Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan.
Chem Asian J. 2012 Jan 2;7(1):225-32. doi: 10.1002/asia.201100639. Epub 2011 Oct 12.
A series of tetrahedral oligothiophenes bearing n-hexyl groups at the α-positions of the terminal thiophene rings, (n-C(6)H(13)(C(4)H(2)S)(n))(4)C (Hex-TnTM; n=1-4), has been synthesized by Kosugi-Migita-Stille coupling as a key reaction. Thanks to the improved solubility afforded by the terminal n-hexyl groups, the largest homologue (n=4) was successfully obtained. Whereas the smaller derivatives (n=1, 2) were obtained as liquid substances, the larger derivatives (n=3, 4) were obtained as solids. Hex-T3 TM partially adopts syn conformations between the adjacent thiophene rings in the crystal, probably owing to the packing force. Hex-T3 TM not only appeared in the crystalline state but also the amorphous state, which was stable to up to 80 °C. Regardless of the terminal groups, the derivatives of n=2 exhibited a broad fluorescence with large Stokes shifts compared to the corresponding linear analogues, thereby suggesting the presence of intramolecular interactions between the bithiophene moieties. Interactions between terthiophene branches was also suggested in the radical cations of Hex-T3 TM by cyclic voltammetry measurements.
一系列在末端噻吩环的α-位带有正己基的四面体寡聚噻吩，（n-C（6）H（13）（C（4）H（2）S）（n））（4）C（Hex-TnTM；n=1-4），通过 Kosugi-Migita-Stille 偶联作为关键反应来合成。由于末端正己基提供了更好的溶解性，成功地得到了最大的同系物（n=4）。虽然较小的衍生物（n=1，2）是液体物质，较大的衍生物（n=3，4）是固体。Hex-T3 TM 在晶体中，相邻噻吩环之间部分采用顺式构象，可能是由于堆积力的原因。Hex-T3 TM 不仅出现在晶态，而且还出现在非晶态，在高达 80°C 的温度下也稳定存在。无论末端基团如何，n=2 的衍生物与相应的线性类似物相比，表现出宽的荧光，具有较大的斯托克斯位移，这表明在联噻吩部分之间存在分子内相互作用。循环伏安法测量还表明，在 Hex-T3 TM 的自由基阳离子中，存在-terthiophene 支链之间的相互作用。
