Non-covalently Functionalized Graphene Oxide-Based Coating to Enhance Thermal Stability and Flame Retardancy of PVA Film

The synergistic effect of conventional flame-retardant elements and graphene has received extensive attention in the development of a new class of flame retardants. Compared to covalent modification, the noncovalent strategy is simpler and expeditious and entirely preserves the original quality of graphene. Thus, non-covalently functionalized graphene oxide(FGO) with a phosphorus–nitrogen compound was successfully prepared via a one-pot process in this study. Polyethyleneimine and FGO were alternatively deposited on the surface of a poly(vinyl alcohol)(PVA) film via layer-by-layer assembly driven by electrostatic interaction, imparting excellent flame retardancy to the coated PVA film. The multilayer FGO-based coating formed a protective shield encapsulating the PVA matrix, effectively blocking the transfer of heat and mass during combustion. The coated PVA has a higher initial decomposition temperature of about 260 °C and a nearly 60% reduction in total heat release than neat PVA does. Our results may have a promising prospect for flame-retardant polymers.

Investigation on Non-covalent Complexes of Cyclodextrins with Li＋ in Gas Phase by Mass Spectrometry

To investigate the non-covalent interaction between cyclodextrins （CD） and lithium ion, a stoichiometry of α-CD, β-CD, heptakis（2,6-di-O-methyl）-β-CD （DM-β-CD）, or heptakis（2,3,6-tri-O-methyl）-β-CD （TM-β-CD） was mixed with lithium salt, respectively, and then incubated at room temperature for 10 min to reach the equilibrium. In posi- tive mode, the electrospray ionization mass spectrometry （ESI-MS） results demonstrated that lithium ion can conjugate to α-, β-, DM-β- or TM-β-CD and form 1：1 stoichiometric non-covalent complexes. The binding of the complexes was further confirmed by collision- induced dissociation. The dissociation constants Kdl of four complexes （Li＋α-CD, Li＋β- CD, Li＋DM-β-CD, and Li＋TM-β-CD） were determined by mass spectrometric titration. The results showed Kdl were 18.7, 26.7, 33.6, 30.5 μmol/L for the complexes of Li＋ with α-CD, β-CD, DM-β-CD, and TM-β-CD, respectively. Kdl for the Li＋ complexes of/3-CD is smaller than that of DM-β-CD due to its steric effect of the partial substituted -CH3. The Kdl for the Li＋ complexes of DM-β-CD is nearly in agreement with that of TM-β-CD, indicating Li＋ is more likely to locate in the small rim of DM-β-CD＇s hydrophobic cavity. The DFT results showed through electrostatic interaction, one Li＋ can strongly conjugate to four neighboring oxygen atoms. For the （α-CD＋Li）＋ complex, one Li＋ may also situate the small rim of α-CD＇s hydrophobic cavity to form a non-specific host-guest complex.

A New Three-dimensional Supramolecular Polymer Built from Non-covalent Bonding Interactions

A new complex, [Ni2（L）4（H2O）8]（1, L1 = 4-（1H-imidazol-4-yl）benzoic acid）, has been hydrothermally prepared and characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental analysis and PXRD. Complex 1 crystallizes in monoclinic, space group P21/c with α = 22.281（2）, b = 7.3959（7）, c = 24.978（3） ？, β = 90.876（10）, V = 4115.6（7） ？3, Z = 8, C20H22N4O8Ni, Mr = 505.13, Dc = 1.630 g/cm3, μ = 1.001 mm-1, S = 1.080, F（000） = 2096, the final R = 0.452 and wR = 0.1152 for 9380 observed reflections （I 〉 2σ（I））. The result of X-ray diffraction analysis revealed three different kinds of Ni（II） centre mononuclear molecules in the asymmetric unit. The independent mononuclear units are bridged to form a three-dimensional supramolecular polymer by extensive hydrogen bonds and C–H… non-covalent bonding interactions.

STUDY ON THE NON-COVALENT INTERACTION OF APIGENIN MOLECULARLY IMPRINTED POLYMERS BY SPECTROMETRY

The non-covalent interaction between apigenin (API) and different functional monomers (α-methylacrylic acid (MAA), acrylamide (AM), 2-vinylpyridine (2-Vpy) and combined functional monomers (AM/2-Vpy)) was determined by UV spectrometry, and a series of apigenin molecularly imprinted polymers (API-MIPs) was synthesized with different functional monomers through molecular imprinting technology. The relationship between the non-covalent interaction of template/functional monomer and absorption of MIPs also was studied. The results showed that the order of the strength of the non-covalent interaction between API and different functional monomers in tetrahydrofuran (THF) is as follows: 2-Vpy> AM/2-Vpy>AM>MAA, which is positive correlation to the absorption capability of corresponding MIPs, and 2-Vpy is the optimum functional monomer among the used monomer for preparing API- MIPs.

Non-covalent interaction between almond protein and sinapic acid: impact on protein structure and antioxidant activity

Plant phenolic acids are good sources of antioxidants and sinapic acid(SA)is one of them that can be applied in protein-based food system.However,little research is available regarding interactions between almond protein(AP)and SA.In this study,structure-affinity interaction between SA and AP,structure and antioxidant activity of proteins were investigated.Different mathematical models showed that Ka of binding SA and AP were 3.27×10^4 L/mol and 3.08×10^4 L/mol.CD(Circular dichroism)spectroscopy and FT-IR(Fourier transform infrared)spectroscopy showed that the amount of random coil andα-helix decreased whileβ-sheet increased in AP-SA complex.In combination,the interaction model of AP-SA complex was static quenching and attributed to hydrophobic interaction.Further,AP-SA complex exerted better DPPH radical scavenging ability(36.97±0.78%),ABTS+radical scavenging ability(47.26±0.45%),and higher ORAC value(2.41±0.23 M trolox/g)compared to AP.In the further,SA can be applied in protein matrix to improve film stability,gel strength and restraining fat oxidation degradation.

Detection and Characterization of Non-covalent Complex between Lappaconitine and β-Cyclodextrin by Electrospray Ionization Tandem Mass Spectrometry

The non-covalent complexes between lappaconitine （LA） and β-cyclodextrin （β-CD） have been detected and characterized by electrospray ionization combined with ion trap tandem mass spectrometry （ESI-MSn）. The experimental results showed that only 1：1 non-covalent complex can be formed in different starting molar ratios of LA to β-CD. Furthermore, the diagnostic fragmentation of the β-CD-LA complex, with a significant contribution of covalent fragmentation of LA leaving the N-acetyl anthranoyl （AN） moiety inserted to β-CD, provided the convincing evidence for the formation of non-covalent complex between LA and β-CD and the cite of LA molecule included to cavity of β-CD assigned to AN residue.

Direct Observation of Non-covalent Complexes for Phosphorylated Flavonoid-protein Interaction by ESI

Diethyl flavon-7-yl phosphate was synthesized by modified Atheron-Todd reaction. The result of ESI shows that the phosphated flavonoids possess stronger binding affinities toward proteins such as myoglobin, insulin and lysozyme and are easier to form the non-covalent complexes with them.

Modulating vectored non-covalent interactions for layered assembly with engineerable properties

Vectored non-covalent interactions—mainly hydrogen bonding and aromatic interactions—extensively contribute to(bio)-organic self-assembling processes and significantly impact the physicochemical properties of the associated superstructures.However,vectored non-covalent interaction-driven assembly occursmainly along one-dimensional(1D)or three-dimensional(3D)directions,and a two-dimensional(2D)orientation,especially that of multilayered,graphene-like assembly,has been reported less.In this present research,by introducing amino,hydroxyl,and phenyl moieties to the triazine skeleton,supramolecular layered assembly is achieved by vectored non-covalent interactions.The planar hydrogen bonding network results in high stability,with a thermal sustainability of up to about 330°C and a Young’s modulus of up to about 40 GPa.Upon introducing wrinkles by biased hydrogen bonding or aromatic interactions to disturb the planar organization,the stability attenuates.However,the intertwined aromatic interactions prompt a red edge excitation shift effect inside the assemblies,inducing broad-spectrum fluorescence covering nearly the entire visible light region(400–650 nm).We show that bionic,superhydrophobic,pillar-like arrays with contact angles of up to about 170°can be engineered by aromatic interactions using a physical vapor deposition approach,which cannot be realized through hydrogen bonding.Our findings show the feasibility of 2D assembly with engineerable properties by modulating vectored non-covalent interactions.

