Critical role of intermediate electronic states for spin-flip processes in charge-transfer-type organic molecules with multiple donors and acceptors
Critical role of intermediate electronic states for spin-flip processes in charge-transfer-type organic molecules with multiple donors and acceptors
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DOI：
10.1038/s41563-019-0465-6
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发表时间：
2019-10-01
期刊：
影响因子：
41.2
通讯作者：
Adachi, Chihaya
中科院分区：
文献类型：
--
作者：
Noda, Hiroki;Chen, Xian-Kai;Adachi, Chihaya
纯有机分子系统中的自旋翻转通常被描述为禁止的过程。然而，它通常被观察到并用于在各种基于有机材料的应用中收获三线态激子。尽管最低单重激发态和最低三重激发态之间的自旋翻转的初始和最终电子态是不言而喻的，但自旋翻转发生的确切过程和中间态的作用还远未得到全面确定。在这里，通过溶液中的实验光物理研究与第一原理量子力学计算相结合，我们证明了多供体-受体电荷转移型有机分子系统中的有效自旋翻转涉及与系统的部分分子结构相对应的中间三重激发态的关键作用。我们提出的机制统一了对各种电荷转移型分子系统中的系间交叉机制的理解，为更好地控制自旋翻转速率开辟了道路。
Spin-flip in purely organic molecular systems is often described as a forbidden process; however, it is commonly observed and utilized to harvest triplet excitons in a wide variety of organic material-based applications. Although the initial and final electronic states of spin-flip between the lowest singlet and lowest triplet excited state are self-evident, the exact process and the role of intermediate states through which spin-flip occurs are still far from being comprehensively determined. Here, via experimental photo-physical investigations in solution combined with first-principles quantum-mechanical calculations, we show that efficient spin-flip in multiple donor-acceptor charge-transfer-type organic molecular systems involves the critical role of an intermediate triplet excited state that corresponds to a partial molecular structure of the system. Our proposed mechanism unifies the understanding of the intersystem crossing mechanism in a wide variety of charge-transfer-type molecular systems, opening the way to greater control over spin-flip rates.