五苯荑衍生之新型光控分子煞車系統

Abstract

五苯荑分子具有三度空間、結構剛硬且具有高對稱性的性質，此外，結構中具有U-及V-形凹槽，所以插入〝栓子〞時就可以達到分子煞車的效果。本篇論文主要合成並探討有別於以往實驗室以單軸為設計概念的分子煞車系統，以五苯荑分子作為轉子(rotor)；stiff-stilbene 兼具定子(stator) 及煞車器(brake-unit) 兩角色，設計出雙軸分子煞車系統化合物3。 我們利用氫譜與碳譜VT-NMR來探討五苯荑分子於室溫轉動快慢，並利用譜線形狀分析(LSA) 得到順式組態轉動的動力學參數。(Z)-3 中轉子與煞車器之間由於立體障礙造成旋轉速度減緩，達到煞車啟動(brake-on)；(E)-3 的X-ray單晶顯示轉子與煞車器之間不具有立體障礙，所以轉子可以自由旋轉，為煞車關閉(brake-off) 的狀態。另外，化合物3 於正己烷溶劑中的光化學控制達轉換效率為26 %，具有可逆性及重複性。化合物 3 除了具分子煞車的功能外，分子也具有聚集誘導放光(AIE) 效應。我們利用(E)-3 及 (Z)-3 來證實五苯荑分子旋轉的快慢將會影響其放光程度，亦即我們所設計的分子煞車系統的放光具有自由旋轉子效應(free rotor effect)。

Molecular brake is a type of molecular devices that could reversibly slow down the motions of a molecular subunit through external stimuli. We have reported a series of light- and electrochemically driven molecular brakes using a rigid and H-shaped pentiptycene group as a four-bladed rotor. In this thesis, we designed molecule 3, which consists of a pentiptycene rotor, an indane brake-unit, and an indane stator, as a new generation of light-gated molecular brake. Experimental results show that rotation of the pentiptycene rotor is fast in (E)-3 but slow in (Z)-3 at 298 K. Furthermore, compound 3 can be reversibly and repetitive switched by light with a net efficiency of 26 % in n-hexane. In addition, compound 3 has the properties of aggregation-induced emission (AIE-effect). A combination of the luminescence and brake properties allows one to prove the concept of free rotor effect on photoluminescence, which cannot be achieved with our previous molecular brake systems.