Strong H-bonds Research Articles

Dynamic anti-correlations of water hydrogen bonds

Water is characterized by strong intermolecular hydrogen bonds (H-bonds) between molecules. The two hydrogen atoms in one water molecule can form H-bonds of dissimilar length. Although intimately connected to water’s anomalous properties, the details and the origins of the asymmetry have remained elusive. We study water’s H-bonds using the O-D stretching vibrations as sensitive reporters of H-bonding of D2O and HOD in dimethylformamide. Broader inhomogeneous linewidths of the OD band of HOD compared to the symmetric and asymmetric OD stretching modes of D2O together with density functional theory calculations provide evidence for markedly anti-correlated H-bonds: water preferentially forms one weak and one strong H-bond. Coupling peaks in the spectra for D2O directly demonstrate anti-correlated H-bonds and these anti-correlations are modulated by thermal motions of water on a sub-picosecond timescale. Experimentally inferred H-bond distributions suggest that the anti-correlations are a direct consequence of the H-bonding potential of XH2 groups, which we confirm for the ND2 group of urea. These structural and dynamic insights into H-bonding are essential for understanding the relationship between the H-bonded structure and phase behavior of water.

Cleavage of a Peroxide Bond via a Dual Attack by Functional Mimics of Glutathione Peroxidase.

Nonmetal-containing peroxidase enzymes, including glutathione peroxidase (GPx), and peroxiredoxins, control cellular redox levels by catalyzing the reduction of H2O2. The remarkably higher reactivity of GPx enzyme as compared to the fully dissociated synthetic selenolate/thiolate molecule is probably due to the dual-attack on the peroxide bond (HO1-O2H) by the enzyme; The first one is a nucleophilic attack of the selenolate/thiolate moiety to O1 atom and the second attack at the O2 atom of the peroxide bond by the acidic "parked proton" from Trp or His residue present at the enzyme's active site, leading to the facile cleavage of O-O bond. Herein, we report two synthetic compounds (1 and 2), having a selenolate (Se-) and a proton donor (imidazolium or -COOH group) moieties, which showed excellent GPx-like activity via dual-attack on the peroxide bond. The combined effect of selenolate moiety that donates electrons to the antibonding (σ*) orbital of O1-O2 bond and the imidazolium or carboxylic acid moiety at the side chain that forms a strong H-bonding with the O2 atom facilitates O-O bond cleavage of H2O2 more efficiently. 1 and 2 exhibit remarkable ability in protecting Cu(I)-complex [TpmCu(CH3CN)]+ (9) against H2O2 by acting as a sacrificial antioxidant, thereby preventing metal-mediated ROS production.

Stringing covalent organic framework particles for preparing highly loaded mixed-matrix membranes for efficient and precise dye separation

Covalent organic frameworks (COFs) based mixed-matrix membranes (MMMs) combining the merits of processable polymers and ordered porosity are potential for molecular separation. However, it remains a challenge to control the interfacial compatibility to prepare high COFs loaded MMMs. Herein, we developed a facile strategy of “Stringing COF particles” for improving the interfacial compatibility to prepare high COFs loaded MMMs with high separation performance. The MMMs could be prepared by simply mixing COF powders with chitosan (CS) solutions, without needing the complicated nanosheetization or modification of COFs. Three typical COFs were synthesized and tested. The suitable large pore size and good hydrophilicity of COFs were confirmed crucial to the “Stringing” strategy. Characterizations indicated CS could enter the larger pores of the COFs (named COF-TADH) and firmly string COF particles together via strong H-bonding to obtain a tightly assembled COF-TADH@CS layer with COFs loading up to 67 wt%. The fabricated 67%COF-TADH@CS/nylon membrane exhibited excellent permeance and stable 100 % rejection to Coomassie brilliant blue (BB), highly competitive compared with other reported membranes. The high COFs loaded MMMs maintain the sieving merits of ordered COF pores, achieving precise separation of the mixed BB/Methyl orange (MO) solution with only MO penetrating through.

Participation of Strong H-Bonding to Acidic Groups Contributes to the Intense Sorption of the Anionic Munition, Nitrotriazolone (NTO) to the Carbon, Filtrasorb 400.

