新型辨識系統之構築及其相對內鎖分子的合成

Abstract

論文摘要 藉由大環分子與分子夾之間所形成之錯合體，我們設計且合成了一種新型的分子開關。在此系統中，分子的開關行為不僅可藉由K+/[2,2,2]cryptand 及NH4+/Et3N的二種模式控制。特別的是在此開關過程中，系統會產生肉眼可見的顏色變化。因此，此系統的作用模式就有如一個NOR的邏輯閘。 經由適當的設計我們構築另一個結構有別於一般冠醚的大環，此環狀分子主要由一個具有3個氧原子的diethylene glycol鏈, phenolic aromatic ring 及一個xylene 連接基所組成。雖然分子間的[N+-H…O]氫鍵作用力可能因氧原子數的減少而減弱但主客體之間良好的前置構型可能增加了[cation…pi], [N+-H…pi] 和 [N+C-H…pi等的非共價作用力，使得此大環分子與DBA+擁有相當強的結合力(Ka = 15000, CD3NO2)。此外，此系統亦可辨識bipyridinium ions且與其形成準車輪烷(pseudorotaxane)；為了證明此準車輪烷結構確實存在溶液中，我們亦合成了其相對應的車輪烷及環連體。

Abstract We have synthesized a new molecular switch—based on a macrocycle–clip complex—whose switching behavior not only can be controlled through the use of either K+/[2,2,2]cryptand or NH4+/Et3N systems but also provides color changes that are visible to the naked eye; consequently, this system operates as a two-input NOR functioning molecular logic gate. We report a new host molecule in which one diethylene glycol chain (i.e., a loop possessing only three oxygen atoms) incorporated along with two phenolic aromatic rings is linked by a xylene spacer into a macroring. The design of the molecular structure of this macrocycle “amplifies” any potential [cation•••pi], [N+-H•••pi] and [N+C-H•••pi]interactions between the dibenzylammonium (DBA+) ion and the phenolic rings of the macrocycle; as such, these species display a very strong binding affinity in CD3NO2 (Ka = 15,000 M–1). The macroring also coordinates to bipyridinium ions in a [2]pseudorotaxane fashion, which makes it the smallest macrocycle (i.e., a 25-membered ring) known to complex both DBA+ and bipyridinium ions in solution. To confirm unambiguously that these pseudorotaxanes exist in solution, we synthesized their corresponding interlocked molecules, namely rotaxanes and catenanes.