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While controlling the wheel shuttling of prototype [2]rotaxanes has been readily achieved, which promotes the development of intelligent supramolecular systems and materials, it remains a grand challenge to access higher ordered rotaxane systems with precisely controllable relative motion between component parts. Herein, a unique tristable [3]rotaxane was synthesized by threading two cyclobis(paraquat-p-phenylene) (CBPQT4+) macrocycles with a dumbbell component, which contained three recognition sites, including a photoactive azobenzene (AB) unit and a redox active tetrathiofulvalene (TTF) unit separated by a dioxynaphthalene (DNP) unit. Upon UV (365 nm)/yellow (> 525 nm) light irradiation, the Z/E photoisomerization of the AB unit could be triggered to drive the CBPQT4+ wheel (A) to shuttle between the AB and DNP units, with the CBPQT4+ wheel (B) maintained on the TTF unit. Furthermore, regulating the redox states of the TTF unit without light irradiation can induce the CBPQT4+ wheel (B) to shuttle between the TTF and DNP units. The construction of this unique orthogonal photo and redox stimuli-responsive [3]rotaxane is conducive to the development of higher ordered rotaxane-based molecular systems with controllable sophisticated properties and functions. [ABSTRACT FROM AUTHOR]

Exploring new noncovalent bonding motifs with reversibly tunable binding affinity is of fundamental importance in manipulating the properties and functions of supramolecular self‐assembly systems and materials. Herein, for the first time, we demonstrate a unique visible‐light‐switchable telluro‐triazole/triazolium‐based chalcogen bonding (ChB) system in which the Te moieties are connected by azobenzene cores. The binding strengths between these azo‐derived ChB receptors and the halide anions (Cl−, Br−) could be reversibly regulated upon irradiation by visible light of different wavelengths. The cis‐bidentate ChB receptors exhibit enhanced halide anion binding ability compared to the trans‐monodentate receptors. In particular, the telluro‐triazolium‐based ChB receptor can achieve both high and significantly photoswitchable binding affinities for halide anions, which enable it to serve as an efficient photocontrolled organocatalyst for ChB‐assisted halide abstraction in a Friedel–Crafts alkylation benchmark reaction. [ABSTRACT FROM AUTHOR]

Although a previous traditional paired meta-analysis involving 35 randomized clinical trials (RCTs) assessed the efficacy of several types of exercise versus control arm, the rough or fuzzy classification of exercise interventions led to considerable heterogeneity in the assessment of exercise intervention outcomes, which reduced the quality of the evidence.[13] The authors did not consider placebo (or sham exercise) effects when selecting control measures. Conclusion Despite limited evidence, exercise interventions have clear benefits for patients with FMS, and the size of the effect varies depending on the type of exercise and the outcome of interest. However, there are still some patients with FMS who cannot tolerate aerobic exercise, with poor muscle strength and flexibility.[9],[10] Other forms of exercise (such as tai chi, yoga, vibration techniques) and lifestyle physical activities have also been introduced.[11] It is important to determine the most effective type of exercise (aerobic, resistance, stretching, sensorimotor training, mind-body exercise, etc.).[12] A review of the last 32 years (1990-2022) of research on this question shows that there is a strong interest in answering it. [Extracted from the article]

A photo‐switchable hetero‐complementary quadruple H‐bonding array, which consists of an azobenzene‐derived ureidopyrimidinone (UPy) module (Azo‐UPy) and a nonphotoactive diamidonaphthyridine (DAN) derivative (Napy‐1), is constructed based on a reversible photo‐locking approach. Upon UV (390 nm)/Vis (460 nm) light irradiations, photo‐switchable quadruple H‐bonded dimerization between Azo‐UPy and Napy‐1 can be achieved with exhibiting 4.8×104‐fold differences in binding strength (ON/OFF ratios). Furthermore, smart polymeric gels with unique photo‐controlled macroscopic self‐assembly behavior can be fabricated by introducing such quadruple H‐bonding array as photo‐regulable noncovalent interfacial connections. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) have many attractive properties. For example, their physical and chemical properties can be tuned by a judicious design of the cations and anions, making them ideal candidates for designable building blocks of stimuli‐responsive materials. Numerous IL‐based stimuli‐responsive materials have been developed by chemical modification (covalent, coordination, or ionic functionalization) or physical blending of ILs with other functional materials. The flexible tunability of ILs provides a great opportunity to achieve the desired physicochemical properties for task‐specific applications, such as sensing, display, gas capture, and so on. This review aims to address the recent advances in IL‐based stimuli‐responsive materials, which are categorized by the type of external stimuli, including gas‐responsive, organic solvent‐responsive, ion‐responsive, pH‐responsive, thermo‐responsive, photo‐responsive, and electro‐responsive materials. [ABSTRACT FROM AUTHOR]

