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Issue 36, 2017
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Probing the solvation structure and dynamics in ionic liquids by time-resolved infrared spectroscopy of 4-(dimethylamino)benzonitrile

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Abstract

In this work we demonstrate the use of the push–pull model system 4-(dimethylamino)benzonitrile (DMABN) as a convenient molecular probe to investigate the local solvation structure and dynamics by means of time-resolved infrared spectroscopy (TRIR). The photochemical features associated with this system provide several advantages due to the high charge separation between the ground and charge transfer states involving the characteristic nitrile bond, and an excited state lifetime that is long enough to observe the slow solvation dynamics in organic solvents and ionic liquids. The conversion from a locally excited state to an intramolecular charge transfer state (LE–ICT) in ionic liquids shows similar kinetic lifetimes in comparison to organic solvents. This similarity confirms that such conversion depends solely on the intramolecular reorganization of DMABN in the excited state, and not by the dynamics of solvation. In contrast, the relative shift of the ν(CN) vibration during the relaxation of the ICT state reveals two distinct lifetimes that are sensitive to the solvent environment. This study reveals a fast time component which is attributed to the dipolar relaxation of the solvent and a slower time component related to the rotation of the dimethylamino group of DMABN.

Graphical abstract: Probing the solvation structure and dynamics in ionic liquids by time-resolved infrared spectroscopy of 4-(dimethylamino)benzonitrile

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Publication details

The article was received on 23 Jul 2017, accepted on 01 Sep 2017 and first published on 04 Sep 2017


Article type: Paper
DOI: 10.1039/C7CP04961G
Citation: Phys. Chem. Chem. Phys., 2017,19, 25151-25157
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    Probing the solvation structure and dynamics in ionic liquids by time-resolved infrared spectroscopy of 4-(dimethylamino)benzonitrile

    R. A. Ando, S. E. Brown-Xu, L. N. Q. Nguyen and T. L. Gustafson, Phys. Chem. Chem. Phys., 2017, 19, 25151
    DOI: 10.1039/C7CP04961G

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