Antiaromaticity in Distal Bisfluorenyl Dications Separated by Multiple Discrete Spacer Units
journal contributionposted on 18.12.2008 by Bart J. Dahl, Nancy S. Mills
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The effect of spacers on the antiaromaticity of bisfluorenyl dications was examined. For systems such as 4a−c 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 2a−c and 3a−c 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 3a−c.