5-Nitro-1,2-dihydro-3H-1,2,4-triazin-3-one ("nitrotriazolone," NTO) is an insensitive munition compound used in modern weaponry. It poses a potential threat to soil and water quality at relevant sites due to its physical properties that cause high mobility in the environment. NTO is polar and predominantly monoanionic (NTO-) at environmental pH (pKa1 = 3.64 and pKa2 = 11.06; determined by two independent methods in this study). Nevertheless, NTO- sorbs strongly to the carbon, Filtrasorb 400 (Freundlich coefficient KF = 1.26 × 104 Ln μmol1-n kg-1 at pH 9.5). We present evidence that sorption is contributed by the interaction of NTO- with functional groups of similar acidity on the carbon to form exceptionally strong, negative charge-assisted hydrogen bonds, (-)CAHB, written (-N-···H+···-O-[Formula: see text]), where -N- is the deprotonated N of NTO, and -O-[Formula: see text] represents a deprotonated surface group. Behaviors consistent with (-)CAHB include (1) a "hump" in the pH-sorption profile centered around pH 4, where maximal complexation is expected to occur; (2) an apparent ∼2.4-unit upward shift in pKa1 due to the enhanced H-bond strength; (3) the consumption of a proton from water to form the complex; and (4) sorption suppression by competing (-)CAHB-capable solutes. Anion exchange played a minor role. The findings help advance our understanding of weak acids sorption by carbonaceous materials.

Proton transport mechanisms in aqueous acids: Insights from abinitio molecular dynamics simulations.

The solvation and transport of protons in aqueous solutions of phosphoric acid (PA), sulfuric acid (SA), and nitric acid (NA) were studied using abinitio molecular dynamics simulations. Systems with acid-to-water ratios of 1:1 and 1:3 were examined to understand the similarities and differences in transport mechanisms. The solvation structure of H3O+ in these systems is similar to that in slightly acidic water, with variations in the strength of hydrogen bonds (H-bonds) accepted by acid molecules. In aqueous PA systems, strong H-bonds between PA molecules are slightly affected by water, leading to significantly greater H3O+ diffusion compared to aqueous SA and NA systems. This enhanced diffusion is attributed to the participation of PA molecules in H3O+ transport, where the PA molecule can shuttle a proton for H3O+, facilitating a large displacement via collective proton hopping. This shuttling mechanism is prominent in aqueous PA but rare in aqueous SA and absent in aqueous NA. Moreover, the decomposition of H3O+ diffusion into vehicular and structural components indicates that the higher diffusion in aqueous PA is primarily due to the structural mechanism with the aid of PA molecules. In the aqueous NA systems, the vehicular diffusion is dominant at low water contents and the increase in water content improves the structural diffusion by forming connected H-bonds within water molecules. Our findings elucidate the role of acid molecules in proton transport within their aqueous solutions, thereby advancing the fundamental understanding of proton transport mechanisms.

On the Origin of Enantioselectivity in Chiral Zeolite Asymmetric Catalyst GTM-3: Host-Guest Transfer of Chirality.

