Effect of local molecular structure on the chain-length dependence of the electronic properties of thiophene-based π-conjugated systems
Effect of local molecular structure on the chain-length dependence of the electronic properties of thiophene-based π-conjugated systems
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DOI：
10.1021/jo034319o
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发表时间：
2003-09-19
影响因子：
3.6
通讯作者：
Roncali, J
中科院分区：
文献类型：
--
作者：
Frère, P;Raimundo, JM;Roncali, J
合成并表征了三个系列的噻吩类π共轭低聚物，这些低聚物由噻吩环和双键的不同组合构成。利用循环伏安法、紫外-可见光谱、红外光谱和拉曼光谱分析了三个系列低聚物的电子、电化学和振动性质与链长的关系。这些不同的研究提供了一致的结果，表明在低聚噻吩结构中引入烯键导致HOMO-LUMO间隙随着链延长而更快地减小，这是由于系统的增强的平面性和较低的整体芳族特性的组合效应。虽然在系统中引入两个连续的双键导致双阳离子状态的稳定，但这种结构修饰不会产生预期的在大链延伸时HOMO-LUMO间隙的进一步减小。这一现象的基础上讨论的芳香性和键长交替之间的相互作用。
Three series of thiophene-based pi-conjugated oligomers built with different combinations of thiophene cycles and double bonds have been synthesized and characterized. The analysis of the chain length dependence of the electronic, electrochemical, and vibrational properties of the three series of oligomers has been carried out using cyclic voltammetry, UV-vis, IR, and Raman spectroscopies. These various investigations provide consistent results showing that incorporation of ethylenic linkages in an oligothiophene structure leads to a faster decrease of the HOMO-LUMO gap with chain extension due to the combined effects of enhanced planarity and lower overall aromatic character of the system. Although the incorporation of two consecutive double bonds in the system leads to a stabilization of the dicationic state, this structural modification does not produce the expected further decrease of the HOMO-LUMO gap at large chain extension. This phenomenon is discussed on the basis of an interplay between aromaticity and bond length alternation.