The high energy of cyclobutadiene (CBD) is not due primarily to "anti-aromaticity," but rather to angle strain, torsional strain, and Pauli repulsion between the parallel CC bonds. Estimations including block-localized wavefunction (BLW) computations conclude that the enormous ring strain (ca. 60 kcal mol(-1)) far exceeds its antiaromatic destabilization (only 16.5 kcal mol(-1)).

The reversal of aromaticity and antiaromaticity upon excitation to the lowest ππ* state impacts on photophysics photoreactivity various annulenes. This unifying principle can guide rationalization a plethora excited-state reactions has strong predictive power in design new photochemical transformations. For more details, see Review by H. Ottosson et al. (DOI: 10.1002/chem.202203748)

Aromaticity is a fundamental concept in chemistry. It is described by Hückel's rule that states that a cyclic planar π-system is aromatic when it shares 4n+2 π-electrons and antiaromatic when it possesses 4n π-electrons. Antiaromatic compounds are predicted to exhibit remarkable charge transport properties and high redox activities. However, it has so far only been possible to measure compounds...

A detailed investigation has been made into the antiaromaticity and chemical reactivity of a planar cyclooctatetraene (COT) molecule fully annelated with bicyclo[2.1.1]hexane units 2. In spite of its planar 8pi-electronic structure, theoretical calculations have indicated that the antiaromaticity of COT 2 is considerably decreased in comparison with a planar COT 16 with D 4h symmetry. This beha...

Abstract A recent Research Article in this journal by Matito and co‐workers claimed that none of the oxidation states a butadiyne‐linked six‐porphyrin nanoring exhibit global aromaticity or antiaromaticity. Here we show conclusion is incorrect. Experimental data from NMR spectroscopy for whole family nanorings provide strong evidence ring currents. The reveal these currents directly, without ne...

Cyclooctatetraene (COT), the first 4nπ-electron system to be studied, adopts an inherently nonplanar tub-shaped geometry of D2d symmetry with alternating single and double bonds, and hence behaves as a nonaromatic polyene rather than an antiaromatic compound. Recently, however, considerable 8π-antiaromatic paratropicity has been shown to be generated in planar COT rings even with the bond alter...