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Antiaromaticity in Distal Bisfluorenyl Dications Separated by Multiple Discrete Spacer Units

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journal contribution
posted on 18.12.2008 by Bart J. Dahl, Nancy S. Mills
The effect of spacers on the antiaromaticity of bisfluorenyl dications was examined. For systems such as 4ac in which extensive delocalization of the positive charge through the π-system is not possible, a relationship based primarily on localized hyperconjugation as well as the distance between the fluorenyl systems and their antiaromaticity was demonstrated. Dications 2ac and 3ac also show the relationship, but it is further modulated by delocalization through the π-system. Calculated assessment of antiaromaticity was supported by experimental shifts for 2a,b and 3ac.