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通过文献报道的方法,高效合成了大环化合物环[2](2,6-二(1H-咪唑基)吡啶[2](1,4-二亚甲基苯)(14+)和环[2](2,6-二(1H-咪唑基)吡啶[2](1,2-二亚甲基苯)(24+).通过溶液中核磁1H谱、气相电喷雾电离质谱(ESI-MS)及固相单晶衍射方法,详细考察了这两个大环主体化合物与一系列体积较小、形状各异的无机阴离子客体间的相互作用.Job’s plot研究结果表明与24+相比,大环主体14+能够结合等量或者更多的阴离子客体;结合常数的计算表明,对于易于形成分子间氢键与大环主体进行复合的阴离子即Cl-,3N-,3NO-或4HSO-,24+与该类阴离子进行1∶1复合的结合常数(Ka1)总是大于甚至是远大于14+.但是对于较难形成分子间氢键,随着离子半径的增大导致极化性增强,更易于发生anion-π作用的离子如Br-和I-,14+与它们的结合常数近于甚至大于24+.推测产生上述现象的原因是由于24+具有紧凑的骨架结构,使四个酸性较强的咪唑盐基2位C—H位点能够有效协同,与体积较小的阴离子同时形成强的分子间氢键;而14+的骨架结构使得上述位点的空间距离较大,具有咪唑盐基团2位C—H键难以全部参与对阴离子的相互作用,而更易于同时与更多的阴离子结合,并更易于发生anion-π的协同作用.上述结果展示了大环主体化合物的骨架结构将控制其空腔的大小、形状及与客体阴离子产生分子间氢键相互作用的C—H键位点的空间分布,从而极大地影响主客体之间复合的模式(如化学计量比和结合常数等).
The synthesis of macrocyclic ring [2] (2,6-bis (1H-imidazolyl) pyridine [2] (1,4-dimethylene) 2] (1,2-dimethylene) (24+) was determined by 1H NMR and GC-ESI-MS ) And solid-state single-crystal diffraction methods, the interactions between the two macrocyclic host compounds and a series of smaller and different shaped inorganic anion guest are investigated in detail.The results of Jacob’s plot show that compared with 24+ The ring body 14+ can bind an equivalent or more number of anionic guest. The calculation of the binding constant shows that for an anion which is easy to form an intermolecular hydrogen bond with the ring host, namely Cl-, 3N-, 3NO- or 4HSO-, 24 + 1: 1 complex with this type of anion is always greater than or even much greater than 14+, but for the more difficult to form intermolecular hydrogen bonds, the polarization increases with increasing ionic radius, and more Ions such as Br- and I- which are prone to anion-π action have a binding constant with them even closer to even greater than 24+. The reason for this phenomenon is presumed to be that 24+ has a compact skeletal structure, The more acidic C 2 H site of imidazole salt group can effectively cooperate with the smaller anion to form strong intermolecular hydrogen bond, while the 14+ backbone structure makes the above space have a large spatial distance, with The C-H bond at the 2-position of the imidazolium salt group is not all involved in the anion interaction, but it is easier to combine with more anions at the same time and the synergistic effect of anion-π is more likely to occur.The above results show that the The framework structure will control the size and shape of the cavity and the spatial distribution of the C-H bond sites that interact with the guest anion to create intermolecular hydrogen bonds, which greatly affects the compound modes between guest and guest (such as stoichiometry and Binding constant, etc.).