The electron spin-spin interaction between the two triplet diphenylcarbene units incorporated in the [2.2]paracyclophane skeleton has been investigated by ESR spectroscopy. The pseudoortho and pseudopara bis(phenylmethylenyl)[2.2]paracyclophanes are in the ground quintet state, while the pseudometa isomer is singlet. A conformational analysis of these high-spin dicarbenes has been carried out by examining their dipolar interaction tensors. The McConnell's theory on the ferromagnetic interaction

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... between two organic radicals has been demonstrated and a new strategy for increasing the dimension of high-spin aromatic molecules was found. On the basis of these findings, the molecular aggregates of some p-alkoxy substituted diphenylcarbenes were generated in the crystals of the precursor diazodiphenylmethanes to give 4 to 8 spins aligned among the neighboring triplet molecules.