含五苯荑金(I)孔洞晶體之烷基鏈長效應對超分子自組裝行為之研究

Abstract

理解分子結構和超分子自組裝之間的關係為晶體工程中最根本的問題。本實驗室先前合成出含五苯荑金(I)錯合物Ph分子，觀察其晶體發現其透過碳鏈、末端苯環與五苯荑之U型凹槽形成榫卯結構，以及四核金中心具豐富之Au-Au、Au-π、π-π作用力共同堆積形成具孔洞之骨架，並為金(I)錯合物之孔洞晶體中最大之孔隙尺寸，此外，亦同時具力致、光致、薰致放光變色之行為。於本研究中，我們調整其烷基鏈長度，合成出一系列Ph-Cn分子 (n = 5-7、9-12、16），探討烷基鏈長度對金(I)錯合物系統之超分子自組裝行為影響，並確立烷基鏈對於多孔框架形成之重要性。 隨烷基鏈長之增加，晶體排列模式以金之核數分類由Au2轉變為Au4再轉變為Au單核形式。研究結果發現形成榫卯結構所需之最佳烷基鍊長度為C8與C9，而親金作用力與CH−π作用力間的競爭對於決定晶體最終排列模式扮演重要之角色。令人驚訝的是，Ph-C11再度呈現出具孔洞結構之晶體排列，且為據我們所知具有最大孔徑比例之金(I)錯合物之多孔框架。此外，透過NMR實驗觀察到Ph-Cn分子於溶液狀態下之自組裝型為：利用二維DOSY數據的計算證明了四聚體的形成，且經由NOE信號證明了榫卯結構之超分子相互作用力。而錯合物Ph-Cn之晶體結構與其刺激響應特性亦具高度相關性。

Understanding the relationship between molecular structure and supramolecular architecture is the most fundamental issue in molecular crystal engineering. We recently discovered an intriguing pentiptycene-containing gold(I) molecular system (Ph) that crystalizes persistently in a porous crystalline framework via tongue-and-groove-like packing, and also shows rich stimuli-responsive behaviors. In this work, we study alkyl chain length effects (Ph-Cn, n = 5-7, 9-12, and 16) on the supramolecular self-assembly of this system to identify the importance of alkyl chains in forming the porous framework. By tuning alkyl chain length, crystal packing modes transfer from supramolecular Au2 to Au4 and to Au along with increased chain lengths. We revealed that the optimal alkyl chain length for the tongue-and-groove joinery is C8 and C9, and the competition between aurophilicity and CH-π interactions plays a critical role in determining the crystal packing mode. To our surprise, Ph-C11 also presents a porous framework with the largest pore size for gold(I) complexes to our knowledge. Moreover, the assembly of Ph-Cn in solution states is detected by NMR experiments. The formation of tetramers is proved by the calculation of 2D DOSY data, and NOE signals evidence of the tongue-and-groove supramolecular interactions. In addition, a correlation between the supramolecular structures and the stimuli-responsive properties is also provided.