Redox-Responsive Complexation between a Pillar[5]arene with Mono(ethylene oxide) Substituents and Paraquat

Host–guest complexation between a pillar[5]arene with mono(ethylene oxide) substituents and paraquat was studied. We demonstrated that this pillar[5]arene can form a 1:1 complex with paraquat in solution and in the solid state. The formation of this complex was confirmed by proton NMR spectroscopy, electrospray ionization mass spectrometry, and single crystal X-ray analysis. Furthermore, this complexation can be reversibly controlled through the sequential addition and removal of Zn powder. The host substituent effect on the complexation ability was also addressed.