHFFFAOYSA-N checkY
  • 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/h1-10H
    Key: VXRUJZQPKRBJKH-UHFFFAOYAF
  • c16ccc2ccc3ccc5c4c(c1c2c34)c(cc5)cc6
  • C1=CC2=CC=C3C=CC4=C5C6=C(C2=C35)C1=CC=C6C=C4
Properties
C20H10
Molar mass 250.29 g/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Corannulene is a

kJ/mol) at −64 °C.[3]

Synthesis

Several synthetic routes exist to corannulene.

nucleophilic displacement–elimination reaction of an octabromide with sodium hydroxide
:

Corannulene synthesis Sygula 2000

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

A kilogram scale synthesis of corannulene has been achieved.[8]

Much effort is directed at functionalization of the corannulene ring with novel functional groups such as ethynyl groups,[3][9][10] ether groups,[11] thioether groups,[12] platinum functional groups,[13] aryl groups,[14] phenalenyl fused [15] and indeno extensions.[16] and ferrocene groups.[17]

Aromaticity

The observed

cation. This model was suggested by Barth and Lawton in the first synthesis of corannulene in 1966.[4]
They also suggested the trivial name 'corannulene', which is derived from the annulene-within-an-annulene model: core + annulene.

annulene-within-an-annulene model

However, later theoretical calculations have disputed the validity of this approximation.[18][19]

Reactions

Reduction

Corannulene can be reduced up to a tetraanion in a series of

supramolecular dimer with two bowls stacked into each other with 4 lithium ions in between and 2 pairs above and below the stack.[20] 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.[21] In a related system 5 lithium ions are sandwiched between two corannulene bowls [22]

In one cyclopenta[bc]corannulene a concave - concave aggregate is observed by

NMR spectroscopy with 2 C–Li–C bonds connecting the tetraanions.[23]

Cyclopenta[bc]corannulene
Cyclopenta[bc]corannulene

Metals tend to bind to the convex face of the annulene. Concave binding has been reported for a cesium / crown ether system [24]

Oxidation

UV 193-nm photoionization effectively removes a π-electron from the twofold degenerate E1-HOMO located in the aromatic network of electrons yielding a corannulene radical cation.[25] Owing to the degeneracy in the HOMO orbital, the corannulene radical cation is unstable in its original C5v molecular arrangement, and therefore, subject to Jahn-Teller (JT) vibronic distortion.

Using electrospray ionization, a protonated corannulene cation has been produced in which the protonation site was observed to be on a peripheral sp2-carbon atom.[25]

Reaction with electrophiles

Corannulene can react with

X-ray diffraction analysis shows that the new carbon-carbon bond is elongated (157 pm) [26]


Bicorannulenyl

Bicorannulenyl is the product of dehydrogenative coupling of corannulene. With the formula C20H9-C20H9, it consists of two corannulene units connected through a single C-C 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 interconvert through multiple bowl-inversions and bond-rotations.[27] When bicorannulenyl is reduced to a dianion with potassium metal, the central bond assumes significant double-bond character. This change is attributed to the orbital structure, which has a LUMO orbital localized on the central bond.[28] When bicorannulenyl is reduced to an octaanion with lithium metal, it self-assembles into supramolecular oligomers.[29] This motif illustrates "charged polyarene stacking".

Research

pi stacking, notably with fullerenes (the buckycatcher) [30][31] but also with nitrobenzene[32]

Alkyl-substituted corannulenes form a thermotropic hexagonal columnar liquid crystalline mesophase.[33] Corannulene has also been used as the core group in a dendrimer.[14] Like other PAHs, corannulene ligates metals.[34][35][36][37][38][39][40] Corannulenes with ethynyl groups are investigated for their potential use as blue emitters.[10] The structure was analyzed by infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy.[41]

See also

Wikimedia Commons has media related to Corannulene.
Look up corannulene in Wiktionary, the free dictionary.

References

  1. ^ Fluoranthene is so named for its fluorescent property. It is not a fluorine compound.
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