Preparation and characterization of supramolecular gel suitable for fractured formations

The excellent mechanical properties of supramolecular gel could adapt to the complex reservoir environment and had broad application prospects in the field of oil and gas drilling and production engineering.In this paper,a supramolecular gel based on hydrophobic association and hydrogen bonding was prepared by micellar copolymerization,which could be used to plug fractures and pores in formations.Supramolecular gel was a gel network system with high performance characteristics formed by self-assembly of non-covalent bond interaction.The rheological properties,mechanical mechanics,temperature resistance and swelling ability of supramolecular gel were studied.The results showed that the supramolecular gel had a dense three-dimensional network structure with open and interconnected pore structures,which could exhibit good rheological properties and strong viscoelastic recovery ability.The mechanical properties of the supramolecular gel were excellent,it had a tensile stress of 0.703 MPa and an elongation at break of 1803%.When the compressive strain was 96%,the compressive stress could reach 14.5 MPa.Supramolecular gel also showed good temperature resistance and swelling properties.At the aging temperature of 135℃,supramolecular gels still maintained good gel strength,and it only took 12 h to reach the equilibrium swelling ratio of 35.87 in 1%NaCl solution.It was also found that supramolecular gel in low concentration saline(1%NaCl solution)showed relatively faster swelling than high concentration saline(25%NaCl solution).The swelling process of the supramolecular gel was non-Fick diffusion(typeⅡ).This indicated that the organic/inorganic permeability network was well formed.Therefore,the diffusion rate of small molecules could be guaranteed to be equal to the relaxation rate of large molecules before and after the phase transition temperature.In addition to the diffusion of water molecules,the swelling process of the supramolecular gel was also affected by the relaxation of gel network and polymer chain segment,the interaction between water molecules and polymer network and the groups of polymer network and other factors.Supramolecular gel particles could be used as plugging materials for drilling fluids,which had excellent ability to plug formation fractures and pores.The plugging ability of the supramolecular gel was up to 6.7 MPa for 0.5 mm fracture width,and 9.6 MPa for porous media with 5 mD permeability.Compared with HT-PPG gel particles commonly used in oil fields,supramolecular gel particles had better plugging ability on fractures and porous media.The development and application of supramolecular gel had far-reaching significance for promoting the functional application of polymer materials in drilling and production engineering.

Extra contribution to the crystal stability of insensitive explosive TATB: The cooperativity of intermolecular interactions

An in-depth analysis on the cooperativity of intermolecular interactions including hydrogen bonding andπ-π stacking in 1,3,5-triamino-2,4,6-trinitrobenzene(TATB) crystal was studied. Two quantities, cooperativity rate and energy, were defined to evaluate the nature and strength of cooperativity in a series of clusters diverging from 1D to 3D prototypes. The origin and mechanism of the cooperative effect were settled to demonstrate that the nature of cooperativity is determined by whether the non-covalent interactions compete or promote with each other, which is manifested by the changing trend of electron transfer. There exists obvious cooperative effect in intra-layer and inter-layer structures as they own the equivalent non-covalent interactions, while anti-cooperative effect is also observed if two interactions correlate with each other. On the whole, in the process of crystal formation, the apparent cooperativity is the check and balance of the two effects, which is capable to support a global interaction among all of molecules and contribute to the stabilization of system. Based on the results, one may get a new insight to understand the relationship between non-covalent interactions and low impact sensitivity.

Functionality of Covalent Organic Framework (COF) in Gas Storage Application: First Principal Study

Industrial growth in recent years led to air pollution and an increase in concentration of hazardous gases such as O3 and NO. Developing new materials is important to detect and reduce air pollutants. While catalytic decomposition and zeolites are traditional ways used to reduce the amount of these gases. We need to develop and explore new promising materials. Covalent organic framework (COF) has become an attractive platform for researcher due to its extended robust covalent bonds, porosity, and crystallinity. In this study, first principal calculations were performed for gases adsorption using COFs containing nitrogen and π-bonds. Different building blocks (BBs) and linkers (LINKs/LINK1 & LINK2) were investigated by means of density functional theory (DFT) calculations with B3LYP and 3-21G basis sets to calculate the binding energies of gases @COF systems. Electrostatic potential maps (ESPM), Mulliken charges and non-covalent interaction (NCI) are used to understand the type of interactions between gas and COFs fragments. O3 was found to bind strongly with COF system in comparison with NO which could make COF a useful selective material for mixed gases environment for sensing and removal application.

Medicinal chemistry strategies towards the development of non-covalent SARS-CoV-2 Mpro inhibitors

The main protease(M^(pro))of SARS-CoV-2 is an attractive target in anti-COVID-19 therapy for its high conservation and major role in the virus life cycle.The covalent M^(pro)inhibitor nirmatrelvir(in combination with ritonavir,a pharmacokinetic enhancer)and the non-covalent inhibitor ensitrelvir have shown efficacy in clinical trials and have been approved for therapeutic use.Effective antiviral drugs are needed to fight the pandemic,while non-covalent M^(pro)inhibitors could be promising alternatives due to their high selectivity and favorable druggability.Numerous non-covalent M^(pro)inhibitors with desirable properties have been developed based on available crystal structures of M^(pro).In this article,we describe medicinal chemistry strategies applied for the discovery and optimization of non-covalent M^(pro)inhibitors,followed by a general overview and critical analysis of the available information.Prospective viewpoints and insights into current strategies for the development of non-covalent M^(pro)inhibitors are also discussed.

