Issue 22, 2023

From closed-shell edge-extended kekulenes to open-shell carbonylated cycloarene diradicaloid

Abstract

The precise synthesis of cycloarenes remains a challenging topic in both organic chemistry and materials science due to their unique fully fused macrocyclic π-conjugated structure. Herein, a series of alkoxyl- and aryl-cosubstituted cycloarenes (kekulene and edge-extended kekulene derivatives, K1–K3) were conveniently synthesized and an unexpected transformation of the anthryl-containing cycloarene K3 into a carbonylated cycloarene derivative K3-R was disclosed by controlling the temperature and gas atmosphere of the Bi(OTf)3-catalyzed cyclization reaction. All their molecular structures were confirmed by single-crystal X-ray analysis. The crystallographic data, NMR measurements, and theoretical calculations reveal their rigid quasi-planar skeletons, dominant local aromaticities, and decreasing intermolecular π–π stacking distance with extension of the two opposite edges. The much lower oxidation potential for K3 by cyclic voltammetry explains its unique reactivity. Moreover, carbonylated cycloarene derivative K3-R shows a remarkable stability, large diradical character, a small singlet–triplet energy gap (ΔES–T = −1.81 kcal mol−1), and weak intramolecular spin–spin coupling. Most importantly, it represents the first example of carbonylated cycloarene diradicaloids as well as the first example of radical-acceptor cycloarenes and will shed some light on synthesis of extended kekulenes and conjugated macrocyclic diradicaloids and polyradicaloids.

Graphical abstract: From closed-shell edge-extended kekulenes to open-shell carbonylated cycloarene diradicaloid

Supplementary files

Article information

Article type
Edge Article
Submitted
10 mar 2023
Accepted
13 mai 2023
First published
15 mai 2023
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2023,14, 6087-6094

From closed-shell edge-extended kekulenes to open-shell carbonylated cycloarene diradicaloid

D. Chang, J. Zhu, Y. Sun, K. Chi, Y. Qiao, T. Wang, Y. Zhao, Y. Liu and X. Lu, Chem. Sci., 2023, 14, 6087 DOI: 10.1039/D3SC01295F

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