Supramolecular Assemblies of a Series of 2-Arylbenzimidazoles at the Air/Water Interface: In Situ Coordination, Surface Architecture and Supramolecular Chirality

The spreading behavior and supramolecular assemblies of some arylbenzimidazoles with 2‐substituted aromatic groups such as phenyl, naphthyl, anthryl and pyrenyl on water surface and the subphase containing AgNO3 were investigated. It was observed that although these compounds lack long alkyl chains, they showed surface activity when spread from chloroform solution on water surface and formed the supramolecular assemblies. When AgNO3 was present in the subphase, a coordination between the imidazole group of the compounds and AgI occurred in situ in the spreading film, which was verified by the surface pressure/area (π–A) isotherms and UV/Vis absorption spectra. Both the spreading films from water and the aqueous AgNO3 subphase were transferred onto solid substrates and their surface morphologies as well as properties were characterized by AFM, UV/Vis absorption and CD spectra. Various surface morphologies such as nanoparticles, block domains and nanoutensils were observed depending on the substituted aromatic groups. Interestingly, although all of these compounds were achiral, supramolecular chirality was obtained for some of the arylbenzimidazole films assembled from either the water surface or the subphase containing AgNO3. It was revealed that chiral assemblies could be obtained from water surface for the benzimidazoles which have pyrenyl or α‐naphthyl groups. For benzimidazole derivative with anthryl group, chiral assemblies could be obtained when spreading on the aqueous AgNO3 subphase. For the benzimidazoles with phenyl or β‐naphthyl groups, no chirality was obtained. It was suggested that both the overcrowded stacking of the aromatic groups and the cooperative arrangement of the molecules on water surface or aqueous AgNO3 subphase play a crucial role in forming the chiral supramolecular assemblies. From achiral molecules to chiral supramolecular assemblies: A series of achiral benzimidazole derivatives, which have no alkyl chains, were found to form chiral supramolecular assemblies either at the air/water interface or through an in situ coordination with AgI ion at the air/aqueous AgNO3 interface (see scheme).