Condensation Reaction Research Articles

Thermal Condensation of Dehydrogenation Polymer (DHP) with Xylose

Conventional adhesives used in wood-based panels typically contain volatile organic compounds, including formaldehyde, which can potentially lower indoor air quality and damage human health. Lignin, a natural adhesive present in wood, offers significant advantages over other materials due to its ready availability, renewable nature, rich aromatic rings, and aliphatic and aromatic hydroxyl groups, as well as quinone groups. However, when modified as an adhesive for wood-based panels, lignin suffers from poor water resistance and formaldehyde release. Dehydrogenation polymer (DHP), as a lignin model compound, possesses a structure similar to lignin and excellent water resistance, making it a potential substitute for lignin as a formaldehyde-free adhesive. A DHP-xylose complex was obtained from a condensation reaction between DHP and xylose in hemicellulose in a simulated hot-pressing environment. The feasibility of DHP bonding with hemicellulose components was verified using FT-IR and NMR spectroscopic methods. In addition, the structure of the adduct and condensation process were also studied. DHP and xylose underwent condensation under simulated hot-pressing conditions. Xylose and DHP may be linked by C-C bonds. The thermal condensation of DHP with xylose was investigated. This may contribute to a better understanding of the adhesive bonding process for xylose during hot-pressing and offer support for practical applications.

Implementation of different fluorogenic condensation reactions for the spectrofluorimetric detection of the banned growth promoter, bacitracin, in water samples: assessment of the greenness of methods

Implementation of different fluorogenic condensation reactions for the spectrofluorimetric detection of the banned growth promoter, bacitracin, in water samples: assessment of the greenness of methods

Synthesis of Acenaphthene Fused Dithiaporphyrin(3.1.1.1)s and N-Fused Triphyrin(3.1.1)s in One-Pot Condensation.

Two different types of novel nonaromatic acenaphthene fused macrocycles such as acenaphthene fused dithiaporphyrin(3.1.1.1)s and acenaphthene fused N-fused triphyrin(3.1.1)s were synthesized in one pot condensation reaction using 5,6-dibromoacenaphthene as a key precursor. The X-ray analysis revealed the oval core-shaped structure for dithiaporphyrin(3.1.1.1)s and intramolecular ring fusion in N-Fused triphyrin(3.1.1)s. The NMR, absorption and DFT studies suggested the non-aromatic nature of both macrocycles which absorb strongly in visible-NIR region. Both macrocycles were stable under electrochemical conditions and showed their electron-rich nature.

Facile Synthesis of 1,2-Disubstituted Benzimidazoles as Potent Cytotoxic Agents.

Benzimidazoles have a broad spectrum of biological and pharmacological properties, including anticancer activity. This study reports the facile synthesis and cytotoxic evaluation of twenty-eight 1,2-disubstituted benzimidazoles (6a-β), based on condensation reactions between N-benzyl o-phenylenediamine and benzylamine. The reactions were solvent-free, with the use of Na2S2O5 as an inexpensive and environmentally friendly oxidizing agent, and progressed rapidly. Cytotoxicity assessments using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay were performed against the A549, HeLa, and MCF-7 cell lines for all synthesized compounds (6a-β). Among them, 6j, 6k, 6l, and 6n displayed good activities against the A549 and MCF-7 cell lines. These compounds possessed IC50 values ranging from 2.55 to 4.50 µM, corresponding to 1.4-fold to 2.4-fold stronger potencies than that of the positive control 5-fluorouracil (5-FU) (IC50 = 6.08 µM) against MCF-7 cells, while 6k (IC50 = 3.22 µM) was consistent with 5-FU on the A549 cell line (IC50 = 3.77 µM). Structure-activity relationship analyses revealed the 3-pyridinyl moiety at C-2 and the CH3, OCH3, or 1,3-dioxolyl groups on the benzene ring at the N-1 position of the benzimidazole heterocycle as key structural features effectuating the observed cytotoxicities.

