Heo Nam Jung, Yang Ju Ho, Lynch Vincent M, Ko Byoung Joon, Sessler Jonathan L, Kim Sung Kuk
Department of Chemistry, Research Institute of Natural Science, Gyeongsang National University Jinju 660-701 Korea
Department of Chemistry, The University of Texas at Austin 105 E. 24th Street-Stop A5300 Austin Texas 78712-1224 USA
Chem Sci. 2020 Jul 24;11(31):8288-8294. doi: 10.1039/d0sc03445b.
Two-phenoxy walled calix[4]pyrroles and strapped with small rigid linkers containing pyridine and benzene, respectively, have been synthesized. H NMR spectroscopic analyses carried out in CDCl revealed that both of receptors and recognize only F and HCO among various test anions with high preference for HCO (as the tetraethylammonium, TEA salt) relative to F (as the TBA salt). The bound HCO anion was completely released out of the receptors upon the addition of F (as the tetrabutylammonium, TBA salt) as a result of significantly enhanced affinities and selectivities of the receptors for F once converted to the TEAHCO complexes. Consequently, relatively stable TEAF complexes of receptors and were formed anion metathesis occurring within the receptor cavities. By contrast, the direct addition of TEAF to receptors and produces different complexation products initially, although eventually the same TEAF complexes are produced as sequential TEAHCO and TBAF addition. These findings are rationalized in terms of the formation of different ion pair complexes involving interactions both inside and outside of the core receptor framework.
已合成了分别带有含吡啶和苯的小刚性连接基团的双苯氧基杯[4]吡咯。在CDCl中进行的¹H NMR光谱分析表明，在各种测试阴离子中，受体1和受体2仅识别F⁻和HCO₃⁻，相对于F⁻（作为四丁基铵，TBA盐），它们对HCO₃⁻（作为四乙铵，TEA盐）具有更高的选择性。一旦转化为TEAHCO₃络合物，由于受体对F⁻的亲和力和选择性显著增强，加入F⁻（作为四丁基铵，TBA盐）后，结合的HCO₃⁻阴离子会完全从受体中释放出来。因此，受体1和受体2形成了相对稳定的TEAF⁻络合物，阴离子复分解反应在受体腔内发生。相比之下，直接将TEAF加入受体1和受体2最初会产生不同的络合产物，尽管最终与依次加入TEAHCO₃和TBAF产生的是相同的TEAF⁻络合物。这些发现可以通过涉及核心受体框架内外相互作用的不同离子对络合物的形成来解释。
