Demonstration of π-π Stacking at Interfaces: Synthesis of an Indole-Modified Monodisperse Silica Microsphere SiO2@IN.

In the present study, a novel silane coupling agent, designated INSi, was synthesized via a facile synthetic route, incorporating indole-functional moieties. This agent was further employed for the surface modification of homemade silica nanomicrospheres (SMPs). The ensuing nanomicrosphere composite, denoted as SiO2@IN, exemplified pronounced interfacial π-π interactions. Optimization of the reaction conditions was conducted using the response surface optimization technique. Subsequent validation of interfacial π-π interactions was accomplished through a synergistic approach, integrating theoretical calculations and comprehensive analyses of spectral and morphological attributes exhibited by the SiO2@IN.

A Heat-Resistant Polymer Based on the Reversible Change in Polymer Skeleton Structure for Self-Anticounterfeiting.

Heat-resistant polymer materials have been widely used in many fields, but their anticounterfeit is still a significant challenge. This work has successfully constructed a heat-resistant polymer material that can achieve self-anticounterfeit. In response to changes in the external environment, the color of polymer changes from yellow-green to red reversibly, which is due to the fact that polymer material's backbone undergoes isomerization. Therefore, this high-performance polymer material can not only be used in a high-temperature environment for a long time but also achieve its anticounterfeit and be used in advanced security applications.

Synthesis, supramolecular aggregation, and NIR-II phosphorescence of isocyanorhodium(i) zwitterions.

Development of new second near-infrared (NIR-II, 1000-1700 nm) luminophores is highly desirable, and d8 square-planar metal complexes with NIR-II phosphorescence have been rarely reported. Herein, we explore an asymmetric coordination paradigm to achieve the first creation of NIR-II phosphorescent isocyanorhodium(i) zwitterions. They show a strong tendency for aggregation in solution, arising from close Rh(i)⋯Rh(i) contacts that are further intensified by π-π stacking interactions and the hydrophilic-hydrophobic effect. Based on such supramolecular aggregation, zwitterions 2 and 5 are found to yield NIR-II phosphorescence emissions centered at 1005 and 1120 (1210, shoulder) nm in methanol-water mixed solvents, respectively. These two bands show red shifts to 1070 and 1130 (1230, shoulder) nm in the corresponding polymer nanoparticles in water. The resulting polymer nanoparticles can brighten in vivo tumor issues in the NIR-II region with a long-circulating time. In view of the synthetic diversity established by the asymmetric coordination paradigm, this work provides an extraordinary opportunity to explore NIR-II luminophores.

Colloidally Stable Graphite Oleogels by Pyrene-Functionalized Telechelic Polymers for Friction and Wear Reduction.

Although graphite derivatives, such as graphene, graphene oxide, and reduced graphene oxide, have been widely used as lubricating oil additives to reduce friction and wear, their synthesis either proceeds with complicated procedures in low yield, suffering from high cost, or involves the utilization of highly corrosive chemicals, raising safety and environmental concerns. Therefore, the direct use of pristine graphite as a lubricating oil additive is indispensable for practical tribological applications. However, the realization of this idea has been seriously hampered by the incompatibility of graphite with lubricating base oils. In this work, we report a rational strategy to directly disperse graphite in base oils in the form of oleogels assisted by pyrene functionalized telechelic polymers under mild condition. The resulting oleogels exhibit long-time colloidal stability for more than one year, wherein the graphite has been exfoliated to in situ form graphene through π-π interactions with the pyrene-containing telechelics. Moreover, compared with the base oil, the graphite-based oleogels are found to exhibit remarkable reductions in friction and wear by up to 52% and 97%, respectively. Significantly, such tribological performances are comparable to those of exfoliated graphite derivatives. Taken collectively, directly using pristine graphite as a lubricating oil additive with superior tribological properties represents a revolutionary approach to create low-cost, green, and high-performance lubricants just based on pristine layered materials without involving any pre-exfoliations.

Synthesis of Platinum(II)-Containing Block Copolymers: Luminescence Enhancement and Controllable Self-Assembly.

