School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India.
Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States.
J Phys Chem Lett. 2022 Jul 28;13(29):6800-6805. doi: 10.1021/acs.jpclett.2c02000. Epub 2022 Jul 20.
Singlet fission (SF) is the process of formation of multiple excitons (triplet) from a locally excited singlet state. The mechanism of SF in polyacenes has been shown to proceed via a charge transfer intermediate state. However, carotenoids are not understood in the context of SF. This is possibly due to the complicated multireference nature of the low-lying excited states of carotenoids and the presence of a dark 2A state below the optically bright B state. In this work, we show that the dark A state in polyenes and/or carotenoids, along with the charge transfer states, plays a pivotal role in the SF process. We notice that the relative importance of these states varies with a change in geometry and the overall presence of multiple pathways is crucial to the success of the SF process in carotenoid aggregates and disordered geometries.
单线态裂变（SF）是指由局部激发的单线态形成多个激子（三重态）的过程。多环芳烃中 SF 的机制已被证明是通过电荷转移中间态进行的。然而，类胡萝卜素在 SF 方面的情况尚不清楚。这可能是由于类胡萝卜素的低能激发态具有复杂的多参考性质，以及在光学上明亮的 B 态之下存在暗 2A 态。在这项工作中，我们表明多烯和/或类胡萝卜素中的暗 A 态以及电荷转移态在 SF 过程中起着关键作用。我们注意到，这些状态的相对重要性随着几何形状的变化而变化，并且存在多种途径对于类胡萝卜素聚集体和无序几何形状中的 SF 过程的成功至关重要。
