The antiaromaticity of a series of dications of p-substituted diphenylmethylidene fluorenes was explored using three criteria attributed to aromaticity/antiaromaticity. The relative stability of the dications (energetic criterion) was measured via the redox potentials obtained by electrochemical oxidation under very fast sweep rates with microelectrodes. Comparison of redox potentials with those of a model system, p-substituted tetraphenylethylenes, ...