Structural Monitoring of the Onset of Excited-State Aromaticity in a Liquid Crystal Phase

Masaki Hada, Shohei Saito, Sei'Ichi Tanaka, Ryuma Sato, Masahiko Yoshimura, Kazuhiro Mouri, Kyohei Matsuo, Shigehiro Yamaguchi, Mitsuo Hara, Yasuhiko Hayashi, Fynn Röhricht, Rainer Herges, Yasuteru Shigeta, Ken Onda, R. J.Dwayne Miller

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21 Citations (Scopus)

Abstract

Aromaticity of photoexcited molecules is an important concept in organic chemistry. Its theory, Baird's rule for triplet aromaticity since 1972 gives the rationale of photoinduced conformational changes and photochemical reactivities of cyclic π-conjugated systems. However, it is still challenging to monitor the dynamic structural change induced by the excited-state aromaticity, particularly in condensed materials. Here we report direct structural observation of a molecular motion and a subsequent packing deformation accompanied by the excited-state aromaticity. Photoactive liquid crystal (LC) molecules featuring a π-expanded cyclooctatetraene core unit are orientationally ordered but loosely packed in a columnar LC phase, and therefore a photoinduced conformational planarization by the excited-state aromaticity has been successfully observed by time-resolved electron diffractometry and vibrational spectroscopy. The structural change took place in the vicinity of excited molecules, producing a twisted stacking structure. A nanoscale torque driven by the excited-state aromaticity can be used as the working mechanism of new photoresponsive materials.

Original languageEnglish
Pages (from-to)15792-15800
Number of pages9
JournalJournal of the American Chemical Society
Volume139
Issue number44
DOIs
Publication statusPublished - Nov 8 2017

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All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Hada, M., Saito, S., Tanaka, SI., Sato, R., Yoshimura, M., Mouri, K., ... Miller, R. J. D. (2017). Structural Monitoring of the Onset of Excited-State Aromaticity in a Liquid Crystal Phase. Journal of the American Chemical Society, 139(44), 15792-15800. https://doi.org/10.1021/jacs.7b08021