Flexible “V-Shaped” Dibenzimidazole Amphiphile: Metal Ion-Driven Microenvironment-Sensitive Reversible Supramolecular Assembly in Aqueous Medium

Abstract

Flexible dibenzimidazole based amphiphilic probe with indole as terminal residue has been synthesized using simple one-step oxidative condensation. The compound formed nanoaggregates in the aqueous medium probably via extended intermolecular hydrogen bonding network involving benzimidazole moieties. The compound in monomer form (in THF) showed metal ion-induced bathochromic shift, while in aggregate state (in water) metal coordination leads to hypsochromic shift. Moreover, in THF medium, compound interacts with large number of metal ions, whereas optical response was specifically observed with Hg2+ and Ag+ in the aqueous medium. Discrimination between Hg2+ and Ag+ was achieved using chloride as masking agent. Mechanistic investigations indicate formation of coordination-driven supramolecular assembly where both benzimidazole and indole moieties participate in metal ion binding. The changes in microenvironment, such as local hydrophobicity, pH etc. showed distinct impact on metal ion sensing properties, both in terms of selectivity and sensitivity. Finally, the quantitative estimation of mercury, beyond its permissible level, was achieved in various natural water samples.