TY - JOUR
T1 - A spiropentasiladiene radical cation
T2 - Spin and positive charge delocalization across two perpendicular Si=Si bonds and UV-vis- NIR absorption in the IR-B region
AU - Honda, Shunya
AU - Sugawara, Ryutaro
AU - Ishida, Shintaro
AU - Iwamoto, Takeaki
N1 - Funding Information:
This work was supported by JSPS KAKENHI grants JP25620020 and JP15K13635 (S.I.).
Publisher Copyright:
© 2021 American Chemical Society
PY - 2021/2/24
Y1 - 2021/2/24
N2 - 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.
AB - 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.
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U2 - 10.1021/jacs.0c12426
DO - 10.1021/jacs.0c12426
M3 - Article
C2 - 33565866
AN - SCOPUS:85101322763
VL - 143
SP - 2649
EP - 2653
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 7
ER -