Electron-donating Research Articles

Synthesis of 5-(4-Formylphenyl)barbituric Acid to Access Enolizable Chromophoric Barbituric Acids

AbstractBarbituric acids mono-substituted at the 5-position show keto–enol tautomerism. In the keto form, conjugation to an aryl substituent is interrupted due to the sp³-hybridized carbon atom at the 5-position of barbituric acid. The enol form generates a conjugated π-system to the aryl substituent and acts as an electron-donating group. If the aryl substituent is electron-deficient, a push-pull system is generated that shows typical UV/Vis absorption. These types of compounds are difficult to access synthetically due to their intrinsic convertibility. The synthesis of barbituric acids with a 4-formylphenyl functionality at the 5-position is reported. This compound, 5-(4-formylphenyl)barbituric acid, could be used to introduce extended π-systems with electron-withdrawing groups in great variety by simple condensation reactions. We demonstrate this by a Horner–Wadsworth–Emmons reaction that forms the enolizable dye (E)-5-(4-(4-nitrostyryl)phenyl)barbituric acid.

Controlling Triboelectric Charge of MOFs by Leveraging Ligands Chemistry.

Metal-organic frameworks (MOFs) have emerged as promising materials for triboelectric nanogenerators (TENGs), but the effects of ligand choice on triboelectric charge remain underexplored. Hence, this paper demonstrates the effect of single, binary, and ternary ligands on TENG performance of cobalt/cerium-based (Co─Ce) bimetallic MOFs utilizing 2-methylimidazole (2Melm), terephthalic acid (BDC), and benzene tricarboxylic acid (BTC) as ligands. The detailed structural characterization revealed that varying ligand chemistries led to distinct MOF features affecting TENG performance. Single ligand bimetallic MOFs (designated as CoCe-2MeIm, CoCe-BDC, CoCe-BTC) has lower performance than binary ligand (designated as CoCe-2MeIm-BDC, CoCe-2MeIm-BTC, CoCe-BDC-BTC) and ternary ligand MOFs (designated as CoCe-2MeIm-BDC-BTC). Among all, the binary ligand MOF, CoCe-2MeIm-BTC, shows the best results (598V, 26.7µA) due to the combined effect of imidazole ring and (─COO─) groups. This is attributed to lone pairs on nitrogen atoms and a delocalized π-electron system in imidazole system in this material. CoCe-BTC has the lowest results (31V, 3.2µA) due to the bulkier nature of the electron-withdrawing (─COO─) groups and their impact on the π-electron system of the benzene ring. This study showcases the potential of ligand chemistry manipulation to control triboelectric charge and thereby enhance MOF-based TENG performance.

Design and synthesis of novel tetrahydronephthalene-1-amine based analogues as cholinesterase inhibitors

Inhibiting cholinesterase (ChE) such as AChE and BChE is thought to be one of the most effective treatments for Alzheimer’s disease (AD) and dementia. In the present work, a new facile method for (1S,4S)-4-(3,4-dichlorophenyl)-n-methyl-1,2,3,4-tetrahydronaphthalen-1-amine based analogues 4 (a–p) in good yield (66–93 %) were synthesized by refluxing demethylsertraline (2) with different aldehydes and ketones 3 (a–p). The newly synthesized analogues 4 (a–p) were characterized by physical and spectroscopic techniques for instance FTIR, LR-MS and HR-MS. The synthesized demethylsertraline based analogues 4 (a–p) were examined for their biological activities against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). In case of AChE activity, electron donating substituents have shown more inhibition as 4–hydroxyphenyl– (4b, IC50, 0.98 ± 0.99 µM) and 3,4–dimethoxyyphenyl– (4c, IC50, 1.0 ± 0.98 µM) and exhibited excellent binding affinity. In case of BChE activity, 4e consisting of electron withdrawing substituent has shown potent inhibition (1.26 ± 0.34 µM). Similarly, 4i and 4n depicted good inhibition with IC50 values 1.66 ± 0.78 µM and 1.66 ± 0.98 µM respectively as they possess weakly donating substituents. The structure activity relationship of BChE inhibition has shown opposite trend than AChE inhibition. It has been scrutinized that strong electron donating substituent decrease the BChE inhibitory activities whereas electron withdrawing groups greatly enhance the enzyme inhibition activity. In silico study of the synthesized compounds 4 (a–p) of the series was carried out. Compound 4b demonstrated excellent interaction with AChE compare with Eserine (standard) with a score of 6228 and an ACE value of –101.33 kcal/mol. Compound 4e demonstrated potent interaction with BChE compare with Eserine (standard) with a score of 6028 and ACE value of –258.53 kcal/mol. Compound 4b has the potential to serve as a lead molecule in medication development for Alzheimer’s disease treatment.

