Constructing multicolor photoluminescence materials that allow for the integration of suitable external stimuli in order to control luminescence color conversions is a challenging objective. Multicolor luminescent output that is regulated in an in situ photo-controlled manner is not a common phenomenon. Herein, a photoluminescent supra­molecular assembly, prepared in two stages, is described that displays in situ photo-tuning broad-spectrum output. Benefiting from the reversible photo-switched constitutional interconversion of diaryl­ethenes, the fluorescence of a guest molecule, styryl­pyridinium-modified diaryl­ethene, can be switched on/off by alternating ultraviolet and visible light irradiation. Upon complexation of this guest with a host, cucurbit[8]­uril, the fluorescence intensity of the resulting binary supra­molecular nanofiber shows a drastic enhancement when compared with that of the free guest, which can also be quenched and recovered reversibly by light irradiation. Significantly, such cationic supra­molecular nanofibers also interact with anionic carbon dots to form broad-spectrum output ternary supra­molecular assemblies, the fluorescence of which can be changed efficiently from yellow to blue in an in situ photo-controlled manner. Pure white light emission can be realized expediently in the luminescence color-conversion process. The use of light as an external stimulus to regulate fluorescent color conversion provides us with an opportunity to design and construct more advanced anti-counterfeiting materials as well as visual display instruments.

Two-photon excited near-infrared fluorescence materials have garnered considerable attention because of their superior optical penetration, higher spatial resolution, and lower optical scattering compared with other optical materials. Herein, a convenient and efficient supramolecular approach is used to synthesize a two-photon excited near-infrared emissive co-crystalline material. A naphthalenediimide-based triangular macrocycle and coronene form selectively two co-crystals. The triangle-shaped co-crystal emits deep-red fluorescence, while the quadrangle-shaped co-crystal displays deep-red and near-infrared emission centered on 668 nm, which represents a 162 nm red-shift compared with its precursors. Benefiting from intermolecular charge transfer interactions, the two co-crystals possess higher calculated two-photon absorption cross-sections than those of their individual constituents. Their two-photon absorption bands reach into the NIR-II region of the electromagnetic spectrum. The quadrangle-shaped co-crystal constitutes a unique material that exhibits two-photon absorption and near-infrared emission simultaneously. This co-crystallization strategy holds considerable promise for the future design and synthesis of more advanced optical materials.

Pumping macrocycles onto surfaces Numerous chemical processes, ranging from water purification to catalysis, involve sorption of small molecules onto surfaces. Typically, spontaneous attractive interactions favor the binding event. Feng et al . report a mechanisorption process that requires redox manipulations to pump macrocycles from bulk solution onto axles immobilized on a metal-organic framework. The resulting rotaxanes store energy through nonequilibrium charge concentration in their mechanical bonds. Ultimately, the technique could also prove useful for actively partitioning compounds with particular functionality between surface and bulk environments. —JSY