Strong Hydrogen-bonding Interactions Research Articles

Elastic Microstaggered Porous Superhydrophilic Framework as a Robust Fogwater Harvester.

A robust fogwater harvester with an elastic microstaggered porous superhydrophilic framework (EMSF) has been designed. The EMSF can be fabricated by using polydimethylsiloxane and polyvinyl alcohol (PVA) via an etching method of sugar crystals pile-up cube as a template. The EMSF possesses a high porosity of 76%, of which the saturated fogwater-capturing capacity is 4 times higher than its weight, achieving a high fogwater harvesting rate (ε) of 62.7 g/cm3·h. It is attributed to the strong hydrogen bond (H-bond) interaction between hydroxyl groups (-OH) in PVA and water molecules for rapidly harvesting water and storing water in a staggered porous structure by means of a capillary force. The elasticity of EMSF allows to achieve a higher fogwater harvesting rate (ε) of 73.2 g/cm3·h via releasing the as-stored water in the EMSF under periodic external pressing. In addition, a durable corrosion resistance is demonstrated on the EMSF. This study offers a way to design novel materials that would further be extended into applications, for example, fog engineering in industry, agriculture, forest, and so forth.

Crystal structure of 4-(dimethylamino)pyridin-1-ium-2,5-dichloro-3,6-dioxocyclohexa-1,4-diene-1,4-bis(olate) 4-dimethylaminopyridine (2:1) water undeca-solvate

The structure of the title compound, 4-(dimethylamino)pyridin-1-ium-2,5-dichloro-3,6-dioxocyclohexa-1,4-diene-1,4-bis(olate) 4-dimethylaminopyridine water undeca-solvate, C57H87Cl5N12O21, obtained from interaction between chloranilic acid (caH2), and dimethyl aminopyridine (DMAP) has been determined by single crystal X-ray diffraction. The title compound, (DMAPH)5(ca)2.5·(DMAP)·11H2O, crystallized in the triclinic crystal system with space group, P (no. 2), a = 13.3824(15) Å, b = 13.4515(17) Å, c = 19.048(2) Å, α = 86.014(4)°, β = 88.821(4)°, γ = 86.367(4)°, V = 3413.3(7) Å3, Z = 2, T = 100(2) K, μ(MoKα) = 0.294 mm-1, Dcalc = 1.414 g/cm3, 59413 reflections measured (3.76° ≤ 2Θ ≤ 56°), 16405 unique (Rint = 0.0517, Rsigma = 0.0589) which were used in all calculations. The final R1 was 0.0460 (I ≥ 2σ(I)) and wR2 was 0.1271 (all data). Using supramolecular chemistry principles, proton donors (chloranilic acid) and acceptor (DMAP) were combined to generate a multicomponent hydrogen-bonded system. Due to the presence of protonated bases (DMAPH+), the dominant interactions are the N+-H···O hydrogen bonds, whereas the negative charges of an acceptor from the chloranilate dianion (ca2-) are delocalized. Additionally, three sets of water clusters in the title compound were identified, namely a cyclic pentamer, a linear, and an acute-shaped trimer water cluster. It was further observed that strong hydrogen bond interactions occurred between the solvated aqua molecule(s) acting as a proton donor and the neutral DMAP acting as a proton acceptor. The crystal packing is further stabilized by O-H···Cl and C-H···Cl weak halogen interactions. The lattice metric strength is further held by observed π-π stacking interactions (centroid-centroid) with inter centroid distances between sets of the DMAPH rings of 3.624(3), 3.642(4), 3.739(3), 3.863(3) and 3.898(3) Å, respectively.

