We report the design, synthesis, and physicochemical properties of an array of phenanthro[2,1-b:7,8-b’]dithiophene (PDT-2) derivatives by introducing five types of alkyl (CnH2n+1; n = 8, 10, 12, 13, and 14) or two types of decylthienyl groups at 2,7-positions of the PDT-2 core. Systematic investigation revealed that the alkyl length and the type of side chains have a great effect on the physicochemical properties. For alkylated PDT-2, the solubility was gradually decreased as the chain length was increased. For instance, C8-PDT-2 exhibited the highest solubility (5.0 g/L) in chloroform. Additionally, substitution with 5-decylthienyl groups showed poor solubility in both chloroform and toluene, whereas PDT-2 with 4-decylthienyl groups resulted in higher solubility. Furthermore, UV-vis absorption of PDT-2 derivatives substituted by decylthienyl groups showed a redshift, indicating the extension of their π-conjugation length. This work reveals that modification of the conjugated core by alkyl or decylthienyl side chains may be an efficient strategy by which to change the physicochemical properties, which might lead to the development of high-performance organic semiconductors.

中文翻译：

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2,7-二取代菲[2,1-b:7,8-b']二噻吩的合成及理化性质

我们通过引入五种类型的烷基 (CnH2n+1; n = 8) 报告了一系列菲 [2,1-b:7,8-b'] 二噻吩 (PDT-2) 衍生物的设计、合成和物理化学性质、10、12、13 和 14) 或在 PDT-2 核心的 2,7-位上的两种类型的癸基噻吩基。系统研究表明，烷基长度和侧链类型对其理化性质有很大影响。对于烷基化的 PDT-2，随着链长的增加，溶解度逐渐降低。例如，C8-PDT-2 在氯仿中的溶解度最高 (5.0 g/L)。此外，用 5-癸基噻吩基取代在氯仿和甲苯中的溶解度都很差，而用 4-癸基噻吩基取代的 PDT-2 溶解度更高。此外，被癸基噻吩基取代的 PDT-2 衍生物的 UV-vis 吸收显示红移，表明它们的 π 共轭长度延长。这项工作表明，通过烷基或癸基噻吩基侧链修饰共轭核可能是改变物理化学性质的有效策略，这可能会导致高性能有机半导体的发展。