Donor-Acceptor Assembly of Amphiphilic Molecules Based on 9,10-Distyrylanthracene Derivatives with Terminal Naphthalene Groups.

Amphiphilic rod-coil compounds have excellent photophysical properties and can be assembled into supramolecular nanostructures of different sizes in water or polar solvents. Herein, we synthesized the amphiphilic compounds 2N-DSA, 4N-DSA, and 6N-DSA with 9,10-distyrylanthracene (DSA) as the core and a naphthalene unit as the terminal group that connected DSA through a tetraethylene glycol chain. These compounds have excellent aggregation-induced emission (AIE) properties in aqueous solution and are assembled into worm-like fragments or different sizes of spherical assemblies, defending the volume ratio of the rod to coil segments. Notably, the donor-acceptor interaction between DSA and electron- deficient compounds 2,4,6-trinitrophenol (TNP), 2,4,5,7-tetranitrofluorenone (TNF), and tetraethylene glycol dinitrobenzoate (TGDNB) forms a charge transfer complex, which can be used as a nanoreactor to improve the yield of the Suzuki coupling reaction about 8-10 times. The experimental results reveal that the synergy effect of the donor-acceptor, intermolecular π-π stacking, and hydrophobic-hydrophilic interactions significantly influences the morphology of aggregates and the efficiency of the nanoreactor.

Correction: Tubular metal organic frameworks from the curvature of 2D-honeycombed metal coordination.

Correction for 'Tubular metal organic frameworks from the curvature of 2D-honeycombed metal coordination' by Junhui Bao et al., Dalton Trans., 2020, 49, 2403-2406, https://doi.org/10.1039/C9DT04668B.

Controlled assembly of photosensitizers through directional interactions for effective photooxidation.

Despite the fact that effective photosensitizers (PSs) can be achieved through rational molecular design, controlling the hierarchical assemblies of individual PSs with distinct function and morphological nanoscopic architectures remains a challenge. Here, very ordered one-dimensional PS polymers and their hollow tubular structures are presented from aqueous assembly of organic PS-based di- or tri-blocked supramolecules. Di-blocked PSs were interdigitated into 1D fibrils, significantly quenching photooxidation. Meanwhile, tri-blocked PSs were tilted with respect to each other to generate hollow tubules, showing remarkable photo-activities as well as photo-stability, which are particularly suited for green chemistry due to their unusual rapid photo-oxidation.

Hierarchical porous photosensitizers with efficient photooxidation.

Photosensitizers (PSs) with nano- or micro-sized pore provide a great promise in the conversion of light energy into chemical fuel due to the excellent promotion for transporting singlet oxygen (1O2) into active sites. Despite such hollow PSs can be achieved by introducing molecular-level PSs into porous skeleton, however, the catalytic efficiency is far away from imagination because of the problems with pore deformation and blocking. Here, very ordered porous PSs with excellent 1O2 generation are presented from cross-linking of hierarchical porous laminates originated by co-assembly of hydrogen donative PSs and functionalized acceptor. The catalytic performance strongly depends on the preformed porous architectures, which is regulated by special recognition of hydrogen binding. As the increasing of hydrogen acceptor quantities, 2D-organized PSs laminates gradually transform into uniformly perforated porous layers with highly dispersed molecular PSs. The premature termination by porous assembly endows superior activity as well as specific selectivity for the photo-oxidative degradation, which contributes to efficient purification in aryl-bromination without any postprocessing.

Stimuli-Responsive Supramolecular Chirality Switching and Nanoassembly Constructed by n-Shaped Amphiphilic Molecules in Aqueous Solution.

Self-assembled nanomaterials composed of amphiphilic oligomers with functional groups have been applied in the fields of biomimetic chemistry and on-demand delivery systems. Herein, we report the assembly behavior and unique properties of an emergent n-shaped rod-coil molecule containing an azobenzene (AZO) group upon application of an external stimulus (thermal, UV light). The n-shaped amphiphilic molecules comprising an aromatic segment based on anthracene, phenyl linked with azobenzene groups, and hydrophilic oligoether (chiral) segments self-assemble into large strip-like sheets and perforated-nanocage fragments in an aqueous environment, depending on the flexible oligoether chains. Interestingly, the nano-objects formed in aqueous solution undergo a morphological transition from sheets and nanocages to small one-dimensional nanofibers. These molecules exhibit reversible photo- and thermal-responsiveness, accompanied by a change in the supramolecular chirality caused by the conformational transitions of the rod backbone. The architecture of n-shaped amphiphilic molecules with a photosensitive group makes them ideal candidates for intelligent materials for applications in advanced materials science.

