Synthesis of Closed-Heterohelicenes Interconvertible between Their Monomeric and Dimeric Forms

Yusuke Matsuo; Chihiro Maeda; Yusuke Tsutsui; Takayuki Tanaka; Shu Seki

doi:10.1002/anie.202314968

Synthesis of Closed-Heterohelicenes Interconvertible between Their Monomeric and Dimeric Forms

Angew Chem Int Ed Engl. 2023 Dec 11;62(50):e202314968. doi: 10.1002/anie.202314968. Epub 2023 Nov 9.

Authors

Yusuke Matsuo^{1

2}, Chihiro Maeda³, Yusuke Tsutsui^{2

4}, Takayuki Tanaka^{1

2}, Shu Seki²

Affiliations

¹ Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
² Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan.
³ Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University, Tsushima, Okayama 700-8530, Japan.
⁴ JST-PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.

PMID: 37883214
DOI: 10.1002/anie.202314968

Abstract

Oxidative fusion reaction of cyclic heteroaromatic pentads consisting of pyrrole and thiophene gave closed-heterohelicene monomers and dimers depending on the oxidation conditions. Specifically, oxidation with [bis(trifluoroacetoxy)iodo]benzene (PIFA) gave closed-[7]helicene dimers connected at the β-position of one of the pyrrole units with remarkably elongated C-C bonds of about 1.60 Å. Although this bond was intact against thermal and physical activations, homolytic bond dissociation took place in DMSO upon irradiation with UV light to give the corresponding monomers. Thus, interconversion between the closed-helicene monomer and dimer was achieved. The optically pure dimer was photo-dissociated into the monomers associated with a turn-on of circularly polarized luminescence (CPL).

Keywords: Bond Dissociation; Circularly Polarized Luminescence; Heterohelicenes; Nanographenes; Oxidative Fusion Reaction.

Abstract

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