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Electronic transitions in conformationally controlled tetrasilanes with a wide range of SiSiSiSi dihedral angles. | LitMetric

Electronic transitions in conformationally controlled tetrasilanes with a wide range of SiSiSiSi dihedral angles.

Chemistry

International Research Center for Elements Science (IRCELS), Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan); Present address: Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku,Tokyo 113-0033 (Japan).

Published: July 2014

AI Article Synopsis

  • The peralkylated n-tetrasilane σ-electron chromophore exhibits significant changes in its electronic spectrum as its silicon backbone twists from syn to anti conformations, altering the SiSiSiSi dihedral angle.
  • A series of spectroscopic techniques, including UV absorption, MCD, and LD, were employed to analyze tetrasilanes and produce a correlation diagram for their lowest valence electronic states.
  • The findings highlight the phenomenon of avoided crossings between specific electronic states, supported by calculations from SAC-CI on various tetrasilane conformers.

Article Abstract

Unlike π-electron chromophores, the peralkylated n-tetrasilane σ-electron chromophore resembles a chameleon in that its electronic spectrum changes dramatically as its silicon backbone is twisted almost effortlessly from the syn to the anti conformation (changing the SiSiSiSi dihedral angle ω from 0 to 180°). A combination of UV absorption, magnetic circular dichroism (MCD), and linear dichroism (LD) spectroscopy on conformationally controlled tetrasilanes 1-9, which cover fairly evenly the full range of angles ω, permitted a construction of an experimental correlation diagram for three to four lowest valence electronic states. The free chain tetrasilane n-Si4 Me10 (10), normally present as a mixture of three enantiomeric conformer pairs of widely different angles ω, has also been included in our study. The spectral trends are interpreted in terms of avoided crossings of 1B with 2B and 2A with 3A states, in agreement with SAC-CI calculations on the excited states of 1-7 and conformers of 10.

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Source
http://dx.doi.org/10.1002/chem.201403495DOI Listing

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