Aster Alexander, Bornhof Anna-Bea, Sakai Naomi, Matile Stefan, Vauthey Eric
Department of Physical Chemistry, University of Geneva, CH-1211 Geneva, Switzerland.
Department of Organic Chemistry, University of Geneva, CH-1211 Geneva, Switzerland.
J Phys Chem Lett. 2021 Jan 28;12(3):1052-1057. doi: 10.1021/acs.jpclett.0c03641. Epub 2021 Jan 20.
The absorption band shape of chromophores in liquid solution at room temperature is usually dominated by pure electronic dephasing dynamics, which occurs on the sub-100 fs time scale. Herein, we report on a series of dyads consisting of a naphthalenediimide (NDI) electron acceptor with one or two phenyl-based donors for which photoinduced intramolecular electron transfer is fast enough to be competitive with pure electronic dephasing. As a consequence, the absorption band of the π-π* transition of these dyads is broader than that of the NDI alone to an extent that scales with the electron transfer rate. Additionally, this reaction is so fast that it leads to the impulsive excitation of a low-frequency vibrational mode of the charge-separated product. Quantum-chemical calculations suggest that this vibration involves the C-N donor-acceptor bond, which shortens considerably upon electron transfer.
室温下，发色团在液体溶液中的吸收带形状通常由纯电子退相动力学主导，这种动力学发生在亚100飞秒的时间尺度上。在此，我们报道了一系列由萘二亚胺（NDI）电子受体与一个或两个苯基供体组成的二元体系，其中光诱导分子内电子转移速度足够快，足以与纯电子退相竞争。因此，这些二元体系的π-π*跃迁吸收带比单独的NDI吸收带更宽，其拓宽程度与电子转移速率成正比。此外，该反应速度极快，以至于导致电荷分离产物的低频振动模式发生脉冲激发。量子化学计算表明，这种振动涉及C-N供体-受体键，该键在电子转移时会大幅缩短。