Combination of oxidative and reductive effects of phenolic compounds on the degradation of aniline disinfection by-products by free radicals

In this study, we selected 13 phenolic compounds containing -COOH, -CHO, -OH, and -COCH3 functional groups as model compounds for dissolved organic matter (DOM), and explored the redox reactions during the co-degradation of phenolic compounds with aniline disinfection by-products (DBPs) at the molecular level. When phenolic compounds and aniline DBPs were degraded, phenoxy radicals and aniline radicals were the most important intermediates. Phenoxy radicals can degrade aniline DBPs via hydrogen atom abstraction (HAA) reactions, and the reaction rates were related to the reduction potentials of the compounds. Compounds containing electron-withdrawing groups were more likely to oxidize aniline DBPs. Aniline DBPs were more easily degraded by phenoxy radicals when they contained electron-donating groups, and the increase in the number of chlorine atoms inhibited the reaction rates of aniline DBPs degradation by phenoxy radicals. Although phenolic compounds can reduce aniline DBPs, there was no significant correlation between the reaction rates and the reduction potentials of the compounds. Considering the redox effects of phenolic compounds on aniline DBPs, co-degradation simulations showed that phenolics inhibited the degradation efficiency of aniline DBPs. This work provided new insights into the transformation mechanisms and degradation efficiencies of DOM and aniline DBPs when they were co-degraded.

Net hydrogen bond interaction driven supramolecular deep eutectic solvent formation: The case of cyclodextrins

Supramolecular deep eutectic solvents (SUPRADESs) as green designer solvents can be applied to facilitate key steps of separation, extraction, catalysis, and drug transport processes. However, so far, the details concerning the formation mechanism of SUPRADESs are still not clear, thus hindering full development. The present study is dedicated to the theoretical exploration of the structural properties of co-formers that can form SUPRADESs with cyclodextrins (CDs) to design better-performing task-specific SUPRADESs and further structural modifications. Firstly, a series of aliphatic organic acids (AOAs) with similar structures were screened for forming the SUPRADESs. The structure-property relationship showed that co-formers with a higher hydrogen-bond donating ability were found to favor the propensity to form SUPRADESs. Based on this finding, an empirical rule originating from molecular surface electrostatic potential (ESP) descriptors was proposed that can preliminarily predict the formation possibility of SUPRADESs. Density functional theory (DFT) calculations in conjunction with molecular dynamics (MD) simulations further demonstrated that the formation of SUPRADESs mainly depends on the net hydrogen donating ability of co-formers, which is affected by the electron-withdrawing substituent, the carbon chain length, and the molecular self-association degree. Overall, this study provides important guidance to develop novel and green functional SUPRADESs, which will greatly simplify the SUPRADES manufacturing process and reduce the time cost.

Rh(III)-Catalyzed Regioselective Alkyne Insertion in the Context of C-H Activation and Lactonization Reactions: Synthesis of Fused 1,2-Oxaphospholenes.

Herein, we report an expedient synthesis of fused phosphorus-containing heterocycles via Rh-catalyzed cascade C-H activation, alkyne insertion, and lactonization reactions. The substrate scope and the group tolerance are good, as various substituted benzoic acids, N-methoxybenzamides, and 2-phenylindoles could go through the reactions smoothly to afford the corresponding products in moderate to high yields. Additionally, excellent regioselectivities are shown in the alkyne insertion with the assistance of an electron-withdrawing phosphonate group.

