Noncovalent interactions on the electrocatalytic oxidation of ethanol on a Pt/C electrocatalyst

Due to their environmentally friendly nature and high energy density,direct ethanol fuel cells have attracted extensive research attention in recent decades.However,the actual Faraday efficiency of the ethanol oxidation reaction(EOR)is much lower than its theoretical value and the reaction kinetics of the EOR is sluggish due to insufficient active sites on the electrocatalyst surface.Pt/C is recognized as one of the most promising electrocatalysts for the EOR.Thus,the microscopic interfacial reaction mechanisms of the EOR on Pt/C were systematically studied in this work.In metal hydroxide solutions,hydrated alkali cations were found to bind with OH_(ad)through noncovalent interactions to form clusters and occupy the active sites on the Pt/C electrocatalyst surface,thus resulting in low Faraday efficiency and sluggish kinetics of the EOR.To reduce the negative effect of the noncovalent interactions on the EOR,a shield was made on the electrocatalyst surface using 4-trifluoromethylphenyl,resulting in twice the EOR catalytic reactivity of Pt/C.

Enhanced Ion-Selective Diffusion Achieved by Supramolecular Interaction for High Thermovoltage and Thermal Stability

Thermoelectric(TE)generators capable of converting thermal energy into applicable electricity have gained great popularity among emerging energy conversion technologies.Biopolymer-based ionic thermoelectric(i-TE)materials are promising candidates for energy conversion systems because of their wide sources,innocuity,and low manufacturing cost.However,common physically crosslinked biopolymer gels induced by single hydrogen bonding or hydrophobic interaction suffer from low differential thermal voltage and poor thermodynamic stability.Here,we develop a novel i-TE gel with supramolecular structures through multiple noncovalent interactions between ionic liquids(ILs)and gelatin molecular chains.The thermopower and thermoelectric power factor of the ionic gels are as high as 2.83 mV K-1 and 18.33μW m^(-1)K^(-2),respectively.The quasi-solid-state gelatin-[EMIM]DCA i-TE cells achieve ultrahigh 2 h output energy density(E_(2h)=9.9 mJ m^(-2))under an optimal temperature range.Meanwhile,the remarkable stability of the supramolecular structure provides the i-TE hydrogels with a thermal stability of up to 80℃.It breaks the limitation that biopolymer-based i-TE gels can only be applied in the low temperature range and enables biopolymer-based i-TE materials to pursue better performance in a higher temperature range.

Synthesis, Structure and Noncovalent Interactions of Palladium(II) Complexes with N-Benzoyl-β-phenylalaninate Dianion and Aromatic Diimine

Two palladium(II) complexes, \[Pd(bipy)(BzPhe N,O)\] and \[Pd(phen)(BzPhe N,O)\]·4H 2 O were synthesized by reactions between Pd(bipy)Cl 2 and BzPheH 2( N benzoyl β phenylalanine), Pd(phen)Cl 2 and BzPheH 2 in water at pH～9, with their structures determined by X ray diffraction analysis. The Pd atom is coordinated by two nitrogen atoms of bipy (or phen), the deprotonated amido type nitrogen atom and one of the carboxylic oxygens of BzPhe (BzPhe= N benzoyl β phenylalaninate dianion). In the complex \[Pd(phen)(BzPhe N,O)\]·4H 2O, the side chain of phenylalanine is located above and approximately parallels to the coordination plane. Both the aromatic aromatic stacking interaction between the phenyl ring of phenylalanine and phen, and the metal ion aromatic interaction between the phenyl ring of phenylalanine and Pd(II) were observed. \[Pd(bipy)(BzPhe N,O)\] has the phenylalanyl side chain oriented outwards from the coordination plane, which is mainly due to the interaction between the carbonyl oxygen atom of the amido group and the phenyl ring of phenylalanine. The reason for the different orientation of phenylalanyl side chain in the complexes was suggested.