Precisely Controlled Multidimensional Covalent Frameworks: Polymerization of Supramolecular Colloids.

Rapid and selective removal of micropollutants from water is important for the reuse of water resources. Despite hollow frameworks with specific functionalized porous walls for the selective adsorption based on a series of interactions, tailoring a stable shape of nanometer- and micrometer-sized architectures for the removal of specific pollutants remains a challenge. Here, exactly controlled sheets, tubes, and spherical frameworks were presented from the crosslinking of supramolecular colloids in polar solvents. The frameworks strongly depended on the architecture of original supramolecular colloids. As the entropy of colloids increased, the initial laminar framework rolled up into hollow tubules, and then further curled into hollow spheres. These shape-persistent frameworks showed unprecedented selectivity as well as specific recognition for the shape of pollutants, thus contributing to efficient pollutant separation.

Tubular metal organic frameworks from the curvature of 2D-honeycombed metal coordination.

A tubular MOF with adequate active sites is prepared by the bending of metal-coordinated honeycombed frameworks via titration and shows fast catalytic kinetics with lower catalytic loading for CO2 conversion. The TON is observed to be 2300 and the corresponding TOF of up to 173 h-1 is achieved for the first time.

Catalytically-active porous assembly with dynamic pulsating motion for efficient exchange of products and reagents.

Despite recent advances in the use of porous materials as efficient heterogeneous catalysts which operate through effectively trapping reagents in a well-defined space, continuously uptaking reagents to substitute products in the cavity for efficient product turnover still remains challenging. Here, a porous catalyst is endowed with 'breathing' characteristics by thermal stimulus, which can enable the efficient exchange of reagents and products through reversible stacking from inflated aromatic hexamers to contracted trimeric macrocycles. The contracted super-hydrophobic tubular interior with pyridine environment exhibits catalytic activity towards a nucleophilic aromatic substitution reaction by promoting interactions between concentrated reagents and active sites. Subsequent expansion facilitates the exchange of products and reagents, which ensures the next reaction. The strategy of mesoporous modification with inflatable transition may provide a new insight for construction of dynamic catalysts.

Two-Dimensional Cationic Networks and Their Spherical Curvature with Tunable Opening-Closing.

Despite many cationic nanomaterials that have been developed for efficient adsorption of anionic pollutants, tailoring a stable shape with denser cations on the surface for advanced removal capability remains challenging. Here, a new strategy is presented for fabricating two-dimensional (2D) cationic laminas and their curvature based on cross-linking of 2D supramolecular networks from hydrogen-bonded trimesic amide derivatives. Owing to the distribution of most cations on the surface, two cationic nanostructures from cross-linking of supramolecular networks show fast sorption kinetics for anionic pollutants. Notably, the removal capacity of the capsule-like curvature adsorbent is more than twice that of lamina  adsorbent for sufficient space around cationic sites in hollow aperture. Moreover, the capsule-like adsorbent is triggered to open and spontaneously release the adsorbed pollutants upon the addition of halogen anions, which can be recovered by subsequent dialysis. Strategy of a capsule-like pocket with tunable opening-closing will provide a new insight for storage and adsorption.

Charge Regulation of Self-Assembled Tubules by Protonation for Efficiently Selective and Controlled Drug Delivery.

Despite the success for targeted delivery in the body, the efficient release without side effects caused by residual drug remains a challenge. For reducing residual drug, the pH-responsive carriers were prepared by self-assembly from aromatic macrocycles, which were non-toxic and biocompatible. The inner surroundings of aromatic macrocycles could be protonated positively by acid inducing the separation of neighboring macrocycles. Thus, Dox-loaded carriers successfully inhibited the proliferation of carcinoma cells (HepG2 and 4T1) rather than normal cells (HL7702). The effects were further proved in vivo without systemic cytotoxicity. Notably, the responsive environment for drug release depended on the concentration of carriers. Particularly, drug release was promoted by carrier separation. Carrier 2 exhibited preferable anticancer efficacy than carrier 1 due to the efficient release of Dox by full separation of the carrier. Collectively, we have developed a novel strategy serving as a selective and controlled drug release platform for cancer therapeutics.