In this work, a novel class of diblock polymer ligands, poly(ethylene oxide)-block-polystyrenes end-functionalized with 2,6-bis(benzimidazol-2'-yl)pyridine (bzimpy), have been synthesized and their coordination reactions with K2PtCl4 have created platinum(II)-containing diblock copolymers. They emit red phosphorescence in both THF-water and 1,4-dioxane-n-hexane mixed solvents, arising from Pt(II)···Pt(II) and/or π-π stacking interactions between the planar [Pt(bzimpy)Cl]+ units. Correspondingly, the block copolymers demonstrate a solvent-tunable self-assembly behavior to controllably generate vesicles and worms with core-shell-corona architectures. In these hierarchical nanostructures, the planar [Pt(bzimpy)Cl]+ blocks are associated together to form cores driven by Pt(II)···Pt(II) and/or π-π stacking interactions. Such cores are completely isolated by PS shells, which are further encapsulated by PEO coronas. It should be highlighted here that diblock polymers as polymeric ligands are coupled with phosphorescence platinum(II) complexes, representing a novel approach to create functional metal-containing polymer materials with hierarchical architectures.

Synthesis of platinum(II)-complex end-tethered polymers: spectroscopic properties and nanostructured particles.

Although metal-containing polymers have been widely studied as a novel class of functional soft materials, the microphase separation between polymeric segments and metal-ligand complexes has been less addressed, which is critical to control their structures and functions. To do this, short-chain polystyrenes (PSs) have been end-functionalized with nanosized square-planar platinum(II) complexes. The platinum(II)-comprising polymers were found to show significant luminescence enhancement in chloroform/methanol solvent mixtures upon increasing the methanol composition. By modulating both the PS length and solvent quality, various self-assembled morphologies formed controllably in the mixed solvents and typical examples include nanofibers, nanoellipsoids, and nanospheres. More interestingly, the inside structures of these polymer particles are shown to be lamellar with sub-10 nm spacings, wherein the PS blocks are alternatively aligned with the platinum(II) units. Such a luminescence enhancement and hierarchical nanostructured particles originate from a subtle combination of directional Pt(II)⋯Pt(II) and/or π-π stacking interactions between the platinum(II) units and the solvophobic effect between the PS blocks. This work suggests that by microphase separating polymer chains with nanosized metal-ligand complexes, metal-containing polymers can self-assemble to form sub-10 nm scale nanostructures showcasing desired properties and functions.

Force-reversible chemical reaction at ambient temperature for designing toughened dynamic covalent polymer networks.

Force-reversible C-N bonds, resulting from the click chemistry reaction between triazolinedione (TAD) and indole derivatives, offer exciting opportunities for molecular-level engineering to design materials that respond to mechanical loads. Here, we displayed that TAD-indole adducts, acting as crosslink points in dry-state covalently crosslinked polymers, enable materials to display reversible stress-responsiveness in real time already at ambient temperature. Whereas the exergonic TAD-indole reaction results in the formation of bench-stable adducts, they were shown to dissociate at ambient temperature when embedded in a polymer network and subjected to a stretching force to recover the original products. Moreover, the nascent TAD moiety can spontaneously and immediately be recombined after dissociation with an indole reaction partners at ambient temperature, thus allowing for the adjustment of the polymer segment conformation and the maintenance of the network integrity by force-reversible behaviors. Overall, our strategy represents a general method to create toughened covalently crosslinked polymer materials with simultaneous enhancement of mechanical strength and ductility, which is quite challenging to achieve by conventional chemical methods.

A "Turn-On" fluorescent probe for detection and removal of Zn2+ in aqueous and its application in living cells.

