Design and synthesis of nanosized conjugated π-electron molecules with specific functionarity

纳米级共轭低聚物作为功能有机材料的发展方向之一，受到了广泛的关注。然而，只有少数定义明确且长度超过10nm的纳米分子尚未被现代STM技术所操纵。在这方面，该项目旨在开发超长的低聚噻吩，这相当于单分散聚合物。合成了一系列高至72聚的低聚噻吩。对长硫代噻吩同源系列的光谱研究有助于澄清α-共轭噻吩体系有效共轭长度的概念，其延伸至20-30个噻吩单位。这些低聚物的掺杂电导率研究也有助于阐明导电多噻吩的导电机理：电导率也依赖于共轭长度，而有效共轭长度对多噻吩的电荷输运起着至关重要的作用。此外，对氧化产物的光谱研究得出了活性载流子既为π二聚体又为双极化子的重要结论。在一项扩展研究中，长寡硫噻吩被用作分子线，允许光诱导电子和/或能量从给予卟啉部分转移到接受富勒烯部分。此外，复杂的低硫噻吩分子线行为被成功地应用于低硫噻吩基光伏器件。

As one of the most promising approaches for the development of functional organic materials, nanosized conjugated oligomers are of current attention. However, only few number of well-defined nanomolecules with over 10 nm length readily manipulated by modern STM techniques have not been known. In this regard, this project has aimed at the development of extraordinarily long oligothiophenes, which correspond to monodisperse polymers. A series of oligothiophenes up to the 72-mer has been synthesized. The spectroscopic studies of the homologous series of the long oligothiophenes served to clarify the concept of an effective conjugation length of α-conjugated thiophene systems, which extends to 20-30 thiophene units. The doped-conductivity studies of these oligomers were also very helpful in elucidating the conduction mechanism of conductive polythiophenes : it turned out that the conductivities are also dependent on the conjugation length, and the effective conjugation length play a critical role in determining the charge transport of polythiophenes. In addition, the spectroscopic studies of the oxidized species led to an important conclusion that the active charge carrier species are both π-dimers and bipolarons. In an extension study, long oligothiophenes were used as a molecular wire allowing photoinduced electron- and/or energy-transfer from the donating porphyrin part to the accepting fullerene part. Furthermore, the molecular-wire behavior of sophisticated oligothiophenes was successfully applied to the oligothiophene-based photovoltaic devices.