Electrostatic Potential for Exploring Electron Delocalization in Infinitenes, Circulenes, and Nanobelts

Abstract

The π-conjugation, aromaticity, and stability of the newly synthesized 12-infinitene and of other infinitenes comprising 8-, 10-, 14-, and 16-arene rings are investigated using density functional theory. The π-electron delocalization and aromatic character rooted in infinitenes are quantified in terms of molecular electrostatic potential (MESP) topology. Structurally, the infinitene bears a close resemblance of its helically twisted structure to the infinity symbol. The MESP topology shows that infinitene possesses an infinity-shaped delocalization of the electron density that streams over the fused benzenoid rings. The parameter, derived from the eigenvalues (λ i ) corresponding to the MESP minima, is used for quantifying the aromatic character of arene rings of infinitene. The structure, stability, and MESP topology features of 8-, 10-, 12-, 14-, and 16-infinitenes are also compared with the corresponding isomeric circulenes and carbon nanobelts. Further, the strain in all such systems is evaluated by considering the respective isomeric planar benzenoid hydrocarbons as reference systems. The 12-infinitene turns out to be the most aromatic and the least strained among all the systems examined.

Carbon Nanobelts: Brief History and Perspective

“…X-ray crystal structure analysis has shown that the combined lamellar and herringbone-like packing structure introduced three-dimensional electronic interactions caused by the infinity shape. Since this report, fascinating properties of infinitene have been predicted. − Wu and Isobe et al synthesized a twisted CNB in 2021 and a fused [5]­helicene dimer in 2023 , as a related molecule of infinitene. In addition to aromatic hydrocarbon-based CNBs, heteroatom-embedded CNBs have also been reported. − In 2019, Tanaka et al synthesized the first oxygen-embedded CNB by rhodium-catalyzed alkyne cyclotrimerization .…”