Aluminum-Catalyzed Cross Selective C3–N1′ Coupling Reactions of N-Methoxyindoles with Indoles

C3–N1′ bond formation of bisindoles has been a great challenge due to the intrinsic reactivity of indoles as both C3 and N1-nucleophilic character. Herein, we demonstrate an C3–N1′ cross-coupling reaction of indoles using N-methoxyindoles as N-electrophilic indole reagents in the presence of Lewis acid. The bisindoles generated in this transformation are latent C3-nucleophile, allowing them to be used as strategic intermediates in sequential C3–N1′–C3′–N1″ triindole formations. The potential synthetic usefulness of this sequential transformation was highlighted upon application to the construction of C3–N1 looped polyindoles.

Transport of Anions across the Dialytic Membrane Induced by Complexation toward Dendritic Receptors

A novel approach to inducing anion transport over the dialytic membrane was proposed and successfully tested using the dihydrogen phosphate anion. The anion receptor based on isophthalamide was anchored on a dendritic skeleton, resulting in a macromolecular structure with a limited possibility to cross the dialytic membrane. The dendritic receptor was placed in a compartment separated from a mother anion solution by a membrane. The resulting anion complexation reduced the actual concentration of the anion and induced the anion transfer across the membrane. The anion concentration in mother solution decreased, while it was found to be increased in the compartment with the dendritic receptor. This phenomenon was observed using dendritic receptors with four and eight complexation sites. A detailed analysis of a series of dialytic experiments by ¹H NMR spectroscopy enabled an assessment of the complexation behavior of both receptors and an evaluation of the dendritic effect on the anion complexation.

Assembling of Reprocessable Polybutadiene-Based Vitrimers with High Strength and Shape Memory via Catalyst-Free Imine-Coordinated Boroxine

Vitrimers endow cross-linked polymers with malleability and reprocessability via exchange reactions. However, designing of reprocessable, shape-memory polymer materials with high strength via a catalyst-free method remains a challenge under mild conditions. Here, we propose a facile strategy to address this dilemma by introducing the exchangeable imine bond and N-coordinated boroxine into a polybutadiene (PB)-based network. Specifically, PB grafted with 2-aminoethanethiol is reacted with the formyl group of phenylboronic acid and dehydrated to form a dual-dynamic covalently cross-linked network at room temperature. The dynamic network draws on the advantage of imine (toughness) and N-coordinated boroxine (strength), making the PB-based materials exhibit favorable malleability, mechanical property, reprocessability, and thermal-induced shape-memory behavior. We can obtain customized high mechanical properties by tuning the cross-linking density, and the tensile strength reaches a high value (12.35 MPa) without fillers or any other additives. Meanwhile, the unique network framework makes the material recycle over several times without sacrificing its property. This work presents a facile and effective approach to achieve a multifunctional polymer with customized attributes. Besides, this strategy can recycle end-of-life rubber to alleviate environmental pollution and provide inspiration for fabricating targeted materials by uniting the dynamic covalent or noncovalent bonds.

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.

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

A recyclable indole-based POP was successfully achieved, which was capable of visual colorimetric iodine capture in water via cation–π and electrostatic interactions.

A novel indole-based conjugated microporous polymer for highly effective removal of heavy metals from aqueous solution via double cation-π interactions

A novel indole-based conjugated microporous polymer (PTIA) with three coplanar indole units, designed and synthesized by an oxidative coupling reaction, was utilized as a platform for removing heavy metals. Owing to the conjugation of the three coplanar indoles, the highly electron-rich large π planes can simultaneously attract six heavy metal atoms via double cation-π interactions, endowing this microporous material with remarkable heavy metal adsorption capacity and efficiency.

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.

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.

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

Facile synthesis of aminated indole-based porous organic polymer for highly selective capture of CO2 by the coefficient effect of π-π-stacking and hydrogen bonding

A new aromatic aminated indole-based porous organic polymer, PIN-NH2, has been successfully constructed, and it was demonstrated that the coefficient effect endows this porous material with outstanding CO2 absorption capacity (27.7 wt%, 1.0 bar, 273 K) and high CO2/N2 (137 at 273 K and 1 bar) and CO2/CH4 (34 at 273 K and 1 bar) selectivity.

A recyclable indole-based polymer for trinitrotoluene adsorption via the synergistic effect of dipole–π and donor–acceptor interactions

A new type of indole-based porous organic polymer with amine units (PAIN) has been constructed, which possesses encouraging and effective adsorption properties for trinitrotoluene by taking advantage of the synergistic effect of dipole–π and donor–acceptor interactions.

A reversible, colorimetric, pH-responsive indole-based hydrogel and its application in urea detection

A new type of pH-responsive indole-based (4-HINF) hydrogel, fabricated by a sol–gel method, was utilized as a platform for colorimetric detection of urea in aqueous solution. The colorimetric sensor was established by virtue of the synergistic effect of cation–π interaction and hydrogen bonding with good regenerative ability. The results exhibited linear response in the range of 0–10 mM with a limit of detection of 10 μM. The prepared 4-HINF hydrogel possessed high selectivity to pH change under complicated environments ensuring further applications in environmental and bio-systems.

A new type of pH-responsive indole-based (4-HINF) hydrogel, fabricated by a sol–gel method, was utilized as a platform for colorimetric detection of urea in aqueous solution.