Tetra‐tert‐butyl‐s‐indacene is a Bond‐Localized C_2h Structure and a Challenge for Computational Chemistry

Abstract

Whether tetra‐tert‐butyl‐s‐indacene is a symmetric D2h structure or a bond‐alternating C2h structure remains a standing puzzle. Close agreement between experimental and computed proton chemical shifts based on minima structures optimized at the M06‐2X, ωB97X‐D, and M11 levels confirm a bond‐localized C2h symmetry, which is consistent with the expected strong antiaromaticity of TtB‐s‐indacene.

Magnetic Antiaromaticity─Paratropicity─Does Not Necessarily Imply Instability

“…It is worth noting that in a study that was published while I was preparing this article, Wu and her co-workers identified that the M11 33 functional works the best for antiaromatic systems. 34 I repeated the computations at the M11/def2TZVPP level and found the same trend as the one reported here. Further information is given in Methods in the SI .…”

“…The 6π-electron radical cations of pyridine and diazines sustain diatropic currents that are comparable to those of their neutral parents. It is worth noting that in a study that was published while I was preparing this article, Wu and her co-workers identified that the M11 functional works the best for antiaromatic systems . I repeated the computations at the M11/def2TZVPP level and found the same trend as the one reported here.…”