Knowledge of how extra-large-pore chiral zeolite asymmetric catalysts based on the -ITV framework imprint their chirality during a catalytic reaction is crucial in order to spread the scope for the catalytic enantioselective production of chiral compounds of interest. In this work, we have carried out a combined experimental and computational study on the catalytic activity of antipode GTM-3 catalysts during the ring-opening of trans-stilbene oxide with 1-butanol. Identification of the enantiomers of all the chiral species unraveled a surprising catalytic behavior: these chiral catalysts promote the transformation of one enantiomer of trans-stilbene oxide in the corresponding unlike product (with inversion of configuration of the attacked C) via an SN2 mechanism, and at the same time, the transformation of the other enantiomer of trans-stilbene oxide via an SN1-like mechanism into the like (with retention of configuration) and secondary products (diphenylacetaldehyde via Meinwald rearrangement and derived products). A computational study based on DFT + D methods suggested a potential explanation for this catalytic behavior, associated with a different orientation of trans-stilbene oxide enantiomers bound on the Ge(T7) positions in d4r units, which is stabilized by the development of intraframework H-bonds between the interrupted T7OH adjacent positions characteristic of this framework. Calculations suggest that each enantiomer of trans-stilbene oxide follows a different reaction pathway, one favoring the SN2 route by addition of butanol from the opposite side to form unlike-products, while the different orientation of the antipode enantiomer disfavors such SN2 route mainly by steric repulsions and at the same time favors the reaction toward the SN1 mechanism to give like- and secondary-products. Our study suggests that the strong enantioselectivity of GTM-3 catalysts for this reaction is associated with the particular orientation adopted by the chiral reactants within the chiral nanospace provided by the -ITV framework, similarly to what occurs with enzymes, and such preferential orientation is directly controlled by the asymmetric cavities where the reaction takes place, by the particular features of the Ge active sites in adjacent interrupted positions and by the presence of several framework OH groups in the nearby nanospace that interact with guest species. The experimental observations and the reaction mechanism proposed suggest that GTM-3 catalysts prepared from the (1S,2S) enantiomer of the N,N-ethyl-methyl-pseudoephedrinium organic agent should be enriched in the P4332 enantiomorphic space group of the -ITV framework and GTM-3 prepared from the (1R,2R) enantiomer in the antipode P4132. Interestingly, resolution of the absolute configuration of GTM-3 materials from 3D-electron diffraction data has been accomplished and confirms such an assignment, giving an average 82% enantio-enrichment in the corresponding chiral polymorph. Structure-solution of the location of the chiral structure-directing agents indicates that the transfer of chirality from the molecular component to the zeolite polymorph is governed by the development of strong H-bonds between the molecular hydroxyl group and the interrupted T(7)OH framework positions.

Regulating H-bonded network of aqueous electrolytes for stable and energy-dense Al-air batteries

Aluminum-air batteries offer unique advantages over other aqueous batteries in terms of environmental friendliness, energy density, resource abundance, and cost-effectiveness. Nevertheless, the parasitic hydrogen evolution reaction (HER) of anode presents severe challenges for stable and long-term operation of batteries. Here we found that the mixed solution with strong H-bond network has a significant inhibitory effect on the self-discharge and HER of Al anode in alkaline electrolyte. And establishing the relationship between the molecular structure of the cosolvent (carbon chain lengths and hydrogen bond acceptors) and the strength of the hydrogen bonding network of the electrolyte. The as-constructed Al-air battery with ethylene glycol (EG) cosolvent demonstrates a remarkable increased discharge specific capacity of 2725 mAh g-1, corresponding to the Al anode utilization of 91.4 %. The operation time also extends to 160 h at 5 mA cm-2. This work provides new avenues to understand the role of H2O in aqueous electrolytes and explore low-cost and effective approaches for the development of next-generation aqueous Al-air batteries.

Water orientation on platinum surfaces controlled by step sites.

In this work, the adsorption structure of deuterated water on the stepped platinum surface is studied under an ultra-high vacuum by using heterodyne-detected sum-frequency generation spectroscopy. On a pristine Pt(553), D2O molecules adsorbed at the step sites act as hydrogen bond (H-bond) donors to the adjacent terrace sites. This ensures the net D-down orientation at the terrace sites away from the steps. In particular, the pre-adsorption of oxygen atoms at the step sites significantly alters the D-down configuration. The oxygen pre-adsorption leads to a spontaneous dissociation of the post-adsorbed water molecules at the step to form hydroxyl (OD) species. Since the hydroxyl at the step acts as a strong H-bond acceptor, D2O at the terrace no longer maintains the D-down configuration and adopts flat-lying configurations, significantly reducing the number of D-down molecules at the terrace. Density-functional theoretical calculations support these pictures. This work demonstrates the critical role of steps in controlling the net orientation of the interfacial water and provides an important reference for future considerations of the reactions at electrochemical interfaces.

Clustering of biphenyl oxamide ions by chiral recognition.

