Electronic Transitions in Conformationally Controlled Peralkylated Hexasilanes |
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| Authors: | Yuki Kanazawa Prof Hayato Tsuji Prof Masahiro Ehara Prof Ryoichi Fukuda Dr Deborah L Casher Prof Kohei Tamao Prof Hiroshi Nakatsuji Prof Josef Michl |
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| Institution: | 1. SOKENDAI, The Graduate University for Advanced Studies, Nishigonaka, Myodaiji, Okazaki, Japan;2. Institute for Molecular Science and Research Center for Computational Science, Nishigonaka, Myodaiji, Okazaki, Japan;3. International Research Center for Elements Science (IRCELS), Institute for Chemical Research, Kyoto University, Uji, Kyoto, Japan;4. Department of Chemistry, Faculty of Science, Kanagawa University, Hiratsuka, Kanagawa, Japan;5. Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Kyoto, Japan;6. Department of Chemistry and Biochemistry, University of Colorado at Boulder, Boulder, Colorado, USA;7. RIKEN, Saitama, Japan;8. Quantum Chemistry Research Institute, Kyoto, Japan;9. Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic |
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| Abstract: | The photophysical properties of oligosilanes show unique conformational dependence due to σ‐electron delocalization. The excited states of the SAS, AAS, and AEA conformations of peralkylated n‐hexasilanes, in which the SiSiSiSi dihedral angles are controlled into a syn (S), anti (A), or eclipsed (E) conformation, were investigated by using UV absorption, magnetic circular dichroism (MCD), and linear dichroism spectroscopy. Simultaneous Gaussian fitting of all three spectra identified a minimal set of transitions and the wavenumbers, oscillator strengths, and MCD B terms in all three compounds. The results compare well with those obtained by using the symmetry‐adapted‐cluster configuration interaction method and almost as well with those obtained by time‐dependent density functional theory with the PBE0 functional. The conformational dependence of the transition energies and other properties of free‐chain permethylated n‐hexasilane, n‐Si6Me14, was also examined as a function of dihedral angles, and the striking effects found were attributed to avoided crossings between configurations of σσ* and σπ* character. |
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| Keywords: | configuration interaction density functional calculations magnetic circular dichroism oligosilanes UV/Vis spectroscopy |
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