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Negatively Curved Nanographene with Heptagonal and [5]Helicene Units.

ABSTRACT: Negatively curved nanographene (NG) 4, having two heptagons and a [5]helicene, was unexpectedly obtained by aryl rearrangement and stepwise cyclodehydrogenations. X-ray crystallography confirmed the saddle-shaped structures of intermediate 3 and NG 4. The favorability of rearrangement over helicene formation following radical cation or arenium cation mechanisms is supported by theoretical calculations. NG 4 demonstrates a reversible mechanochromic color change and solid-state emission, presumably benefiting from its loose crystal packing. After resolution by chiral high-performance liquid chromatography, the circular dichroism spectra of enantiomers 4-(P) and 4-(M) were measured and showed moderate Cotton effects at 350 nm (|??| = 148 M-1 cm-1).

SUBMITTER: Qiu Z

PROVIDER: S-EPMC7472433 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Negatively Curved Nanographene with Heptagonal and [5]Helicene Units.

Qiu Zijie Z Asako Sobi S Hu Yunbin Y Ju Cheng-Wei CW Liu Thomas T Rondin Loïc L Schollmeyer Dieter D Lauret Jean-Sébastien JS Müllen Klaus K Narita Akimitsu A

Journal of the American Chemical Society 20200824 35

Negatively curved nanographene (NG) 4, having two heptagons and a [5]helicene, was unexpectedly obtained by aryl rearrangement and stepwise cyclodehydrogenations. X-ray crystallography confirmed the saddle-shaped structures of intermediate 3 and NG 4. The favorability of rearrangement over helicene formation following radical cation or arenium cation mechanisms is supported by theoretical calculations. NG 4 demonstrates a reversible mechanochromic color change and sol ...[more]

PMID: 32809808

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