Surfactants Based on Bis-Galactobenzimidazolones: Synthesis, Self-Assembly and Ion Sensing Properties

A series of new non-ionic amphiphiles based on bis-galactobenzimidazolones have been synthesized by grafting alkyl bis-benzimidazolone units as hydrophobic tails on hydroxypropyloxygalacto-pyranose moieties as hydrophilic heads. Their surface and self-aggregation properties in water were evaluated. The compounds show very low critical micellar concentrations (CMCs) that decrease with increasing chain length; values for the minimal area per molecule at the interface (A (min)) follow the same trend. The synthesized compounds also form hexagonal liquid crystals in water for a certain range of hydrophobic tail lengths. On the other hand, the new amphiphiles show characteristic UV-Vis absorption and fluorescence emission bands associated with the benzimidazolone moiety. The fluorescence emission is quenched with a certain degree of selectivity by cations, due to their strong affinity towards the benzimidazolone group, which shows ion complexation properties. Hence, the reported new amphiphiles are candidates as self-assembling chemosensors. The quenching efficiency and also ion sensing sensitivity is higher in the monomeric state as compared to the micellar state. The fluorescence emission intensity is higher for compounds with a shorter alkyl chain.