寡聚物探討：寡聚二乙炔與梯蕃

Abstract

聚二乙炔(PDAs)是由交互出現的E型烯類與炔類所組成的一維共軛高分子。聚二乙炔具有變色性質，變色的原因大多被認為是有效共軛長度變化和高分子鏈之間的相互作用所導致。文獻上也有許多E型的寡聚二乙炔曾被合成並研究。然而，Z型的寡聚二乙炔則鮮少被探討。 一系列叔丁基取代的Z型寡聚二乙炔可以從丙二烯基/炔丙基鋅試劑與硫縮酮取代的炔丙基醛反應生成β-硫烷高炔丙基醇，接著通過有立體獨特性的Mitsunobu條件進行脫去反應生成烯類產物。產物的立體化學根據NOE實驗可以得知為Z型無誤。另外，六聚體的X-ray單晶結構也成功地獲得，在其中可以明確地觀察到每一個雙鍵都是Z型。合成所得的Z型寡聚二乙炔的進行了光物理性質測量，發現在聚集條件下吸收光譜的λmax會有藍移的現象。 以六苯並暈苯 (HBC) 衍生物作為連接基團的梯蕃可以利用相應的雙降冰片烯單體以第一代Grubbs催化劑進行開環複分解聚合 (ROMP) 反應來獲得。含有六苯並暈苯發色團的梯蕃從其吸收光譜中可以發現HBC發色團吸收強度相較單體有明顯的下降。而在螢光光譜中可以發現由於相鄰的HBC發色團相互作用而生成的受激二聚物的螢光。除了二維芳香性發色團可被用為梯蕃的連接基團外，三維碳氫化合物也可以作為連接基團。楔烷，立方烷的價鍵異構物，其衍生物也可以當作連接基團並順利地以類似的合成法獲得相應的梯蕃產物。在掃描穿隧式電子顯微鏡(STM)影像上顯示含有HBC連接基團的梯蕃為雙股結構。在高定向热解石墨 (HOPG)上可以觀察到藉由發色團之間以及不同條的梯蕃端基之間的相互作用形成一維自組裝結構，進而在表面形成有序的二維陣列。

Polydiaceylenes (PDAs) are linear conjugated polymer constructed by alternative E-olefin and alkyne moieties. PDAs show color change properties which might be contributed by changes in effective conjugation length and interactions between PDA chains (chromophores). Several E-oligodiacetylenes (E-ODAs) have been synthesized and studied. Z-oligodiacetylenes (Z-ODAs) have sporadically explored. A series of tBu-substituted Z-ODAs are synthesized from the reactions of allenyl/propargylic zinc reagents with dithiolane-substituted propargylic aldehydes to form β-thioalkoxy alcohols which undergo stereospecific elimination under Mitsunobu conditions. The stereochemical assignments are based on NOE experiments. The X-ray structure of the hexamer further supports the Z configuration for each of the double bonds in these ODAs. The photophysical properties of these Z-ODAs have been examined. The absorption maxima shift to shorter wavelength upon aggregation. Double-stranded polymeric ladderphane with a hexabenzocoronene (HBC) derivative as linkers is synthesized by the ring-opening metathesis polymerization (ROMP) of the corresponding bisnorbornene monomer using the first-generation Grubbs catalyst. The absorption intensity of the polymer is much lower than that of corresponding monomer. In addition, excimer emission is found in the polymer due to the interactions between adjacent chromophore. Instead of the two dimensional aromatic chromophores being served as linker in ladderphanes, the three dimensional hydrocarbons can be used as linker. Cuneane, the valence isomer of cubane, is applied as linking group in the ladderphane. Double-stranded ladderphane having cuneane linker is synthesized similarly. The STM image of HBC-incorporated ladderphane shows double strained nature and typical properties of polybisnorbornene which would self-assemble to form ordered two-dimensional arrays on the HOPG surface.