Regioregular Organoborane-Functionalized Poly(3-alkynylthiophene)s

In our quest to develop regioregular borane acceptor-modified thiophene polymers, we prepared a series of new alkynylphenylborane-functionalized monomers and explored their polymerization. The regioregular polymer rr-P1 and an alternating copolymer with 3-hexylthiopene, rr-P2, were successfully obtained by Stille-type polymerization. An X-ray crystal structure of the bithiophene model system 2-Br revealed coplanar thiophene rings and the formation of π-stacks, despite the presence of bulky dimesitylborane moieties. For the polymers, rr-P1 showed the most bathochromic absorption (520 nm) and emission bands (620 nm), indicating the importance of high regioregularity and the beneficial effect of alkynyl relative to alkyl pendent groups. A higher energy absorption at ca. 340 nm could be assigned to charge transfer to the borane pendent groups based on DFT calculations on molecular model compounds that mimic the polymer repeat units. This assignment was further supported by fluoride anion binding studies.

本研究旨在开发区域规整性硼烷受体修饰噻吩聚合物，我们合成了一系列新型炔基苯基硼烷功能化单体，并对其聚合反应进行了探究。通过施蒂勒聚合（Stille-type polymerization）反应，成功制备得到区域规整性聚合物rr-P1，以及与3-己基噻吩共聚得到的交替共聚物rr-P2。对模型联噻吩体系2-Br的X射线晶体结构（X-ray crystal structure）分析表明，尽管存在大体积的二均三甲苯基硼基（dimesitylborane moieties），噻吩环仍保持共面构型，并形成了π堆积（π-stacks）结构。针对该系列聚合物，rr-P1展现出最大程度的红移吸收带（520 nm）与发射带（620 nm），这印证了高区域规整性的重要性，以及炔基侧链相较于烷基侧链的积极作用。在约340 nm处的高能吸收峰，可归因为电荷向硼烷侧基转移，该结论基于对模拟聚合物重复单元的分子模型化合物开展的密度泛函理论（DFT）计算结果。该归属结论进一步通过氟离子结合实验得到了验证。