How do the Huckel and Baird Rules Fade away in Annulenes?

ABSTRACT: Two of the most popular rules to characterize the aromaticity of molecules are those due to Hückel and Baird, which govern the aromaticity of singlet and triplet states. In this work, we study how these rules fade away as the ring structure increases and an optimal overlap between p orbitals is no longer possible due to geometrical restrictions. To this end, we study the lowest-lying singlet and triplet states of neutral annulenes with an even number of carbon atoms between four and eighteen. First of all, we analyze these rules from the Hückel molecular orbital method and, afterwards, we perform a geometry optimization of the annulenes with several density functional approximations in order to analyze the effect that the distortions from planarity produce on the aromaticity of annulenes.

SUBMITTER: Casademont-Reig I 

PROVIDER: S-EPMC7037833 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature