Imidazole Functional Groups Research Articles

Differing Effects of Nonlinearity around the Proton Acceptor on CH··O and NH··O H-Bond Strength within Proteins.

The effects of deviations from nonlinearity around the carbonyl proton acceptor of an amide group are assessed by DFT quantum chemical calculations for both CH··O and NH··O H-bonds. The proton donors are the imidazole functional group of His and the indole of Trp, which are paired respectively with N-methylacetamide and acetamide. The displacement of either CH or NH group toward the carbonyl O sp2 lone pairs stabilizes the system and strengthens the H-bond. But the two donor groups differ in their response to a shift out of the amide plane. While the NH··O H-bond is weakened by this displacement, a substantial strengthening is observed when the CH donor is moved out of this plane, in one direction versus the other. This pattern is explained on the basis of simple Coulombic considerations.

Harnessing Guanidinium and Imidazole Functional Groups: A Dual-Charged Polymer Strategy for Enhanced Gene Delivery.

Histidine and arginine are two amino acids that exhibit beneficial properties for gene delivery. In particular, the imidazole group of histidine facilitates endosomal release, while the guanidinium group of arginine promotes cellular entry. Consequently, a dual-charged copolymer library based on these amino acids was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The content of the N-acryloyl-l-histidine (His) monomer was systematically increased, while maintaining consistent levels of methyl N-acryloyl-l-argininate hydrochloride (ArgOMe) or N-(4-guanidinobutyl)acrylamide hydrochloride (GBAm). The resulting polymers formed stable, nanosized polyplexes when complexed with nucleic acids. Remarkably, candidates with increased His content exhibited reduced cytotoxicity profiles and enhanced transfection efficiency, particularly retaining this performance level at lower pDNA concentrations. Furthermore, endosomal release studies revealed that increased His content improved endosomal release, while ArgOMe improved cellular entry. These findings underscore the potential of customized dual-charged copolymers and the synergistic effects of His and ArgOMe/GBAm in enhancing gene delivery.

Imidazoanthraquinone Derivative as a Surface Passivator for Enhanced and Stable Perovskite Solar Cells.

Hybrid organic-inorganic perovskites have been investigated for their potential to serve in next-generation perovskite solar cells (PSCs). While PSC technology is approaching commercialization, thermal and moisture stabilities remain a concern. Here, we describe the assembly of PSCs using an imidazoanthraquinone derivative (AQ) as a small organic additive to enhance the device performance and stability. Unlike polymer additives, AQ is easy to synthesize and is more economical. AQ was synthesized because it has both carbonyl and imidazole functional groups. The presence of C=O and N-H groups results in coordination interaction with Pb2+ and I- of the perovskite. Addition of the AQ molecule to methylammonium lead iodide leads to the formation of a superior crystalline perovskite film with fewer defects and enhanced stability under humid conditions. The use of optimized perovskite films enhanced device power conversion efficiency (PCE = 17.21%) compared to pristine perovskite (PCE = 13.88%). Unencapsulated optimized devices retained 90% of the initial power conversion efficiency for 30 days at a relative humidity of nearly 35%. The optimized films also exhibited superior thermal stability to that of pristine perovskite films.

An Efficient Synthesis of Benzimidazole‐pyrazines via the Sequential Ugi/Hydroamination/Cyclization Reactions

AbstractThis study reported an efficient two‐step method based on the sequential post‐Ugi hydroamination reaction for synthesizing a novel class of benzimidazole‐pyrazines with high yields. First, a Ugi fourcomponent reaction (Ugi‐4CR) is carried out using readily available starting materials, i. e., 1H‐benzo[d]imidazole‐2‐carboxylic acid, aldehydes, propargylamine, and isocyanides, in methanol at ambient temperature. Afterward, the Ugi products undergoes a sequential intramolecular hydroamination/cyclization reaction between a nitrogen of imidazole and alkyne functional group in aqua media in the presence of AuCl3 as a catalyst to obtain benzimidazole‐pyrazine products. These heterocyclic compounds may have a potential to be utilized in designing modern drugs with desirable features.

