A polyaromatic dumbbell-based micelle capable of binding large dyes under organic solvent-rich conditions

Abstract

Micelles are typical molecular assemblies formed in water. To develop new micelles usable even under organic solvent-rich conditions, we designed and synthesized a dumbbell-shaped polyaromatic amphiphile composed of two bent bisanthracene dimers linked by a long dicationic spacer. The dissolved dumbbells quantitatively assemble into a spherical polyaromatic micelle with a core diameter of ∼2 nm in water, exhibiting extremely high stability against dilution (up to 1.2 μM). Through a simple grinding–sonication protocol, organic and metal–organic dyes are efficiently encapsulated by the micelle in water. Strikingly, the resulting host–guest composites retain excellent stability even after addition of a large amount of organic solvent (e.g., 75% v/v methanol), owing to multiple chelate-type π–π and CH–π interactions. The importance of both the long spacer and the dumbbell design is demonstrated by control experiments using an analogous dumbbell possessing a shorter spacer and an amphiphilic semi-dumbbell.