氮雜環碳烯鈀金屬錯合物催化直接碳氫鍵芳基化反應於聚(3-己基噻吩)、聚(3-己基硒吩)及噻吩硒吩交替共聚物之合成

Abstract

本研究成功地將氮雜環碳烯鈀金屬錯合物催化引入直接碳氫鍵芳基化反應中，並且利用氮雜環碳烯鈀金屬錯合物催化劑進行直接碳氫鍵芳基化反應合成聚(3-己基噻吩) (P3HT)、聚(3-己基硒吩) (P3HS)與噻吩硒吩交替共聚物 (P3HTS) 三種不同的高分子光電材料。 在此催化系統下，我們合成的P3HT具有高分子量 (Mn = 26.9 k, PDI = 3.56) 及高立體規則度 (94%) 等特性，而我們同樣以此方法合成了P3HS，目前文獻中尚未有以直接碳氫鍵芳基化反應合成P3HS的研究報導。在氮雜環碳烯鈀金屬錯合物催化系統下，可以有較廣的反應溫度 (70 °C到140 °C)，相較於以膦配體醋酸鈀作為催化劑在高溫下有較好的穩定性，反應的再現性也有明顯地提升。我們也利用直接碳氫鍵芳基化反應，第一個成功地合成高立體規則度的噻吩硒吩交替共聚物 (P3HTS)，產物的分子量高達20000，而在此之前並沒有良好的方法能進行噻吩硒吩交替共聚物的合成。我們也針對P3HTS的熱性質、光學性質及電化學性質做了一系列的探討。P3HTS保留了許多P3HT和P3HS的優點，如相似的吸光範圍 (300-700 nm)、 良好的結晶性和高熱穩定性 (Td = 428 °C)。由於P3HTS為噻吩與硒吩兩者交替排列，因此也有許多與P3HT和P3HS不同的性質，如比P3HT更加紅位移的吸收波長 (462 nm)、較低的LUMO (−2.67 eV) 及能隙 (2.21 eV)，相較於P3HS有更好的溶解度，更易於光電元件的製作。本論文的研究結果利用碳氫鍵直接芳基化反應，成功地提供了更方便、也更經濟的方法，進行噻吩與硒吩的交替共聚物的合成。也為其它噻吩、硒吩和碲吩等不同的共聚物合成，提供了一個可行的方向。

In this study, we have successfully introduced commercial N-heterocyclic carbene-based palladium catalysts to conduct direct C-H bond arylation polymerization and poly(3-hexylthiohphene) (P3HT), poly(3-hexylselenophene) (P3HS), and poly(3-hexylthiophene-alt-3-hexylselenophene) (P3HTS) were synthesized accordingly. Under our optimized conditions, high molecular weight P3HT (Mn = 26.9 k, PDI = 3.56) with high head-to-tail regioregularity (94%) was prepared through C-H bond arylation polymerization catalyzed by NHC-Pd(II) [1,3-Bis(2,6-diisopropylphenyl)imidazol-2-ylidene]chloro[3-phenylallyl]palladium(II). P3HS was obtained by a similar manner and this is the first example of preparing P3HS by direct C−H bond arylation. NHC-Pd(II) exhibits a wide range of working temperature spanning from 70°C to 140°C) and good catalytic reproducibility relative to conventional phosphine-based palladium catalysts. For this first time head-to-tail poly(3-hexylthiophene-alt-3-hexylselenophene) was prepared by direct C-H bond arylation polymerization by the help of NHC-Pd(II), offering an opportunity to study the physical properties of P3HTSThe results reveal that P3HTS retains many advantageous properties of P3HT and P3HS, including broad UV-Vis absorption, good crystallinity, and high thermal stability (Td = 428 °C). Moreover, owing to the regular alternating arrangement of thiophene and selenophene units, it also exhibits various advantages over either P3HT or P3HS, such as more red-shifted absorption maximum (462 nm) than P3HT, narrower electrochemical HOMO−LUMO gap (2.21 eV) and better solubility relative to P3HS. In brief, our results provide an economical and convenient method for the direct C−H bond arylation polymerization of thiophene-selenophene alternating copolymer. It is envisaged that the employed methodology in this study can be further applied to synthesis of other alternating copolymers such as thiophene-tellurophene andselenophene-tellurophene alternating copolymers.