Adsorption of 2-Mercapto-1-methylimidazole on the (√3 × 22) Reconstructed and (1 × 1) Phases of an Ordered Au(111) Electrode under Potential Control

The self-assembled monolayers (SAMs) of organosulfur compounds bearing an imidazole (Im) functional group can form hydrogen bonds with others and tailor specific interfacial structures used for CO2 reduction, biosensing, and corrosion prevention. The current study employed cyclic voltammetry and in situ scanning tunneling microscopy (STM) to address the adsorption and structure of 2-mercapto-1-methylimidazole (MMI) on the reconstructed and unreconstructed Au(111) electrodes as a function of potential. The adsorbed MMI molecule assumed the unprotonated form, allowing its S- and N-ends to bind with the Au electrode at a positive potential. Molecular resolution STM images showed an ordered Au(111)–(√21 × √21)R10.9°–MMI structure. The Au–N bond could weaken and be broken at a negative potential, leading to a disordered MMI adlayer. This restructuring event was coupled with the protonation of the Im group. These processes resulted in a sharp peak, which shifted negatively by 60 mV with an increase of 1 pH unit. MMI admolecules were desorbed at a more negative potential to unveil a pitted Au surface, resulting from etching of MMI adsorption. This feature supports the S–Au–S motif for MMI adsorbed to the Au(111) electrode, irrespective of the initial Au surface structure. The effect of MMI as an additive to the deposition bath of Ni was also explored.

Rational engineering of multifunctional ionic covalent organic frameworks for metal-free and efficient chemical fixation of CO2 under mild conditions

The transformation of CO2 into high value-added chemicals such as cyclic carbonates provide a promising technology to solve the exceeding CO2 emission. In the absence of solvent and co-catalyst, the development of highly efficient and recyclable metal-free catalyst with excellent performance under mild conditions still remains a great challenge. Herein, a series of multifunctional ionic covalent organic frameworks (COFs) was synthesized via post-synthesis modification strategy of covalently grafting functionalized imidazole on triazine-based COF skeleton. The influence of bridged alkyl chain, imidazole functional group, nucleophile and grafting amount on catalytic activity was investigated in the cycloaddition of CO2 with epichlorohydrin. Remarkably, IM-COF-Br-Vinyl could afford 96.49% yield and > 99% selectivity with a turnover frequency (TOF) value of 5434 h−1 at 0.5 MPa CO2 pressure and 100 ℃ for 6 h, which was superior to other reported COF catalysts. The excellent catalytic performance was mainly ascribed to its excellent CO2 adsorption capacity and the synergistic effect of CO2-philic basic sites, hydrogen bond donors and nucleophilic anions. Additionally, the reusability and versatility of the catalyst was considered and the proposal catalytic mechanism was speculated according to the above conclusions. This strategy not only avoided the environmental pollution caused by catalytic system itself but also ensured the safety and low-energy consumption by realizing highly efficient catalytic conversion of CO2 under mild conditions. This provides an effective avenue for the design and synthesis of ionic liquid functionalized COF catalysts and the development of CO2 activation and utilization.

Preventing Vanishing Gradient Problem of Hardware Neuromorphic System by Implementing Imidazole-Based Memristive ReLU Activation Neuron.

With advances in artificial intelligent services, brain-inspired neuromorphic systems with synaptic devices have recently attracted significant interest to circumvent the von Neumann bottleneck. However, the increasing trend of deep neural network parameters causes huge power consumption and large area overhead of a nonlinear neuron electronic circuit, and it incurs a vanishing gradient problem. Here, we present a memristor-based compact and energy-efficient neuron device to implement a rectifying linear unit (ReLU) activation function. To emulate the volatile and gradual switching of the ReLU function, we propose a copolymer memristor with a hybrid structure using a copolymer/inorganic bilayer. The functional copolymer film developed by introducing imidazole functional groups enables the formation of nanocluster-type pseudo-conductive filaments by boosting the nucleation of Cu nanoclusters, causing gradual switching. The ReLU neuron device is successfully demonstrated by integrating the memristor with an amorphous InGaZnO thin-film transistors, and achieves 0.5 pJ of energy consumption based on sub-10μA operation current and high-speed switching of 650ns. Furthermore, device-to-system-level simulation using neuron devices on the MNIST dataset demonstrates that the vanishing gradient problem is effectively resolved by five-layer deep neural networks. The proposed neuron device will enable the implementation of high-density and energy-efficient hardware neuromorphic systems. This article is protected by copyright. All rights reserved.

Thermally Activated Delayed Fluorescence and Room-Temperature Phosphorescence in Materials with Imidazo-pyrazine-5,6-dicarbonitrile Acceptors.

Three donor-acceptor compounds based on the imidazo-pyrazine-5,6-dicarbonitrile (IPDC) acceptor were synthesized. The IPDC emitters exhibit blue to near-infrared (NIR) emission with up to 54 % photoluminescent quantum yield. 9,9-Dimethyl-9,10-dihydroacridine (ACR), phenoxazine (POX), and phenothiazine (PTZ) served as electron donors. IPDC-POX displayed NIR emission in toluene solution, while showing room-temperature phosphorescence in the solid state. IPDC-ACR exhibited yellow thermally activated delayed fluorescence. Interestingly, dual-emissive behavior as well as excitation-dependent thermally activated delayed fluorescence (TADF) was found for IPDC-PTZ, arising from the two conformers of phenothiazine derivatives. Overall, this work describes a novel strong electron acceptor from the fusion of imidazole, pyrazine, and nitrile functional groups into one conjugated heterocycle for materials exhibiting NIR emission, TADF, and/or room-temperature phosphorescence (RTP).

Structural Determinants of Indole-2-carboxamides: Identification of Lead Acetamides with Pan Antimycobacterial Activity.

Tuberculosis (TB), caused by Mycobacterium tuberculosis (M.tb), is one of the leading causes of death in developing countries. Non-tuberculous mycobacteria (NTM) infections are rising and prey upon patients with structural lung diseases such as chronic obstructive pulmonary disease (COPD) and cystic fibrosis. All mycobacterial infections require lengthy treatment regimens with undesirable side effects. Therefore, new antimycobacterial compounds with novel mechanisms of action are urgently needed. Published indole-2-carboxamides (IC) with suggested inhibition of the essential transporter MmpL3 showed good potency against whole-cell M.tb, yet had poor aqueous solubility. This project focused on retaining the required MmpL3 inhibitory pharmacophore and increasing the molecular heteroatom percentage by reducing lipophilic atoms. We evaluated pyrrole, mandelic acid, imidazole, and acetamide functional groups coupled to lipophilic head groups, where lead acetamide-based compounds maintained high potency against mycobacterial pathogens, had improved in vitro ADME profiles over their indole-2-carboxamide analogs, were non-cytotoxic, and were determined to be MmpL3 inhibitors.

Artificial metalloenzyme with peroxidase-like activity based on periodic mesoporous organosilica with ionic-liquid framework

Artificial enzymes were developed as alternatives to natural enzymes. Considering the unique characteristics of periodic mesoporous organosilica (PMO) materials, a rational design approach was investigated to simulate the coordination sphere around the iron active center in natural horseradish peroxidase (HRP) and fabricate a new peroxidase-like nanozyme. Well-ordered mesoscopic structure, high surface area, tunable pore size, high thermal-hydrothermal stability, and facile surface functionalization are unique properties of PMOs which allow them be potential candidate for enzyme mimic catalysis. In the present study, a monofunctional PMO with ionic-liquid framework (PMO-IL) was prepared as a support to incorporate the iron protoporphyrin IX hemin. The interior surface of mesochannels were also modified by imidazole functional groups. The synthetic peroxidase-like nanomaterial was fully characterized using several techniques such as N2 adsorption-desorption analysis, Thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) spectroscopy, powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray analysis (EDAX). Peroxidase-like activity of the current nanomaterial was evaluated using 2,2′-Azinobis [3-ethylbenzothiazoline-6-sulfonic acid]-diammonium salt (ABTS) in the presence of hydrogen peroxide in neutral pH condition. Michaelis-Menten kinetic parameters indicated enhanced affinity toward substrate. Results imply that the biomimetic pathways can be developed to achieve a new generation of nanozymes with excellent thermal stability and long-term storage stability which are promising as peroxidase mimics for various applications.

