A spiropentasiladiene radical cation: Spin and positive charge delocalization across two perpendicular Si=Si bonds and UV-vis- NIR absorption in the IR-B region

Shunya Honda, Ryutaro Sugawara, Shintaro Ishida, Takeaki Iwamoto

Research output: Contribution to journalArticlepeer-review

Abstract

Spiroconjugation, that is, through-space orbital interactions between two perpendicular π orbitals, is a key concept in the contemporary molecular design of spirocyclic π-electron systems. We synthesized spiropentasiladiene radical cation salt 1 as a dark-green solid via the one-electron oxidation of the stable spiropentasiladiene 2. Characterization of the molecular structure combined with theoretical studies indicated that the spin and positive charge are delocalized across the two perpendicular Si=Si double bonds of 1. Two π(Si=Si) orbitals are split into HOMO and SOMO with a small energy gap owing to the second-order Jahn-Teller distortion and steric repulsion between bulky alkyl groups upon one-electron oxidation. In the UV-vis-NIR spectrum, the longest-wavelength absorption band of 1 (λmax = 1972 nm) covers the IR-B region (1400-3000 nm; 0.89-0.41 eV) despite having the smallest possible spiroconjugation motif. The unprecedented absorption band in the IR region was assigned to the HOMO → SOMO transition that arises from the delocalized π-orbitals in the spirocyclic Si5 skeleton.

Original languageEnglish
Pages (from-to)2649-2653
Number of pages5
JournalJournal of the American Chemical Society
Volume143
Issue number7
DOIs
Publication statusPublished - 2021 Feb 24

ASJC Scopus subject areas

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

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