The Unexpected Chemistry of Thiacalix[4]arene Monosulfoxide

Thiacalix[4]arene monosulfoxide 4 possesses a very unusual chemistry, as demonstrated by several unprecedented derivatives in calixarene chemistry. Interestingly, compound 4 cannot be prepared by the dealkylation of its corresponding tetramethoxy derivative using BBr₃. Instead, the borate complex is formed with a boron bound by the two neighboring phenolic oxygens and a sulfoxide group. A similar type of borate complex with a spirodienone fragment was then isolated as a by-product. The oxidation of monosulfoxide with Chloramine-T did not provide the expected spirodienone moiety, but rather a complex oxathiane-based spiroheterocyclic part containing a chlorine atom. X-ray analyses confirmed the structures of the unusual products and feasible formation mechanisms were proposed. These results provide further evidence of the distinction between thiacalixarene chemistry and the chemistry of classical CH₂ analogues.

Fluorescent cyclophanes and their applications

With the serendipitous discovery of crown ethers by Pedersen more than half a century ago and the subsequent introduction of host-guest chemistry and supramolecular chemistry by Cram and Lehn, respectively, followed by the design and synthesis of wholly synthetic cyclophanes-in particular, fluorescent cyclophanes, having rich structural characteristics and functions-have been the focus of considerable research activity during the past few decades. Cyclophanes with remarkable emissive properties have been investigated continuously over the years and employed in numerous applications across the field of science and technology. In this Review, we feature the recent developments in the chemistry of fluorescent cyclophanes, along with their design and synthesis. Their host-guest chemistry and applications related to their structure and properties are highlighted.

Pillararene-based AIEgens: research progress and appealing applications

The pillararene-based AIEgens and AIE materials, constructed using different assembly forms, show attractive applications in various areas.

Calixarene-Based Supramolecular AIE Dots with Highly Inhibited Nonradiative Decay and Intersystem Crossing for Ultrasensitive Fluorescence Image-Guided Cancer Surgery

Host-guest complexation between calix[5]arene and aggregation-induced emission luminogen (AIEgen) can significantly turn off both the energy dissipation pathways of intersystem crossing and thermal deactivation, enabling the absorbed excitation energy to mostly focus on fluorescence emission. The co-assembly of calix[5]arene amphiphiles and AIEgens affords highly emissive supramolecular AIE nanodots thanks to their interaction severely restricting the intramolecular motion of AIEgens, which also show negligible generation of cytotoxic reactive oxygen species. In vivo studies with a peritoneal carcinomatosis-bearing mouse model indicate that such supramolecular AIE dots have rather low in vivo side toxicity and can serve as a superior fluorescent bioprobe for ultrasensitive fluorescence image-guided cancer surgery.

Tuning the fluorescence based on the combination of TICT and AIE emission of a tetraphenylethylene with D–π–A structure

A simple D–π–A structured tetraphenylethylene with two electron-rich methyloxy groups and two electron withdrawing cyano groups, which features both twisted intramolecular charge-transfer (TICT) and aggregation-induced emission (AIE) properties, namely TPEOMeCN has been prepared. The emission of TPEOMeCN examined in various solvents is dependent on the polarities of solvents, which indicates the TICT character. The emission intensity of the compound also enhances with the increasing water fraction in H₂O–DMSO mixtures, demonstrating the typical AIE property. Excitingly, the TICT and AIE emission could be observed separately or simultaneously by adjusting the water fraction or viscosity of the solvent. Encouragingly, the combined emission of the TPEOMeCN derived from this single molecule could be readily tuned via regulating the viscosity of the system, resulting in a broad emission peak which covers the visible spectrum (400–700 nm). This work provides a general strategy for designing molecules combining TICT emission and AIE for application as full-color emitters.

The combination of the TICT and AIE properties in a tetraphenylethylene based molecule with D–π–A structure is observed by simply adjusting the viscosity of the solvent.

Regulating the emission of tetraphenylethenes by changing the alkoxyl linkage length between two neighboring phenyl moieties

Alkoxyl linkages with different carbon lengths are employed to link the two neighboring ortho carbons of the two phenyl moieties at the same ethylene carbon of the tetraphenylethene framework, resulting in successful regulation of the molecular conformation and in turn the emission properties.

Macrocycles and cages based on tetraphenylethylene with aggregation-induced emission effect

Syntheses, photophysical properties and applications of macrocycles and cages based on tetraphenylethylene with aggregation-induced emission (AIE) effect.

Conformation-controlled emission of AIE luminogen: a tetraphenylethene embedded pillar[5]arene skeleton

Incubation of a guest 1,4-dicyanobutane molecule inside a tetraphenylethene-embedded pillar scaffold induces a significant change in the molecular conformation, shutting down the AIE properties.