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Tracking Structural Evolution during Symmetry‐Breaking Charge Separation in Quadrupolar Perylene Bisimide with Time‐Resolved Impulsive Stimulated Raman Spectroscopy
Author(s) -
Kim Woojae,
Kim Taeyeon,
Kang Seongsoo,
Hong Yongseok,
Würthner Frank,
Kim Dongho
Publication year - 2020
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202002733
Subject(s) - raman spectroscopy , perylene , spectroscopy , chemistry , chemical physics , population , symmetry breaking , molecular physics , photochemistry , molecule , physics , optics , organic chemistry , quantum mechanics , demography , sociology
Elucidating structural roles in photoinduced charge transfer is indispensable, as nuclear rearrangements are simultaneously usually involved in the dynamics. However, it is hard to evaluate whether the structural changes occur or not by using conventional time‐resolved electronic spectroscopy. Here, time‐resolved impulsive stimulated Raman spectroscopy is applied to record the evolution of vibrational snapshots during charge‐separation dynamics of donor–acceptor–donor‐type quadrupolar perylene bisimide in real time. Drastic frequency shifts were observed for several Raman bands with their population kinetics, thus symmetry‐breaking charge separation accompanies significant structural changes, as supported by (TD)‐DFT calculations. A comparison between time‐resolved Raman spectra of the neutral S 1 state and the radical anion species shows that the spectral signatures, especially in high‐frequency regions, provide important clues to bond length alternation patterns in the PBI core.