Independent Pathway Formation of Guest?Host in Host Ternary Complexes Made of Ammonium Salt, Calixarene, and Cyclodextrin

摘要

The interaction between γ-cyclodextrin andnamphiphilic p-sulfonatocalix[4]arenes was studied using NMRnand isothermal titration calorimetry techniques. The resultsnindicate that these calixarenes are able to form 1:1, 1:2, and 2:1nhost−guest complexes with the cyclodextrin. The ROESYnspectra suggest that the cyclodextrin binds the calixarenesnthrough the hydrophobic alkyl chains. p-Sulfonatocalix[4]-narenes, which are traditionally used as host molecules, act as guests in the presence of γ-cyclodextrin. However, their recognitionnsite remains active upon complexation with the cyclodextrin, and ternary complexes can be devised. Here, we also demonstratenthe formation of such complexes using tetramethylammonium chloride as a model guest. Moreover, it is also demonstrated thatnthe recognition properties of the calixarene are unaffected upon complexation with the cyclodextrin.