Evaluating the antidiabetes and antioxidant activities of halogenated Schiff bases derived from 4-(diethylamino)salicylaldehyde: in vitro antidiabetes, antioxidant and computational investigation

Six Schiff bases with general name 5-(diethylamino)-2-(((halophenyl)imino)methyl)phenol (where halo = 4-fluoro (H1), 2-fluoro (H2), 2-bromo (H3), 4-bromo (H4), 4-chloro (H5) and 3-chloro-4-fluoro (H6)) were prepared by the condensation reaction between 4-(diethylamino)salicylaldehyde and suitable halogenated aromatic amines. The six halogenated Schiff bases were elucidated using different spectroscopic techniques and the structure of H3 and H6 were confirmed using single-crystal X-ray crystallography. The bond lengths of C7–N1, C7–C8 and C8–C9 obtained from structural analysis for both compounds depicted their enol-tautomeric characteristic form. The Hirshfeld analysis revealed that H‧‧‧H intermolecular contacts contributed most towards the Hirshfeld surfaces of both H3 (47.6%) and H6 (39.9%). Quantum chemical calculation studies showed that H1 and H2 have the highest and lowest energy band gap (∆E = 3.80 eV for H1 and ∆E = 3.73 eV for H2), depicting H2 and H1 as the most and least chemically reactive respectively among all the compounds. α-Amylase and α-glucosidase assay were used to evaluate the antidiabetes prowess of the synthesized compounds. All the compounds exhibited lower IC50 values than acarbose (reference drug) in α-amylase assay experiments and H5 with lowest IC50 value of 63.54 μM could be suggested to have the highest α-amylase inhibitory potential among the test samples. For α-glucosidase assay, H1–H6 displayed good antidiabetic potential. However, none of the compounds outshined acarbose with H6 having highest α-glucosidase inhibitory potential when compared to others i.e., IC50 of H6 = 60.89 μM and IC50 of acarbose = 51.42 μM. We measured the antioxidant potential of H1–H6 exploring 2,2-diphenyl-1-picrylhydrazyl (DPPH), nitric oxide (NO) and ferric reducing ability power (FRAP) assays. The DPPH as well as NO radical scavenging assay showed that all the compounds exhibited excellent antioxidant results with some of the compounds surpassing catechin (reference drug). Compound H5 with IC50 values of 30.32 mM and 31.73 mM outshined catechin with IC50 values of 31.17 mM and 140.62 mM for DPPH and NO assays respectively. All the compounds fell within the threshold of Lipinski’s Ro5 projecting them as orally bioavailable and less toxic future therapeutics.

Size and shape matter for micellar catalysis using light-responsive azobenzene surfactants.

The micellar catalysis of a model Claisen-Schmidt aldol condensation reaction using heterogeneous nanoreactors based on cationic azobenzene trimethylammonium bromide (AzoTAB) photosurfactants is investigated. Under UV irradiation, AzoTABs undergo a trans-cis photoisomerisation, which changes not only the critical micelle concentration, but also the shape and size of the micelle. The effect of surfactant structure (tail and spacer lengths), concentration and temperature on the reaction yield were investigated. Monitoring of the zeta potential during the reaction indicated that it proceeds at the micelle/water interface for AzoTABs, with the enolate intermediate stabilised in micelle/water interface (i.e. the Stern layer). The reaction yield was found to correlate directly to micellar shape and size, with smaller, more spherical micelles typical of cis-AzoTABs favouring higher reaction efficiencies.