Supramolecular Nanopumps with Chiral Recognition for Moving Organic Pollutants from Water.

Since organic pollutants in water resources have raised concerns on aquatic ecosystems and human health, mechanical machines such as a nanopump for rapid and efficient removal of pollutants from water with regeneration properties remains a challenge. Here, a pH-responsive artificial pump from left-handed porous tubules into right-handed solid fibers was presented by the self-assembly of bent-shaped aromatic amphiphiles. The bent-shaped amphiphile with a pH-sensitive segment was demonstrated in aromatic hexameric macrocycles, which could contract into dimeric disks. Such a switchable aromatic pore with superhydrophobicity was well-suited for an efficient removal and controlled release of organic pollutants from water through pulsating motion. The removal efficiency is found to be 78% for ethinyloestradiol and 82% for bisphenol. Additionally, the pumping accompanied by chiral inversion was endowed with a rapid removal and convenient regenerable ability. The inflation from right-handed solid fibers into left-handed tubules for efficient removal pollutants was remarkably promoted by (-)-acidic enantiomer of malic acid, whereas the contraction with full desorption of pollutants was incisively responsive to alkaline with (+)-conformation. The kinetically regulable porous device with a chiral recognition will provide a promising platform for the construction of rapid responsible machine for sewage treatment.

Intelligent Mesoporous Materials for Selective Adsorption and Mechanical Release of Organic Pollutants from Water.

Despite recent advances in the porous materials for efficient removal of dissolved organic pollutants from water, the regeneration of porous characteristics for reuse with preventing secondary contamination remains a challenge. Here, novel supramolecular absorbents with hydrophobic pore are prepared by the self-assembly of propeller-shaped aromatic amphiphiles. The assembly of folded propeller provides a mesoporous environment within aromatic segments, which is suitable for the removal of organic pollutants from waste water. The removal efficiency is found to be 92% and 90% for ethinyl oestradiol (Eo) and bisphenol A (BPA). Notably, the folded architecture of propeller is observed to be flattened by the salt addition, which results in the strong π-π interaction driving the porous materials closed and forms solid fibers. It is found that most of the removed pollutants are spontaneously released by the dynamic porous assembly, and subsequent dialysis triggers the porous materials to be recovered.

Supramolecular Nanotubules as a Catalytic Regulator for Palladium Cations: Applications in Selective Catalysis.

Despite the recent development of highly efficient and stable metal catalysts, conferral of regulatory characteristics to the catalytic reaction in heterogeneous systems remains a challenge. Novel supramolecular nanotubules were prepared by alternative stacking from trimeric macrocycles, which was found to be able to coordinate with Pd cations. The Pd complexes exhibited a high catalytic performance for C-C coupling reaction. Notably, the tubular catalyst was observed to be controlled by supramolecular reversible assembly and showed superior heterogeneous catalytic activity, which was maintained for a number of cycles or reuse under an aerobic environment. Furthermore, the supramolecular catalyst showed unprecedented selectivity for the multifunctional coupling reaction and was able to serve as a new constructor of asymmetrical compounds.

Guest-driven inflation of self-assembled nanofibers through hollow channel formation.

The highlight of self-assembly is the reversibility of various types of noncovalent interactions which leads to construct smart nanostructures with switchable pores. Here, we report the spontaneous formation of inflatable nanofibers through the formation of hollow internal channels triggered by guest encapsulation. The molecules that form this unique nanofibers consist of a bent-shaped aromatic segment connected by a m-pyridine unit and a hydrophilic dendron at its apex. The aromatic segments self-assemble into paired dimers which stack on top of one another to form thin nanofibers with pyridine-functionalized aromatic cores. Notably, the nanofibers reversibly inflate into helical tubules through the formation of hollow cavities triggered by p-phenylphenol, a hydrogen-bonding guest. The reversible inflation of the nanofibers arises from the packing rearrangements in the aromatic cores from transoid dimers to cisoid macrocycles driven by the reversible hydrogen-bonding interactions between the pyridine units of the aromatic cores and the p-phenylphenol guest molecules.

Pulsating tubules from noncovalent macrocycles.