Nitrogen Doping of Graphite Oxide with 2,3‐Diaminomaleonitrile: A Study of the Structural, Morphological, and Electrochemical Behavior

Graphite oxide (GrO) and 2,3‐diaminomaleonitrile‐doped GrO (GrODAMN) materials are synthesized by the modified Hummers method. Oxidation and N‐doping treatments increase the C/O ratio from 2.49 to 2.88 for GrO and GrODAMN materials, respectively. GrODAMN material shows higher thermal resistance from room temperature to 800 °C compared with GrO material. Furthermore, the hydroxyl, epoxy, and carboxyl vibrational bands observed for GrO are masked after N‐doping and the intensity of the D‐band increases with respect to the intensity of the G‐band. These changes in dipole moment and polarizability of the molecules are associated with defects and disorders in the carbon lattice, which modify the microstructure order caused by the creation of carbon–nitrogen functional groups. GrODAMN material shows 6.14 atomic % nitrogen associated with imine, amide, and/or imidazole functional groups formed during N‐doping. High‐resolution transmission electron microscopy micrographs show polycrystalline regions with irregular polygons, where the interaction between layers of both materials is dominated by van der Waals forces and electrostatic interactions, showing interplanar distances of 3.35 and 7.39 Å. Finally, GrODAMN shows a specific pseudocapacitance value 49% higher than for the GrO material, associated with less reversible processes in redox reactions.

Dual‐crosslinked hydrogels with metal coordination from novel co‐polyaspartamide containing 1,2‐dihydroxy and imidazole pendant groups

AbstractHerein, a series of new polyaspartamide derivatives, PolyAspAm(API/APD)s, is prepared from polysuccinimide, which is the thermal polycondensation product of aspartic acid, via successive ring‐opening using 1‐(3‐aminopropyl)imidazole (API) and 3‐amino‐1,2‐propanediol (APD). Metal‐coordinated hydrogels are generated by adding divalent metal ions (Cu2+, Zn2+) to the aqueous polymer solution. The resulting gels can adhere strongly to various substrates. Further, novel dual‐crosslinked hydrogels are prepared, where the first network is generated via acetal formation between the massive 1,2‐hydroxyl groups of the polymer and glutaldehyde as the crosslinker. Subsequent immersion of the product gel in various metal ion‐containing solutions forms a second network via metal coordination, thereby affording mechanically robust hydrogels. Multiple metal‐coordination interactions are expected to occur between the imidazole functional groups and metal cations. The mechanical properties of resulting gel vary depending on the metallic species. These novel kinds of hydrogels are expected to find biomedical applications as adhesives and antibacterial soft matter.

Nickel-Carnosine complex: A new carrier for enzymes immobilization by affinity adsorption

Immobilization is an effective method to promote the application of enzyme industry for improving the stability and realizing recovery of enzyme. To some extent, the performance of immobilized enzyme depends on the choice of carrier material. Therefore, the development of new carrier materials has been one of the key issues concerned by enzyme immobilization researchers. In this work, a novel organic–inorganic hybrid material, nickel-carnosine complex (NiCar), was synthesized for the first time by solvothermal method. The obtained NiCar exhibits spherical morphology, hierarchical porosity and abundant unsaturated coordination nickel ions, which provide excellent anchoring sites for the immobilization of proteins. His-tagged organophosphate-degrading enzyme (OpdA) and ω-transaminase (ω-TA) were used as model enzymes to evaluate the performance of NiCar as a carrier. By a simple adsorption process, the enzyme molecules can be fixed on the particles of NiCar, and the stability and reusability are significantly improved. The analysis of protein adsorption on NiCar verified that the affinity adsorption between the imidazole functional group on the protein and the unsaturated coordination nickel ions on NiCar was the main force in the immobilization process, which provided an idea way for the development of new enzyme immobilization carriers.