Discovery and characterization of novel potent non-covalent small molecule inhibitors targeting papain-like protease from SARS-CoV-2

To the Editor:The papain-like protease(PL^(pro)),as one of the most important proteases of SARS-CoV-2,has emerged as a highly promising target protein,its inhibitor probably holds dual potentials,namely blocking the cleavage of viral polyprotein and intercepting the deubiquitination and deISGylation functions to restore antiviral immunity1.

Melamine/Stearic Acid Composite Nanowires and Vesicles with an Intercalated Nanostructure Prepared through NCCM Method

A solvent-non-solvent method invented in our laboratory for preparing non-covalently con- nected micelles （NCCM） was used to intercalate melamine （MA） molecules into stearic acid （SA） bilayers to form tile composite nanoparticles with an intercalated nanostructure in which a melamine bilayer is sandwiched between two stearic acid bilayers, NCCM method helps to sufficiently mix the two components in nanospace and meanwhile inhibits the strong tendency of self-crystallization of MA, leading to the intercalation. Although the nanopar- ticles have a regular inner structure, the primary MA/SA nanoparticles have an irregular morphology. Regular nanoparticles were obtained through annealing the suspension of the primary nanoparticles. Through annealing at different temperatures, the MA/SA compos- ite nanowires and vesicles with an intercalated structure were prepared respectively. It is proposed that the morphological change results from the change in the intercalated structure.

Synthesis and Crystal Structure of [La(BTC)(H_2O)_6]_n

The title compound, [La（BTC）（H2O）6]n1 （H3BTC = benzene-1,3,5-tricarboxylic acid）, has been synthesized by the hydrothermal reaction of La（NO3）3·3H2O with H3BTC and Na2CO3, and its structure was determined by single-crystal X-ray diffraction. The crystal structure is of monoclinic, space group Cc with a = 11.5289（3）, b = 18.0383（7）, c = 7.3507（3） A, β= 119.5680（10）°, V = 1329.59（8）A^3, C9H15LaO12, Mr = 454.12, Z = 4, Dc = 2.269 g/cm^3,μ = 3.280 mm^-1, Flack parameter = 0.07（4）, F（000） = 888, R = 0.0316 and wR = 0.0774 for 1312 observed reflections（I〉 2σ（I））. Complex 1 features a one-dimensional （l-D） parallel ribbon-like structure. There are extensive hydrogen-bonding interactions involving coordinated water molecules and free carboxylate oxygen atoms. In addition, π-π interactions via benzoic multicarboxylate ligands are discussed. These non-covalent interactions lead to the formation of a 3-D framework.

Functionalized graphene oxide-reinforced electrospun carbon nanofibers as ultrathin supercapacitor electrode

Graphene oxide has been used widely as a starting precursor for applications that cater to the needs of tunable graphene. However, the hydrophilic characteristic limits their application, especially in a hydrophobic condition. Herein, a novel non-covalent surface modification approach towards graphene oxide was conducted via a UV-induced photo-polymerization technique that involves two major routes; a UV-sensitive initiator embedded via pi-pi interactions on the graphene planar rings, and the polymerization of hydrophobic polymeric chains along the surface. The functionalized graphene oxide successfully achieved the desired hydrophobicity as it displayed the characteristic of being readily dissolved in organic solvent. Upon its addition into a polymeric solution and subjected to an electrospinning process,non-woven random nanofibers embedded with graphene oxide sheets were obtained. The prepared polymeric nanofibers were subjected to two-step thermal treatments that eventually converted the polymeric chains into a carbon-rich conductive structure. A unique morphology was observed upon the addition of the functionalized graphene oxide, whereby the sheets were embedded and intercalated within the carbon nanofibers and formed a continuous structure. This reinforcement effectively enhanced the electrochemical performance of the carbon nanofibers by recording a specific capacitance of up to 140.10 F/g at the current density of 1 A/g, which was approximately three folds more than that of pristine nanofibers.It also retained the capacitance up to 96.2% after 1000 vigorous charge/discharge cycles. This functionalization technique opens up a new pathway in tuning the solubility nature of graphene oxide towards the synthesis of a graphene oxide-reinforced polymeric structure.

