近年來化學家們對於苯乙炔共軛高分子構形不同在光物理性質上造成的影響深感興趣。目前為止，透過實驗的方式僅能在吸收光譜上看出平面構形與扭轉構形的差異，放射光譜主要為平面構形的放光。原因為扭轉構形的苯乙炔高分子受光激發後會先經振動鬆弛至能量最低點的平面構形才放光。本論文中我們將五苯荑架構引入不同共軛長度的苯乙炔寡聚物中，設計出化合物2-dOO、3-dOO、4-dOO、5-dOO、6-dOO與7-dOO，結構如下圖(a)所示。因為AM1與ZINDO理論計算結果顯示，引入五苯荑架構至苯乙炔寡聚物中，能造成基態與激發態位能曲線的改變，並使扭轉構形位於區域性能量低點。透過變溫實驗，我們首次在80 K時量測到化合物3-dOO扭轉構形的螢光，並比較平面構形與扭轉構形在光物理性質上的差異。化合物4-dOO、5-dOO、6-dOO與7-dOO在80 K時同樣可以量測數種不同扭轉構形的放光，結果也暗示此系列化合物扭轉構形中相鄰苯環傾向互相垂直，彼此間電子偶合作用極弱。 五苯荑架構形成的扭轉能障是苯乙炔寡聚物能觀測到扭轉構形放光的關鍵，為了探討立體效應對扭轉能障的影響，我們設計出化合物PBP-dOO、PDP-dOO與PTP-dOO，結構如下圖(b)所示，並與化合物3-dOO做比較。理論計算結果顯示化合物PBP-dOO、PDP-dOO與PTP-dOO位能曲線平滑，變溫光物理實驗同樣顯示最大放射峰不隨溫度有明顯的變化，為激發態平面構形主導放光。 為了合成5-dOO、6-dOO與7-dOO及增加五苯荑架構的應用性，我們完成一系列雙鹵素取代五苯荑分子 1-dB、1-dI與1-BI的合成，結構如下圖(c)所示。此系列化合物能進行鈀金屬催化之Heck、Suzuki與Sonogashira偶合反應，未來可以應用在含五苯荑架構高分子的合成，增加五苯荑架構在材料化學上的應用性。 Chemists are always interested in the relationship between conformation and photophysical properties. However the literature only shows the differences in the absorption spectrum but not the emission one, between the twist and planar form. Due to the smooth excited-state potential energy surface and thus fast structural relaxation, fluorescence emission always result from the planar form, regardless the structure of the Franck-Condon excited state. We designed and synthesized compounds 2-dOO、3-dOO、4-dOO、5-dOO、6-dOO and 7-dOO by using pentiptycene building blocks. The chemical structures were show in Fig.(a). Due to the pentiptycene scaffold, we can get the different situation in potential energy surface by theorical AM1 and ZINDO calculation. Compound 3-dOO showed the emission of twist form at lower the temperature 80 K. We also got the difference in photophysical properties between planar and twist form. Compound 4-dOO、5-dOO、6-dOO and 7-dOO also showed the emission of twist conformers, regardless the conjugation length. These results reveals that in the excited state the neighboring benzene rings in twist form are orthogonal and the electronic coupling between two neighboring benzene was negligible. In order to study the torsional barrier which was caused by bulky pentiptycene building block, we have designed and synthesized compounds PBP-dOO、PDP-dOO and PTP-dOO where the central ring was different from pentiptycene. The chemical structures were shown in Fig.(b). The theorical AM1 and ZINDO calculations and the the experimental results shows flat potential energy surface in groud state and excited state. In order to synthesis compounds 5-dOO、6-dOO and 7-dOO and to increase the application of pentipycene derivatives, we have also synthesized dihalogen substituted pentipycene 1-dB、1-dI and 1-BI. The chemical structures were show in Fig.(c). Compounds 1-dB showed moderate reactivity for Heck、Suzuki and Sonogashira coupling reaction.