Using 3-hydroxy-2-naphthoic acid hydrazine and 4-(diethylamino) salicylaldehyde. as raw materials, compound L with an acylhydrazones structure was synthesized. The structure of compound L was characterized by nuclear magnetic resonance spectroscopy, X-ray single crystal diffraction, Fourier transform infrared spectroscopy, and mass spectrometry. The results show that Compound L can quickly and selectively recognize zinc ions in the H2O/DMSO (V:V = 3:7) solvent system. After that, the spectral performance of probe L was studied by fluorescence spectroscopy and UV-vis spectroscopy. The results show that the combination with Zn2+ can significantly enhance the fluorescence intensity of probe L while being almost unaffected by other coexisting ions. After that, Job's curve method, nuclear magnetic titration analysis, and mass spectrometry were used to study the binding mechanism of probe L and Zn2+. The results showed that probe L coordinated with Zn2+ is 1:1. The linear equations of different concentrations of Zn2+ and fluorescence intensity were obtained by fitting, and the detection limit of probe L for Zn2+ was determined to be 6.75 × 10-9 mol/L. The experimental study of standard addition and recovery showed that probe L could be used for the quantitative detection of Zn2+ in natural water samples. After that, we prepared L-doped sodium alginate hydrogel (SAL). The research results show that SAL has obvious adsorption capacity for Zn2+ in solution, and the color change before and after adsorption can be easily distinguished by the naked eye under ultraviolet light. SEM-EDS study showed that the microscopic morphology and composition of SAL changed significantly before and after adsorption. This fluorescent probe can be used for detection and removal of Zn2+ in aqueous solution. Also, probe L is effective for sensing for zinc (II) in living tumor cells. Overall, this work allows us to obtain a great potential to be applied to detect and remove Zn2+.

A Toughening and Anti-Counterfeiting Benzotriazole-Based High-Performance Polymer Film Driven by Appropriate Intermolecular Coordination Force.

It is of great significance to circumvent the inherent trade-off between strength and extensibility for epoxy resins. Herein dynamic Cu-benzotriazole cross-links are incorporated, as the appropriate intermolecular coordination interaction, into high performance epoxy networks, and the resulting epoxy resins exhibits outstanding thermal stability and mechanical properties, their strength and extensibility are simultaneously improved. Additionally, local manipulation of coordination crosslinking confers the film with anti-counterfeiting function.

Rh(III)-Catalyzed Oxidative C-H Activation/Domino Annulation of Anilines with 1,3-Diynes: A Rapid Access to Blue-Emitting Tricyclic N,O-Heteroaromatics.

Disclosed herein is a rhodium-catalyzed oxidative C-H activation/domino annulation of N-Boc-anilines with 1,3-diynes for the construction of tricyclic N,O-heteroaromatics. This reaction features easily available substrates, mild reaction conditions, high regioselectivity, mono/diannulation selectivity, and intra/intermolecular annulation selectivity. Moreover, this synthetic protocol enables the rapid assembly of a library of blue-emitting molecules with high quantum yields, among of which two fluorophores with pure blue-emission in toluene are discovered.

Recyclable and Dual Cross-Linked High-Performance Polymer with an Amplified Strength-Toughness Combination.

Supramolecular chemistry has provided versatile and affordable solutions for the design of tough, flexible polymers. However, application of supramolecular chemistry has been limited to the production of rigid, high-performance polymers due to weak segment mobility. This paper describes a new method of toughening rigid high-performance polymers using the synergistic effect between dual Cu2+ -coordination bonds as a crosslink. These dual Cu2+ -coordination cross-linked high-performance polymers are a class of rigid polymers with an outstanding combination of strength and toughness. The distinct lifetimes and binding strengths of the dual Cu2+ -coordination bonds in a rigid polymer network elicit different dynamic behaviors to improve its energy dissipation and mechanical properties. Moreover, the reformation and removal of Cu2+ -coordination bonds by pyrophosphoric acid endows these cross-linked high-performance polymers with recyclability.

An indole-derived porous organic polymer for the efficient visual colorimetric capture of iodine in aqueous media via the synergistic effects of cation-π and electrostatic forces.

We have successfully synthesized a novel type of recyclable indole-based porous polymer, which possesses highly effective capture behavior for iodine in aqueous solution via the synergistic effects of cation-π and electrostatic forces. More interestingly, the absorption performance can be efficiently detected via a visual colorimetric assay using a smartphone.

Unprecedented toughening high-performance polyhexahydrotriazines constructed by incorporating point-face cation-π interactions in covalently crosslinked networks and the visual detection of tensile strength.

We described a new concept for the design of high-performance supramolecular thermosets by incorporating point-face cation-π interactions in covalently crosslinked networks. Our findings showed an unprecedented increase in tensile strength and extensibility at once, a previously unknown behavior for stiff high performance polymers.

Cation-π induced lithium-doped conjugated microporous polymer with remarkable hydrogen storage performance.

A cation-π induced lithium-doped conjugated microporous polymer, Li+-PTAT, was constructed. It was proved that the point to face cation-π interactions between Li+ and indole can endow the resulting Li+-PTAT with high Li+ content and without agglomeration, which further leads to its encouraging hydrogen storage capacity.