Exploring dynamic bonds and their applications in fabricating dynamic materials has received great attention. A photoinduced [2]rotaxane‐based dynamic mechanical bond (DMB) features visible‐light‐triggered dynamic bonding behavior that is essentially distinguished from conventional dynamic chemical bonds. In this DMB, a photoisomerizable ortho‐fluoroazobenzene unit is introduced as a steric‐controllable stopper, the visible‐light‐induced dynamic wagging movement of which enables the photoregulated threading of the macrocycle. This allows reversible in situ de‐/reforming of the mechanical bond without involving dynamic chemical linkage. The DMB‐cross‐linked polymeric gel shows interesting photoinduced degradation behavior upon visible light irradiation. Benefiting from the distinctive dual dynamic nature of reversible bonding behavior and mechanical interlocked structure, this DMB is expected to serve as a new type of dynamic bond that can be applied in designing dynamic soft materials. [ABSTRACT FROM AUTHOR]

Abstract: The development of artificial self‐assembling systems with dynamic photo‐regulation features in aqueous solutions has drawn great attention owing to the potential applications in fabricating elaborate biological materials. Here we demonstrate the fabrication of water‐soluble cucurbit[8]uril (CB[8])‐mediated supramolecular polymers by connecting the fluorinated azobenzene (FAB) containing monomers through host‐enhanced heteroternary π–π stacking interactions. Benefiting from the unique visible‐light‐induced E→Z photoisomerization of the FAB photochromophores, the encapsulation behaviors between the CB[8] macrocycle and the monomers could be regulated upon visible light irradiation, resulting in the depolymerization of such CB[8]‐mediated supramolecular polymers. [ABSTRACT FROM AUTHOR]

Photochromic [2]rotaxanes with bidirectional photoswitchability were fabricated, whose colored states exhibit remarkable visible-light and thermal stabilities as revealed by systematically spectroscopic investigations. [ABSTRACT FROM AUTHOR]

Binding of long aliphatic chains in water-soluble container compounds is driven by the hydrophobic effect: the CH2 groups of the guests are buried from water and solvate the inner aromatic surface of the host. The hydrophobic forces and the CH-π attractions are often sufficient to contort the guests into otherwise unfavorable shapes. Here we show that alkanes, α,ω-diols, α,ω-diacids and their methyl esters assume folded, J-shaped conformations in a water-soluble cavitand. The environment of the guest’s ends interconvert rapidly on the NMR timescale through yo-yo like motions. The applications of water-soluble cavitands to reaction processes are discussed in the context of moving vs. fixed guest ends. [ABSTRACT FROM AUTHOR]

Light-triggered photoisomerization of the azobenzene (AB) unit in bistable [2]rotaxanes can cause the shuttling of the macrocycle on the dumbbell, resulting in distinctive dual spectral variation characteristics: (1) the spectral change of the photochromic unit and (2) the variation of the charge-transfer band. By employing the CT bond region as an output signal, non-destructive readout of optical information could be achieved. [ABSTRACT FROM AUTHOR]

Multicomponent surface architectures are introduced that operate with three different dynamic covalent bonds. Disulfide exchange under basic conditions accounts for the growth of π stacks on solid surfaces. Hydrazone exchange under acidic conditions is used to add a second coaxial string or stack, and boronic ester exchange under neutral conditions is used to co-align a third one. The newly introduced boronic ester exchange chemistry is compatible with stack and string exchange without interference from the orthogonal hydrazone and disulfide exchange. The functional relevance of surface architectures with three different dynamic covalent bonds is exemplified with the detection of polyphenol natural products, such as epigallocatechin gallate, in competition experiments with alizarin red. These results describe synthetic strategies to create functional systems of unprecedented sophistication with regard to dynamic covalent chemistry. [ABSTRACT FROM AUTHOR]