Construction of Chiral Covalent Organic Frameworks Through a Linker Decomposition Chiral Induction Strategy for Circularly Polarized Light Detection

AbstractExploring new strategies for construction of chiral covalent organic frameworks (COFs) is of paramount importance yet remains a challenge. Herein, we report the rational design and construction of chiral COFs through a linker decomposition chiral induction (LDCI) strategy. Three pairs of azine‐linked chiral COFs are successfully synthesized by the condensation reactions of C3‐symmetric 4,4′,4′′‐(1,3,5‐triazine‐2,4,6‐triyl)tribenzaldehyde (Tz) with flexible chiral dihydrazide linkers derived from malic acid, aspartic acid and tartaric acid, respectively. Remarkably, upon complete or partial decomposition from flexible chiral dihydrazides to hydrazine during COF synthesis, the homochirality of these COFs, originating from the single‐handedness conformation of propeller‐like Tz cores, is well preserved. Such a stereoselective chiral memory realized via the LDCI strategy is confirmed by time‐dependent powder X‐ray diffraction (PXRD), Fourier transform infrared (FT‐IR) and diffuse reflectance circular dichroism (DRCD). Moreover, the resultant azine‐linked chiral COFs are used as the active materials to fabricate photodetectors to directly distinguish circularly polarized light (CPL), showing impressive recognition performances on the identification of left‐handed circularly (LHC) and right‐handed circularly (RHC) polarized lights. Notably, the residual undecomposed flexible chiral linkers within the COFs are found to be conducive to improving the polarization discrimination ratio. This work highlights LDCI as a new and effective strategy for constructing homochiral COFs with promising future in chiral optical application.

Construction of Chiral Covalent Organic Frameworks Through a Linker Decomposition Chiral Induction Strategy for Circularly Polarized Light Detection

AbstractExploring new strategies for construction of chiral covalent organic frameworks (COFs) is of paramount importance yet remains a challenge. Herein, we report the rational design and construction of chiral COFs through a linker decomposition chiral induction (LDCI) strategy. Three pairs of azine‐linked chiral COFs are successfully synthesized by the condensation reactions of C3‐symmetric 4,4′,4′′‐(1,3,5‐triazine‐2,4,6‐triyl)tribenzaldehyde (Tz) with flexible chiral dihydrazide linkers derived from malic acid, aspartic acid and tartaric acid, respectively. Remarkably, upon complete or partial decomposition from flexible chiral dihydrazides to hydrazine during COF synthesis, the homochirality of these COFs, originating from the single‐handedness conformation of propeller‐like Tz cores, is well preserved. Such a stereoselective chiral memory realized via the LDCI strategy is confirmed by time‐dependent powder X‐ray diffraction (PXRD), Fourier transform infrared (FT‐IR) and diffuse reflectance circular dichroism (DRCD). Moreover, the resultant azine‐linked chiral COFs are used as the active materials to fabricate photodetectors to directly distinguish circularly polarized light (CPL), showing impressive recognition performances on the identification of left‐handed circularly (LHC) and right‐handed circularly (RHC) polarized lights. Notably, the residual undecomposed flexible chiral linkers within the COFs are found to be conducive to improving the polarization discrimination ratio. This work highlights LDCI as a new and effective strategy for constructing homochiral COFs with promising future in chiral optical application.

Synthesis and Spectroscopic Properties of Diarylethene-Subporphyrinoid Hybrids.

Two novel diarylethene-fused subporphyrinoids were prepared and characterized. A mono diarylethene derivative was obtained via a statistical condensation reaction with 2 eq. of 1,2-dicyanobenzene and 1 eq. of thiophene-disubstituted butenedinitrile. The symmetric triply diarylethene-fused subporphyrazine was synthesized via a cyclotrimerization reaction of the thiophene-disubstituted butenedinitrile derivative. These compounds were characterized by NMR spectroscopy and high-resolution mass spectrometry. The spectroscopic properties have been measured in hexane and in chloroform. The mono diarylethene-fused-type compound showed photochromism at 580 nm and >700 nm wavelength, accompanied by degradation. According to DFT calculations, photoreactivity likely depends on the contribution of aromatic feature of pyrrole ring bonded to two thiophene rings.

