Synthesis and Properties of a Series of the Longest Oligothiophenes up to the 48-mer
作者:Naoto Sumi、Hidetaka Nakanishi、Shinpei Ueno、Kazuo Takimiya、Yoshio Aso、Tetsuo Otsubo
DOI:10.1246/bcsj.74.979
日期:2001.5
A series of the longest class of oligothiophenes extended at intervals of seven thiophene units from the 6-mer up to the 48-mer has been synthesized by a combination of the random Eglinton coupling reaction of mono- and di-ethynylsexithiophenes and a subsequent sodium sulfide-induced cyclization reaction of the resulting oligo(sexithienylene-diethynylene)s. Their structures were well characterized by MALDI-TOF MS and 1H NMR spectroscopy. The molecular weights of the oligothiophenes and oligo(sexithienylene-diethynylene)s, measured by gel-permeation liquid chromatography using the polystyrene standard, are nearly double the actual ones, indicating that they keep highly rigid rod-type shapes. According to a molecular model, the molecular lengths of the longest oligothiophene 48-mer and the longest oligo(sexithienylene-diethynylene) reach approximately 18.6 nm and 25.0 nm, respectively. In the electronic absorption and emission spectra, the π–π* transitions of the oligothiophenes demonstrate progressive red shifts with increasing chain length up to the 20-mer. In the cyclic voltammograms, furthermore, the first oxidation potentials tend to continue negative shifts up to the 34-mer. In accordance with these spectral changes, the doped conductivities steadily increase and approach that of a structurally related polymer.
通过单乙炔基和二乙炔基噻吩的无规埃格林顿偶联反应,以及随后硫化钠诱导的低聚(噻吩-二乙炔)环化反应,合成了一系列最长的低聚噻吩,这些低聚噻吩从 6-聚合体一直延伸到 48-聚合体,每隔 7 个噻吩单元。它们的结构通过 MALDI-TOF MS 和 1H NMR 光谱得到了很好的表征。以聚苯乙烯为标准,通过凝胶渗透液相色谱法测得的低聚噻吩和低聚(sexithienylene-diethynylene)s 的分子量几乎是实际分子量的两倍,表明它们保持着高刚性的棒状形状。根据分子模型,最长的低聚噻吩 48-mer 和最长的低聚(sexithienylene-diethynylene)的分子长度分别约为 18.6 nm 和 25.0 nm。在电子吸收光谱和发射光谱中,低聚噻吩的 π-π* 转变随着链长的增加而逐渐发生红移,直至 20-mer。此外,在循环伏安图中,第一氧化电位趋于继续负移,直至 34 个聚合物。根据这些光谱变化,掺杂后的电导率稳步上升,并接近结构相关聚合物的电导率。