Donor/Acceptor-Substituted Chiral Molecular Clips - Synthesis and Host-Guest Complex Formation
Donor/Acceptor-Substituted Chiral Molecular Clips - Synthesis and Host-Guest Complex Formation
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供体/受体取代的手性分子夹 - 合成和主客体复合物形成
DOI：
10.1002/ejoc.201200112
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发表时间：
2012
影响因子：
2.8
通讯作者：
Y. Inoue
中科院分区：
文献类型：
--
作者：
F.-G. Klaerner;S. Madenci;M. C. Kuchenbrandt;D. Blaeser;R. Boese;G. Fukuhara;Y. Inoue
报道了一些取代的立体异构的二亚甲基桥分子夹的合成、分离和表征，这些分子夹在萘侧壁的尖端带有供体或受体基团，在中心苯间隔单元处带有两个乙酰氧基、羟基或甲氧基基团。研究了这些取代的分子夹作为主体分子与1，2，4，5-四氰基苯（TCNB）、N-甲基-对甲氧羰基吡啶碘（Kosower's salt，KS）和N-甲基烟酰胺碘（NMNA）作为客体分子形成的主-客体复合物。通过NMR滴定实验获得的结合常数Ka和客体信号的络合诱导的1H NMR位移Δδmax与母体二乙酰氧基苯、对苯二酚或二甲氧基苯夹的报告值进行了比较。的二乙酰氧基苯夹，承载供体吡咯烷基基团在两个萘侧壁的尖端，形成最稳定的配合物与TCNB和KS，压倒相应的复合物的母体剪辑和剪辑承载一个硝基或甲氧羰基基团在一个萘侧壁的尖端。在两个萘侧壁的尖端上具有两个受体基团（两个硝基或甲氧羰基）的夹子在NMR检测的范围内不与TCNB，KS或NMNA形成任何复合物。客体信号的大络合诱导的1H NMR位移提供了很好的证据，即在每个络合物中，客体分子通过吸引性芳香π-π和CH-π相互作用夹在主体分子的萘侧壁之间，如力场计算所示。复合物的这种结构分配进一步通过单硝基取代的剪辑的KS复合物的单晶结构证实，其类似于具有KS的母体剪辑的复合物结构。夹子的静电势表面之间的良好相关性（EPS;通过DFT计算的供体或受体取代的分子夹）和主客体复合物的稳定性证实了这样的假设，即在氯仿溶液中，（由吸引的芳香族π-π和CH-π相互作用产生）本质上主要是静电的，而EPS值与甲醇溶液中发现的结合常数不相关，表明额外的结合力（例如由疏溶剂效应产生）有助于主体-客体结合。在萘侧链上被一个或两个甲氧羰基取代的光学活性二乙酰氧基苯夹是未来手性分子识别和有机催化研究的良好起点。
The synthesis, separation, and characterization of some substituted stereoisomeric dimethylene‐bridged molecular clips bearing donor or acceptor groups at the tips of the naphthalene sidewalls and two acetoxy, hydroxy, or methoxy groups at the central benzene spacer unit are reported. The host–guest complex formation was studied for these substituted molecular clips as host molecules with 1,2,4,5‐tetracyanobenzene (TCNB),N‐methyl‐p‐(methoxycarbonyl)pyridinium iodide (Kosower's salt, KS), andN‐methylnicotinamideiodide (NMNA) as guest molecules. The binding constants,Ka, and the complexation‐induced1H NMR shifts of the guest signals, Δδmax, obtained by NMR titration experiments, are compared with those reported for the parent diacetoxybenzene, hydroquinone, or dimethoxybenzene clips. The diacetoxybenzene clip, bearing donor pyrrolidinyl groups at the tips of both naphthalene sidewalls, forms the most stable complexes with TCNB and KS, overwhelming the corresponding complexes of the parent clip and the clips bearing one nitro or methoxycarbonyl group at the tip of one naphthalene sidewall. The clips bearing two acceptor groups (two nitro or methoxycarbonyl groups) at the tips of both naphthalene sidewalls do not form any complex with TCNB, KS, or NMNA within the limits of NMR detection. The large complexation‐induced1H NMR shifts of the guest signals provide good evidence that in each complex the guest molecule is clipped between the naphthalene sidewalls of the host molecule by attractive aromatic π–π and CH–π interactions, as suggested by force‐field calculations. This structural assignment of the complexes is further confirmed by a single‐crystal structure of the KS complex of the mono‐nitro‐substituted clip, which resembles the complex structure of the parent clip with KS. The good correlation between the clip's electrostatic potential surface (EPS; calculated by DFT for the donor‐ or acceptor‐substituted molecular clips) and the host–guest complex stability confirms the assumption that in chloroform solution the host–guest binding (resulting from attractive aromatic π–π and CH–π interactions) is largely electrostatic in nature, whereas the EPS values do not correlate with the binding constants found in methanol solution, indicating that additional binding forces (resulting for example from solvophobic effects) contribute to the host–guest binding. The separated optically active diacetoxybenzene clips substituted by one or two methoxycarbonyl groups at the naphthalene sidewalls are a good starting point for future studies of chiral molecular recognition and organic catalysis.