Synthesis and Evaluation of 1,4-Dihydropyridine-Based Urea Derivatives as Polyphenol Oxidase Inhibitors

This study investigated the potential inhibitory effects of nine novel synthesized urea-substituted 1,4-dihydropyridine derivatives (DT-DEN-1-9) on polyphenol oxidase (PPO) activity. The compounds were synthesized via the Hantzsch reaction, providing a series of structurally diverse urea and thiourea-modified 1,4-dihydropyridines. Polyphenol oxidase enzyme was extracted from banana (Musa cavendishii) and purified using affinity chromatography with a Sepharose 4B-L-tyrosine-p-aminobenzoic acid affinity gel. The purified enzyme's activity was measured spectrophotometrically using catechol as the substrate, monitoring the increase in absorbance at 420 nm. The inhibitory effects of the synthesized compounds on PPO activity were evaluated through in vitro assays. Various concentrations of each compound were incorporated into the enzyme reaction mixture, and the residual PPO activity was determined. The percentage of PPO activity was calculated relative to a control reaction without inhibitors. IC50 values, representing the concentration of inhibitor required to reduce enzyme activity by 50%, were determined using Lineweaver-Burk plots. Among the tested compounds, DT-DEN-6, featuring a phenyl thiourea substituent, exhibited the most potent inhibition with an IC50 value of 100.14 μM. DT-DEN-8, containing a 2,5-dichlorophenyl thiourea moiety, also showed strong inhibitory activity with an IC50 below 150 μM. Structure-activity relationships were observed, with electron-withdrawing substituents generally enhancing inhibitory potency. Conversely, DT-DEN-5, bearing a 4-(trifluoromethyl)phenyl thiourea substituent, exhibited the weakest inhibition profile (IC50: 233.33 μM). Our findings provide valuable insights for the design of next-generation PPO inhibitors, potentially leading to the development of novel anti-browning agents for applications in food preservation and other industries where control of enzymatic browning is crucial.

The Substituent Effects of Suzuki Coupling in Aqueous Micelles.

The Suzuki coupling in aqueous micelles has received much attention, but few attempts focus on its substituent effects. In view of the significant substituent effects on this reaction, it is necessary and practical to investigate its substituent effects. Herein, the substituent effects of Suzuki coupling in aqueous micelles are well established through Hammett plots and kinetic studies. In the cases of aryl halides, the rate-determining step of the reaction will shift from the oxidation addition step to the transmetalation step as the substituents' electron withdrawing ability increases, so aryl halides with weak electron-withdrawing groups exhibit better reactivity than ones containing strong electron-withdrawing or electron-donating groups. For arylboronic acids, the electron donating groups are beneficial to the Suzuki reaction, while the electron withdrawing group is unfavorable for the reaction. The Suzuki reactions of substituent exchange between arylboronic acids and aryl halides further confirm these substituent effects.

Hydroxyl group modification improves the selectivity of metal single atom on poly(heptazine imide) for electrocatalytic acetylene semi-hydrogenation

Electrocatalytic semi-hydrogenation of acetylene to ethylene has recently attracted attention as a process for removing acetylene from ethylene-rich gas streams due to its mild conditions and energy-saving advantages. However, developing catalysts with low cost and high selectivity for acetylene semi-hydrogenation remains a huge challenge. Here, we investigated the effect of hydroxyl group modification on the acetylene semi-hydrogenation selectivity of poly(heptazine imide) (PHI) supported metal single atom catalyst under alkaline conditions by density functional theory calculations. The results show that hydroxyl group as ligand not only increases the steric resistance of acetylene adsorption, but also acts as electron-withdrawing group to delocalize the electrons of metal atoms, weaken the interaction with acetylene and subsequent intermediates, and make the adsorption moderate, which is beneficial to the desorption of ethylene and avoid over-hydrogenation. The Ni-OH/PHI and Fe-2OH/PHI are capable of achieving the selective hydrogenation of acetylene to ethylene and have good thermodynamic stability, which can be used as ideal catalysts for the electrocatalytic semi-hydrogenation of acetylene to selectively generate ethylene. This study provides theoretical guidance for the rational design of electrocatalysts for the selective semi-hydrogenation of acetylene.

