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Protonation induced ultrafast torsional dynamics in 9-anthrylbenzimidazole : A pH activated molecular rotor

Abstract

We report photophysical properties and excited state dynamics of 9- anthrylbenzimidazole (ANBI) which exhibits protonation induced molecular rotor property. In contrast to highly emissive behavior of neutral ANBI, protonation of benzimidazole group of ANBI induces efficient nonradiative deactivation by ultrafast torsional motion around the bond connecting anthracene and benzimidazole units, as revealed by ultrafast transient absorption and fluorescence spectroscopy. Contrary to viscosity independent fluorescence of neutral dye, protonated ANBI is shown to display linear variation of emission yield and lifetime with solvent viscosity. Protonation induced molecular rotor property in the studied system is shown to be driven by enhanced charge transfer and is corroborated by quantum chemical calculations. Potential application as microviscosity sensor of acidic region in a heterogeneous environment by this proton activated molecular rotor property of ANBI is discussed.

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Publication details

The article was received on 15 Dec 2017, accepted on 01 Feb 2018 and first published on 02 Feb 2018


Article type: Paper
DOI: 10.1039/C7CP08408K
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
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    Protonation induced ultrafast torsional dynamics in 9-anthrylbenzimidazole : A pH activated molecular rotor

    R. Ghosh, A. Nandi, A. Kushwaha and D. Das, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C7CP08408K

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