Comparative study of cerium-manganese ratios in the design of Ce-Mn-binuclear LDH-based Cu complex: a potent nanocatalyst for the green synthesis of spiro[acridine-9,3’-indole]triones

The Ce-Mn binuclear LDH was prepared at four different molar ratios of Ce to Mn (1:1, 1:2, 1:3, and 1:4), modified with both 3-chloropropyltrimethoxysilane (CPTMS) and N-amino-phthalimide (NAP), complexed with Cu(II), and characterized by the FT-IR, ICP, XPS, XRD, BET, UV/Vis, EDX, SEM, SEM-mapping, TEM, and TGA-DTA techniques. The ICP, XPS, BET, and UV-vis techniques showed that the 1:4 molar ratio of Ce to Mn is the best, therefore it was used as a heterogeneous nanocatalyst for the green synthesis of fourteen spiro[acridine-indole]triones from the three-component condensation reaction of isatin, aniline, and 1,3-diketone in mild reaction conditions. The advantages of this method include the absence of harmful organic solvents, easy separation of the catalyst and products, and rapid achievement of excellent yields. Furthermore, the activity of the catalyst was maintained even after four consecutive runs without a significant loss of activity.

Insights into the effect of various supports on hydrothermal liquefaction of food waste over iron-oxide nano-catalysts

This work investigates the effect of supported iron-oxide nano-catalysts for hydrothermal conversion of food waste. The studied supports were Vulcan carbon (VC), CeO2, ZSM-5 and amorphous SiO2-Al2O3. Catalytic hydrothermal liquefaction experiments were carried out in a batch reactor at 16 MPa and 300 °C maintained for 1 h. Different fractions of Fe(0), Fe2+ and Fe3+ alter its tendency toward deoxygenation, hydrogenations and condensation reactions, which influence the bio-crude yield, elemental compositions, and energy recoveries. The fresh and spent catalysts were characterized using X-ray photoelectron spectroscopy, physisorption analysis, thermogravimetric analysis, transmission and scanning electron microscopy. It was found that the change in catalyst support influences HTL pathways and product compositions. The results reveal that the inclusion of FeOx catalyst on Vulcan carbon, SiO2-Al2O3 and ZSM-5 supports can increase the bio-crude yield by ~7–9 wt% compared to their FeOx-free yields. The increase in bio-crude yield was associated with the decrease in the surface ratios of Fe3+/Fe2+ at the range of 0.8–1.6. In overall, catalysts that had higher tendencies in converting amines into oil-soluble compounds increased the bio-crude yield, while catalysts that promoted dehydration and decarboxylation route decreased the bio-crude yield. The maximum energy recovery in bio-crude was obtained using FeOx/SiO2-Al2O3 catalyst with values ~95 %. The deactivation of catalysts was associated with the increase in Ca and P poisonous elements on catalytic sites, which decreased the energy recovery of recycled FeOx/SiO2-Al2O3 to ~85 % after three cycles.

Experimental and computational investigations of new organotin(IV) complexes derived from hydrazone ligands: Synthesis, structural analysis and biological assessment

In this article, we have presented the synthesis, structural analysis, and biological assessments of twelve new diorganotin(IV) complexes (derived from heterocyclic hydrazone ligands through condensation reaction between 9-formyl-8-hydroxyjulolidine and aromatic hydrazide derivatives) to discover potent biological agents. The synthesized compounds have been thoroughly characterized using numerous spectroscopic and physicochemical methods, including (1H, 13C and 119Sn) NMR, FT-IR, mass spectrometry, powder XRD and SEM. These scrutinizes indicate that complexes exhibited a pentacoordinated geometry, coordinating through azomethine nitrogen atom, enolic oxygen atom, phenolic oxygen atom and carbon atoms of alkyl/aryl groups of organotin derivatives. DFT (Density functional theory) studies were conducted at the B3LYP/LanL2DZ/6-311G level of hypothesis to investigate the quantum chemical aspects of specified compounds. These properties were facilitated through analyses of charge distribution and molecular orbitals. The antioxidant effectiveness of the prepared compounds was examined employing the DPPH assay and the results revealed that complex 7 exhibited strong antioxidant potential, having an IC50 value of 2.3 µM. Moreover, the prepared compounds were assessed for their effectiveness against four bacterial (B. cereus, B. subtilis, P. aeruginosa, E. coli) as well as two fungal strains (C. albicans and A. niger) using serial dilution approach. Complexes 7, 11, 14 and 15 having MIC values ranging from 0.0051-0.0048 µmol/mL have highest antimicrobial potency equivalent to reference drugs, Fluconazole (MIC = 0.0051 µmol/mL) and Ciprofloxacin (MIC = 0.0048 µmol/mL).

