Charged paracyclophanes behave as annulenes with enhanced anisotropy

Abstract

Paracyclophanes, in which benzene units are linked at the 1,4 positions by ethylene bridges (1–4), show annulene characteristics upon charging. The dependence of the magnetic properties of these charged rigid systems on the number of π-electrons in the peripheries has been studied systematically. For the first time it can be shown that upon extensive reduction, two observable diatropic anionic stages exist (for 3). The results of advanced DFT calculations are in line with the experimental results.

The limit on the number of π-electrons in the periphery of annulenes, which still exhibit aromatic or anti-aromatic behavior, is extended far beyond the number of 26.

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