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

纳米共轭低聚物作为有机功能材料最有前途的发展方向之一，受到了广泛的关注。然而，只有少数明确的纳米分子超过10 nm的长度容易操纵的现代STM技术还不知道。在这方面，该项目的目标是开发非常长的低聚噻吩，这相当于单分散聚合物。合成了一系列72聚体的低聚噻吩。通过对长链寡聚噻吩同系物系列的光谱研究，阐明了α-共轭噻吩体系有效共轭长度的概念，其共轭长度可扩展到20-30个噻吩单元。这些低聚物的掺杂导电性研究也非常有助于阐明导电聚噻吩的导电机制：结果表明，导电性也取决于共轭长度，有效共轭长度在决定聚噻吩的电荷传输中起着关键作用。此外，氧化物种的光谱研究得出了一个重要的结论，即活性电荷载流子物种是π-二聚体和双极化子。在一项扩展研究中，长的低聚噻吩被用作分子导线，允许光诱导的电子和/或能量从卟啉的捐赠部分转移到富勒烯的接受部分。此外，复杂的寡聚噻吩的分子线行为被成功地应用于基于寡聚噻吩的光伏器件。

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.