Synthesis and Properties of Fluorenone-Containing Cycloparaphenylenes and Their Late-Stage Transformation

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Cycloparaphenylenes (CPPs) are the smallest possible armchair carbon nanotubes, the properties of which strongly depend on their ring size. They can be further tuned by either peripheral functionalization or by replacing phenylene rings for other aromatic units. Here we show how four novel donor–acceptor chromophores were obtained by incorporating fluorenone or 2-(9H-fluoren-9-ylidene)malononitrile into the loops of two differently sized CPPs. Synthetically, we managed to perform late-stage functionalization of the fluorenone-based rings by high-yielding Knoevenagel condensations. The structures were confirmed by X-ray crystallographic analyses, which revealed that replacing a phenylene for a fused-ring-system acceptor introduces additional strain. The donor–acceptor characters of the CPPs were supported by absorption and fluorescence spectroscopic studies, electrochemical studies (displaying the CPPs as multi-redox systems undergoing reversible or quasi-reversible redox events), as well as by computations. The oligophenylene parts were found to comprise the electron donor units of the macrocycles and the fluorenone parts the acceptor units.

Original languageEnglish
Article numbere202303490
JournalChemistry - A European Journal
Volume30
Issue number5
Number of pages12
ISSN0947-6539
DOIs
Publication statusPublished - 2024

Bibliographical note

Funding Information:
The Novo Nordisk Foundation (NNF20OC0061574) is acknowledged for financial support. T.W.P. and R.J. were supported by the U.S. National Science Foundation (CHE‐2102567).

Publisher Copyright:
© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.

    Research areas

  • chromophores, cross-coupling, donor–acceptor systems, macrocycles, strained molecules

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