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Transient Glass Formation around a Quadrupolar Photoexcited Dye in a Strongly H-Bonding Liquid Observed by Transient 2D-IR Spectroscopy


Dereka, Bogdan; Helbing, Jan; Vauthey, Eric (2018). Transient Glass Formation around a Quadrupolar Photoexcited Dye in a Strongly H-Bonding Liquid Observed by Transient 2D-IR Spectroscopy. Angewandte Chemie Internationale Edition:Epub ahead of print.

Abstract

Intermolecular H-bonding dynamics around a photoexcited quadrupolar dye is directly observed using transient 2D-IR spectroscopy. Upon solvent-induced symmetry breaking, the H-bond accepting abilities of the two nitrile end-groups change drastically, and in extreme protic (‘superprotic’) solvents, a tight Hbond complex forms at one end. The time evolution of the 2D C≡N lineshape in methanol points to rapid, 2-3 ps, spectral diffusion due to fluctuations of the H-bonding network. Similar behaviour is observed in a superprotic solvent shortly after photoexcitation of the dye. However, at later time, the completely inhomogeneous band does not exhibit spectral diffusion for at least 5 ps, pointing to a glass-like environment around one side of the dye. About half of the excited dyes show this behaviour attributed to the tight H-bond complex, whereas the others are loosely bound. A weak cross peak indicates partial exchange between these excited state subpopulations.

Abstract

Intermolecular H-bonding dynamics around a photoexcited quadrupolar dye is directly observed using transient 2D-IR spectroscopy. Upon solvent-induced symmetry breaking, the H-bond accepting abilities of the two nitrile end-groups change drastically, and in extreme protic (‘superprotic’) solvents, a tight Hbond complex forms at one end. The time evolution of the 2D C≡N lineshape in methanol points to rapid, 2-3 ps, spectral diffusion due to fluctuations of the H-bonding network. Similar behaviour is observed in a superprotic solvent shortly after photoexcitation of the dye. However, at later time, the completely inhomogeneous band does not exhibit spectral diffusion for at least 5 ps, pointing to a glass-like environment around one side of the dye. About half of the excited dyes show this behaviour attributed to the tight H-bond complex, whereas the others are loosely bound. A weak cross peak indicates partial exchange between these excited state subpopulations.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:English
Date:2 November 2018
Deposited On:21 Nov 2018 16:12
Last Modified:21 Nov 2018 16:14
Publisher:Wiley-VCH Verlag
ISSN:1433-7851
OA Status:Closed
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1002/anie.201808324

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