Exploring the hygroscopic behavior of highly energetic oxidizer ammonium dinitramide(ADN)at different temperatures and humidities using an innovative hygroscopic modeling

Ammonium dinitramide(ADN)is a new type of green energetic oxidizer with excellent energy density and low pollution combustion characteristics.However,the strong hygroscopicity has a significant impact on its practical application.To assist in the research on moisture-proof modification of ADN materials,an innovative hygroscopic modeling approach was proposed to evaluate the hygroscopicity of ADN at various temperatures and humidities.By investigating the diffusion coefficient of water molecules in molecular dynamics processes,a visual insight into the hygroscopic process of ADN was gained.Furthermore,analyzing the non-covalent interactions between ADN and water molecules,the hygroscopicity of ADN could be evaluated qualitatively and quantitatively.The energy analysis revealed that electrostatic forces play a dominant role in the process of water adsorption by ADN,whereas van der Waals forces impede it.As a whole,the simulation results show that ADN presents the following hygroscopic law:At temperatures ranging from 273 K to 373 K and relative humidity(RH)from 10%to 100%,the hygroscopicity of ADN generally shows an increasing trend with the rise in temperature and humidity based on the results of three simulations.According to the non-hygroscopic point(298 K,52%RH)of ADN obtained by experiment in the literature,a non-hygroscopic range of temperature and humidity for ADN can be depicted when the simulation results in relative hygroscopicity is less than or equal to 17%.This study can provide effective strategies for screening anti-hygroscopic modified materials of ADN.

Theoretical Study on Xe…N non-Covalent Interactions:Three Hybridization N with XeO_(3) and XeOF_(2)

The interactions of complexes of XeOF_(2) and XeO_(3) with a series of different hybridization N-containing donors are studied by means of DFT and MP_(2) calculations.The aerogen bonding interaction energies range from 6.5 kcal/mol to19.9 kcal/mol between XeO_(3) or XeOF_(2) and typical N-containing donors.The sequence of interaction for N-containing hy-bridization is sp^(3)>sp^(2)>sp,and XeO_(3)is higher than XeOF_(2).For some donors of sp^(2)and sp^(3) hybridization,the steric effect plays a minor role in the interaction with the evidence of reduced density gradient plots.The dominant stable part is the electrostatic interaction.In complex of XeO_(3),the weight of polarization is larger than dispersion,while the situation is opposite for XeOF_(2)complexes.Except for the sum of the maximum value of molecular electrostatic potential on Xe atom and minimum value of molecular electrostatic potential on N atom,the other five interaction parameters including the potential energy density at bond critical point,the equilibrium distances,interaction energies with the basis set superposition error correction,localized molecular orbital energy decomposition analysis interaction energies,and the electron charge density,show great linear correlation coefficients with each other.

Metal Ion-Coordinated Biomolecular Noncovalent Glass with Ceramic-like Mechanics

Glass materials play a vital role in scientific research and engineering applications.Biomolecular noncovalent glasses(BNG),based on amino acids and peptides,have been proposed as the next-generation glass materials to meet the demand of a sustainability and circular economy.However,bulk BNG with remarkable mechanics and tunable photoluminescence are still rare due to the nature of weak noncovalent interactions and oversimplified molecular structures.Herein,we report the design and creation of metal ion-coordinated BNG(MIBNG)based on a simple amino acid derivative and metal ions.The obtained MIBNG exhibit ceramic-like mechanics,including the hardness,elasticity,and wear resistance,that are unattainable by the pure BNG counterpart.Such remarkable mechanics can be attributed to the enhanced noncovalent crosslinking network connectivity of biomolecules within MIBNG resulting from the incorporation of strong metal coordination interaction with hydrogen bonding and aromatic interactions.Moreover,fluorescence emission of MIBNG can be tuned feasibly through precisely modulating the types of metal ions coordinated.This study sheds light on the crucial role of multiple noncovalent interactions in the construction of BNG and advances the exploration and potential applications of BNG-based functional materials with tunable mechanical and optical properties in such fields as electronics and optics.