Microporous organic hydroxyl-functionalized polybenzotriazole for encouraging CO2 capture and separation.

We report a mild, hydroxyl functionalized and thermal stable benzotriazole-based aerogel (HO-PBTA), which is inspired by phenolic resin chemistry. Taking advantage of the synergistic adsorption interactions between hydroxy-benzotriazole and CO2, and the phobic effect between benzotriazole and nitrogen (N2), the CO2 uptake capacity of the HO-PBTA reaches an encouraging level (6.41 mmol g-1 at 1.0 bar and 273 K) with high selectivity (CO2/N2 = 76 at 273 K).

A novel carboxylic-functional indole-based aerogel for highly effective removal of heavy metals from aqueous solution via synergistic effects of face-point and point-point interactions.

A new type of carboxylic-functional indole-based aerogel (CHIFA) has been successfully prepared via a facile sol-gel technology, which possessed a highly effective removal of heavy metals from aqueous solution through the synergistic effects of face-point and point-point interactions.

Renewable 4-HIF/NaOH aerogel for efficient methylene blue removal via cation-π interaction induced electrostatic interaction.

A novel porous organic material 4-hydroxyindole-formaldehyde/NaOH (4-HIF/NaOH) aerogel was prepared via a facile polymerization, soaking in NaOH aqueous solution and ambient drying method. 4-HIF/NaOH aerogel porous polymer networks with high surface area have been applied as efficient adsorbents to remove methylene blue from wastewater via synergistic effects of cation-π interaction induced electrostatic interaction, electrostatic interaction and π-π interaction. The adsorption capacity calculated by adsorption isotherms at 303 K was 1016.9 mg g-1 which is higher than those observed for methylene blue on other aerogels and most other materials. Furthermore, the methylene blue loaded 4-HIF aerogel can easily be regenerated with 0.1 M HCl solution and ethanol wash, retaining over 75% of the adsorption capacity after recycling five times.

Rational design of a boron-dipyrromethene-based fluorescent probe for detecting Pd2+ sensitively and selectively in aqueous media.

A novel fluorescent probe for Pd2+ based on the BODIPY fluorophore exploiting the PET (Photoinduced Electron Transfer) mechanism was designed and successfully synthesized. The fluorescent probe 1 was prepared by introducing m-bisimidazolylbenzene which was connected by phenyl acetylene to the BODIPY dye at the meso position. It exhibited a rapid response and high sensitivity and selectivity toward Pd2+. Probe 1 presented a rapid quenched fluorescence response in aqueous buffer media (pH 5.5) and the detection limit estimated from the titration results was 2.9 × 10-7 M. Meanwhile, other common metal ions did not interfere with the recognition process. The DFT calculation proved that coordination of bisimidazole ligands with Pd2+ effectively decreases the LUMO energy of m-bisimidazolylbenzene which was located between the HOMO and LUMO energies of the BODIPY dye leading to fluorescence quenching via the d-PET mechanism.

A recyclable hydroxyl functionalized polyindole hydrogel for sodium hydroxide extraction via the synergistic effect of cation-π interactions and hydrogen bonding.

We have successfully constructed a new type of recyclable indole-based hydrogel, which exhibited highly effective extraction behavior for hydroxide via the synergistic effect of cation-π interactions and hydrogen bonds. More interestingly, the absorption performance could be visually detected by taking advantage of the color altering effect of the host-guest interactions.

Recyclable Crosslinked High-Performance Polymers via Adjusting Intermolecular Cation-π Interactions and the Visual Detection of Tensile Strength and Glass Transition Temperature.

Crosslinked high-performance polymers have many industrial applications but are difficult to recycle. Visual detection of the physical properties of the crosslinked high-performance polymers is useful, but is difficult to achieve. The crosslinked high-performance polymers (SPIN) are constructed by using cation-π interactions. The cation-π interaction between the polymer side chains can be easily installed and removed by aqueous treatments at high or low pH, respectively, which endow the crosslinked polymer with a recyclable behavior. Additionally, the tensile strength and glass transition temperature of the SPIN films could be visually detected by taking advantage of the transparency decreasing effect of cation to an adjacent indole unit.