Gels created by self-assembly of small organic molecules are dynamic soft materials that have unique properties and demanding characterization. Four chiral gelators, with two valinol- or leucinoloxamido arms attached to the 2,2'-positions of the proatropisomeric biphenyl group were chosen to show that the electrospray ionization mass spectrometry (ESI-MS) could be used to differentiate the gelation feature of the chiral compounds 1-4 and also to shed light on the gelation processes. By inspecting the gelation of several solvents, we showed that 1 (R, R) proved to be the most efficient gelator, forming the largest observable assemblies in the gas phase. The strong intermolecular H-bonds hold single-charged assemblies consisting of up to five monomer units detectable by ESI MS. Enantiomer 1 (R, R) is a good gelator due to favorable intramolecular interactions that remain preserved in the gas phase. Compound 3 (meso) does not have gelator properties and detected signals of larger assemblies in the gas phase. So, the detected signals correlate with the conformations of the studied compounds. MS could be used to elucidate the preferential type of noncovalent interaction due to the chiral recognition. The study paves a novel way to investigate the influence of chirality on the molecular assembly and consequently macroscopic properties and functions of materials.

1-Trinitromethyl-3,5-dinitro-4-nitroaminopyrazole: Intramolecular Full Nitration and Strong Intermolecular H-Bonds toward Highly Dense Energetic Materials.

Full nitration is one of the most effective strategies used in synthesizing high-density energetic materials, but this strategy has reached its limit because the resultant compounds cannot be further functionalized. To overcome this limitation, we present the synergistic action of full nitration and strong intermolecular H-bonding in designing and synthesizing 1-trinitromethyl-3,5-dinitro-4-nitroaminopyrazole (DNTP) with a density that exceeds those of the reported monocyclic CHON compounds. The detonation velocity and specific impulse of DNTP exceed those of 1-trinitromethyl-3,4,5-trinitropyrazole (TTP), HMX, and ADN.

Spherulite formation in green nonaqueous media: The impact of urea on gelation in glycerol

HypothesisLarge macroscopic assemblies formed by a surfactant, sodium dodecylsulfate (SDS), and glycerol, can be directed to assemble in a hierarchical manner by the addition of a strong hydrogen-bond donor/acceptor, such as urea. ContextSelf-assembly in complex media is important to a range of applications, for instance in biological media, which are multi-component, to industrial formulations, where additives are present for flavour, texture, and preservation. Here, the gelation and self-assembly of sodium dodecylsulfate (SDS) in glycerol is explored in the presence of an additive, urea. Urea was chosen due to its importance both fundamentally and industrially, but also because of its ability to form strong H-bonds and interact with both glycerol and SDS. ExperimentalTo cover the variety of length scales present in the gel-like phase, a combination of optical microscopy and small-angle X-ray scattering techniques were used to probe the micro- to nanoscale. FindingsOn the microscale, the formation of a spectacular spherulite phase, even at low urea contents - 0.1 wt%, upon cooling was observed, a stark difference to the microfibrillar phase observed in the absence of urea. Interestingly, the nanostructure of the two crystalline phases were similar and showed negligible differences. This suggests that urea is not involved in the SDS/glycerol microfibril formation but instead directs the assembly of spherulites by bundling the microfibrils. These ternary systems are also probed as a function of urea content, SDS concentration, and temperature. The observations in this work highlight the importance of small molecules in the self-assembly process, which is relevant both fundamentally but also industrially, where small molecules are often added to formulations.

The Valence-Dependent Activity of Colloidal Molecules as Ice Recrystallization Inhibitors.

Inspired by advances in cryopreservation techniques, which are essential for modern biomedical applications, there is a special interest in the ice recrystallization inhibition (IRI) of the antifreeze protein (AFPs) mimics. There are in-depth studies on synthetic materials mimicking AFPs, from simple molecular structure levels to complex self-assemblies. Herein, we report the valence-dependent IRI activity of colloidal organic molecules (CMs). The CMs were prepared through polymerization-induced particle-assembly (PIPA) of the ABC-type triblock terpolymer of poly(acryloxyethyl trimethylammonium chloride)-b-poly(benzyl acrylate)-b-poly(diacetone acrylamide) (PATAC-b-PBzA-b-PDAAM) at high monomer conversions. Stabilized by the cationic block of PATAC, the strong intermolecular H-bonding and incompatibility of the PDAAM block with PBzA contributed to the in situ formation of Janus particles (AX1) beyond the initial spherical seed particles (AX0), as well as the high valency clusters of linear AX2 and trigonal AX3. Their distribution was controlled mainly by the polymerization degrees (DPs) of PATAC and PDAAM blocks. IRI activity results of the CMs suggest that the higher fraction of AX1 results in the better IRI activity. Increasing the fraction of AX1 from 27% to 65% led to a decrease of the mean grain size from 39.8% to 10.9% and a depressed growth rate of ice crystals by 58%. Moreover, by replacing the PDAAM block with the temperature-responsive one of poly(N-isopropylacrylamide) (PNIPAM), temperature-adjustable IRI activity was observed, which is well related to the reversible transition of AX0 to AX1, providing a new idea for the molecular design of amphiphilic polymer nanoparticle-based IRI activity materials.