Cyanide-Bridged Polynuclear and One-Dimensional FeIII-MnIII/II Bimetallic Complexes Based-on Pentacyanoferrite(III) Building Block: Synthesis, Crystal Structures, and Magnetic Properties

In this contribution, based-on the structurally confirmed pentacyanometallate (PPh4)2[Fe(CN)5(imidazole)]·(imidazole)·H2O (1) and the manganese compounds [Mn(L)(H2O)2]ClO4 (L = N,N-ethylenebis(3-methoxysalicylideneiminate) or [Mn(MAC)(H2O)Cl]ClO4 (MAC = 2,13-dimethyl-3,6,9,12,18-pentaazabicyclo-[12.3.1]octadeca-1(18),2,12,14,16-pentaene), two new cyanide-bridged bimetallic FeIII-MnIII/II complexes [Mn(L)(H2O)]3[Fe(CN)5(imidazole)](ClO4) (2) and [Mn(MAC)][Fe(CN)5(imidazole)]·CH3OHn (3) were successfully synthesized and characterized by elemental analysis, IR spectroscopy and X-ray structure determination. Single X-ray diffraction analysis reveals the cationic FeMn3 tetranuclear entity for complex 2, which can be further assembled into supramolecular 1D ladder-like double chain by the strong intermolecular hydrogen bond interactions. For complex 3, it can be structurally characterized as neutral one-dimensional linear single infinite chain. The magnetic investigations discover the ferromagnetic coupling between the FeIII-MnIII units in complex 2 and the antiferromagnetic coupling in complex 3 between the FeIII-MnII units through the bridging cyanide group, respectively.

Controlled fabrication of orchid-like nitrogen-doped hierarchical porous carbon and hollow carbon nanospheres

Flower-like porous carbon has fascinated significant attention due to its outstanding and exceptional properties. However, controlled synthesis of porous carbon with adjustable morphology, highly active sites and cross-linked pore channels remains still a great challenge. Herein, an inimitable dissolution–reassembly anisotropic growth strategy was firstly demonstrated for the fabrication of idiographic orchid-like hierarchical porous carbon with ultra-thin multilayer carbon sheets, high specific surface area (1063 m2 g−1), large pore volume (0.82 cm3 g−1) and rich nitrogen content (7.6 wt%). Highly reactive phloroglucinol and EDA aggregated magically and SiO2 acted as a pore former. Ingeniously, acetone acted as a “surgical knife,” which cut the composite of SiO2@phloroglucinol–EDA into many tiny units and further anisotropic growth into orchid-like polymers. The width and thickness of the carbon petals can be effectively controlled with the diversification of acetone concentration. Intriguingly, monodisperse hollow carbon nanospheres could be harvested with silicon-deficient system, which may offer new insight into the construction of functionalized carbon materials with hollow architecture. Owing to the unmatched superstructures, orchid-like carbon materials can be employed as an ideal drug carrier and dye adsorbent. Figure Schematic illustration of solid carbon nanosphere, hollow carbon nanosphere and OHPC-25. For the first time, a novel dissolution–reassembly route based on strong hydrogen-bonding interaction was developed to prepare unique orchid-like hierarchical porous carbon, in which phloroglucinol acted as a carbon precursor and EDA both as a base catalyst and as a nitrogen precursor. The critical step to this synthetic approach was the ingeniously employed acetone as a “surgical knife” to cut the composite of SiO2@phloroglucinol–EDA into many tiny units, and these units were reassembled into orchid-like polymers. After adding acetone, the morphology of carbon materials has changed from solid nanospheres to hollow nanospheres. This strategy did not use any template as the cavity, which may offer a new insight into the comprehension of synthesized functionalized carbon materials with hollow architecture.

Autonomous self-healing hydrogel with anti-drying properties and applications in soft robotics

Mimicking nature's self-healing ability has always been desired in science, especially when devices accumulate damage over time with performance, including the loss of function due to deterioration. SHAP (Self-Healing AETA([2-(acryloyloxy)ethyl]trimethylammonium chloride)-based Polymer), a hydrogel with autonomous self-healing ability that can be applied for the development of a pneumatic artificial muscle, is presented here. Unlike other self-healing hydrogels, SHAP does not require any external stimulus to self-heal and it presents outstanding anti-drying properties. Few-layer graphene is also incorporated into the polymer network of the hydrogel in order to study the possible influence that the nanomaterial has on the properties of the scaffolds. The mechanical behavior and the self-healing abilities of the resulting hydrogels are analyzed. Moreover, the mechanism of self-healing is discussed in terms of experimental results and theoretical calculations. The data suggest a mechanism based on strong hydrogen-bonding interactions between the water molecules that remain inside SHAP, which keeps the material wet and soft under ambient conditions. Finally, the development of a SHAP-based artificial muscle is presented. The results show good performance of the healed artificial muscles after damage, even with healing periods as short as 10 minutes.