Bio-inspired hydroxylation imidazole linked covalent organic polymers for uranium extraction from aqueous phases

• High selectivity imidazole was introduced as linkage in varying degree hydroxylation covalent organic polymers. • Benefiting from the introduction of hydroxyl groups, the uranium adsorption capacities were largely enhanced. • The TpDAB endowed prominent selectivity towards multiple metal ions including vanadium. • The hydroxyl groups significantly influenced the uranium coordination mechanism of imidazole functional group. Highly effective and reliable adsorbents for uranium extraction are vital significant for environmental protection and social development. Herein, inspired by the interaction between imidazole affinity ligand of histidine and uranium, a series of varying degree hydroxylation imidazole linked covalent organic polymers were developed for the first time via one step facile reaction without any post treatment between 2,4,6-triformylphloroglucinol (Tp), 2,4,6-triformylresorcinol (Bd), 2,4,6-triformylphenol (Hb) and 3,3′-diaminobenzidine (DAB), denoted as TpDAB, BdDAB, and HbDAB, respectively. Benefiting from the hierarchical structure of the covalent organic polymer and synergistic effects originating from hydroxyl groups and imidazole linkages, TpDAB, BdDAB, and HbDAB displayed as the promising adsorbents for uranium extraction with high extraction ability and fast capture kinetics. X-ray photoelectron spectroscopy results revealed that both nitrogen atoms in imidazole and oxygen atom in hydroxyl took part in uranium coordination. With the increasing of hydroxyl group amounts, TpDAB achieved highest extraction capacity of uranium. Furthermore, TpDAB with imidazole affinity group possessed eminent selectivity for uranium in the multiple metal ions solution, and especially overcome the unavoidable problem of vanadium interfering with amidoxime adsorption uranium. This work provided a promising uranium extraction strategy with high selectivity and easy preparation for environmental protection and human health.

Mechanical properties and electrical surface charges of microfibrillated cellulose/imidazole-modified polyketone composite membranes

In the present work, microfibrillated cellulose (MFC) suspensions were produced by high-pressure homogenization and subsequently used to fabricate MFC membranes (C-1) by vacuum filtration followed by hot-pressing. A polyketone (PK50) was chemically modified by Paal-Knorr reaction to graft imidazole (IM) functional groups along its backbone structure. The resulting polymer is referred to as PK50IM80. By solution impregnation, C-1 was immersed in an aqueous solution of PK50IM80 and subsequently hot pressed, resulting in the fabrication of MFC/PK50IM80 composite membranes (C-IMP). Another method, referred to as solution mixing, consisted in adding MFC into an aqueous solution of PK50IM80 followed by vacuum filtration and hot-pressing to obtain MFC/PK50IM80 composite membranes (C-MEZC). C-IMP and C-MEZC were characterized by a wide range of analytical techniques including, X-ray photoelectron spectroscopy, Fourier-transform infrared chemical imaging, scanning electron microscopy, atomic force microscopy, dynamical mechanical analysis, tensile testing as well as streaming zeta potential, and compared to C-1 (reference material). The results suggested that C-IMP possess a more homogeneous distribution of PK50IM80 at their surface compared to C-MEZC. C-IMP was found to possess significantly enhanced Young's modulus compared to C-1 and C-MEZC. The tensile strength of C-IMP was found to improve significantly compared to C-1, whereas C-1 possessed significantly higher tensile index than C-IMP and C-MEZC. Furthermore, the presence of PK50IM80 at the surface of MFC was found to significantly shift the isoelectric point (IEP) of the membranes from pH 2.3 to a maximum value of 4.5 for C-IMP. Above the IEP, C-IMP and C-MEZC were found to possess significantly less negative electrical surface charges (plateau value of −25 mV at pH 10) when compared to C-1 (plateau value of −42 mV at pH 10). Our approach may have implication to broaden the range of filtration applications of MFC-based membranes.