Exploring the antiviral inhibitory activity of Niloticin against the NS2B/NS3 protease of Dengue virus (DENV2)

Dengue virus (DENV2) is the cause of dengue disease and a worldwide health problem. DENV2 replicates in the host cell using polyproteins such as NS3 protease in conjugation with NS2B cofactor, making NS3 protease a promising antiviral drug-target. This study investigated the efficacy of ‘Niloticin’ against NS2B/NS3-protease. In silico and in vitro analyses were performed which included interaction of niloticin with NS2B/NS3-protease, protein stability and flexibility, mutation effect, betweenness centrality of residues and analysis of cytotoxicity, protein expression and WNV NS3-protease activity. Similar like acyclovir, niloticin forms strong H-bonds and hydrophobic interactions with residues LEU149, ASN152, LYS74, GLY148 and ALA164. The stability of the niloticin-NS2B/NS3-protease complex was found to be stable compared to the apo NS2B/NS3-protease in structural deviation, PCA, compactness and FEL analysis. The IC50 value of niloticin was 0.14 μM in BHK cells based on in vitro cytotoxicity analysis and showed significant activity at 2.5 μM in a concentration-dependent manner. Western blotting and qRT-PCR analyses showed that niloticin reduced DENV2 protein transcription in a dose-dependent manner. Besides, niloticin confirmed the inhibition of NS3-protease by the SensoLyte 440 WNV protease detection kit. These promising results suggest that niloticin could be an effective antiviral drug against DENV2 and other flaviviruses.

Tailoring a decatungstate-incorporated metal-organic framework for light-driven [3+2] cyclization of phenols with olefins

Photocatalytic oxidative [3+2] cycloaddition of phenol-olefin is an economy and green strategy to synthesize 2,3-Dihydrobenzofurans (2,3-DHBs) compared with the thermal catalysis with noble metals under harsh conditions. Thus, it is urgent to design noble metal-free heterogeneous photocatalyst that combined single-electron transfer (SET) and hydrogen-atom transfer (HAT) dual function. Decatungstate [W10O32]4− is considered as an ecofriendly photocatalyst for HAT and SET, but it is commonly used in homogeneous catalysis. Herein, we report CuW10-TIPA as a white-light-activated heterogeneous photocatalyst for synthesizing 2,3-dihydrobenzofurans via [3+2] cycloaddition of phenols with olefins, a crucial step in relevant pharmaceutical structural motifs. The coordination bonds between Cu(I) and TIPA, strong H-bonds between TIPA and [W10O32]4− and anion∙∙∙π interactions between [W10O32]4− and TIPA dramatically promote the separation of photoinduced electron-hole and facilitate the charge transfer among each component. Our approach is characterized by its mildness, scalability, and recyclability. We delve into the discussion on [W10O32]4− anions-mediated C-H bond activation via the HAT pathway, with the cooperation of the photosensitizer TIPA and Cu(I), which enhances absorption in the visible region and narrows the energy band.

Comparison of rhodamine B adsorption and desorption on the aged non-degradable and degradable microplastics: Effects of charge-assisted hydrogen bond and underline mechanism

