Host-aided pH-controlled substitution reaction of aryl diazonium salts and sodium azide

Aided by a host molecule, cucurbit[6]uril (CB[6]), pH-controlled substitution reaction between 4-methoxybenzenediazonium tetrafluoroborate and sodium azide was developed. The interaction of CB[6] and aryl diazonium salt was investigated by UV-Vis absorption spectroscopy, mass spectrometry, and 1 H NMR titration. The results indicated that under strong acidic conditions (pH < 1) CB[6] and aryl diazonium salt form a 1 : 1 inclusion complex. When the pH value was adjusted to ~3, aryl diazonium salt is gradually released from the supramolecular assemblies and reacted with NaN 3 . When the pH of the reaction solution was lowered to pH < 1.0, aryl diazonium salt and CB[6] again formed a supra-molecular assemble.