Facile synthesis of Metal-Organic Framework/Chitosan cryogel as a robust Scavenger for Diclofenac sodium

Diclofenac sodium (DS), a commonly detected contaminant in aquatic environments, poses a a significant risk to both the ecological balance and the safety of aquatic products. Therefore, efficient removal of DS from water is ergently needed but remains a major challenge. In this study, an environmentally friendly Fe-based metal–organic framework/chitosan (NH2-MIL-53(Fe)/CS) cryogel was prepared through a Schiff base condensation reaction under mild conditions. Taking advantage of the catalytic role of the MOF in accelerating the reaction between CS and 1,3,5-triformylphloroglucinol, NH2-MIL-53(Fe) powders were incorporated into the polymeric networks within 30 s. Owing to the rich binding sites, the resulting NH2-MIL-53(Fe)/CS cryogel demonstrated remarkable efficacy in eliminating DS from water. The adsorption process reached equilibrium within 120 min with a maximum adsorption capacity of 728.6 mg g−1. A comprehensive mechanistic investigation revealed that the exceptional adsorption capability of the NH2-MIL-53(Fe)/CS cryogel for DS was attributed to the synergistic effect of multiple interactions, including favorable hydrophilicity, electrostatic forces, π-π stacking, hydrogen bonding, and coordination. Thus, this study provides a straightforward and rapid synthesis route for MOF/CS cryogel, offering a promising adsorbent that combines exceptional adsorption performance with ease of separation. The resulting MOF/CS cryogel holds great potential for the treatment of DS-contaminated wastewater.

One-pot synthesis of tricyclic pyrano[3.2-c]chromene derivatives and their evaluation through in vitro immunomodulatory activity against T cells; Molecular docking investigations and ADME-Tox prediction studies

The aim of this work is the in vitro determination of the immunomodulation effect of pyrano[3,2-c]chromenes on the proliferation of T lymphocyts. These tricyclic heterocycles were prepared at room temperature via a one-pot, three-component condensation reaction involving 4-hydroxy-2H-chromen-2-one, aromatic aldehydes, and malononitrile, using morpholine as a catalyst in a 1:1 ethanol/water mixture. This multicomponent reaction affords the product in high yields, in accordance with the criteria of green chemistry. The structure elucidation was accomplished by spectral data, IR, NMR (1H, 13C, 2D). We determined the in vitro effects of 2-amino-4-(3-hydroxy-5-methoxyphenyl)-5-oxo-4H,5H-pyrano[3,2-c]chromene-3-carbonitrile (AC09) the 2-amino-5-oxo-4-(thiophen-2-yl)-4H,5H-pyrano[3,2-c]chromene-3-carbonitrile (AC11) derivatives, on the proliferative responses of human T lymphocyts cells, cytokine secretion and intracellular redox status. The study revealed that compounds AC09 and AC11 are efficient immunostimulants in a dose-dependent manner.Human lymphocytes were less sensitive to AC11 at high concentrations compared to the potency of AC09. Human lymphocyte IL-2, IFNγ and IL-4 secretions were significantly enhanced by those pyrano[3,2-c]chromenes derivatives in a dose-dependent manner. The levels of intracellular lymphocytes glutathione (GSH), were unaffected by AC09 and AC11 at any concentrations. AC09 and AC11 induce a significant increase in hydroperoxide and carbonyl protein contents at high concentrations. Conversely, a computational study using molecular modelling revealed that compounds AC09 and AC11 exhibit a strong affinity for the active site residues of Interferon-γ (IFN-γ; PDB ID: 6E3K) target. This is confirmed by the low score energy value and the formation of different types of interactions such as: hydrogen bonds, hydrophobic interactions, and van der Waals forces. Moreover, all Drug likeness's rules were validated, and no toxicity is presented by these compounds. Finally, in vitro studies, molecular docking techniques and ADME-T (Absorption, Distribution, Metabolism, Excretion and Toxicity) evaluations were successfully conducted, aiding in the identification of new IFN-γ target inhibitors. A comparative analysis /or studies was then carried out to highlight the complementary effects of the two approaches.

