The Multi-Stage Molecular Switches Based on the Molecular Cage

第一章 具按鈕式及輪轉式兩種開關模式的兩階段分子伸縮集線器之研究 我們合成出來以一個以分子籠為基礎的 [2]車輪烷，其桿狀部分的一端由34員環的開口穿出。透過適當的試劑操作，可展現出來兩階段的伸長模式，類似集線器具有一條伸縮自如的纜線。我們以此三種狀態作為開關研究的基礎，分別可以模擬出輪轉式的控制器行為，或是按鈕式的控制器行為。在使用 KPF6/cryptand 和 TBAF/Ca(BF4)2 這兩組試劑對進行開關操作時，三種狀態的切換互相連續，此與轉動輪轉式控制器做切換的過程雷同；若是以 Ba(ClO4)2/TBAF 操作時，在 state I 和 state II 之間則必會經過 state 0 ，就與選按按鈕式控制器做切換時的情形類似。藉這一能控制自如的分子集線器，我們完成其能模擬兩種控制器開關行為之研究。 第二章 以冠醚與雙烷基銨鹽為主客系統之穿透前鍵結研究 準車輪烷的生成是由客體分子穿透主體分子的空腔所獲得的結果，但穿透前的鍵結模式卻苦於其穿透速率過快而難以觀察研究。本實驗室發展出來具兩邊DB24C8結構之分子籠在雙烷基銨鹽客體分子穿透前先與之鍵結，生成能量穩定且可被1H NMR及X-ray單晶繞射實驗證實之以面-對-面 (face-to-face) 錯合的中間體。利用動力學追蹤研究線形分子上取代基電性差異與立障大小對其穿透速率的影響，我們推測一般冠醚與雙烷基銨鹽的主客系統可能也是透過類似的穿透機制來形成準車輪烷。Chapter 1 We report a molecular cage–based [2]rotaxane, which behaves as a retractable cable in which lengths of the threadlike component are pulled out through one of the 34-membered-ring faces of the molecular cage component in two different elongation stages. Operating this molecular switch using KPF6/cryptand and TBAF/Ca(BF4)2 transforms it among its three different states continuously, thereby mimicking a rotary controller. Using Ba(ClO4)2 and TBAF to operate the molecular switch, the transitions between state I and state II naturally occur via state 0, similar to the behavior of a mechanical push-button controller. Chapter 2 Using 1H NMR spectroscopy to monitor the threading processes in solution and isolating face-to-face complexes in the solid state, we have demonstrated that the formation of face-to-face–associated host–guest intermediates and their subsequent dissociation are two steps that occur prior to the threading of guest cations through the DB24C8-like openings of the molecular cage 1—and, therefore, more generally in the generation of pseudorotaxanes from DAA ions and crown ethers