The accumulation of microplastics (MPs) in the environment and their role as carriers for ionic organic pollutants are increasingly attracting attention. This study evaluated the adsorption-desorption characteristics of the cationic organic pollutant on virgin and UV-aged non-degradable polystyrene (PS) as well as degradable poly(butylene succinate) (PBS) and poly(butylene adipate-co-terephthalate) (PBAT) MPs. The results showed that aging treatment made the surface of MPs rougher and more porous, causing the adsorption to shift from monolayer to multilayer adsorption. Aging increased the oxygen-containing groups on MPs, significantly enhancing the H bond (HB) donor capabilities of degradable aged PBS and PBAT, thereby improving adsorption by more than 10 times. This significant increase in adsorption is mainly due to the combined effects of strong HB (including ordinary HB (OHB) and charge-assisted HB (CAHB)), electrostatic interactions, and π-π interactions. Notably, the stronger HB enabled aged PBS and PBAT to achieve efficient and stable adsorption of rhodamine B over a wide pH range, with significant desorption hysteresis (HI > 1.80). This indicates that degradable aged MPs can act as carriers for long-distance pollutant transport. The significant total desorption of cationic pollutants from aged PBS and PBAT in simulated animal gastrointestinal fluids confirmed the greater environmental hazards of degradable aged MPs. This work is the first to demonstrate that degradable aged MPs, as unique HB donors, can primarily adsorb ionic organic pollutants through strong HB (CAHB and OHB), which helps assess the environmental fate of biodegradable microplastics and pollutants in aquatic systems.

Novel NO-TZDs and trimethoxychalcone-based DHPMs: design, synthesis, and biological evaluation as potential VEGFR-2 inhibitors

Novel series of nitric oxide-releasing thiazolidine-2,4-diones (NO-TZD-3a-d,5,6) and 3,4,5-trimethoxychalcone-based multifunctional 1,4-dihydropyrimidines (CDHPM-10a-g) have been designed and synthesised as potent broad-spectrum anticancer agents with potential VEGFR-2 inhibition. The designed analogs were evaluated for their anticancer activities towards a full panel of NCI-60 tumour cell lines and CDHPM-10a-g emerged mean %inhibitions ranging from 76.40 to 147.69%. Among them, CDHPM-10e and CDHPM-10f demonstrated the highest MGI% of 147.69 and 140.24%, respectively. Compounds CDHPM-10a,b,d-f showed higher mean %inhibitory activity than the reference drug sorafenib (MGI% = 105.46%). Superiorly, the hybrid CDHPM-10e displayed the highest potencies towards all the herein tested subpanels of nine types of cancer with MGI50 of 1.83 µM. Also, it revealed potent cytostatic single-digit micromolar activity towards the herein examined cancer cell lines. The designed compounds CDHPM-10a-g were exposed as potent non-selective broad-spectrum anticancer agents over all NCI subpanels with an SI range of 0.66–1.97. In addition, the target analog CDHPM-10e revealed potency towards VEGFR-2 kinase comparable to that of sorafenib with a sub-micromolar IC50 value of 0.11 µM. Also, CDHPM-10e could effectively induce Sub-G1-phase arrest and prompt apoptosis via caspase and p53-dependent mechanisms. Furthermore, CDHPM-10e revealed significant anti-metastatic activity as detected by wound healing assay. The modelling study implies that CDHPM-10e overlaid well with sorafenib and formed a strong H-bond in the DFG binding domain. The ADMET studies hinted out that CDHPM-10e met Pfizer’s drug-likeness criteria. The presented novel potent anticancer agent merits further devotion as a new lead product in developing more chalcone-based VEGFR-2 inhibitors.

A novel approach to design structural natural fiber composites from sustainable CO[formula omitted]-derived polyhydroxyurethane thermosets with outstanding properties and circular features

We herein propose capitalizing on strong hydrogen bonding from novel bio-CO2-derived dynamic thermosets to achieve high-performance natural fiber composites (NFC) with circular features. CO2- and biomass-derived polyhydroxyurethane (PHU) thermosets were selected, for the first time of our knowledge, as matrices for their ability to make strong H-bond, resulting in outstanding mechanical properties for NFC. Exploiting this H-bond key feature, exceptional interface bonding between flax and PHU was confirmed by atomic force microscopy and rationalized by atomistic simulation. Without any treatment, an increase of 30% of stiffness and strength was unveiled compared to an epoxy benchmark, reaching 35 GPa and 440 MPa respectively. Related to the thermoreversible nature of hydroxyurethane moieties, cured flax-PHU were successfully self-welded and displayed promising properties, together with recyclability features. This opens advanced opportunities that cannot be reached with epoxy-based composites. Implementing CO2-derived thermosets in NFC could lead to more circular materials, critical for achieving sustainability goals.

