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Strain-Induced Quinoidal Character in a Carbon Nanoring Embedding Anthracene Units
Tomohiko Nishiuchi1,2, Yuta Makihara1, Takashi Kubo1,2,3
1Department of Chemistry, Graduate School of Science, The University of Osaka, Osaka 560-0043, Japan.
None:
We report a carbon nanoring, [2.2]cyclo(9,10)anthrylene-paraphenylene ([2.2]CAPP), featuring alternating anthracene and phenylene units within a [4]cycloparaphenylene (CPP) framework. The molecule was synthesized via a six-step metal-free route and structurally characterized by single-crystal X-ray diffraction. The high ring strain induces significant distortion in the anthracene units, resulting in a quinoidal electronic structure with a suppressed aromaticity. Despite possessing a 16π-electron conjugation pathway, no global antiaromaticity was observed. This work demonstrates that strain engineering in carbon nanorings enables control over the aromaticity and open-shell character through rational molecular design.
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