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Photophysical Properties and Conformational Effects on the Circular Dichroism of an Azobenzene–Cyclodextrin [1]Rotaxane and Its Molecular Components

Authors

  • Dr. Simone Di Motta,

    1. Dipartimento di Chimica “G. Ciamician”, Università di Bologna, Via F. Selmi, 2, 40126 Bologna (Italy)
    2. Italian Interuniversity Consortium on Materials Science & Technology (INSTM), Unit of Research (UdR), Bologna (Italy)
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  • Dr. Tommaso Avellini,

    1. Dipartimento di Chimica “G. Ciamician”, Università di Bologna, Via F. Selmi, 2, 40126 Bologna (Italy)
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  • Dr. Serena Silvi,

    1. Dipartimento di Chimica “G. Ciamician”, Università di Bologna, Via F. Selmi, 2, 40126 Bologna (Italy)
    2. Interuniversity Center for the Chemical Conversion of Solar Energy (SolarChem), Bologna Unit via Selmi 2, 40126 Bologna (Italy)
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  • Prof. Margherita Venturi,

    1. Dipartimento di Chimica “G. Ciamician”, Università di Bologna, Via F. Selmi, 2, 40126 Bologna (Italy)
    2. Interuniversity Center for the Chemical Conversion of Solar Energy (SolarChem), Bologna Unit via Selmi 2, 40126 Bologna (Italy)
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  • Dr. Xiang Ma,

    1. Labs for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237 (P.R. China)
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  • Prof. He Tian,

    Corresponding author
    1. Labs for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237 (P.R. China)
    • Labs for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237 (P.R. China)
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  • Prof. Alberto Credi,

    Corresponding author
    1. Dipartimento di Chimica “G. Ciamician”, Università di Bologna, Via F. Selmi, 2, 40126 Bologna (Italy)
    2. Interuniversity Center for the Chemical Conversion of Solar Energy (SolarChem), Bologna Unit via Selmi 2, 40126 Bologna (Italy)
    • Dipartimento di Chimica “G. Ciamician”, Università di Bologna, Via F. Selmi, 2, 40126 Bologna (Italy)
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  • Prof. Fabrizia Negri

    Corresponding author
    1. Dipartimento di Chimica “G. Ciamician”, Università di Bologna, Via F. Selmi, 2, 40126 Bologna (Italy)
    2. Italian Interuniversity Consortium on Materials Science & Technology (INSTM), Unit of Research (UdR), Bologna (Italy)
    • Dipartimento di Chimica “G. Ciamician”, Università di Bologna, Via F. Selmi, 2, 40126 Bologna (Italy)
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Abstract

The photophysical properties of a multicomponent [1]rotaxane bearing a β-cyclodextrin ring covalently connected to an axle comprising an azobenzene photoisomerisable moiety and a naphthalimide-type fluorescent stopper are investigated by a combined experimental and computational study. The absorption and fluorescence spectra, and particularly the induced circular dichroism (ICD) signal, are determined. The latter shows a sign relation that cannot be rationalised in terms of the simple general rules commonly employed to analyse the ICD spectra of achiral guests encircled by chiral hosts. To assist the interpretation of experimental results, DFT and time-dependent (TD) DFT calculations are performed to explore the availability of low-energy conformations and to model their spectroscopic response. Molecular dynamics simulations performed in water show the interconversion of a number of conformers, the contribution of which to the ICD signal is in agreement with the observation.

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