highlight 2 2024

We are investigating excited-state symmetry breaking (ESSB) in quadrupolar dyes dissolved in binary mixtures of non-polar and polar solvents using time-resolved IR spectroscopy. Upon ESSB, the electronic excitation, initially distributed evenly over the whole molecule, localises, at least partially on one donor-acceptor (DA) branch. So far, this process was only reported in polar media. The figure on the left illustrates how the IR spectrum of the equilibrated excited DAD dye, measured in the -C≡C- stretching region in solvents of increasing polarity, changes depending on the extent of ESSB. The figure on the right reveals that, in a solvent mixture, the degree of ESSB depends on the excitation wavelength. This is due to the inhomogeneity of the solvent composition around the dye. Those dyes surrounded by more polar solvent absorb at longer wavelength and undergo both faster and stronger ESSB.

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Eric Vauthey

Physical Chemistry Department - Sciences II - University of Geneva
30, Quai Ernest Ansermet - CH-1211 Geneva 4 (Switzerland)

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