Analysis of supramolecular self-assembly of two chromene derivatives: Synthesis, crystal structure, Hirshfeld surface, quantum computational and molecular docking studies

Two 4H-chromene derivatives (1C and 1F) were synthesized by the multicomponent condensation reactions (MCRs) and spectroscopically characterized. The 3-D structures of both the compounds were determined using single crystal X-ray diffraction method. The similar structural conformations are observed in both the compounds but they are stabilized with different packing modes. The supramolecular synthons constructed by strong hydrogen bond interactions plays a major role in the supramolecular self-assembly of molecules in the solid state. Hirshfeld surface analysis is used to assess the various intermolecular interactions in both the structure that driven the self-assembly of molecules in crystal lattices. The propensity of inter-molecular contacts to construct the supramolecular assembly were analyzed using enrichment ratios. The geometrical optimization of both the structures were done by electronic structure method using density functional theory (DFT) to identify the active sites and to explore the chemically reactive parameters of the molecules. Further, novel 1C and 1F compounds were docked with DNA gyrase protein of S. aureus to analyze the binding affinity with targeted protein.

Sugar-based natural deep eutectic solvents as potential absorbents for NH3 capture at elevated temperatures and reduced pressures

Exploring biocompatible and biodegradable materials for application in chemical processes is an important task of green chemistry. In this work, deep eutectic solvents (DESs) composed of natural compounds−choline chloride (ChCl) and sugars−were proposed as NH3 absorbents for the first time. The capture of NH3 from industrial tail gas is of great significance, to control air pollution and recycle N resources. The physiochemical properties of DESs were characterized, and the NH3 capture performance was examined systematically. Due to the presence of abundant hydroxyl groups that enable strong hydrogen-bond interaction with NH3 in DESs, the absorption of NH3 displays non-ideal behavior, and the NH3 capacities show small decrease as temperatures increase. Thus, ChCl+sugar DESs exhibit the ability to effectively capture NH3 from dilute sources at elevated temperatures (e.g., 1.745 mol/kg at 343.2 K and 14.0 kPa), which is very important for practical application. The mechanism of NH3 absorption was validated by spectroscopic characterizations and quantum chemistry calculations. Moreover, the absorption of NH3 in ChCl+sugar DESs also show excellent selectivities over other components in industrial tail gas (e.g., N2, H2 and CO2), as well as good reversibility.

Biodegradable films based on chitosan and defatted Chlorella biomass: Functional and physical characterization

Biodegradable films based on chitosan, glycerol, and defatted Chlorella biomass (DCB) were prepared and characterized in terms of thermal stability, mechanical, water barrier, and optical properties. Increasing DCB content from 5 to 25 wt% increased tensile strength of chitosan films by 235%. The incorporation of DCB decreased both moisture content and swelling degree of chitosan/defatted Chlorella biomass (Cs/DCB) films. Furthermore, increasing the content of defatted algal biomass decreased light transmission and reduced water vapor permeability of composite films by more than 60%. As confirmed by scanning electron microscopy and Fourier transform infrared analysis, such improvement in functional and physical properties is mainly due to the homogeneous and uniform distribution of DCB into the polymeric matrix along with the establishment of strong hydrogen bond interactions between chitosan and algal biomass constituents. Moreover, Cs/DCB composite films showed more than 50% of degradation in 60 days soil burial test.

Substitution Effects Regulate the Formation of Butterfly-Shaped Tetranuclear Dy(III) Cluster and Dy-Based Hydrogen-Bonded Helix Frameworks: Structure and Magnetic Properties.