Synthesis, structure, and photochromic properties of Zn-coordination polymers derived from hexyl viologen cations

This study presents the synthesis, structural characterization, and investigation of the photochromic properties of two Zn-coordination polymers, formulated as {(HV)0.5[Zn(MIC)(HMIC)]·H2O}n (1) and {(HV)2[Zn4(BTEC)3]}n (2) (H2MIC = 5-methylisophthalic acid, H4BTEC = 1,2,4,5-benzenetetracarboxylic acid, HVBr2 = 1,1′-bis(n-hexyl)-4,4′-bipyridinium dibromide), derived from hexyl viologen cations. Compound 1 is characterized by a one-dimensional (1D) structure, while compound 2 exhibits a three-dimensional (3D) architecture, both crystallizing in distinct space groups and showcasing unique assembly and composition. Detailed structural analysis reveals the coordination modes of Zn(II) ions within these polymers. The photochromic behavior of two compounds under UV light exposure was thoroughly examined through ultraviolet-visible (UV–vis) and electron paramagnetic resonance (EPR) spectroscopy, demonstrating reversible color changes from light yellow to blue upon irradiation, with distinct rates of decolorization indicative of the stability of photo-induced viologen radicals. This reversibility was successfully replicated over multiple cycles, underscoring the durability of the photochromic transition. Furthermore, powder X-ray diffraction (PXRD) data confirmed the maintenance of crystal structures throughout the photochromic process, dismissing photolysis or photo-induced isomerization as underlying mechanisms. Instead, the observed photochromism is attributed to efficient electron transfer facilitated by the proximity between electron-donating and electron-withdrawing groups within the coordination polymers. This study highlights the influence of structural parameters on the photochromic properties of viologen-based coordination polymers, offering insights into the design of photo-responsive materials.

Surface engineering and concentration-dependent emission activated flexible tunable fluorescence from lignin-based N-doped carbon dots

Achieving the flexible and tunable fluorescence of lignin-based N-doped carbon dots (LCDs) remains a win–win yet challenging strategy. In this study, combining the surface engineering and concentration regulation strategy enabled the flexible adjustment of LCDs fluorescence emission from blue to yellow regions (345 to 560 nm). The surface electron-donor –OH groups not only enhanced the photoluminescence quantum yield (PLQY) to 14.75 % but activated the spectral shift of reduced LCDs (RLCDs). These arose from the reinforced π-electron conjugation and generated new –OH-related extrinsic defects with elevating concentration. Conversely, the electron-withdrawing CO groups participated in the blue-to-green fluorescence modulation. Still, they drastically reduced the PLQY of oxidized LCDs (OLCDs) to 2.13 %, due to the larger particle size and more non-radiative transfer induced by CO groups. Based on these, CDs/PVA films and printed fluorescent patterns with multicolor fluorescence were realized for anti-counterfeiting, and the RLCDs@Al2O3 hybrid facilitated the precise fluorescence fingerprint tracking and recognition. This study provided a facile strategy for enriching and developing novel LCDs with flexible fluorescence for their advanced applications.

Boosting photocatalytic performance of polymeric carbon nitride by adjusting its donor-acceptor structure via functional group modification strategy

Solar-driven photodegradation of pollutant is attractive for environmental remediation. Herein, we designed and synthetized a new kind of group-modified polymeric carbon nitride (PCN) photocatalyst with urea and 4-Nitro-o-phenylenediamine by one-pot method and applied to degrade bisphenol A (BPA) in aqueous solution. The light response range of photocatalyst had been extended a lot due to conjugation and electron-withdrawing properties of nitrobenzene. Physical analysis shows that 4-Nitro-o-phenylenediamine grafting brings an improved charge separation capacity. EPR and DFT results demonstrate the charge separation is significantly affected by the donor-acceptor structure of PCN, which can be altered via aromatic electron-withdrawing group. The kinetic constant of photocatalytic degradation for BPA was promoted by 8.8-times greater than unmodified PCN and a good recyclability was achieved. To verify the universality of group modification strategies, we prepared other two kinds of photocatalysts via electron-withdrawing group modification strategy and their photocatalytic performance all had been improved obviously.

