Supramolecular asymmetric catalysis mediated by crown ethers and related recognition systems

Traffic Lights for Catalysis: Stimuli‐Responsive Molecular and Extended Catalytic Systems

“…[50] Overall, crown ether derivatives have been used as PTCs in many organic reactions because of their ability to solubilize ionic species in organic solvents through coordination of the ions within the crown ether structure. [70][71][72] For example, chelation of the cationic species of a salt by crown ethers stabilizes the cation and enhances the solubility of the salt. Consequently, the anionic species can exhibit increased basicity or nucleophilicity since it is no longer stabilized by the counterion.…”

Ampeln für die Katalyse: Stimulus‐reaktive molekulare und erweiterte katalytische Systeme

“…[50] Kronenether-Derivate werden als PTCs in vielen organischen Reaktionen eingesetzt, da sie ionische Verbindungen in organischen Lösungsmitteln durch die Koordination der Ionen innerhalb der Kronenetherstruktur lösen können. [70][71][72] Beispielsweise stabilisiert die Chelatbildung des Kations eines Salzes durch Kronenether das Kation und erhöht die Löslichkeit des Salzes. Folglich kann die anionische Spezies eine erhöhte Basizität oder Nukleophilie aufweisen, da sie nicht mehr durch das Gegenion stabilisiert wird.…”

Light-Driven Aqueous Dissipative Pseudorotaxanes with Tunable Fluorescence Enabling Deformable Nano-Assemblies

“…Supramolecular systems rely on non-covalent molecular interactions, including hydrophobic, hydrogen bonding, electrostatic, van der Waals, and π–π stacking. A strategy in which a macrocyclic host recognizes a guest moiety, with high-level molecular self-organization used to construct an artificial molecular machine, may lead to stimuli-responsive architectures in terms of component motions, photophysical properties, topological structures, , aimed at realizing various applications including drug delivery, catalysis, information encryption, and imaging. , Among diverse stimuli used to control the artificial molecular machines, light is the most favorable because it is conveniently applied and removed both temporally and spatially, easily tuned by adjusting wavelength, polarization, or power density and provides a non-invasive strategy that does not involve additional chemicals or waste in the system. − Various photoresponsive molecular switches (e.g., azobenzenes, stilbenes, spiropyrans, diarylethenes, anthracenes, and coumarins) have been designed to interact with macrocyclic molecules to construct light-driven molecular machines, including catenanes, rotaxanes, and pseudorotaxanes (PRs), through specific host–guest complexation. − Recently, the construction of light-responsive molecular machines has drawn broad attention, especially those involving constantly dissipation of energy from external light to maintain the far-from-equilibrium state. − However, the characterization of the dissipative states based on photoswitches remains a great challenge, especially kinetics in the dissipative cycles …”

“…14 Supramolecular systems rely on non-covalent molecular interactions, including hydrophobic, hydrogen bonding, electrostatic, van der Waals, and π−π stacking. A strategy in which a macrocyclic host recognizes a guest moiety, with highlevel molecular self-organization used to construct an artificial molecular machine, may lead to stimuli-responsive architectures in terms of component motions, photophysical properties, 15 topological structures, 16,17 aimed at realizing various applications including drug delivery, 18 catalysis, 19 information encryption, 20 and imaging. 21,22 Among diverse stimuli used to control the artificial molecular machines, light is the most favorable because it is conveniently applied and removed both temporally and spatially, easily tuned by adjusting wavelength, polarization, or power density and provides a non-invasive strategy that does not involve additional chemicals or waste in the system.…”