Cyclodextrin‐Confined Supramolecular Lanthanide Photoswitch

Abstract

The utilization of azobenzene‐based photoisomerization cannot only control the morphology of supramolecular assemblies, but can also regulate many biological processes. However, the design of azobenzene‐involved nanoconstructs with switchable photoluminescence remains challenging because of the light‐quenching ability of azobenzene. Herein, an azobenzene‐derived multicomponent nanosystem is reported and its function as a supramolecular lanthanide photoswitch is explored. The metal chelation between lanthanide ions (Ln3+ = Eu3+ and Tb3+) and 2,6‐pyridinedicarboxylic acid is utilized as the light‐emitting center but its inherent fluorescence emission is completely suppressed via the disordered motion of the adjoining azophenyl unit. Interestingly, the hydrophobic cavity of α‐cyclodextrin can provide a confined microenvironment to immobilize the molecular conformation of trans‐azobenzene, thus leading to the recovery of characteristic lanthanide luminescence both in aqueous solution and the hydrogel state. Also, the luminescence can be reversibly turned off when the cis‐azobenzene is expelled from the cavity of α‐cyclodextrin upon alternating light irradiation. This mutual cooperation arising from host–guest complexation and metal–ligand coordination confers the desired photoswitchable luminescence abilities on the commonly used azobenzenes, which may hold great promise in the creation of more advanced light‐responsive smart materials.

Click Chemoselective Probe with a Photoswitchable Handle for Highly Sensitive Determination of Steroid Hormones in Food Samples

“…It was found that the conversion efficiency of trans-to-cis was slightly reduced after adding α-CD, mainly caused by the strong binding affinity between α-CD and Azo-N 3 that hindered the effective trans-to-cis isomerization in solution. 41 Additionally, the 2D rotating-frame Overhauser effect spectroscopy (ROSEY) spectra indicated that strong nuclear Overhauser effect (NOE) correlation peaks were found between the protons of the azobenzene moiety and the protons belonging to the hydrophobic cavity of α-CD (Figure 3C), confirming the formation of the host−guest inclusion complex. 41 In comparison, nearly no NOE correlation could be observed after irradiation of UV light, indicating that most trans-Azo-N 3 was transferred to the cis-isomer and escaped from the inner cavity of α-CD (Figure 3D).…”

Green materials with promising applications: cyclodextrin-based deep eutectic supramolecular polymers

“…Exploration of the exciting combinations of macrocyclic host molecules other than CDs with deep eutectic systems should be an exciting scientific challenge. Exploring the application possibilities of DESPs in supramolecular switches, 101–103 supramolecular sensors, and multifunctional surfactants is extremely challenging. At the same time, other non-covalent interactions can be introduced to facilitate the formation of supramolecular networks together with hydrogen bonding.…”

Photoresponsive reversible self-assembly of rod-coil amphiphiles containing spiropyran groups

“…[1][2][3][4][5][6][7][8] The elementary molecular structure and assembly environment are two crucial elements that simultaneously determine the non-covalent interactions of the assembly systems, and further influence the morphology of the aggregates and the application prospects of supramolecular soft materials. [9][10][11][12][13][14][15] Therefore, stimuli-responsive self-assembly is a convenient technique for obtaining various assembled nanostructures by modifying the assembly environment under external stimuli (e.g., light, heat, pH, or ions). [16][17][18][19][20][21][22] Among the possible kinds of stimuli-sensitive self-assembly, photo-controlled selfassembly is considered to be an ideal method to form diverse functional nanoassemblies, due to the characteristic properties of light.…”

“…1–8 The elementary molecular structure and assembly environment are two crucial elements that simultaneously determine the non-covalent interactions of the assembly systems, and further influence the morphology of the aggregates and the application prospects of supramolecular soft materials. 9–15 Therefore, stimuli-responsive self-assembly is a convenient technique for obtaining various assembled nanostructures by modifying the assembly environment under external stimuli ( e.g. , light, heat, pH, or ions).…”