Syntheses and properties of a series of novel surface active salts based on 1,4-dialkyl-1,4-diazoniabicyclo[2.2.2]octane and their supermolecular interactions with cucurbit[6]uril

A series of novel surface active salts, 1,4-dialkyl-1,4-diazoniabicyclo[2.2.2]octane bromides (2CxDABCOBr2), have been synthesized and characterized. Their melting points show a U-shaped curve with increasing alkyl chain length, while the decomposition temperatures do not show significant differences. Critical aggregation concentration (cac) of 2C6DABCOBr2 determined by the concentration dependence of 1H NMR chemical shifts is about 100 mmol L−1, which is in good agreement with the cac obtained by electrical conductivity and surface tension measurement. The aggregation number of 2C6DABCOBr2 in aqueous solutions studied with a detailed analysis of 1H NMR is 36. The interaction between 2C6DABCOBr2 and cucurbit[6]uril in aqueous solution has also been investigated by 1H NMR and spin-lattice relaxation time measurement (T1), indicating the formation of a complex with one alkyl chain of 2C6DABCOBr2 inserted into the cavity of CB[6].