Molecular Interactions in Atomically Precise Metal Nanoclusters

For nanochemistry, precise manipulation of nanoscalestructures and the accompanying chemical properties atatomic precision is one of the greatest challenges today. Thescientific community strives to develop and design customizednanomaterials, while molecular interactions often serve as key toolsor probes for this atomically precise undertaking. In thisPerspective, metal nanoclusters, especially gold nanoclusters,serve as a good platform for understanding such nanoscaleinteractions. These nanoclusters often have a core size of about 2nm, a defined number of core metal atoms, and protecting ligandswith known crystal structure. The atomically precise structure ofmetal nanoclusters allows us to discuss how the molecularinteractions facilitate the systematic modification and functionalization of nanoclusters from their inner core, through the ligandshell, to the external assembly. Interestingly, the atomic packing structure of the nanocluster core can be affected by forces on thesurface. After discussing the core structure, we examine various atomic-level strategies to enhance their photoluminescent quantumyield and improve nanoclusters’ catalytic performance. Beyond the single cluster level, various attractive or repulsive molecularinteractions have been employed to engineer the self-assembly behavior and thus packing morphology of metal nanoclusters. Themethodological and fundamental insights systemized in this review should be useful for customizing the cluster structure andassembly patterns at the atomic level.

Non-covalent Bonded 3D Supramolecular Architectures Based on Acid-base Adducts

Two novel acid-base adducts,[H2L1^2＋]（Hpbda）2（1,L1 = 1,4-di（lH-imidazol-4-yl）benzene,H2pbda = 1,4-benzenedicarboxylic acid） and[H2L2^2＋]（NO3）2（2,L2 = l,4-di（l-carboxymethyl-imidazol-4-yl）benzene）,have been prepared and characterized by single-crystal X-ray diffraction,IR spectroscopy and elemental analysis.Compound 1 crystallizes in monoclinic,space group P21/n with a = 5.3525（11）,b = 9.1471（19）,c = 19.314（4） ？,β = 92.342（3）°,V= 944.8（3） A°3,Z = 2,C16H16N6O（10）,Mr = 452.35,Dc = 1.590 g/cm^3,μ = 0.135 mm^-1,S = 1.058,F（000） = 468,the final R = 0.0661 and wR = 0.1887 for 2298 observed reflections（I〉 2σ（I））.Compound 2 crystallizes in monoclinic,space group P21/c with a = 9.6923（10）,b = 17.2950（17）,c = 7.1880（7） ？,β =94.801（2）°,V= 1200.7（2）A°3,Z = 2,C（28）H（22）N4O8,Mr = 542.50,Dc = 1.501 g/cm^3,μ = 0.112 mm^-1,S= 1.060,F（000） = 564,the final R = 0.0394 and wR = 0.1017 for 2768 observed reflections（I 〉2σ（I））.In the title compounds,both of L1 and L2 ligands act as weak base to accept protons to exhibit diprotonated H2L1^2＋ and H2L2^2＋ form,which can effectively employ as hydrogen bonding donors to combine anion moieties to form binary adducts respectively.In the crystal packing diagram of two polymers,there exist extensive noncovalent interactions including charge-transfer interactions,C（N）-H…π and N-H…O,C-H…O,O-H…O hydrogen bonding interactions between co-crystal moieties which consolidate the structures of supramolecular polymers,thus generating three-dimensional（3D） frameworks.

Substituent Effects on the Hydrogen Bonding Between Phenolate and HF, H_2O and NH_3

B3LYP/6 31+g( d ) calculations were performed on the hydrogen bonded complexes between substituted phenolates and HF, H 2O as well as NH 3. It was found that some properties of the non covalent complexes, including the interaction energies, donor acceptor (host guest) distances, bond lengths, and vibration frequencies, could show well defined substituent effects. Thus, from the substituent studies we can not only understand the mechanism of a particular non covalent interaction better, but also easily predict the interaction energies and structures of a particular non covalent complex, which might otherwise be very hard or resource consuming to be known. This means that substituent effect is indeed a useful tool to be used in supramolecular chemistry and therefore, many valuable studies remain to be carried out.

Conformation preference and related intramolecular noncovalent interaction of selected short chain chlorinated paraffins