Dual dynamic H-bonds crosslink side chains support a robust polysiloxane elastomer and its self-repairing and recycling properties

Owning excellent mechanical properties and mild repair conditions simultaneously has always been a paradox in the field of self-healing polysiloxane elastomer research. In this work, a robust polysiloxane elastomer with autonomic self-repairing at r. t. and recyclable properties was firstly designed and synthesized. The double strong H-bonds ensure the strength of the elastomer, while the urea bond with relatively weak bond energy also acts as a sacrifice bond to dissipate energy and further bolster the mechanical properties. Meanwhile the double dynamic bonds located in the side chain with stronger molecular activity ability help to get good self-healing performance. Additionally, the material that can be recycled by crushing/remolding and dissolving/remolding methods without compromising their mechanical robustness and self-repairing properties is environmentally friendly.

Aqueous Electrolyte With Weak Hydrogen Bonds for Four-Electron Zinc-Iodine Battery Operates in a Wide Temperature Range.

In the pursuit of high-performance energy storage systems, four-electron zinc-iodine aqueous batteries (4eZIBs) with successive I-/I2/I+ redox couples are appealing for their potential to deliver high energy density and resource abundance. However, susceptibility of positive valence I+ to hydrolysis and instability of Zn plating/stripping in conventional aqueous electrolyte pose significant challenges. In response, polyethylene glycol (PEG 200) is introduced as co-solvent in 2 m ZnCl2 aqueous solution to design a wide temperature electrolyte. Through a comprehensive investigation combining spectroscopic characterizations and theoretical simulations, it is elucidated that PEG disrupts the intrinsic strong H-bonds of water by global weak PEG-H2O interaction, which strengthens the O─H covalent bond of water and intensifies the coordination with Zn2+. This synergistic effect substantially reduces water activity to restrain the I+ hydrolysis, facilitating I-/I2/I+ redox kinetics, mitigating I3 - formation and smoothening Zn deposition. The 4eZIBs in the optimized hybrid electrolyte not only deliver superior cyclability with a low fading rate of 0.0009% per cycle over 20000 cycles and a close-to-unit coulombic efficiency but also exhibit stable performance in a wide temperature range from 40°C to -40°C. This study offers valuable insights into the rational design of electrolytes for 4eZIBs.

Theoretical and experimental study of a new antioxidant xanthone: Solvent and intramolecular hydrogen bond effects

Free radicals are harmful reactive species that cause various problems in the human body. Antioxidant compounds, such as xanthones found in natural products, can help prevent these effects. This study focuses on the antioxidant behavior of ravenelin (RVL) and ravenelin B (RVLB), a newly discovered xanthone in the Exserohilum rostratum fungus. Both experimental and in silico tests were conducted, comparing them to ascorbic acid, a standard antioxidant. The results showed that RVL has a lower bond dissociation energy (312 kJ/mol) than ascorbic acid (313 kJ/mol), indicating comparable antioxidant performance. This difference is mild but agrees with the experiment that indicates RVL efficiency is equivalent to ascorbic acid at low concentrations. RVLB, however, demands higher dissociation energy (323 kJ/mol) and consequently it has a lower antioxidative efficiency. Thus, antioxidant capacity is found as RVL>ascorbic acid>RVLB. From experimental assays, the RVL performance was confirmed through experimental tests at different solute concentrations. The study also examines the effects of solvents and intramolecular hydrogen bonds. Ravenelin molecules present three hydroxyl groups involved in intramolecular OH⋯O interactions. However, analysis based on the infrared spectra, as well as Bader's theory and non-covalent interactions done in water solvent showed that the two strongest H-bonds (≈−37 kJ/mol) better stabilize the molecular structure, but are not favorable to antioxidant reactions, indicating that hydrogen scavenging occurs at the less hydrogen-bonded hydroxyl group. The solvent also plays an active role first in facilitating hydrogen abstraction besides changing the hydrogen scavenging mechanism according to the environmental polarizability. Additionally, the antioxidant mechanism of ravenelin molecules changes from nonpolar to polar solvents, allowing for hydrogen abstraction.