Photomodulated Fluorescence of Supramolecular Assemblies of Sulfonatocalixarenes and Tetraphenylethene

Abstract

Self-assembled fluorescent nanoparticles responding to specific stimuli are highly appealing for applications such as labels, probes, memory devices, and logic gates. However, organic analogues are challenging to prepare, due to unfavorable aggregation-caused quenching. We herein report the preparation of self-assembled fluorescent organic nanoparticles in water by means of calixarene-induced aggregation of a tetraphenylethene derivative (QA-TPE) mediated by p-sulfonatocalix[4]arenes. The self-assembled nanoparticles showed interesting photoswitching behaviors, and the fluorescence output of the generated nanoparticles was opposite to that of free QA-TPE both before and after irradiation. Free QA-TPE is nonfluorescent, owing to intramolecular rotations of the phenyl rings. In contrast, the self-assembled nanoparticles that formed upon complexation of QA-TPE with p-sulfonatocalix[4]arene exhibited aggregation-induced emission fluorescence (λ(em) = 480 nm, Φ = 14%), as a result of the inhibition of rotations. Upon UV light irradiation, free QA-TPE was cyclized to the corresponding diphenylphenanthrene, which showed typical fluorescence of a π-conjugated system (λ(em) = 385 nm, Φ = 9.3%), whereas the nanoparticles were nonfluorescent upon irradiation due to the aggregation-caused quenching. In effect, this system allows programmed modulation of TPE fluorescence at two different emission wavelengths by means of host-guest complexation and irradiation. Relative to a single-mode stimulus-responsive system, our new developed system of highly integrated modes into a single molecular unit that can exhibit modulation of fluorescence by multiple stimulus is expected to be more adaptable for practical applications and to show enhanced multifunctionality.

Effect of Macrocycle Size on the Self-Assembly of Methylimidazolium Surfactant with Sulfonatocalix[n]arenes

“…[8][9][10] For example, they induced the aggregation of tetraphenylethene derivatives to strongly fluorescent nanoassemblies 11 and their emission properties could be tuned by irradiation with UV light. 12 The binding to SCXn facilitates the aggregation of aromatic or amphiphilic molecules. [13][14][15][16][17] The interaction of the macrocycle homologue comprised of four sulfonatophenol units (SCX4) with a natural cationic protein, protamine resulted in supramolecular vesicle which disintegrated in a controlled manner upon addition of trypsine.…”

Photolysis of an Amphiphilic Assembly by Calixarene-Induced Aggregation

“…SC4A not only induced compact packing between anthracenes but also inhibited the fluorescence quenching of AnPy, which is favorable for photosensitization. Interestingly, the photodecomposition of aggregated AnPy was significantly promoted, while it was reported that the fluorescence of photosensitizers could be generally self-quenched after aggregation, 16 resulting in greatly reduced ability for singlet oxygen generation and lower photoreactivity. 17 The supramolecular assembly exhibited efficient photolysis with visible light in the presence of exogenous photosensitizers.…”

Selected applications of calixarene derivatives

“…[5][6][7] Calixarenes form metal nanoparticles, [8][9][10] e.g. AuNPs 8,9 and AgNPs, 10 as well as organic NPs, 11 and serve for construction of sensors; [12][13][14] they also may be used as extractants of f-elements. 15,16 The present paper is a continuation of our previous reviews concerning covalently and noncovalently bound calixarene assemblies, 17 calixarenes functionalized at wide and narrow rims, 18 calixarenes substituted at meso positions, 19 calixarene complexes with metal ions, 20 as well as calixarenes and resorcinarenes.…”