highlight 6 2019

In polar solvents, centrosymmetric acceptor-donor-acceptor (ADA) or DAD type molecules undergo excited-state symmetry breaking (ES-SB) after electronic excitation. Using time-resolved IR (TRIR) spectroscopy, we could show that this process is triggered by the fluctuations of the solvent field and occurs on the timescale of solvent motion. Until now, we have mostly investigated ES-SB in linear quadrupolar molecules. The above figure illustrate TRIR data obtained in a polar solvent with a A(A-π)D(π-A)A type multibranched pyrrolopyrrole derivative synthesised in the group of D. Gryko in Warsaw. The spectral evolution points to a complex dynamics following optical excitation. Several ES-SB pathways can be envisaged, but the presence of the C≡C bleach during the whole excited-state lifetime suggests that excitation is localised at least partially on one of the A-π branches.

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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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