Switchable Complexation between (O‑Methyl)₆‑2,6-helic[6]arene and Protonated Pyridinium Salts Controlled by Acid/Base and Photoacid

Complexation between (O-methyl)₆-2,6-helic­[6]­arene and protonated pyridinium salts was investigated by ¹H NMR, ESI-MS, and calculations. It was found that the host and the tested guests could form stable complexes and the binding and release process of the guests in the complexes could be reversibly controlled by acid–base stimulus. Notably, the switchable complexation could also be efficiently controlled by light stimulus in the presence of protonated merocyanine 1-MEH.