Hybrid conjugated polymers with alternating dithienosilole or dithienogermole and tricoordinate boron units
Hybrid conjugated polymers with alternating dithienosilole or dithienogermole and tricoordinate boron units
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DOI：
10.1039/c7py01790a
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发表时间：
2018-01-21
影响因子：
4.6
通讯作者：
Ohshita, Joji
中科院分区：
文献类型：
--
作者：
Adachi, Yohei;Ooyama, Yousuke;Ohshita, Joji
由三配位的硼和pi共轭单元组成的共轭聚合物与p(B-pi)相互作用产生的相对较低的Lumo具有扩展的共轭。然而，以三有机硼烷和高度富含电子的供体交替为特征的供体-受体(D-A)聚合物仍然很少。我们在这里提出了一类新的杂化D-A聚合物，它将富含电子的二硫代硅烷或二硫杂化硅分子与高度坚固的三配位硼烷受体结合在一起。通过钯催化的双(卤代噻吩基)硼烷和二茂铁基二硫硅烷的Stille偶联反应，可以容易地合成中等到高相对分子质量的聚合物。聚合物为暗红色固体，在空气中稳定，在普通有机溶剂中可溶。在约500-550 nm处的长波UV-Vis吸收表明沿着主链的有效的圆周率共轭和显著的D-A相互作用。在溶液中，发射峰位于波长大于600 nm处，并且随着溶剂极性的增加，发射峰进一步向低能量方向移动，这表明激发态具有较强的分子内电荷转移(ICT)特性。循环伏安法(CV)分析表明，聚合物结构中的硼烷共单体单元具有很强的受主特征，这表明聚合物的LUMO能级相对较低，从而增强了D-A相互作用。模型低聚物的密度泛函理论(DFT)计算进一步支持了这些实验观察结果。
Conjugated polymers composed of tricoordinate boron and pi-conjugated units possess extended conjugation with relatively low-lying LUMOs arising from p(B-pi) interactions. However, donor-acceptor (D-A) polymers that feature triorganoboranes alternating with highly electron-rich donors remain scarce. We present here a new class of hybrid D-A polymers that combine electron-rich dithienosiloles or dithienogermoles with highly robust tricoordinate borane acceptors. Polymers of modest to high molecular weight are readily prepared by Pd-catalyzed Stille coupling reaction of bis(halothienyl) boranes and distannyldithienosiloles or -germoles. The polymers are obtained as dark red solids that are stable in air and soluble in common organic solvents. Long wavelength UV-vis absorptions at ca. 500-550 nm indicate effective pi-conjugation and pronounced D-A interactions along the backbone. The emission maxima occur at wavelengths longer than 600 nm in solution and experience further shifts to lower energy with increasing solvent polarity, indicative of strong intramolecular charge transfer (ICT) character of the excited state. The powerful acceptor character of the borane comonomer units in the polymer structures is also evident from cyclic voltammetry (CV) analyses that reveal relatively low-lying LUMO levels of the polymers, enhancing the D-A interaction. Density functional theory (DFT) calculations on model oligomers further support these experimental observations.