Exploring the electronic influence on coordination complexes formed from appended pyrrolidine azothioformamide ligands and copper(I) salts

Redox-active arylazothioformamide (ATF) ligands have seen attention through their unique coordination complexes formed with salts of late transition metals and their known ability to oxidatively dissolve zerovalent metals. When mixed with Cu(I) salts, ATF ligands form both 2:1 and 2:2 coordination complexes remaining neutral without undergoing any redox event. Herein, a series of para-substituted pyrrolidine-ATFs were synthesized, incorporating both electron-donating groups (i.e., -OMe and -Me) as well as electron-withdrawing groups (i.e., -CF3, and -CN). These ligands were then mixed with Cu(I) salts, including CuBr, CuI, and [(CH3CN)4Cu](BF4) to form coordination complexes. The resulting complexes underwent thorough characterization, with several producing X-ray quality crystals for detailed structural analysis. Both strong and weak intermolecular interactions were found through Hirshfeld surface analysis and the redox activity of the complexes was probed using cyclic voltammetry in the voltage range of -1.8 to 1.8 V. Through a UV–Vis titration study, the binding interactions between the ligand host and Cu(I) metal salt guest molecules were determined and ranged from 4,000 – 100,000 M-1. Computational modeling was employed to calculate the change in Gibbs free energy (ΔG) for the formation of the complexes, revealing the optimal orientations between the ligand and the metal. These studies have confirmed that para-substituted pyrrolidine-ATFs containing electron-donating groups exhibit a higher binding affinity towards Cu(I) metal salts compared to those with electron-withdrawing groups. With a thorough understanding of ATF-metal coordination, further ligand design can lead to exciting new catalysts and/or selective metal dissolution agents.

Chlorophyll Pigments and Their Synthetic Analogs.

Oxygenic phototrophs use chlorophylls (Chls) as photosynthetically active pigments. A variety of Chl molecules have been found in photosynthetic eukaryotes including green plants, algae, and cyanobacteria. Here we review their molecular structures with stereochemistry, occurrence in light-harvesting antennas and reaction centers, biosyntheses in the late stage, chemical stabilities, and visible absorption maxima in diethyl ether. The observed maxima are comparable to those of semisynthetic Chl analogs, methyl pyropheophorbides, in dichloromethane. The effects of their peripheral substituents and core π-conjugation on the maxima of the monomeric states are discussed. Notably, the oxidation along the molecular x-axis in Chl-a produces its accessory pigments, Chls-b/c, and introduction of an electron-withdrawing formyl group along the y-axis perpendicular to the x-axis affords far-red light absorbing Chls-d/f.

Functional Group-Driven Competing Mechanism in Electrochemical Reaction and Adsorption/Desorption Processes toward High-Capacity Aluminum-Porphyrin Batteries.

Nonaqueous organic aluminum batteries are considered as promising high-safety energy storage devices due to stable ionic liquid electrolytes and Al metals. However, the stability and capacity of organic positive electrodes are limited by their inherent high solubility and low active organic molecules. To address such issues, here porphyrin compounds with rigid molecular structures present stable and reversible capability in electrochemically storing AlCl2 +. Comparison between the porphyrin molecules with electron-donating groups (TPP-EDG) and with electron-withdrawing groups (TPP-EWG) suggests that EDG is responsible for increasing both highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels, resulting in decreased redox potentials. On the other hand, EWG is associated with decreasing both HOMO and LUMO energy levels, leading to promoted redox potentials. EDG and EWG play critical roles in regulating electron density of porphyrin π bond and electrochemical energy storage kinetics behavior. The competitive mechanism between electrochemical redox reaction and de/adsorption processes suggests that TPP-OCH3 delivers the highest specific capacity ~171.8 mAh g-1, approaching a record in the organic Al batteries.

