以五苯荑-烯酮衍生物為主體之分子煞車合成與性質研究

Abstract

本篇論文主要是合成與探討新型分子煞車系統（化合物1），以五苯荑分子當作轉子，茚酮分子之羰基當作煞車器，以期應用於分子機械元件之設計。我們利用變溫1H 和 13C NMR圖譜、DFT理論計算，探討轉子之旋轉動能，且結合光化學與電化學控制其異構化行為，使煞車行為能夠順利的進行轉換。由於在化合物Z-1中羰基對五苯荑之立體障礙影響較大，使得在室溫下（298 K），當從化合物E-1（煞車關閉）轉換為化合物Z-1（煞車啟動）時，旋轉速率會減慢約500倍。 在乙腈中化合物E-1以290 nm波長之光源激發，當達到光反應穩定狀態時，兩者的比例為11：89（E-1：Z-1），此乃由於化合物E-1之異構化量子產率比化合物Z-1來得大，因此經由光異構化反應可有效率的得到化合物Z-1；另一方面，利用電化學的方法，經由陰離子自由基之中間體，化合物Z-1能夠有效率的異構化為化合物E-1，轉換效率高達96 %，所以E-Z之間的轉換不僅可逆，且總轉換效率可高達85 %。雖然也能利用酸催化進行加成-離去反應，將使化合物Z-1有效率的異構化為化合物E-1（96 %），但由於加入化學物質為不理想的方法，因此最後我們選用光化學和電化學方法使化合物1能夠有效率且連續的進行E-Z之間的交替異構化，使分子煞車系統順利的運作。

In this thesis, the synthesis and brake performance of a new molecular system (1) that consists of a pentiptycene rotor and an indanone brake are reported. The rotation kinetics of the rotor was probed by both variable-temperature 1H and 13C NMR spectroscopy and DFT calculations, and the switching between the brake-on and brake-off states were conducted by a combination of photochemical and electrochemical isomerization. Due to a larger steric hindrance between the rotor and the brake units in Z-1 than E-1, rotation of the rotor is slowed down by 500-fold at room temperature (298 K) on going from E-1 to Z-1, corresponding to the brake-off and brake-on states, respectively. The E-1 → Z-1 photoisomerization in acetonitrile is efficient and reaches a 11:89 （E-1:Z-1）ratio in the photostationary state upon excitation at 290 nm, attributable to a larger isomerization quantum efficiency for E-1 vs Z-1. An efficient Z-1 → E-1 isomerization (96%) was also achieved through the radical anionic intermediates by electro chemical treatments. Consequently, the reversibility of E-Z switching of 1 is as high as 85%. The Z-1 → E-1 acid-catalyzed isomerization is also efficient (96%) through addition-elimination mechanism, but chemical energy is not as clean as light or electrical energy. Thus, we adopt alternating photochemical and electrochemical treatments to carry out consecutive E-Z switching of 1.