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cistrans Isomerisation of Substituted Aromatic Imines: A Comparative Experimental and Theoretical Study

Authors

  • Ying Luo,

    1. Freie Universität Berlin, Institut für Chemie und Biochemie, Takustraße 3, D-14195 Berlin (Germany), Fax: (+49) 30-838-53357
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  • Manuel Utecht,

    1. Universität Potsdam, Institut für Chemie, Karl-Liebknecht-Straße 24–25, D-14476 Potsdam-Golm (Germany), Fax: (+49) 331-977-5058
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  • Dr. Jadranka Dokić,

    1. Freie Universität Berlin, Institut für Chemie und Biochemie, Takustraße 3, D-14195 Berlin (Germany), Fax: (+49) 30-838-53357
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  • Dr. Sergey Korchak,

    1. Freie Universität Berlin, Institut für Experimentalphysik, Arnimallee 14, D-14195 Berlin (Germany)
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  • Prof. Dr. Hans-Martin Vieth,

    1. Freie Universität Berlin, Institut für Experimentalphysik, Arnimallee 14, D-14195 Berlin (Germany)
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  • Prof. Dr. Rainer Haag,

    Corresponding author
    1. Freie Universität Berlin, Institut für Chemie und Biochemie, Takustraße 3, D-14195 Berlin (Germany), Fax: (+49) 30-838-53357
    • Freie Universität Berlin, Institut für Chemie und Biochemie, Takustraße 3, D-14195 Berlin (Germany), Fax: (+49) 30-838-53357
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  • Prof. Dr. Peter Saalfrank

    Corresponding author
    1. Universität Potsdam, Institut für Chemie, Karl-Liebknecht-Straße 24–25, D-14476 Potsdam-Golm (Germany), Fax: (+49) 331-977-5058
    • Universität Potsdam, Institut für Chemie, Karl-Liebknecht-Straße 24–25, D-14476 Potsdam-Golm (Germany), Fax: (+49) 331-977-5058
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Abstract

The cistrans isomerisation of N-benzylideneaniline (NBA) and derivatives containing a central C[DOUBLE BOND]N bond has been investigated experimentally and theoretically. Eight different NBA molecules in three different solvents were irradiated to enforce a photochemical transequation imagecis isomerisation and the kinetics of the thermal backreaction cisequation imagetrans were determined by NMR spectroscopy measurements in the temperature range between 193 and 288 K. Theoretical calculations using density functional theory and Eyring transition-state theory were carried out for 12 different NBA species in the gas phase and three different solvents to compute thermal isomerisation rates of the thermal back reaction. While the computed absolute rates are too large, they reveal and explain experimental trends. Time-dependent density functional theory provides optical spectra for vertical transitions and excitation energy differences between trans and cis forms. Together with isomerisation rates, the latter can be used to identify “optimal switches” with good photochromicity and reasonable thermal stability.

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