Monomeric Fe(III)-Hydroxo and Fe(III)-Aqua Complexes Display Oxidative Asynchronous Hydrogen Atom Abstraction Reactivity.

This paper presents the synthesis and characterization of a series of novel monomeric aqua-ligated iron(III) complexes, [FeIII(L5R)(OH2)]2+ (R=OMe, H, Cl, NO2), supported by an amide-containing pentadentate N5 donor ligand, L5R [HL5R=2-(((1-methyl-1H-imidazol-2-yl)methyl)(pyridin-2-yl-methyl)amino)-N-(5-R-quinolin-8-yl)acetamide]. The complexes were characterized by various spectroscopic and analytical techniques, including electrochemistry and magnetic measurements. The Fe(III)-hydroxo complexes, [FeIII(L5R)(OH)]1+, were generated in situ by deprotonating the corresponding aqua complexes in a pH ~7 aqueous medium. In another way, adding one equivalent of a base to a methanolic solution of the Fe(III)-aqua complexes also produced the Fe(III)-hydroxo complexes. The study uses linoleic fatty acid as a substrate to explore the hydrogen atom abstraction (HAA) reactivity of both hydroxo and aqua complexes. The investigation highlights the substitution effect of the L5R ligand on reactivity, revealing a higher rate when an electron-withdrawing group is present. Hammett analyses and(or) determination of the asynchronicity factor (η) suggest an oxidative asynchronous concerted proton-electron transfer (CPET) pathway for the HAA reactions. Aqua complexes exhibited a higher asynchronicity in CPET, resulting in higher reaction rates than their hydroxo analogs. Overall, the work provides insights into the beneficial role of a higher imbalance in electron-transfer-proton-transfer (ET-PT) contributions in HAA reactivity.

One-Pot Preparation of Nitro-Functionalized Bimetallic UiO-66(Zr-Hf) with Hierarchical Porosity for Oxidative Desulfurization Performance.

Preparation of multifunctional metal-organic frameworks (MOFs) offers new opportunities to obtain ultrahigh synergistic catalytic performance for heterogeneous reactions; however, the application of a one-pot method for preparing multifunctional MOFs remains challenging. Herein, we develop a one-pot green route for synthesizing bimetallic nitro-functionalized UiO-66(Zr-Hf)-NO2 with hierarchical porosity under solvent-free conditions. The optimal UiO-66(Zr-Hf0.6)-NO2 shows an ultrahigh enhancement of oxidative desulfurization (ODS) efficiency to oxidize sulfur compounds (1000 ppm sulfur) in a model fuel at 40 °C within 12 min due to the introduction of more active Hf sites in the nodes, the increased Lewis acidity of Zr/Hf-O nodes by the electron-withdrawing NO2 group, and the enhanced diffusion rates by the mesopores. The turnover frequency (TOF) over UiO-66(Zr-Hf0.6)-NO2 at 40 or 50 °C reaches 145.3 or 217.0 h-1 that surpasses the TOF of most reported MOF-based catalysts in the ODS reaction. Quenching and electron paramagnetic resonance experiments confirm that the formed Hf-OH on the Zr/Hf-O nodes can easily decompose the oxidant (H2O2) for generating a Hf-OOH-active intermediate and dominate the ODS efficiency. This contribution provides a one-pot solvent-free avenue to synthesize multifunctional MOFs for enhancing their catalytic activities for targeted applications.