The generation of two types of complexes with different topological connections and completely different structural types merely via the substitution effect is extremely rare, especially for -CH3 and -C2H5 substituents with similar physical and chemical properties. Herein, we used 3-methoxysalicylaldehyde, 1,2-cyclohexanediamine, and Dy(NO3)3·6H2O to react under solvothermal conditions (CH3OH:CH3CN = 1:1) at 80 °C to obtain the butterfly-shaped tetranuclear DyIII cluster [Dy4(L1)4(μ3-O)2(NO3)2] (Dy4, H2L1 = 6,6'-((1E,1'E)-(cyclohexane-1,3-diylbis(azanylylidene))bis(methanylylidene))bis(2-methoxyphenol)). The ligand H2L1 was obtained by the Schiff base in situ reaction of 3-methoxysalicylaldehyde and 1,2-cyclohexanediamine. In the Dy4 structure, (L1)2- has two different coordination modes: μ2-η1:η2:η1:η1 and μ4-η1:η2:η1:η1:η2:η1. The four DyIII ions are in two coordination environments: N2O6 (Dy1) and O9 (Dy2). The magnetic testing of cluster Dy4 without the addition of an external field revealed that it exhibited a clear frequency-dependent behavior. We changed 3-methoxysalicylaldehyde to 3-ethoxysalicylaldehyde and obtained one case of a hydrogen-bonded helix framework, [DyL2(NO3)3]n·2CH3CN (Dy-HHFs, H2L2 = 6,6'-((1E,1'E)-(cyclohexane-1,3-diylbis(azanylylidene))bis(methanylylidene))bis(2-ethoxyphenol)), under the same reaction conditions. The ligand H2L2 was formed by the Schiff base in situ reaction of 3-ethoxysalicylaldehyde and 1,2-cyclohexanediamine. All DyIII ions in the Dy-HHFs structure are in the same coordination environment (O9). The twisted S-shaped (L2)2- ligand is linked by a Dy(III) ion to form a spiral chain. The spiral chain is one of the independent units that is interconnected to form Dy-HHFs through three strong hydrogen-bonding interactions. Magnetic studies show that Dy-HHFs exhibits single-ion-magnet behavior (Ueff = 68.59 K and τ0 = 1.10 × 10-7 s, 0 Oe DC field; Ueff = 131.5 K and τ0 = 1.22 × 10-7 s, 800 Oe DC field). Ab initio calculations were performed to interpret the dynamic magnetic performance of Dy-HHFs, and a satisfactory consistency between theory and experiment exists.

Identification of bioactive molecule from Withania somnifera (Ashwagandha) as SARS-CoV-2 main protease inhibitor

SARS-CoV-2 is the causative agent of COVID-19 and has been declared as pandemic disease by World Health Organization. Lack of targeted therapeutics and vaccines for COVID-2019 have triggered the scientific community to develop new vaccines or drugs against this novel virus. Many synthetic compounds and antimalarial drugs are undergoing clinical trials. The traditional medical practitioners widely use Indian medicinal plant Withania somnifera (Ashwagandha) natural constituents, called withanolides for curing various diseases. The main protease (Mpro) of SARS-CoV-2 plays a vital role in disease propagation by processing the polyproteins which are required for its replication. Hence, it denotes a significant target for drug discovery. In the present study, we evaluate the potential of 40 natural chemical constituents of Ashwagandha to explore a possible inhibitor against main protease of SARS-CoV-2 by adopting the computational approach. The docking study revealed that four constituents of Ashwagandha; Withanoside II (-11.30 Kcal/mol), Withanoside IV (-11.02 Kcal/mol), Withanoside V (-8.96 Kcal/mol) and Sitoindoside IX (-8.37 Kcal/mol) exhibited the highest docking energy among the selected natural constituents. Further, MD simulation study of 100 ns predicts Withanoside V possess strong binding affinity and hydrogen-bonding interactions with the protein active site and indicates its stability in the active site. The binding free energy score also correlates with the highest score of −87.01 ± 5.01 Kcal/mol as compared to other selected compounds. In conclusion, our study suggests that Withanoside V in Ashwagandha may be serve as a potential inhibitor against Mpro of SARS-CoV-2 to combat COVID-19 and may have an antiviral effect on nCoV. Communicated by Ramaswamy H. Sarma

Hydrogen bond donors promoted organocatalyzedcycloaddition of CO<sub>2</sub> with epoxides

