Scientific article
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Direct Visualization of Excited-State Symmetry Breaking Using Ultrafast Time-Resolved Infrared Spectroscopy

Published inJournal of the American Chemical Society, vol. 138, no. 13, p. 4643-4649
Publication date2016

Most symmetric quadrupolar molecules designed for two-photon absorption behave as dipolar molecules in the S1 electronic excited state. This is usually explained by a breakup of the symmetry in the excited state. However, the origin of this process and its dynamics are still not fully understood. Here, excited-state symmetry breaking in a quadrupolar molecule with a D-π-A-π-D motif, where D and A are electron donating and accepting units, is observed in real time using ultrafast transient infrared absorption spectroscopy. The nature of the relaxed S1 state was found to strongly depend on the solvent polarity: (1) in nonpolar solvents, it is symmetric and quadrupolar; (2) in weakly polar media, the quadrupolar state observed directly after excitation transforms to a symmetry broken S1 state with one arm bearing more excitation than the other; and (3) in highly polar solvents, the excited state evolves further to a purely dipolar S1 state with the excitation localized entirely on one arm. The time scales associated with the transitions between these states coincide with those of solvation dynamics, indicating that symmetry breaking is governed by solvent fluctuations.

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Citation (ISO format)
DEREKA, Bogdan et al. Direct Visualization of Excited-State Symmetry Breaking Using Ultrafast Time-Resolved Infrared Spectroscopy. In: Journal of the American Chemical Society, 2016, vol. 138, n° 13, p. 4643–4649. doi: 10.1021/jacs.6b01362
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ISSN of the journal0002-7863

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