Inter/Intrachain Interactions Behind the Formation of Charge Transfer States in Polyspirobifluorene: A Case Study for Complex Excited-State Dynamics in Different Polarity Index Solvents
Inter/Intrachain Interactions Behind the Formation of Charge Transfer States in Polyspirobifluorene: A Case Study for Complex Excited-State Dynamics in Different Polarity Index Solvents
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聚螺二芴中电荷转移态形成背后的链间/链内相互作用：不同极性指数溶剂中复杂激发态动力学的案例研究
DOI：
10.1021/jp512467g
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
Aydemir M
中科院分区：
文献类型：
--
作者：
Aydemir M
在这项工作中，我们证明了复杂的激发态性质的共轭聚合物，聚螺二芴（PSBF），使用稳态和时间分辨光谱技术来了解激发电荷转移态（CT）的形成和它们的贡献的起源总的光致发光（PL）。测量进行了比较，在两种溶剂中具有不同的极性，例如，甲基环己烷（MCH）和2-甲基四氢呋喃（2-MeTHF），这使我们能够揭示溶剂的质量和温度依赖的CT状态的形成所产生的“间/链内”的相互作用现象。链间/链内相互作用的解释通过空间构象变化的聚合物链的配置，如卷曲和崩溃的骨干伴随侧链重组。结果表明，室温下的PL发射是一种混合态结构，其中包含1（π，π*）激发态的贡献，沿着CT态的贡献，其光谱是由两种发射物质的混合物产生的.然而，随着温度的降低，145 K（凝固点之前）在2-MeTHF中，这两种发射物种变得分离，与CT状态的发射显示出随温度降低而红移。在145 K，我们观察到一个非结构化的全新的发射带的形成，它相对于1（π，π*）激发态有强烈的红移，并呈现经典的高斯线形。这种发射归因于“链间/链内”CT状态的形成。在冷冻溶液（1090 K）的情况下，光谱显着蓝移，并失去了所有的贡献，从“间/链内”的物种，和发射，然后完全从纯的“链内”CT激子状态。聚合物的行为强烈依赖于溶剂质量和温度对激发态几何松弛的影响，通过局部溶剂-溶质相互作用稳定CT状态，由于新电荷分布的溶剂化，并且还通过操纵能量势垒改变过渡态。
In this work, we demonstrate the complex excited-state nature of the conjugated polymer, polyspirobifluorene (PSBF), using steady-state and time-resolved spectroscopy techniques to understand the origin of excited charge transfer state (CT) formation and their contribution to the total photoluminescence (PL). The measurements were compared in two solvents with different polarity, for example, methyl cyclohexane (MCH) and 2-methyltetrahydrofuran (2-MeTHF), which allow us to reveal solvent quality and temperature dependent CT state formation arising from “inter/intrachain” interaction phenomena. The inter/intrachain interactions are explained by means of spatial conformational changes of the polymer chain configuration, such as coiling and collapse of the backbone with concomitant side chain reorganization. It has been found that the PL emission at room temperature (RT) demonstrates a mixed state configuration containing contributions from1(π, π*) excited states along with the CT states contribution, with the spectra arising from a mixture of the two emissive species. However, with decreasing temperatures to ca. 145 K (prior to the freezing point) in 2-MeTHF, the two emissive species become separated, with the emission from the CT state showing a red-shift with decreasing temperature. At 145 K, we observe the formation of an unstructured, wholly new emission band, which is strongly red-shifted relatively to the1(π, π*) excited-state and shows classic Gaussian line shape. This emission is attributed to the formation of “inter/intrachain” CT states. In the case of frozen solutions (∼90 K), the spectra dramatically blue-shifts and loses all contribution from the “inter/intrachain” species, and emission then arises completely from the pure “intrachain” CT excitonic state. The behavior of the polymer is strongly dependent on both solvent quality and temperature effects on the excited state geometry relaxation by means of the local solvent–solute interactions that stabilize the CT states, due to solvation of the new charge distribution, and also changes on the transition states via manipulating energy barriers.
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DOI：
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发表时间：
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期刊：
影响因子：
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DOI：
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发表时间：
2005
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