The binding behavior of a cavitand introduced by de Mendoza is explored with new guest species. to hydrogen-bonded capsules occurs in the presence of appropriate guests, including alkanes, alkylated arenes, stilbenes, benzanilides, and carbodiimides. Peripheral tetraethylene glycol groups are attached to the cavitand to improve solubility. Encapsulation of hydrophobic compounds can be observed in aqueous media. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The construction of supramolecular systems in aqueous media is still a great challenge owing to the limited sources of building blocks. In this study, a series of 4-aryl- N-methylpyridinium derivatives have been synthesized. They formed very stable host-guest (1:2) complexes with CB[8] in water (binding constants up to 1014 M−2) with the two guest molecules arranged in a head-to-tail manner and the complexes showed high thermostability, which was revealed by 1H NMR and UV/Vis spectroscopic studies, ITC, and crystallographic analysis. [ABSTRACT FROM AUTHOR]

The self-assembly of a new type of three-dimensional (3D) supramolecular polymers from tetrahedral monomers in both organic and aqueous media is described. We have designed and synthesized two tetraphenylmethane derivatives T1 and T2, both of which bear four tetrathiafulvalene (TTF) units. When the TTF units were oxidized to the radical cation TTF.+, their pre-organized tetrahedral arrangement remarkably enhanced their intermolecular dimerization, leading to the formation of new 3D spherical supramolecular polymers. The structure of the supramolecular polymers has been inferred on the basis of UV/Vis absorption, electron paramagnetic resonance, cyclic voltammetry, and dynamic light scattering (DLS) analysis, as well as by comparing these properties with those of the self-assembled structures of mono-, di-, and tritopic control compounds. DLS experiments revealed that the spherical supramolecular polymers had hydrodynamic diameters of 68 nm for T1 (75 μ M) in acetonitrile and 105 nm for T2 (75 μ M) in water/acetonitrile (1:1). The 3D spherical structures of the supramolecular polymers formed in different solvents were also supported by SEM and AFM experiments. [ABSTRACT FROM AUTHOR]

Reverse vesicles exhibiting functions similar to thoseof normalvesicles have been constructed through the self-assembly of TTF/CBPQT4+-based pseudo[2]rotaxanes in a nonpolar solvent. The endsof the threads of the pseudo[2]rotaxanes are attached with a Fréchet-typeG-3 dendron and a hydrogen-bonded arylamide foldamer. These vesiclesexhibit a response to redox. By exploiting the dynamic featurespontaneouslyslow disassociation of the pseudorotaxanesthe sustained releaseof dyes embedded in the reverse vesicles has been demonstrated, whichcan be further tuned by changing the solvent polarity. [ABSTRACT FROM AUTHOR]

Encapsulation of amphiphilic guests in a water-soluble cavitand is enhanced by the addition of hexafluoroisopropanol (HFIP). While binding of n-alkanes in cavitands in HFIP/D2O mixtures was similar to that observed in 100% D2O, the binding of guests with terminal polar groups was quite different. Several α,̉-bolaamphiphiles: alkyldiols (C10–C12), a dinitrile (C14) and a diacid (C16) became encapsulated in HFIP/D2O solutions. As little as 15% HFIP v/v in D2O moves the guest from cavitand to the dimeric capsule. The unusual binding of polar functional groups inside the confined space is deduced from NMR COSY spectra and supported by DFT calculations. Alkane guests are also encapsulated in 100% HFIP. [ABSTRACT FROM AUTHOR]

A cavitand with ionic, but nonionizable “feet” folds around hydrophobic guests in D2O. Short alkanes and ibuprofen are included and exchange rates are slow on the NMR timescale. Normal octanoyl groups show good affinity for the cavitand and the gastric peptide ghrelin is bound at low pH and physiological temperature. [ABSTRACT FROM AUTHOR]

