Frère Pierre, Raimundo Jean-Manuel, Blanchard Philippe, Delaunay Jacques, Richomme Pascal, Sauvajol Jean-Louis, Orduna Jesus, Garin Javier, Roncali Jean
Groupe Systèmes Conjugués Linéaires, IMMO, UMR CNRS 6501, Université d'Angers, 2 Bd Lavoisier, 49045 Angers, France.
J Org Chem. 2003 Sep 19;68(19):7254-65. doi: 10.1021/jo034319o.
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.
我们合成并表征了由噻吩环和双键的不同组合构建的三系列基于噻吩的π共轭低聚物。利用循环伏安法、紫外可见光谱、红外光谱和拉曼光谱对这三系列低聚物的电子、电化学和振动性质的链长依赖性进行了分析。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会由于体系平面性增强和整体芳香性降低的综合作用，导致随着链的延伸，HOMO-LUMO能隙更快地减小。尽管在体系中引入两个连续的双键会导致双阳离子态的稳定，但这种结构修饰在长链延伸时并没有产生预期的HOMO-LUMO能隙的进一步减小。基于芳香性和键长交替之间的相互作用对这一现象进行了讨论。
