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Si us plau utilitzeu sempre aquest identificador per citar o enllaçar aquest document: https://hdl.handle.net/2445/225924
The (Anti)aromatic Properties of Cyclo[n]Carbons: Myth or Reality?
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Recent advances in on-surface chemistry have enabled the synthesis and structural characterization of even-numbered cyclo[n]carbons, traditionally classified as either doubly aromatic (n = 4k + 2) or doubly antiaromatic (n = 4k) based on their in-plane and out-of-plane π-electron circuits. However, recent studies have increasingly questioned this classification, suggesting instead that these molecules are more accurately described as non-aromatic. In this work, we computationally examine the electron affinities and (anti)aromatic character of cyclo[n]carbons with n = 16–30 using energetic, structural, and electronic aromaticity descriptors. Adiabatic electron affinity (AEA) analysis reveals a high degree of uniformity across the series of both nominally aromatic and antiaromatic members. Aromatic stabilization energy (ASE) values, derived from homodesmotic and disproportionation reactions, indicate slight destabilization only for C16 and C20, and low stabilization for the remaining systems. In particular, ASE is less than 2 kcal/mol for cyclo[n]carbons with n ≥ 24. This suggests that neither aromatic nor antiaromatic character significantly contributes to the thermodynamic stability of larger cyclocarbons. EDDB analysis further supports this conclusion, with only about 22%–27% of π-electrons participating in delocalization. While delocalization is slightly greater in cyclo[n]carbons with n = 4k + 2, the difference diminishes with increasing size. Upon two-electron reduction to the dianionic state, all cyclo[n]carbons exhibit bond length equalization and increased delocalization. These results suggest that only small cyclo[n]carbons (n < 24) can be classified as weakly (anti)aromatic, while larger cyclo[n]carbons (n ≥ 24) are more appropriately classified as non-aromatic systems. The aromaticity of all considered cyclocarbons becomes more pronounced in corresponding dianionic forms due to cooperative structural and electronic effects. Thus, this work provides a unified framework for interpreting and predicting the electronic behavior of cyclocarbons.
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STASYUK, O. a., GEORGE, G., CURUTCHET BARAT, Carles e., PLASSER, F., STASYUK, A. j.. The (Anti)aromatic Properties of Cyclo[n]Carbons: Myth or Reality?. _Journal of Computational Chemistry_. 2025. Vol. 46, núm. 31. [consulta: 25 de gener de 2026]. ISSN: 0192-8651. [Disponible a: https://hdl.handle.net/2445/225924]