Tetrabenzo fulvalene dication

Levy, A. Rakowitz, A. Mills, N. S. Dications of fluorenylidenes. The effect of substituent electronegativity and position on the antiaromaticity of substituted tetrabenzo[5.5]fulvalene dications, 7. Org. Chem. 2003,68,3990-3998. 

The tetrabenzo[5.5]fulvalene dication 49 and derivatives have been generated experimentally " and studied computationally. The H NMR spectrum of 49 has signals at d 5.07—5.87 with a center of gravity of d 5.41, and the upheld shifts from the neutral precursor, with a center of gravity of <5 7.75 ppm, indicate a substantial paratropic ring current, suggesting the species is antiaromatic. The NICS values and magnetic susceptibility exaltation of 49... 

The aromaticity of the dianion (1) and the antiaromaticity of the correponding dication of tetrabenzo[5.5]fulvalene have been evaluated through magnetic criteria, ll... 

Replacing one heptagon in 21 with a pentagon leads to tetrabenzo[5,7] fulvalene (31), as shown in Figure 4.9, which was studied by the Mills group for the examination of aromaticity/antiaromaticity within the same carbon framework [34,35]. Oxidation of 31 with SbFj in SO2CIF yielded the dication (31 " ), which was found to contain an antiaromatic fluorenyl cation as indicated by a paratropic shift in the NMR spectrum and an aromatic dibenzotropylium cation. Reduction of31 with lithium resulted in the dianion (31 ), which was characterized with NMR... 

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