Two-Dimensional Electronic Spectroscopy Reveals Excitation Energy-Dependent State Mixing during Singlet Fission in a Terrylenediimide Dimer
Two-Dimensional Electronic Spectroscopy Reveals Excitation Energy-Dependent State Mixing during Singlet Fission in a Terrylenediimide Dimer
复制标题
DOI：
10.1021/jacs.8b08627
复制
发表时间：
2018-12-26
影响因子：
15
通讯作者：
Wasielewski, Michael R.
中科院分区：
文献类型：
--
作者：
Mandal, Aritra;Chen, Michelle;Wasielewski, Michael R.
单重态裂变（SF）是一种自旋允许的过程，其中两个或更多个发色团的组装体内的单重态激子（1）（S1 S 0）经由多激子相关三重态对状态（1）（T1 T1）自发地下转换成两个三重态激子。为了阐明参与的电荷转移（CT）状态和电子振动耦合在SF中，我们进行了二维电子光谱（2DES）上的共价连接，滑移堆叠Terrylene-3，4：11，12-双（二甲酰亚胺）（TDI）二聚体的稀溶液。该二聚体在非极性1，4-二氧六环中进行有效的SF，在极性二氯甲烷中进行电荷分离。1，4-二氧六环中的各种2DES光谱特征显示出不同的泵浦波长依赖性，支持存在具有随时间演变的变量（1）（S1 S 0）、（1）（T1 T1）和CT贡献的混合态。在二氯甲烷中的2DES光谱的分析揭示了在电荷分离期间存在主要具有（1）（T1 T1）特征的状态。因此，（1）（T1 T1）多激子态在TDI二聚体的电子物理中起着重要的作用，与溶剂极性无关。
Singlet fission (SF) is a spin-allowed process in which a singlet exciton, (1)(S1S0), within an assembly of two or more chromophores spontaneously down-converts into two triplet excitons via a multiexciton correlated triplet pair state, (1)(T1T1). To elucidate the involvement of charge transfer (CT) states and vibronic coupling in SF, we performed 2D electronic spectroscopy (2DES) on dilute solutions of a covalently linked, slip-stacked terrylene-3,4:11,12-bis-(dicarboximide) (TDI) dimer. This dimer undergoes efficient SF in nonpolar 1,4-dioxane and symmetry-breaking charge separation in polar dichloromethane. The various 2DES spectral features in 1,4-dioxane show different pump wave-length dependencies, supporting the presence of mixed states with variable (1)(S1S0), (1)(T1T1) and CT contributions that evolve with time. Analysis of the 2DES spectra in dichloromethane reveals the presence of a state having largely (1)(T1T1) character during charge separation. Therefore, the (1)(T1T1) multiexciton state plays an important role in the photophysics of this TDI dimer irrespective of solvent polarity.