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Electron-Deficient Heteroacenes that Contain Two Boron Atoms: Near-Infrared Fluorescence Based on a Push–Pull Effect

preprint
submitted on 12.05.2021, 11:29 and posted on 18.05.2021, 08:41 by Masato Ito,, Mika Sakai, Naoki Ando, Shigehiro Yamaguchi
Electron-deficient heteroacenes that contain two tricoordinate boron atoms in their acene skeletons and planarized phenyl ether moieties at their periphery were synthesized via the borylation of the corresponding silicon-bridged precursors. X-ray crystallographic analysis revealed quinoidal structures, which give rise to two-step reversible redox processes for both the reduction and oxidation. These compounds exhibit intense absorption and sharp fluorescence bands with vibronic structures in the near-infrared (NIR) region. These properties originate from the push–pull effect along the long axis of the molecule derived from the electron-donating ether moiety and the electron-accepting boron moieties. Of particular note is the NIR emission of the thienothiophene-centered heteroacene, which has a maximum at 952 nm with a narrow band width of 309 cm–1 in cyclohexane. A Franck–Condon analysis revealed the crucial role of the sterically less-hindered thienothiophene spacer in achieving this sharp emission band.

Funding

The Japan Society for the Promotion of Science (JSPS), KAKENHI grants 18H03909, 18H05261, and 20K15258

History

Email Address of Submitting Author

yamaguchi@chem.nagoya-u.ac.jp

Institution

Nagoya University

Country

Japan

ORCID For Submitting Author

0000-0003-0072-8969

Declaration of Conflict of Interest

The authors declare no conflict of interest.

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