Heterowheel [4]Pseudorotaxane Exhibiting Solid-State Near-Infrared Photochromism, Amine-Selective Vapochromism, and Tunable Fluorescence over a Broad Excitation Range

by three macrocycles, the resultant [4]pseudorotaxane exhibited intriguing near-infrared (NIR) photochromism and amine-selective vapochromism, as confirmed by UV-vis diffuse reflectance (DR) and ESR spectroscopy. Moreover, benefiting from the macrocyclic confinement effect, the [4]pseudorotaxane exhibited solid-state fluorescence with a broad excitation range (from 254 to 430 nm). The combination of exceptional stimuli-responsive chromism and strong fluorescence emission renders the [4]pseudorotaxane promising for practical applications in erasable inkless printing and multiple anti-counterfeiting.