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Updated: May 5, 2026

Ultrafast Time-resolved Near-IR Stimulated Raman Measurements of Functional π-conjugate Systems
Published on: February 10, 2020
Excited-state dynamics of thiophene substituted betaine pyridinium compounds
Stéphane Aloïse1, Zuzanna Pawlowska, Olivier Poizat
1Laboratoire de Spectrochimie Infrarouge et Raman CNRS UMR 8516, Université de Lille1 Sciences et Technologies, Université Lille Nord de France, Bat C5, 59655 Villeneuve d'Ascq Cedex, France. stephane.aloise@univ-lille1.fr.
Abstract:
This work deals with the photophysics of novel pyridinium betaine based on 2-pyridin-1-yl-1H-benzimidazole (SBPa) substituted symmetrically by mono- (Th2SBPa) and bi-thiophene fragments (Th4SBPa). The study is based on a combination of steady-state, femtosecond transient absorption spectroscopic measurements supported by PCM-(TD)DFT calculations. It is found that the two step ICT process (S0 → S2 excitation followed by S2(CT) → S1(CT) internal conversion) occurring for the parent molecule remains unaffected for Th2SBPa while the situation is less clear for Th4SBPa. Actually, for both molecules, a new decay route involving the π-electron system localized in thiophenic groups is responsible for the production of triplet states. Involvement of this new route in the parallel production of S1(CT) is strongly suspected.
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