Dereka Bogdan, Balanikas Evangelos, Rosspeintner Arnulf, Li Zhiquan, Liska Robert, Vauthey Eric
Department of Chemistry, University of Zurich, CH-8057 Zurich, Switzerland.
Department of Physical Chemistry, University of Geneva, CH-1211 Geneva, Switzerland.
J Phys Chem Lett. 2024 Aug 15;15(32):8280-8286. doi: 10.1021/acs.jpclett.4c01694. Epub 2024 Aug 6.
Electronic excitation in quadrupolar conjugated molecules rapidly localizes on a single electron donor-acceptor (DA) branch when in polar environments. The loss of center of inversion upon this excited-state symmetry breaking (ES-SB) can be monitored by exploiting the relaxation of the exclusion rules for IR and Raman vibrational transitions. Here, we compare ES-SB in a right-angled () and a centrosymmetric () DAD dyes using time-resolved IR spectroscopy. We show that the localization of the excitation can also be identified with the bent molecule . We find that contrary to dye , subpopulations with localized and delocalized excitation coexist for in weak to medium polar solvents. This difference originates from the torsional disorder present in the excited state of but not of . Additionally, irreversible localization in a bent molecule is shown to require higher solvent polarity than in a centrosymmetric one.
在极性环境中，四极共轭分子中的电子激发会迅速定域在单个电子供体-受体（DA）支链上。通过利用红外和拉曼振动跃迁的禁戒规则的弛豫，可以监测这种激发态对称性破缺（ES-SB）时反演中心的丧失。在此，我们使用时间分辨红外光谱比较了直角（）和中心对称（）DAD染料中的ES-SB。我们表明，激发的定域也可以用弯曲分子来识别。我们发现，与染料不同，在弱到中等极性溶剂中，对于，具有定域和离域激发的亚群共存。这种差异源于中存在但中不存在的扭转无序。此外，弯曲分子中的不可逆定域显示出比中心对称分子需要更高的溶剂极性。
