Fine-tuning macrocycle cavity to selectively bind guests in water for near-infrared photothermal conversion

The rational and specific synthesis of the required organic macrocycles to bind size-matched targeted guests without undesired macrocyclic byproducts remains a great challenge. Herein, based on a new naphthalimide (NDI) syn-atropisomer as the highly preorganized precursor, we employ length-variable linkers from phenyl to naphthyl and biphenyl groups to efficiently construct a class of organic macrocycles, namely the ‘trapezoid’ boxes (TBox2+), with gradually extended internal cavities. As water-soluble macrocyclic receptors, they can maximally accommodate rod-like diacetylene, phenyl and larger fused-ring (including naphthalene, fluorene and phenanthrene) guests in water, respectively, indicating an evident size-matching effect between the host cavity and guest molecule. Moreover, one of the host-guest products formed via charge transfer interaction shows intense near-infrared absorption, resulting in excellent 808 nm photothermal activity for antibacterial application.