Carbon dioxide (CO2) is the greenhouse gas which is generated by the consumption of petrochemicals or fossil resources. CO2 is an abundant and renewable C1 building block. The utilization of CO2 as a C1 raw material in organic synthesis is an environmentally friendly method, which can not only solve the environmental and climate problems, but also facilitates the energy transformation from fossil materials to renewable resources. Thus, the research to transform CO2 into valuable chemicals has attracted attention in the field of green and sustainable chemistry. In the field, cyclic carbonates generated from CO2 and epoxides has been widely investigated. Cyclic carbonate is an important chemical raw material, which is widely applied in high-boiling polar aprotic solvents and electrolytes in batteries. The method of preparing cyclic carbonate with CO2 and epoxides as raw materials is a green synthetic transformation of 100% atomic economy for the utilization of greenhouse gas CO2. There are two kinds of catalysts for cycloaddition, including metal-based catalysts and organocatalysts. Compared with metal catalyst, organic catalysts have the advantages of low cost, simple synthesis steps and no metal contaminants, but harsh reaction conditions and/or higher catalyst loading are often needed. In order to overcome this problem, introduction of hydrogen bond donor to catalytic systems has been prevalent and has provided a simple and efficient protocol for synthesis of cyclic carbonates from CO2 and epoxides. Recent developments in the area of hydrogen bond donor functionalized organocatalysts have demonstrated that the acidity of hydrogen bond donor is crucial for achieving the boosting activity of catalysts in the cycloaddition of CO2 with epoxides. Hydroxyl functionalized organocatalysts are one of the earliest and most widely studied organocatalysts promoted by hydrogen bond donors in the cycloaddition reaction of CO2 with epoxides. The literature results showed that the organocatalysts bearing phenol hydroxyl group showed higher catalytic activity than those with alcohol hydroxyl group, which may be the reason of the stronger acidity of phenol hydroxyl group compared with alcohol hydroxyl group. Increasing the acidity of hydrogen bond donor in certain scale can effectively improve its catalytic activity, but further to increase acidity of hydrogen bond donor may lead to the decrease of catalytic activity. This is because properly increasing the acidity of hydrogen bond donor is beneficial for enhancing the hydrogen bond interaction between hydrogen bond donor and epoxide, thus promoting the ring-opened step of epoxide. However, the excessive enhancement of acidity will lead to too strong hydrogen bond interaction to induce the finally ring-closed step of intermediates. Therefore, the acidity of hydrogen bond donor is very important to the activity of catalyst. In addition to the traditional hydrogen bond donors, some special hydrogen bond donors, such as water and azaphosphatranes, are also employed as hydrogen bond donors in the cycloaddition reaction of CO2 with epoxides. It is particularly noteworthy that water is a kind of abundant and environmentally friendly hydrogen bond donor. All these indicate that the development of a kind of abundant, commercially available, and environmentally friendly hydrogen bond donor is one of the hot topics in the design and synthesis of high efficiency organocatalysts in the future. In this review, the advancement on cycloaddition of CO2 with epoxide promoted by hydroxyl group, carboxyl group, amino group, multi-hydrogen bond donor and special hydrogen bond donor has been summarized over the years. We expected the knowledge from these literatures to provide insight to the rational design of highly active organocatalysts.

New Insights into the Stability of Anhydrous 2H-Imidazolium Fluoride and its High Dissolution Capability toward a Strongly Hydrogen-Bonded Compound.

Fluorides have been widely applied in pharmaceutical, medicinal, and materials science as well as in fine chemical manufacturing. The performance of fluorides, however, can be markedly affected by the water content. One previous study (Maiti, A.; et al. Phys. Chem. Chem. Phys. 2008, 10, 5050) suggested that anhydrous 1,3-dimethylimidazolium fluoride ([DMIm]F) was unstable since the fluoride undergoes a self-decomposition reaction. Herein we first show quantum-chemical calculation evidence that although gas-phase [DMIm]F is unstable, the bulk phase of anhydrous [DMIm]F is quite stable. We then demonstrate the successful synthesis of the anhydrous [DMIm]F compound via the reaction between 1,3-dimethylimidazolium iodide and silver fluoride. Importantly, we find that anhydrous [DMIm]F possesses a high dissolution capability toward 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), although it is known that TATB is hardly dissolved in many common organic solvents. Our Born-Oppenheimer molecular dynamics (BOMD) simulations further show that the high dissolving ability of anhydrous [DMIm]F toward TATB can be attributed to the chemical reaction between the F- anion and the TATB molecules, which disrupts the strong hydrogen-bonding interaction among the TATB molecules. Alternatively, water molecules in hydrous [DMIm]F tend to form a hydration layer around the F- anion, thereby preventing F- from reacting with the TATB molecule. This result explains why TATB is barely dissolved in hydrous [DMIm]F.

