Six‐Cyclic Crown Ether‐Type Pillar[5]Arene: Enhanced Binding Ability to Bispyridinium Derivatives

A six‐cyclic crown ether‐type pillar[5]arene was synthesized, and the five ethylene oxide loops were located outside the cavity and not affected by temperature changes which was confirmed by variable‐temperature NMR experiment in DMSO‐d6 and CDCl3 and 2D 1H−1H NOESY experiment in CDCl3. The six‐cyclic pillar[5]‐crown also showed greater binding ability of host‐guest with bis(pyridinium) derivatives than conventional alkoxy pillar[5]arenes that illustrated through 1H NMR titration spectroscopic experiment in acetone‐d6/CDCl3 (1 : 1) and UV‐vis titration experiments in CHCl3 at room temperature. The five benzocrown ethers at the periphery were able to bind metal cations by 1H NMR titration spectroscopic experiment in CD2Cl2/methanol‐d4(9 : 1). A new six‐cyclic crown ether‐type pillar[5]arene was synthesized, and the five ethylene oxide loops at the periphery were able to bind metal cations and the cavity of pillararene skeleton showed greater binding ability of host‐guest with bispyridinium derivatives than conventional alkoxy pillar[5]arenes.