Review: 73 refs. [ABSTRACT FROM AUTHOR]

A photo-switchable hetero-complementary quadruple H-bonding array, which consists of an azobenzene-derived ureidopyrimidinone (UPy) module (Azo-UPy) and a nonphotoactive diamidonaphthyridine (DAN) derivative (Napy-1), is constructed based on a reversible photo-locking approach. Upon UV (390 nm)/Vis (460 nm) light irradiations, photo-switchable quadruple H-bonded dimerization between Azo-UPy and Napy-1 can be achieved with exhibiting 4.8×10 4 -fold differences in binding strength (ON/OFF ratios). Furthermore, smart polymeric gels with unique photo-controlled macroscopic self-assembly behavior can be fabricated by introducing such quadruple H-bonding array as photo-regulable noncovalent interfacial connections., (© 2021 Wiley-VCH GmbH.)

Developing new photoswitchable noncovalent interaction motifs with controllable bonding affinity is crucial for the construction of photoresponsive supramolecular systems and materials. Here we describe a unique "photolocking" strategy for realizing photoswitchable control of quadruple hydrogen-bonding interactions on the basis of modifying the ureidopyrimidinone (UPy) module with an ortho -ester substituted azobenzene unit as the "photo-lock". Upon light irradiation, the obtained Azo-UPy motif is capable of unlocking/locking the partial H-bonding sites of the UPy unit, leading to photoswitching between homo- and heteroquadruple hydrogen-bonded dimers, which has been further applied for the fabrication of novel tunable hydrogen bonded supramolecular systems. This "photolocking" strategy appears to be broadly applicable in the rational design and construction of other H-bonding motifs with sufficiently photoswitchable noncovalent interactions., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Exploring dynamic bonds and their applications in fabricating dynamic materials has received great attention. A photoinduced [2]rotaxane-based dynamic mechanical bond (DMB) features visible-light-triggered dynamic bonding behavior that is essentially distinguished from conventional dynamic chemical bonds. In this DMB, a photoisomerizable ortho-fluoroazobenzene unit is introduced as a steric-controllable stopper, the visible-light-induced dynamic wagging movement of which enables the photoregulated threading of the macrocycle. This allows reversible in situ de-/reforming of the mechanical bond without involving dynamic chemical linkage. The DMB-cross-linked polymeric gel shows interesting photoinduced degradation behavior upon visible light irradiation. Benefiting from the distinctive dual dynamic nature of reversible bonding behavior and mechanical interlocked structure, this DMB is expected to serve as a new type of dynamic bond that can be applied in designing dynamic soft materials., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The development of artificial self-assembling systems with dynamic photo-regulation features in aqueous solutions has drawn great attention owing to the potential applications in fabricating elaborate biological materials. Here we demonstrate the fabrication of water-soluble cucurbit[8]uril (CB[8])-mediated supramolecular polymers by connecting the fluorinated azobenzene (FAB) containing monomers through host-enhanced heteroternary π-π stacking interactions. Benefiting from the unique visible-light-induced E→Z photoisomerization of the FAB photochromophores, the encapsulation behaviors between the CB[8] macrocycle and the monomers could be regulated upon visible light irradiation, resulting in the depolymerization of such CB[8]-mediated supramolecular polymers., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Linear tetrathiafulvalene (TTF) oligomers were synthesized, which could not only form a pleated TTF˙ + radical cation foldamer under oxidation conditions, but also interlocked with CBPQT 4+ to form folded donor-acceptor [3]pseudorotaxane in the neutral state of TTF. Moreover, switchable transformation between these two folded supramolecular structures was achieved under the alternative regulation of the redox states of TTF units.

Cyclization reactions are common processes in organic chemistry and show familiar patterns of reaction rates vs ring size. While the details vary with the nature of bond being made and the number of unsaturated atoms, small rings typically form quickly despite angle strain, medium size rings form very slowly due to internal strains, and large rings form slowly (when they form at all) because fewer and less probable conformations bring the ends of the substrate together. High dilution is commonly used to slow the competing bi- and higher molecular processes. Here we apply cavitands to the formation of medium size lactams from ω-amino acids in aqueous (D2O) solution. The cavitands bind the amino acids in folded conformations that favor cyclization by bringing the ends closer together. Yields of a 12-membered lactam are improved 4.1-fold and 13-membered lactam 2.8-fold by the cavitand template. The results open possibilities for moving organic reactions into water even when the processes involve dehydration.

