Micelle-like Molecular Capsules with Anthracene Shells as Photoactive Hosts

摘要

Micelles are spherical assemblies of amphiphilic molecules and one of the oldest classes of supramolecules. They are used in a wide range of practical applications, such as dissolution, separation, preservation, and as reaction vessels.'The amphiphiles are typically linear molecules with hydrophilic "heads" and hydrophobic "tails", so that hydrophobic interactions in water induce the spontaneous formation of spherical aggregates (Figure 1 a). Inspired by the assembly of micelle structures, we envisaged that aromatic-aromatic interactions between large aromatic rings could replace the requisite long hydrophobic tail and favor the assembly of a new class of nanometer-sized molecular capsules (Figure lb) with potential applications as functional contain-ers and reactors. Large aromatic compounds have received much attention as planar and photo-/electrochemi-cally active mesogens; derivatives decorated with flexible hydrophilic or hydrophobic side chains can generate infinite columnar assemblies that exhibit extensive aromatic-aro- matic interactions. However, discrete capsule-like micel-lar assemblies cannot readily form from such rigidly planar aromatic compounds. Although molecular capsules formed through noncovalent hydrogen-bonding,coordinative metal-ligand, hydrophobic, and van der Waals/CH-π interactions1 have been studied, the majority of these capsules, and known micelles, do not contain extended aromatic frameworks and are typically not photoactive. Thus, systems capable of efficient energy transfer between a host and a guest are needed to enrich the photofunctionality of the molecular capsules.