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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Solvent-Controlled Branching of Localized versus Delocalized Singlet Exciton States and Equilibration with Charge Transfer in a Structurally Well-Defined Tetracene Dimer
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Solvent-Controlled Branching of Localized versus Delocalized Singlet Exciton States and Equilibration with Charge Transfer in a Structurally Well-Defined Tetracene Dimer

机译：局部化与截匙偏移激子状态的溶剂控制分支，并在结构明确定义的四环二聚体中与电荷转移的平衡

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摘要

A detailed photophysical picture is elaborated for a structurally well-defined and symmetrical bis-tetracene dimer in solution. The molecule was designed for interrogation of the initial photophysical steps (S-1 - (TT)-T-1) in intramolecular singlet fission (SF). (Triisopropylsilyl)acetylene substituents on the dimer TIPS-BT1 as well as a monomer model TIPS-Tc enable a comparison of photophysical properties, including transient absorption dynamics, as solvent polarity is varied. In nonpolar toluene solutions, TIPS-BT1 decays via radiative and nonradiative pathways to the ground state with no evidence for dynamics related to the initial stages of SF. This contrasts with the behavior of the previously reported unsubstituted dimer BT1 and is likely a consequence of energetic perturbations to the singlet excited-state manifold of TIPS-BT1 by the (trialkylsilyl)acetylene substituents. In polar benzonitrile, two key findings emerge. First, photoexcited TIPS-BTI shows a bifurcation into both arm-localized (S1-loc) and dimer-delocalized (S1-dim) singlet exciton states. The S1-loc decays to the ground state, and weak temperature dependence of its emissive signatures suggests that once it is formed, it is isolated from S1-dim Emissive signatures of the S1-dim state, on the other hand, are strongly temperature-dependent, and transient absorption dynamics show that S1-dim equilibrates with an intramolecular charge-transfer state in 50 ps at room temperature. This equilibrium decays to the ground state with little evidence for formation of long-lived triplets nor (TT)-T-1. These detailed studies spectrally characterize many of the key states in intramolecular SF in this class of dimers but highlight the need to tune electronic coupling and energetics for the S-1 - (TT)-T-1 photoreaction.
机译：在溶液中阐述了在结构良好定义的和对称的双链二甲烯的结构上进行了详细的光物理图像。该分子被设计用于在分子内单次裂变（SF）中的初始光学步骤（S-1 - ＆GT;（TT）-1）的询问。 （三异丙基甲硅烷基）二聚体提示-BT1上的乙炔取代基以及单体模型提示-TC能够比较光学性质，包括瞬态吸收动力学，因为溶剂极性变化。在非极性甲苯溶液中，TIPS-BT1通过辐射和非接近通向的地面状态衰减，没有证据与SF的初始阶段有关的动态。这与先前报告的未取代二聚体BT1的行为形成对比，并且可能对（三烷基甲硅烷基）乙炔取代基具有能量扰动对TIPS-BT1的单线兴奋状态歧管的结果。在极性苯氮化物中，出现了两个主要结果。首先，采用光透明的提示-BTI显示进入ARM定位（S1-LOC）和二聚体分层（S1-DIM）单态激素状态的分叉分叉。将S1-LOC衰减衰变到地状态，其发射签名的弱温度依赖性表明，一旦形成，就从S1-DIM状态的S1-DIM发射签名中分离，另一方面是强烈的温度 - 依赖性和瞬态吸收动力学表明，在室温下，用分子内电荷转移状态下的S1-昏暗平衡。这种平衡衰减到地面状态，几乎没有证据形成长寿三胞胎，也不是（TT）-T-1。这些详细的研究在这类二聚体中分解在分子内SF中的许多关键状态，但突出了S-1 - ＆GT的电耦合电子耦合和能量学的需要; （tt）-t-1光反应。

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