水溶性六元瓜环衍生物与1,ω-亚烷基吡啶主客体配合物的^1HNMR及晶体结构

Host-guest complexes of a water soluble cucurbit[6]uril derivative with some dications of 1,ω-alkyldipyridines: ～1H NMR and X-ray structures

利用1HNMR技术以及单晶X衍射技术考察对称四甲基取代六元瓜环(TMeQ[6])与几种1,ω-亚烷基吡啶阳离子(ω=2,4,6,8,10)客体的相互作用.在这些包结配合物中,TMeQ[6]的端口效应以及空腔效应同时存在,其主客体作用模式随着客体亚烷基碳链长短不一而各不相同.对于客体1,2-二乙基吡啶(Edpy),TMeQ[6]包结Edpy的带正电荷的吡啶环部分,形成一不对称的包结配合物;对于客体1,4-二丁基吡啶(Bdpy),TMeQ[6]选择性包结Bdpy的吡啶环部分或烷基部分存在竞争作用和快速交换;而具有较长碳链的客体1,6-二己基吡啶(Hdpy)和1,8-二丁庚基吡啶(Odpy)与TMeQ[6]通过空腔的疏水作用以及外部的离子-偶极作用形成稳定的类轮烷包结配合物;客体1,10-二癸基吡啶(Ddpy)的两个吡啶环分别被两个TMeQ[6]包结形成哑铃型的包结配合物.

Interactions between a symmetrical tetramethyl-substituted cucurbit[6]uril （host： TMeQ[6]） and 1,ω-alkylenedipyridine（ω = 2, 4, 6, 8,10） dicationic guests were investigated using ^1H NMR spectroscopy and single crystal X-ray crystallography. In these inclusion complexes, combined cavity and portal binding in TMeQ[6] were observed, and the length of the bridged alkylene plays an important role not only in balancing the overall hydrophilic/hydrophobic interaction between the host and guest, but also in defining the structure of the resulting inclusion complexes. For the guest 1,2-ethylenedipyridine （Edpy）, TMeQ[6] includes a positively charged pyridine ring of Edpy to form an unsymmetrical inclusion complex; for the guest 1,4-butylenedipyridine （Bdpy）, TMeQ[6] includes a positively charged pyridine ring of Bdpy, but the different competitive interactions in and between the related inclusion complexes could lead to a fast exchange between the hosts and guests. For guests with longer bridge chains, such as 1,6-hexamethylenedipyridine （Hdpy） or 1,8-octylenedipyridine （Odpy）, a stable pseudorotaxane inclusion complex is formed by combining the hydrophobic cavity and the outer portal dipole-ion interactions. However, for 1,10-decatylenedipyridine （Ddpy）, the two TMeQ[6] hosts molecules include the two end pyridine rings of Ddpy and form a dumbbell inclusion complex.