Grafting of cinchonine onto rice husk nanosilica and its potential application in the synthesis of 2‐arylideneindan‐1,3‐diones and 2‐arylidene-5,5-dimethyl-1,3-cyclohexanedione

In this study, an eco-friendly and green procedure for Knoevenagel condensation reaction of aromatic aldehydes with indan-1,3-dione and dimedone was reported utilizing a rice husk silica‐anchored cinchonine nanocomposite as a heterogeneous catalyst in aqueous media. Without the need for an additional surfactant, rice husk was utilized as a raw material to create nanosilica. Through the grafting of 3-mercaptopropyl) trimethoxysilane, the rice husk nanosilica was modified. Next, azobisisobutylonitrile initiator was used to trigger the thiol-ene free radical interaction of the SH groups with the Cinchonine's alkene function. The morphology and structure of the nano SiO2-S-cinchonine were characterized using fourier transform infrared spectra, field emission scanning electron microscope, and energy-dispersive X-ray spectroscopy. The catalytic activity of the nanocomposite was investigated in the synthesis of 2-arylideneindan-1,3-diones and 2-arylidene-5,5-dimethyl-1,3-cyclohexanedione through an aqueous medium at 80 °C by the Knoevenagel condensation reaction. The advantages of this method are simple methodology, high yields, easy work-up, and green solvent.

A needle-like covalent organic framework with highly accessible phenazine and π-conjugated structure for potassium storage and its reaction mechanism

Covalent organic frameworks (COFs) with features of light elements, tailored functional groups, and designable structures are regarded as promising candidates for future potassium ion batteries (PIBs), while the low electronic conductivity and intricate reaction mechanism restrict their practical application. Herein, a needle-like COF material, marked as CPT, was synthesized by an acid-catalyzed condensation reaction between cyclohexanehexone and 2,3,7,8-phenazine tetramine. It was constructed by interconnected phenazine with π-conjugated structures, displaying the advantages of rich electron delocalization, thin sheet thickness, and low dissolution in electrolytes. When applied as the anode of PIBs, the CPT anode delivered a high reversible capacity of 305 mAh g−1 at 0.1 A g−1 over 200 cycles. Besides, it also exhibited promising potential for “high-temperature” application potential by retaining a capacity of 400 mAh g−1 at 0.1 A g−1 after 100 cycles at 45 °C. Full cells with CPT anode and potassiathed organic cathode displayed good cycling and rate performances. Furthermore, the step-wise K-storage mechanism was jointly determined by in-situ characterization techniques and theoretical calculations. This study not only presents a molecular engineering approach for designing organic materials but also provides novel insights into the underlying mechanism governing potassium storage.

