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首页> 外文期刊>Chemistry: A European journal >Optical and Redox properties of a Series of 3,4-Ethylenedioxythiophene Oligomers
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Optical and Redox properties of a Series of 3,4-Ethylenedioxythiophene Oligomers

机译：一系列3,4-乙二氧基噻吩低聚物的光学和氧化还原特性

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摘要

The optical and redox properties of a series f 3,4-ethylenedioxythiophene oligomers (EDOTn, n = 1-4) and their #beta#,#beta#'-unsubstituted analogues (Tn, n = 1-4) are described. Both series are end capped with phenyl groups to prevent irreversible #alpha#-coupling reactions during oxidative doping. Absorption and fluorescence spectra of both series reveal a significantly higher degree of intrachain conformational order in the EDOTn oligomers. Oxidation potentials (E_(PA1) and E_(PA2)) determined by cyclic voltammetry reveal that those of EDOTn are significantly lower than the corresponding Tn oligomers as a consequence of the electron-donating 3,4-ethylenedioxy substitution. Linear fits of E_(PA1) and E_(PA2) versus the reciprocal number of double bonds reveal significantly steeper slopes for the EDOTn than for the Tn oligomers. This could indicate a more effective conjugation for the EDOTn series, confirmed by the fact that coalescence of E_(PA1) and E_(PA2) is reach3ed already at relatively short chain lengths (approx=5 EDOT units) in contrast to the Tn series (>10 thiophene units). The stepwise chemical oxidation of the EDOTn and Tn oligomers in solution was carried out to obtain radical cations and dications. The energies of the optical transitions of the radical cations and dications as determined by UV/Vis/NIR spectroscopy were similar for the two series. These spectroscopic observations are consistent with quantum-chemical calculations performed on the singly charged molecules. Cooling solutions containing T2~((centre dot)+), T3~((centre dot)+), EDOT2~((centre dot)+), and EDOT3~((centre dot)+) revealed the reversible formation of dimers, albeit with a somewhat different tendency, expressed in the values for the dimerization enthalpy.
机译：描述了一系列f 3,4-亚乙二氧基噻吩低聚物（EDOTn，n = 1-4）及其#beta＃，＃beta＃'-未取代的类似物（Tn，n = 1-4）的光学和氧化还原特性。两个系列均用苯基封端，以防止在氧化掺杂过程中发生不可逆的＃alpha＃偶联反应。这两个系列的吸收光谱和荧光光谱均显示出EDOTn低聚物中链内构象顺序的程度明显更高。通过循环伏安法测定的氧化电位（E_（PA1）和E_（PA2））表明，由于供电子3,4-乙二氧基取代，EDOTn的氧化电位明显低于相应的Tn低聚物。 E_（PA1）和E_（PA2）的线性拟合与双键倒数的关系表明，EDOTn的斜率比Tn低聚物的斜率大得多。这可能表明EDOTn系列的共轭更有效，这一事实得到了证实，与Tn系列相比，E_（PA1）和E_（PA2）的聚结已经在相对较短的链长（大约= 5 EDOT单位）处实现了（ > 10噻吩单位）。对溶液中的EDOTn和Tn低聚物进行逐步化学氧化，以获得自由基阳离子和阳离子。由UV / Vis / NIR光谱确定的自由基阳离子和阳离子的光学跃迁的能量对于这两个系列是相似的。这些光谱观察结果与对单电荷分子进行的量子化学计算是一致的。包含T2〜（（中心点）+），T3〜（（中心点）+），EDOT2〜（（中心点）+）和EDOT3〜（（中心点）+）的冷却液显示出可逆的二聚体形成，尽管趋势有所不同，但以二聚焓值表示。

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