Catalytic conversion of fructose to 1,3-dihydroxyacetone under mild conditions

A novel zwitterionic catalyst containing imidazole, carboxyl and amino functional groups was synthesized to catalyze the retro-aldol condensation of fructose. The catalyst displayed efficiently catalytic activity for the conversion of fructose to 1,3-dihydroxyacetone (DHA). The yield of DHA and selectivity of DHA achieved 27.9% and 46.5% after reaction 2 h, respectively, at pH 9.5, 85 °C. A possible catalytic mechanism was suggested. The charged functional groups on the catalyst exhibited synergistic effect and played role in electron induction and proton transfer, which leaded to a good selectivity of DHA in the conversion of fructose under mild conditions.

Tumor-targeting and imaging micelles for pH-triggered anticancer drug release and combined photodynamic therapy

Herein, we construct a charge - switchable polymer nano micelles poly (2-(hexamethyl eneimino) ethyl methacrylate) - b - poly (ethylene glycol) monomethyl ether methacrylate) - b - poly (diethyl enetriaminepentaacetic acid methacrylate) - b - poly (1-vinyl imidazole) - b - poly (4-vinyl phenylboronic acid) (PC7A-PEG-DTPA-VI-PBA) in different pH solutions. DOX released faster from micelles in a weakly acidic environment (pH 5.0) than at pH 7.4. In order to enhance the anti-tumor effect, the imidazole functional groups in the polymer were used to coordinate CdSeTe quantum dots (QDs) for photodynamic treatment (PDT). In addition, the surfaces of the micelles were further decorated with phenylboronic acidas a targeting group, using DTPA chelating 99mTc for SPECT imaging.It has been successfully demonstrated that the nanoparticles have a good cumulative effect on the tumor site.The structure of the polymer was characterized by 1HNMR. The morphology and particle size of the micelles were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The drug loading capacity (DLC) and drug loading efficiency (DLE) of the micelles were analyzed by ultraviolet visible spectroscopy. And the pH-sensitive drug release and cytotoxicity of the micelles were verified in vitro. In vitro experiments showed that the nano micelles were noncytotoxic to different cell lines, while DOX@CdSeTe@PC7A-PEG-DTPA-VI-PBA inhibited the proliferation and promoted the apoptosis of B16F10 cells. An in vivo study with C57BL tumor-bearing mice indicated that DOX@CdSeTe@PC7A-PEG-DTPA-VI-PBA nano micelles efficiently inhibited tumor growth. Results showed that the nano micelles had good pH responsibility and biocompatibility, and the loaded DOX could be released in the weak acidic environment of tumor cells, and it was expected to be a good drug delivery system.

Engineering of aggregation-induced emission luminogens by isomeric strategy to achieve high-performance optoelectronic device