Two new types of supramolecular polymers have been constructed via the self-assembly of rigid rod-like monomers and cucurbit[8]uril (CB[8]) in water. These supramolecular polymers possessed rigid backbones and further aggregated into stick-like bunched fibres.

The construction of supramolecular systems in aqueous media is still a great challenge owing to the limited sources of building blocks. In this study, a series of 4-aryl-N-methylpyridinium derivatives have been synthesized. They formed very stable host-guest (1:2) complexes with CB[8] in water (binding constants up to 10(14)  M(-2)) with the two guest molecules arranged in a head-to-tail manner and the complexes showed high thermostability, which was revealed by (1) H NMR and UV/Vis spectroscopic studies, ITC, and crystallographic analysis., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We report here a widened, deep cavitand host that binds hydrophobic and amphiphilic guests in D2O. Small alkanes (C6 to C11) are bound in compressed conformations and tumble rapidly within the space. Longer n-alkanes (C13 to C14), n-alcohols, and α,ω-diols are taken up in folded conformations. The guests' termini are exposed to solvent while atoms near the alkane's center are buried and protected. The cavitand acts as a concave template that pushes terminal atoms of the guest closer together. The unexpected binding modes are interpreted in terms of the size and shape of the space accessible in the new cavitand.

The self-assembly of a new type of three-dimensional (3D) supramolecular polymers from tetrahedral monomers in both organic and aqueous media is described. We have designed and synthesized two tetraphenylmethane derivatives T1 and T2, both of which bear four tetrathiafulvalene (TTF) units. When the TTF units were oxidized to the radical cation TTF(.+) , their pre-organized tetrahedral arrangement remarkably enhanced their intermolecular dimerization, leading to the formation of new 3D spherical supramolecular polymers. The structure of the supramolecular polymers has been inferred on the basis of UV/Vis absorption, electron paramagnetic resonance, cyclic voltammetry, and dynamic light scattering (DLS) analysis, as well as by comparing these properties with those of the self-assembled structures of mono-, di-, and tritopic control compounds. DLS experiments revealed that the spherical supramolecular polymers had hydrodynamic diameters of 68 nm for T1 (75 μM) in acetonitrile and 105 nm for T2 (75 μM) in water/acetonitrile (1:1). The 3D spherical structures of the supramolecular polymers formed in different solvents were also supported by SEM and AFM experiments., (Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Hydrogen-bonded capsules constrain molecules into small spaces, where they exhibit behavior that is inaccessible in bulk solution. Water competes with the formation of hydrogen bonds, and other forces for assembly, such as metal/ligand interactions or hydrophobic effects, have been applied. Here we report the reversible assembly of a water-soluble cavitand to a robust capsule host in the presence of suitable hydrophobic guests. The complexes are characterized by conventional NMR methods. Selectivity for guest length and fluorescence quenching of a stilbene guest are used as evidence for hydrogen bonding in the capsule.

The self-assembly of well-defined 2D supramolecular polymers in solution has been a challenge in supramolecular chemistry. We have designed and synthesized a rigid stacking-forbidden 1,3,5-triphenylbenzene compound that bears three 4,4'-bipyridin-1-ium (BP) units on the peripheral benzene rings. Three hydrophilic bis(2-hydroxyethyl)carbamoyl groups are introduced to the central benzene ring to suppress 1D stacking of the triangular backbone and to ensure solubility in water. Mixing the triangular preorganized molecule with cucurbit[8]uril (CB[8]) in a 2:3 molar ratio in water leads to the formation of the first solution-phase single-layer 2D supramolecular organic framework, which is stabilized by the strong complexation of CB[8] with two BP units of adjacent molecules. The periodic honeycomb 2D framework has been characterized by various (1)H NMR spectroscopy, dynamic light scattering, X-ray diffraction and scattering, scanning probe and electron microscope techniques and by comparing with the self-assembled structures of the control systems.