Despite recent advances in synthetic nanometer-scale tubular assembly, conferral of dynamic response characteristics to the tubules remains a challenge. Here, we report on supramolecular nanotubules that undergo a reversible contraction-expansion motion accompanied by an inversion of helical chirality. Bent-shaped aromatic amphiphiles self-assemble into hexameric macrocycles in aqueous solution, forming chiral tubules by spontaneous one-dimensional stacking with a mutual rotation in the same direction. The adjacent aromatic segments within the hexameric macrocycles reversibly slide along one another in response to external triggers, resulting in pulsating motions of the tubules accompanied by a chiral inversion. The aromatic interior of the self-assembled tubules encapsulates hydrophobic guests such as carbon-60 (C(60)). Using a thermal trigger, we could regulate the C(60)-C(60) interactions through the pulsating motion of the tubules.

Multivalent nanofibers of a controlled length: regulation of bacterial cell agglutination.

Control of the size and shape of molecular assemblies on the nanometer scale in aqueous solutions is very important for the regulation of biological functions. Among the well-defined supramolecular structures of organic amphiphiles, one-dimensional nanofibers have attracted much attention because of their potential applications in biocompatible materials. Although much progress has been made in the field of self-assembled nanofibers, the ability to control the fiber length remains limited. The approach for control of the fiber length presented herein overcomes this limitation through the coassembly of amphiphilic rod-coil molecules in which the crystallinity of the aromatic segment can be regulated by π-π stacking interactions. The introduction of carbohydrate segments into the fiber exterior endows the nanofibers with the ability to adhere to bacterial cells. Notably, the fiber length systematically regulates the agglutination and proliferation of bacterial cells exposed to these fibers.

Responsive nematic gels from the self-assembly of aqueous nanofibres.

Aqueous nanofibres constructed by the self-assembly of small amphiphilic molecules can become entangled to form hydrogels that have a variety of applications including tissue engineering, and controlled drug delivery. The hydrogels are formed through the random physical cross-linkings of flexible nanofibres. Here we report that self-assembled nanofibres with a nematic substructure are aligned into a nematic liquid crystal and are spontaneously fixed in the aligned state to give rise to anisotropic gels. The liquid-crystal gels respond to temperature by transforming into a fluid solution upon cooling. Thus, the nanofibre solution can be mixed with cells at room temperature and then can be transformed into gels to encapsulate the cells in a three-dimensional environment upon being heated to physiological temperatures. We found that the cells grow within the three-dimensional networks without compromising the cell viability, and that subsequent cooling triggers the encapsulated cells to be released through a sol-gel transition.

Aqueous nanofibers with switchable chirality formed of self-assembled dumbbell-shaped rod amphiphiles.

We have demonstrated that fibrillar aggregates formed from the self-assembly of a dumbbell-shaped rod amphiphile undergo a reversible chiral-non-chiral transition triggered by temperature.

Rigid-flexible block molecules based on a laterally extended aromatic segment: hierarchical assembly into single fibers, flat ribbons, and twisted ribbons.

Self-assembling rigid-flexible block molecules consisting of a laterally extended aromatic segment and different lengths of hydrophilic coils were synthesized and characterized. The block molecule based on a long poly(ethylene oxide) coil (1), in the melt state, shows an unidentified columnar structure, whereas the molecule with a shorter poly(ethylene oxide) coil (2) self-organizes into an oblique columnar structure. Further decrease in the poly(ethylene oxide) coil length as in the case of 3, on heating, induces a rectangular columnar structure in addition to an oblique columnar mesophase. In diethyl ether, 1 and 2 were observed to self-assemble into uniform nanofibers with bilayer packing. Remarkably, these elementary fibers were observed to further aggregate in a lateral way to form well-defined flat ribbons (1) and twisted ribbons (2) with solvent exchange of diethyl ether into methanol. Furthermore, the ribbons formed in methanol dissociated into elementary fibers in response to the addition of aromatic guest molecules. This transformation between ribbons and single fibers in response to the addition of guest molecules is attributed to the intercalation of aromatic substrates within the rigid segments and subsequent loosening of the aromatic stacking interactions. These results demonstrate that the introduction of a laterally extended aromatic segment into an amphiphilic molecular architecture can lead to the hierarchical formation from elementary fibers of nanoribbons with a tunable twist through controlled lateral interactions between aromatic segments.