Exploring the Role of Asp1116 in Selective Drug Targeting of CREBcAMP- Responsive Element-binding Protein Implicated in Prostate Cancer.

The selective targeting of CREB-cAMP-responsive element-binding protein (CBP) has recently evolved as a vital therapeutic approach for curtailing its aberrant upregulation associated with the development of prostate cancer. Inhibition of CBP has been discovered to be an important therapeutic option in androgen receptor signalling pathway mediated prostate cancer. Y08197, a novel selective inhibitor of CBP, has shown promising therapeutic outcome in prostate carcinogenesis over non-selective analogues such as CPI-637. Herein, we used molecular dynamics simulation to gain insights into the mechanistic and selective targeting of Y08197 at the bromodomain active site. Molecular Mechanics/ Poisson-Boltzmann Surface Area (MM/PBSA) analysis revealed a similar inhibitory effect between Y08197 and CPI-637. Furthermore, in exploring the selective affinity of Y08197 towards CBP in combination with Bromodomain and PHD finger-containing protein 1(BRPF1), our findings highlighted Asp1116 as the 'culprit' residue responsible for this selective targeting. Upon binding, Asp1116 assumed a conformation that altered the architecture of the bromodomain active site, thereby orienting the helices around the active site in a more compacted position. In addition to some specific structural perturbations mediated by Asp1116 on the dynamics of CBP, our study revealed that the strong hydrogen bond interaction (N-H...O) elicited in CBP-Y08197 sequestered Y08197 tightly into the CBP bromodomain active site. Conclusively, the inhibition and selective pattern of Y08197 can be replicated in future structure-based CBP inhibitors and other bromodomain implicated in carcinogenesis.

Identification of new anti-nCoV drug chemical compounds from Indian spices exploiting SARS-CoV-2 main protease as target

The 2019-novel coronavirus (nCoV) has caused a global health crisis by causing coronavirus disease-19 (COVID-19) pandemic in the human population. The unavailability of specific vaccines and anti-viral drug for nCoV, science demands sincere efforts in the field of drug design and discovery for COVID-19. The novel coronavirus main protease (SARS-CoV-2 Mpro) play a crucial role during the disease propagation, and hence SARS-CoV-2 Mpro represents as a drug target for the drug discovery. Herein, we have applied bioinformatics approach for screening of chemical compounds from Indian spices as potent inhibitors of SARS-CoV-2 main protease (PDBID: 6Y84). The structure files of Indian spices chemical compounds were taken from PubChem database or Zinc database and screened by molecular docking, by using AutoDock-4.2, MGLTools-1.5.6, Raccoon virtual screening tools. Top 04 hits based on their highest binding affinity were analyzed. Carnosol exhibited highest binding affinity -8.2 Kcal/mol and strong and stable interactions with the amino acid residues present on the active site of SARS-CoV-2 Mpro. Arjunglucoside-I (-7.88 Kcal/mol) and Rosmanol (-7.99 Kcal/mol) also showed a strong and stable binding affinity with favourable ADME properties. These compounds on MD simulations for 50 ns shows strong hydrogen-bonding interactions with the protein active site and remains stable inside the active site. Our virtual screening results suggest that these small chemical molecules can be used as potential inhibitors against SARS-CoV-2 Mpro and may have an anti-viral effect on nCoV. However, further validation and investigation of these inhibitors against SARS-CoV-2 main protease are needed to claim their candidacy for clinical trials.Communicated by Ramaswamy H. Sarma

Highly Efficient Separation of Anionic Organic Pollutants from Water via Construction of Functional Cationic Metal–Organic Frameworks and Mechanistic Study

