Kim Juno, Teo Hao Ting, Hong Yongseok, Liau Yuan Cheng, Yim Daniel, Han Yi, Oh Juwon, Kim Hyungjun, Chi Chunyan, Kim Dongho
Department of Chemistry, Spectroscopy Laboratory for Functional π-Electronic Systems, Yonsei University, Seoul 03722, Korea.
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
J Am Chem Soc. 2023 Sep 13;145(36):19812-19823. doi: 10.1021/jacs.3c05660. Epub 2023 Sep 1.
Singlet exciton fission in organic chromophores has received much attention during the past decade. Inspired by numerous spectroscopic studies in the solid state, there have been vigorous efforts to study singlet exciton fission dynamics in covalently bonded oligomers, which aims to investigate underlying mechanisms of this intriguing process in simplified model systems. In terms of through-space orbital interactions, however, most of covalently bonded pentacene oligomers studied so far fall into weakly interacting systems since they manifest chain-like structures based on various (non)conjugated linkers. Therefore, it remains as a compelling question to answer how through-space interactions in the solid state intervene this photophysical process since it is hypersensitive to displacements and orientations between neighboring chromophores. Herein, as one of experimental studies to answer this question, we introduced a tight-packing dendritic structure whose mesityl-pentacene constituents are coupled via moderate through-space orbital interactions. Based on the comparison with a suitably controlled dendritic structure, which is in a weak coupling regime, important mechanistic viewpoints are tackled such as configurational mixings between singlet, charge-transfer, and triplet pair states and the role of chromophore multiplication. We underscore that our through-space-coupled dendritic oligomer in a quasi-intermediate coupling regime provides a hint on the interplay of multiconfigurational excited-states, which might have drawn complexity in singlet exciton fission kinetics throughout numerous solid-state morphologies.
在过去十年中，有机发色团中的单线态激子裂变受到了广泛关注。受固态中大量光谱研究的启发，人们积极努力研究共价键合低聚物中的单线态激子裂变动力学，旨在研究简化模型系统中这一有趣过程的潜在机制。然而，就空间轨道相互作用而言，目前研究的大多数共价键合并五苯低聚物都属于弱相互作用体系，因为它们基于各种（非）共轭连接体呈现出链状结构。因此，由于固态中的空间相互作用对相邻发色团之间的位移和取向极为敏感，它如何干预这一光物理过程仍是一个亟待回答的重要问题。在此，作为回答这一问题的实验研究之一，我们引入了一种紧密堆积的树枝状结构，其均三甲苯基-并五苯成分通过适度的空间轨道相互作用耦合。通过与处于弱耦合状态的适当控制的树枝状结构进行比较，探讨了重要的机理观点，如单线态、电荷转移和三重态对态之间的构型混合以及发色团倍增的作用。我们强调，处于准中间耦合状态的空间耦合树枝状低聚物为多构型激发态的相互作用提供了线索，这可能在众多固态形态的单线态激子裂变动力学中引入了复杂性。