Effect of Hierarchical Architecture of Nickel Modified Mesoporous Catalysts on the Knoevenagel Condensation Reaction

AbstractA series of ordered mesoporous silicas (MCM‐41, SBA‐15 and KIT‐6) were successfully synthesized and modified with nickel by incipient wetness impregnation method. The supports and catalysts were characterized by N2 adsorption‐desorption, XRD, TEM, H2‐TPR, UV vis‐DR, XPS, ICP and Py FT‐IR techniques. All the materials were evaluated in the Knoevenagel condensation reaction between vanillin and malononitrile under microwave irradiation. The catalytic results show the key role that the chosen porous structure plays in the deposition of the active phase and its catalytic behaviour. Thus, by designing a suitable mesoporous catalyst it was possible to carry out such Knoevenagel condensation to obtain 2‐(4‐hydroxy‐3‐methoxybenzylidene) malononitrile through a highly efficient and environmentally friendly process, without solvents and reducing reaction times by employing microwave heating.

A Fully Saturated Covalent Organic Framework.

We report the design and synthesis of the first aliphatic covalent organic framework (COF), NUS-119, and its subsequent conversion to NUS-120, marking the first fully saturated COF. NUS-119 is built by imine-linkages exhibiting high crystallinity and porosity, achieved by using a Lewis acid as a reaction modulator to circumvent compatibility issues between the Brønsted acid and the strong basic monomer. The structure was successfully solved using 3D microelectron diffraction (microED) techniques. NUS-119 and NUS-120 demonstrated remarkable catalytic performance in base-catalyzed Knoevenagel condensation reactions, exhibiting high conversion rates, excellent size selectivity, and good recyclability. This work advances the understanding of COF materials and paves the way for future research and applications.

Accelerated Zymonic Acid Formation from Pyruvic Acid at the Interface of Aqueous Nanodroplets.

To explore the role of the liquid interface in mediating reactivity in small compartments, the formation kinetics of zymonic acid (ZA) is measured in submicron aerosols (average radius = 240 nm) using mass spectrometry. The formation of ZA, from a condensation reaction of two pyruvic acid (PA) molecules, proceeds over days in bulk solutions, while in submicron aerosols, it occurs in minutes. The experimental results are replicated in a kinetic model using an apparent interfacial reaction rate coefficient of krxn = (0.9 ± 0.2) × 10-3 M-1 s-1. The simulation reveals that surface activity of PA coupled with an enhanced interfacial reaction rate drives accelerated ZA formation in aerosols. Experimental and simulated results provide compelling evidence that the condensation reaction of PA occurs exclusively at the aerosol interface with a reaction rate coefficient that is enhanced by 4 orders of magnitude (∼104) relative to what is estimated for macroscale solutions.

A Strongly Reducing sp2 Carbon‐Conjugated Covalent Organic Framework Formed by N‐Heterocyclic Carbene Dimerization

AbstractCovalent organic frameworks linked by carbon‐carbon double bonds (C=C COFs) are an emerging class of crystalline, porous, and conjugated polymeric materials with potential applications in organic electronics, photocatalysis, and energy storage. Despite the rapidly growing interest in sp2 carbon‐conjugated COFs, only a small number of closely related condensation reactions have been successfully employed for their synthesis to date. Herein, we report the first example of a C=C COF, CORN‐COF‐1 (CORN=Cornell University), prepared by N‐heterocyclic carbene (NHC) dimerization. In‐depth characterization reveals that CORN‐COF‐1 possesses a two‐dimensional layered structure and hexagonal guest‐accessible pores decorated with a high density of strongly reducing tetraazafulvalene linkages. Exposure of CORN‐COF‐1 to tetracyanoethylene (TCNE, E1/2=0.13 V and −0.87 V vs. SCE) oxidizes the COF and encapsulates the radical anion TCNE⋅− and the dianion TCNE2− as guest molecules, as confirmed by spectroscopic and magnetic analysis. Notably, the reactive TCNE⋅− radical anion, which generally dimerizes in the solid state, is uniquely stabilized within the pores of CORN‐COF‐1. Overall, our findings broaden the toolbox of reactions available for the synthesis of redox‐active C=C COFs, paving the way for the design of novel materials.