Achieving non-doped organic light-emitting diodes (OLEDs) with high electroluminescent (EL) performance is essential for both illumination source and display applications. A source of this difficulty is the aggregation-induce quenching effect of emitters in the solid state, which results in low EL efficiency and severe roll-off. Herein, four isomeric aggregation-induced emission luminogens (AIEgens), namely TPE-3Cz-mPBI, TPE-3Cz-pPBI, TPE-2Cz-mPBI, and TPE-2Cz-pPBI, are constructed by varying the linkage positions of electron-accepter 1,2-diphenyl-1H-benzo[d]imidazole (PBI), electron-donor carbazole, and AIE-active triphenylethene functional groups. A comprehensive investigation is carried out, and the results indicate that position isomerism dramatically affects electronic structures, photophysical properties, carrier transport capabilities, and device performances. Compared with TPE-3Cz-mPBI and TPE-3Cz-pPBI, TPE-2Cz-mPBI, and TPE-2Cz-pPBI exhibit more excellent AIE-active with the fluorescence quantum yield up to 72.5% and 89.7% in the neat films. Moreover, TPE-2Cz-mPBI shows high electron transport property and appropriate energy level, which favor balanced charge carrier injection/transporting in OLEDs. Hence, non-doped device based on TPE-2Cz-mPBI exhibits the best EL performance with external quantum efficiency, current efficiency, and power efficiency of 3.2%, 7.8 cd A−1, and 7.7 lm W−1, respectively. The isomeric strategy presents a promising method to extend the structural diversity of highly efficient AIE emitters, optimize optoelectronic properties, and construct high-performance non-doped devices. Due to intrinsic twisted structure and accessible protonated N-electron in molecular framework, the isomers exhibit impressive mechanochromism and acidochromism.

Cycling Performance of Vanadium Redox Flow Battery Using Anion Exchange Membrane Based on Im-bPPO

In this work, imidazole group containing brominated poly(phenylene oxide) (Im-bPPO), in which imidazole functional groups are introduced to brominated poly(phenylene oxide), are synthesized and used as a low-cost, hydrocarbon-based anion exchange membrane for vanadium redox flow battery (VRFB). Although the imidazole group containing brominated poly(phenylene oxide) (Im-bPPO) membrane has a room temperature ionic conductivity of 0.02 S cm-1, which is somewhat lower than that of Nafion 212 (0.08 S cm-1), it shows three orders of magnitude lower VO2+ permeability of 1.75×10-9 cm2 min-1 compared with Nafion 212 (1.41×10-6 cm2 min-1), suggesting its benefit of easier rebalancing control during VRFB operation. In comparison with the single cells using Nafion 212, the Im-bPPO membrane-based cell has a higher coulombic efficiency (CE) because of its excellent rejection of vanadium ions. However, the voltage efficiency (VE) of the Im-bPPO-based cell is lower than that of Nafion 212-based cell due to the lower ionic conductivity of the Im-bPPO membrane. Also, the cycle life of the Im-bPPO-based cell is 15 times shorter than the Nafion 212-based cell because of the chemical deterioration by highly oxidative VO2 + ions as observed for other hydrocarbon-based membranes. These results demonstrate the advantage of hydrocarbon-based anion exchange membrane in preventing vanadium crossover, but present a challenge in improving chemical stability for practical usage. Keywords: Vanadium Redox Flow Battery; Anion Exchange Membrane; Imidazole; Polyphenylene Oxide (PPO) Figure 1

Simple Design of an Enzyme-Inspired Supported Catalyst Based on a Catalytic Triad

Summary Enzyme active sites afford an intricate interplay of functional groups to mediate complex organic and inorganic reactions. Many hydrolytic enzymes use a catalytic triad comprising three different functional residues—(Ser(-OH), Hist(-imidazole), Asp(-CO 2 H))—that catalyze the hydrolysis of numerous unique substrates. Inspired by this design, we have developed a simple one-step synthesis for preparing a new supported catalytic system in which the three reactive groups of the catalytic triad (alcohol, imidazole, and carboxylate) are incorporated into a single functional unit. These artificial active sites can be coupled to a solid-phase support (Merrifield resin) by copper(I)-catalyzed azide-alkyne cycloaddition "click chemistry," and their effectiveness as esterolysis catalysts was demonstrated. Furthermore, tuning the local hydrophobicity of the resin particles with an approach analogous to the native enzyme hydrophobic pocket increased the catalytic efficiency. Quantum mechanics and molecular dynamics computational modeling were used to probe the catalytic effect and suggested a concerted two-step mechanism and hydrophobic nanoenvironment similar to that of hydrolytic enzymes.