Organic anions possess various functional properties; however, their presence in wastewater causes environmental pollution. Thus, coupling the separation of such species with the resultant function could be highly desirable. Herein, we propose a "killing two birds with one stone" strategy for highly efficient separation of organic pollutant anions from water at room temperature through direct construction of functional cationic metal-organic frameworks (CMOFs) based on the organic anions as charge-balancing anions. To illustrate this strategy, 2,4,6-trinitrophenolate anion (PA-) is chosen as a typical anion, while 4,4'-azo-triazole (atrz) is strategically chosen as a suitable neutral ligand. The resultant positive framework exhibits a high adsorption capacity and selectivity for PA-. Remarkably, its adsorption capacity is 869.6 mg g-1, which is more than 30 times that of multiwalled carbon nanotubes and 15 times that of activated carbon. Its capacity is even higher than that of BUT-13 (865 mg g-1), the highest adsorbent ever known. 1H NMR and single-crystal X-ray diffraction show that the high capacity is attributed to strong electrostatic interaction between the positive framework and PA-, which leads to all the pores being completely occupied by PA- anions. 1H NMR titration reveals that the selectivity comes from stronger hydrogen-bonding interaction between the ligand of the positive framework and PA-, which is confirmed from the eight times length of the shifted signal of atrz due to the addition of PA- compared with the competing anions. The stronger interaction is further confirmed from the high stability of the resultant CMOF in high-concentration salt solutions containing the competing anions, particularly in 100-fold molar NaNO3 and Na2SO4 solutions. Meanwhile, first-principles simulation shows that the high binding energy between the positive framework and PA- contributes to enhancing the selectivity. Moreover, the resultant CMOF is a potential energetic material with an improved oxygen balance, high heat of formation, and heat of detonation.

Superior strength and toughness of graphene/chitosan fibers reinforced by interfacial complexation

Graphene fibers have been fabricated by wet spinning, in which interfacial interactions including hydrogen bond, ionic bond, covalent bond and π-π interaction were usually constructed to achieve effective translation of the extraordinary properties inherent in graphene microscopic building blocks to macroscopic bulk materials. However, the interactions would induce the aggregation of graphene oxide (GO) spinning dope, leading to the local inhomogeneity and deteriorating mobility which was unfavorable for the translation of GO inherent performance. In order to overcome the contradiction, an interfacial polyelectrolyte complexation (IPC) spinning not involving in the usage of organic solvents was proposed to in-situ build a hierarchical assembly structure of well-ordered GO sheets and chitosan molecules by mimicking natural nacre. After partial reduction of GO fibers using HI, strong and tough graphene fibers with tensile strength of 875.5 MPa and toughness of 17.85 MJ/m3 were obtained due to strong ionic bond and hydrogen bond interactions between rGO and chitosan. Molecular dynamics simulation revealed the fracture mechanism of the graphene fibers that was the slippage of rGO sheets and chitosan molecules accompanied by the breaking and reforming of interfacial bonds. Combing the considerable electrical conductivity, the fibers exhibited a promising application potential as wearable electronics and conductors.

Electrochemical behavior of 1,2-dihydroxyanthraquinone dianion in aprotic solvents-DMSO and DMF: understanding the hydrogen bonding phenomena and protonation effect in biochemical systems

In this work, we report, the electrochemical properties of 1,2-dihydroxyanthraquinone through cyclic voltammetry (CV) and square wave voltammetry (SWV) in two aprotic solvents—DMSO and DMF. It is investigated that 1,2-dihydroxyanthraquinone undergoes two single-electron reduction processes. The first electron transfer process corresponds to formation of anion radical while the second electron transfer corresponds to dianion of 1,2-dihydroxyanthraquinone. Concentration effect and scan rate effect on CV of 1,2-dihydroxyanthraquinone is also studied. Effect of different alcohols (hydrogen-bonding agents) and organic acids (protonating agents) on the CVs and SWVs of 1,2-dihydroxyanthraquinone is also investigated. It is found that addition of alcohols shifts the peak potential of the dianion towards less negative potential whereas addition of organic acids) inhabits the formation of dianion. Furthermore, it is also observed that methanol has strong hydrogen-bonding interaction with 1,2-dihydroxyanthraquinone as compared to ethanol and propanol. The hydrogen bonding equilibrium constant and hydrogen-bonding rate constants are evaluated from the shift in CV curves using Gupta and Linchtiz equation. It is inferred that the anion radical has a very weak hydrogen bonding interaction with alcohols as compared to dianion.