Non-fused medium bandgap electron acceptors for efficient organic photovoltaics

The cost-effective organic semiconductors are strongly needed in organic photovoltaics(OPVs). Herein,two medium bandgap(MBG) electron acceptors, TPT4F and TPT4Cl are developed via the new design of multi-noncovalent interaction assisted unfused core, flanked with two electron withdrawing end groups. These fullly non-fused MBG acceptors adapt the planar and rigid conformation in solid, therefore exhibiting the ordered face-on stacking and strong photoluminescence in films. As results, TPT4Cl^(-)based OPVs, upon blending with the PBDB-TF polymer donor, have achieved a power conversion efficiency of 10.16% with a low non-radiative loss of 0.27 e V, representing one of the best fullly non-fused medium bandgap acceptors with desirable cost-efficiency balance.

Structure of Co-crystals Formation from Imidazolium and Aromatic Ligands

In this study, two new co-crystals based on rigid imidazolium ligand （2,2＇-（（1,1’- biphenyl）-4,4＇-diyl）bis（2H-imidazo[1,5-a]pyridine-4-ium） hexafluorophosphate （L）） and 4,4＇- bipyridine （Bpy） and benzene （Ben）, formulated as L（Bpy）0.5 （co-crystal 1） and L（Ben） （co-crystal 2）, were obtained. Crystal data for 1： Pī space group with α = 10.921（4）, b = 16.998（6）, c = 17.666（6） A, α = 95.720（7）, β = 104.272（7）, γ = 93.340（6）°, V = 3150.5（19） A^3 and Z = 2; and crystal data for 2： monoclinic C2/m space group with α = 25.90（2）, b = 9.631（9）, c = 6.371（6） A, β = 95.26（2）°, V = 1583（2） A3 and Z = 2. Co-crystal 1 was dependent on hydrogen bonds and π···π stacking, while only hydrogen bonds are present in 2. Two new co-crystals were characterized by IR, NMR spectra, thermogravimetric and ultraviolet absorption analyses.

Two Three-dimensional Supramolecular Polymer Built from Mixed N-Donor and Carboxylate Ligands

Two new complexes, [Mn（L）（mmbda）（H_2O）]（1） and [Co（L）（btc）（H_2O）]·H_2O（2）, were synthesized by reacting the corresponding metal（Ⅱ） salts with rigid ligand 1,4-di（1Himidazol-4-yl）benzene（L） and two different carboxylic acids of 5-methylisophthalic acid（H_2mmbda） and 1,2,4-benzenetricarboxylic acid（H_3btc）, respectively. The structures of the complexes were characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental analysis and PXRD. Complex 1 crystallizes in triclinic, space group P1 with a = 6.9436（4）, b = 9.7306（6）, c = 15.5302（10） ？, α = 73.7430（10）, β = 85.1010（10）, γ = 70.0360（10）o, V = 946.75（10） ？~3, Z = 2, C_（21）H_（20）N_4O_5 Mn, M_r = 463.33, D_c = 1.618 g/cm^3, μ = 0.742-1, S = 1.002, F（000） = 474, the final R = 0.0285 and wR = 0.0600 for 4328 observed reflections（I 〉 2σ（I））. Complex 2 crystallizes in monoclinic, space group P2_1/n with a = 12.5216（12）, b = 7.3312（8）, c = 22.510（2） ？, β = 93.104（2）o, V = 2063.3（4） ？~3, Z = 4, C_（21）H_（18）N_4O_8Co, M_r = 513.31, D_c = 1.646 g/cm^3, μ = 0.892^（-1） mm, S = 1.096, F（000） = 1044, the final R = 0.0673 and wR = 0.1780 for 3594 observed reflections（I 〉 2σ（I））. Both of complexes are one-dimensional（1D） chain structures and rich hydrogen bonds extend such 1D chains to form three-dimensional（3D） supramolecular polymers.

One-dimensional Copper（Ⅱ） Complex Constructed with Nitrate Counter-anion as Bitopic Connector

Coordination polymer {[Cu（NPPCA）3（NO3）（H20）]-NOyH20}n 1 （ NPPCA = N-（4＇- nitrophenyl）-4-pyridinecarboxamide） has been synthesized by the reaction of NPPCA with copper（H） nitrate in ethanol-water solution and characterized by X-ray diffraction. 1 crystallizes in the monoclinic space, group P21/n, a = 17.341（6）A, b = 6.744（2）A, c = 34.555（12）A, β = 100.493（6）°, V = 3974（2） A^3, Z = 4. Each copper（H） ion has a distorted octahedral coordination geometry. Nitrate anion adopts the unusual coordination mode linking two adjacent copper（H） ions to form a one-dimensional coordination polymer and these chains are further linked by noncovalent interactions.