α,αâ²-Didecylquater-, -quinque- and -sexi-thiophenes were synthesized by Kumada cross-coupling and oxidative coupling reactions. For the former reaction Pd(dppf)Cl2 was found to be a more efficient catalyst than the usually applied Ni(dppp)Cl2. Thermal behaviour of all new oligothiophenes was investigated by differential scanning calorimetry and polarizing optical microscopy. It was shown that all these compounds possess not only crystal phases but also high temperature ordered smectic mesophases and that the clearing point increases linearly with the number of conjugated thiophene rings. A degree of order in the crystal phase was estimated on the basis of thermodynamic data. The highest degree of order was proposed for α,αâ²-didecylquaterthiophene, which explains why the mobility of end-α,αâ²-capped quaterthiophenes in FET (field effect transistor) devices is comparable or sometimes better than those of corresponding quinque- and sexi-thiophene derivatives.
通过 Kumada 交叉偶联和氧化偶联反应合成了δ,δ,δ²-二癸基季
铵盐、
奎宁盐和六
噻吩。在前一种反应中,发现
钯(dppf)Cl2 是比通常使用的
镍(dppp)Cl2 更有效的催化剂。通过差示扫描量热法和偏振光学显微镜研究了所有新型低聚
噻吩的热性能。结果表明,所有这些化合物不仅具有晶体相,而且还具有高温有序共晶介相,其清澈点随共轭
噻吩环数量的增加而线性增加。根据热力学数据估算了晶体相的有序度。δ,δâ²-二癸基四联
噻吩的有序度最高,这也解释了为什么在 FET(场效应晶体管)器件中,末端δ,δâ²-封端的四联
噻吩的迁移率与相应的五联
噻吩和六联
噻吩衍
生物相当,有时甚至更好。