Isomers of n-Type Poly(thiophene-alt-co-thiazole) for Organic Thermoelectrics.

n-Type polythiophene represents a promising category of n-type polymer thermoelectric materials known for their straightforward structure and scalable synthesis. However, n-type polythiophene often suffers from a twisted backbone and poor stacking property when introducing high-density electron-withdrawing groups for a lower lowest unoccupied molecular orbital (LUMO) level, which is considered to be beneficial for n-doping efficiency. Herein, we developed two isomers of polythiophene derivatives, PTTz1 and PTTz2, by inserting thiazole units into the polythiophene backbone composed of thieno[3,4-c]pyrrole-4,6-dione (TPD) and thiophene-3,4-dicarbonitrile (2CNT). Although PTTz1 and PTTz2 share a similar polymer skeleton, they differ in thiazole configuration, with the nitrogen atoms of the thiazole units oriented toward TPD and 2CNT, respectively. The insertion of thiazole units significantly planarizes the polythiophene backbone while largely preserving low LUMO levels. Notably, PTTz2 exhibits a more coplanar backbone and closer π-stacking compared to PTTz1, resulting in a greatly enhanced electron mobility. Both PTTz1 and PTTz2 can be easily n-doped due to their deep LUMO levels. PTTz2 demonstrates superior thermoelectric performance, with an electrical conductivity of 50.3 S cm-1 and a power factor of 23.8 μW m-1 K-2, which is approximately double that of PTTz1. This study highlights the impact of the thiazole unit on n-type polythiophene derivatives and provides valuable guidelines for the design of high-performance n-type polymer thermoelectric materials.

Evaluation of chitosan composites with functionalized carbon nano-onions for supercapacitor applications

The growing need for devices boasting substantial energy and power storage capabilities, like capacitors, is driving extensive research and development efforts toward novel materials endowed with superior electrochemical properties. An example of a promising material in this field is found in carbon nanoonions (CNOs). These carbon-based nanostructures boast remarkable properties such as high conductivity, surface area, and stability. Unfortunately, their low energy density and capacitance act as a hindrance to their potential electrochemical application. To bypass this issue, chemical treatment is often employed as a means to improve the sorption processes and, thus, optimize the charge/discharge dynamics. Herein, three types of materials were prepared using commercially available chitosan (Chit) and unfunctionalized carbon nano-onions (p-CNOs), as well as functionalized CNOs with carboxylic fragments (ox-CNOs) and benzoic groups (benz-CNOs). The capacitance of each material was evaluated through cyclic voltammetry using different electrolytes (1.0 M), obtaining values of 34.1, 23.7, 14.1, 43.0, 59.3, and 36.2 Fg-1 for p-CNOs, benz-CNOs, ox-CNOs, p-CNOs/Chit 2:1, benz-CNOs/Chit 2:1, and ox-CNOs 3:1, respectively in Na2SO4, and for the composite p-CNOs/Chit 2:1 in MgSO4, with a specific capacitance of 43.0 Fg-1. We also used electrochemical impedance spectroscopy (EIS) to study the charge/discharge process at the electrodes, concluding that the fragments of the electron-withdrawing groups in the materials improved their electrochemical properties without compromising other intrinsical properties.

BioLindlar Catalyst: Ene-Reductase-Promoted Selective Bioreduction of Cyanoalkynes to Give (Z)-Cyanoalkenes.

The direct synthesis of alkenes from alkynes usually requires the use of transition-metal catalysts. Unfortunately, efficient biocatalytic alternatives for this transformation have yet to be discovered. Herein, the selective bioreduction of electron-deficient alkynes to alkenes catalysed by ene-reductases (EREDs) is described. Alkynes bearing ketone, aldehyde, ester, and nitrile moieties have been effectively reduced with excellent conversions and stereoselectivities, observing clear trends for the E/Z ratios depending on the nature of the electron-withdrawing group. In the case of cyanoalkynes, (Z)-alkenes were obtained as the major product, and the reaction scope was expanded to a wide variety of aromatic substrates (up to >99 % conversion, and Z/E stereoselectivities of up to >99/1). Other alkynes containing aldehyde, ketone, or ester functionalities also proved to be excellent substrates, and interestingly gave the corresponding (E)-alkenes. Preparative biotransformations were performed on a 0.4 mmol scale, producing the desired (Z)-cyanoalkenes with good to excellent isolated yields (63-97 %). This novel reactivity has been rationalised through molecular docking by predicting the binding poses of key molecules in the ERED-pu-0006 active site.