An In‐Depth Mechanistic Study of Ru‐Catalysed Aqueous Methanol Dehydrogenation and Prospects for Future Catalyst Design

AbstractHerein we provide mechanistic insights into the dehydrogenation of aqueous methanol catalysed by the [Ru(trop2dae)] complex (which is in‐situ generated from [Ru(trop2dad)], trop2dad=1,4‐bis(5H‐dibenzo[a,d]cyclohepten‐5‐yl)‐1,4‐diazabuta‐1,3‐diene), established by density functional theory based molecular dynamics (DFT‐MD) and static DFT calculations incorporating explicit solvent molecules. The aqueous solvent proved to participate actively in various stages of the catalytic cycle including the catalyst activation process, and the key reaction steps involving C−H activation and hydrogen production. The aqueous solvent forms an integral part of the reactive system for the C−H activation steps in the [Ru(trop2dae)] system, with strong hydrogen bond interactions with the anionic oxygen (RO−, R=CH3, CH2OH, HCO) and hydride moieties formed along the reaction pathway. In contrast to the [Ru(trop2dad)] catalyst, C−H activation and hydrogen production does not proceed via a metal‐ligand cooperative pathway for the [Ru(trop2dae)] system. The pKa of the coordinated amine donors in these complexes provides a rationale for the divergent reactivity, and the obtained mechanistic information provides new guidelines for the rational design of active and additive free catalytic systems for aqueous methanol dehydrogenation.

Development of antioxidant and antimicrobial packaging films based on chitosan, D-α-tocopheryl polyethylene glycol 1000 succinate and silicon dioxide nanoparticles

Antioxidant and antimicrobial packaging were developed by adding D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) and/or silicon dioxide nanoparticles (nano-SiO2) into chitosan (CS) films. The microstructures, physical and functional properties of CS, CS-TPGS, CS-SiO2 and CS-TPGS-SiO2 films were compared. Results showed the simultaneous addition of TPGS and nano-SiO2 into CS film produced a compact inner microstructure and strong intermolecular hydrogen bond interactions. Meanwhile, the addition of TPGS slightly increased the crystallinity of CS-TPGS and CS-TPGS-SiO2 films. By comparing different films, CS-TPGS-SiO2 film presented the lowest moisture content, water vapor and oxygen permeability, whereas the highest tensile strength and elongation at break. Moreover, CS-TPGS and CS-TPGS-SiO2 films possessed stronger free radical scavenging activity than CS and CS-SiO2 films. CS-SiO2 and CS-TPGS-SiO2 films showed higher antimicrobial activity than CS and CS-TPGS films. Notably, CS-TPGS and CS-TPGS-SiO2 film packaging effectively increased the oxidative stability of soybean oil. Our results suggest CS-TPGS-SiO2 film can be used as a novel antioxidant and antimicrobial packaging material in food industry.

Hydrogen bond promoted thermal stability enhancement of acetate based ionic liquid

Acetate-based imidazolium ionic liquids (ILs) are of great importance and widely applied in biomass processing and engineering but under stability issue due to the structure self–rearrangement induced by C2–H deprotonation, by which the IL based biomass processing will be challenging. Herein, we demonstrated that the thermal stability of normal acetate-based imidazolim [C8C1Im][OAc] could be significantly improved by changing its cation and anion environment with the presence of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide IL ([C4C1Im][NTf2]). When the molar fraction of [C8C1Im][OAc] was 0.3, the thermal stability of [C8C1Im][OAc] could be significantly improved (ΔT5%dec = + 43 °C). Detailed information obtained from thermal gravimetric analysis (TGA) and nuclear magnetic resonance (NMR) revealed that the addition of [C4C1Im][NTf2] played a significant role in enhancing the thermal stability of [C8C1Im][OAc]. It was proposed that the formation of an anion–π+ structure network between [C8C1Im][OAc] and [C4C1Im][NTf2] via strong hydrogen bond interactions greatly affects the environment of hydrogen atom in the imidazolium ring of each IL.