Short chain chlorinated paraffins （SCCPs） are not only research focus of environmental issues but also interesting model mol- ecules for organic chemistry which exhibit diverse conformation preference and intramolecular noncovalent interactions （NCIs）. A systematic study was conducted to reveal the conlk）rmation preference and the related intramolecular NCIs in two C^-isomers of SCCPs, 5,5,6,6-tetrachlorodecane and 4,4,6,6-1etrachlorodecane. The overall conformation profile was deter- mined on the basis of relative energies calculated at the MP2/6-311＋＋G（d,p） level with the geometries optimized by B3LYP/6-31 l＋＋G（d,p） method. Then, quantum theory of atoms in molecules （QTAIM） has been adopted to identify the NCls in the selected conformers of the model molecules at both B31~YP/6-31 l＋＋G（d,p） and M06-2X/aug-cc-pvdz level. Different chlorine substitution modes result in varied conformation preference. No obvious gauche effect can be observed tk）r the SCCPs with chlorination on adjacent carbon atoms. The most stable conformer of 5,5,6,6-tetrachlorodecane （tTt） has its three dihedral angles in the T configuration, and there is no intramolecular N（3s found in this molecule. On the contrary, the chlorination on interval carbon atoms favors the adoption of gauche configmation for the H C C CI axis. Not only inlramolecular H-..CI contacts but also H---H interactions have been identified as driving forces to compensate the instability from steric crowding ot the gauche configuration. The gggg and g＇g＇g＇g＇ conformers are the most popular ones, while the populations of tggg and tg＇g＇g＇ conformer are second to those of the gggg and g＇g＇g＇g＇ conformers. Meanwhile, the M06-2X method with large basis sets is preferred for identification of subtle intramolecular NCIs in large molecules like SCCPs.

Synergistic regulation of intermolecular interactions to control chiral structures for chiral recognition

Understanding the regulatory mechanism of self-assembly processes is a necessity to modulate nanostructures and their properties. Herein, we have studied the mechanism of self-assembly in the C3 symmetric 1,3,5-benzentricarboxylic amino acid methyl ester enantiomers(TPE) in a mixed solvent system consisting of methanol and water. The resultant chiral structure was used for chiral recognition. The formation of chiral structures from the synergistic effect of multiple noncovalent interaction forces was confirmed by various techniques. Molecular dynamics simulations were used to characterize the time evolution of TPE structure and properties in solution. The theoretical results were consistent with the experimental results. Furthermore, the chiral structure assembled by the building blocks of TPE molecules was highly stereoselective for diamine compounds.

Precise Orientational Control of Electroactive Units Using a Tripodal Triptycene Scaffold to Direct Noncovalent Pairing at the Single Molecular Level

A break junction technique has been established to explore conductive behavior at the single molecular level,and recent interest has shifted toward the evaluation of bimolecular systems interacting through noncovalent intermolecular forces.This requires precise control over the orientation of the two molecules so that they can adapt an appropriate face-to-face arrangement between two electrodes.Herein,we present an approach using a tripodal triptycene scaffold that allows for accurate positioning of electroactive subunits with an upright configuration on substrate surfaces.We incorporated electron-donating tetrathiafulvalene or electron-accepting anthraquinone into the molecular scaffold and confirmed that the resulting molecules retain the electronic properties particular to their attached subunits.Self-assembled monolayers(SAMs)of these molecules were prepared on Au(111)and characterized by XPS and STM.STM break junction techniques were applied to the SAMs,revealing two electrical conduction regimes;one arises from single-molecules sandwiched between two electrodes,and the second from intermolecularly interacting homodimers that bridge between electrodes.This observation demonstrates the validity of the approach of using tripodal triptycene scaffolds to precisely direct electroactive subunits to undergo intermolecular pairing.We believe that the present work will provide a new avenue for evaluating the heterodimers at the single molecular level.

Dinuclear Copper(Ⅱ) Complex with a New Polycarboxylate Ligand:Syntheses,Characterization and Crystal Structure

A dinuclear copper（Ⅱ） complex,[Cu2（HL）2（H2O）6] 1（H3L = 2,4,6-tri（3-carboxy-phenylthio）-1,3,5-triazine）,was synthesized hydrothermally and characterized by single-crystal X-ray diffraction,IR and thermal analysis.Single-crystal X-ray diffraction reveals that complex 1 is a dinuclear copper（Ⅱ） complex,which is further extended to a 3D network by weak interactions such as O…H-O hydrogen bonds and noncovalent S...S interactions.The crystal of compound 1 belongs to monoclinic,space group C2/c,with a = 50.15（2）,b = 6.789（3）,c =15.667（8） ,β = 90.588（9）o,V = 5334（4） 3,Z = 4,C48H38Cu2N6O18S6,Mr = 1306.28,Dc = 1.627 g/cm3,F（000） = 2664,Rint = 0.0631,T = 293（2） K,μ = 1.112 mm-1,the final R = 0.0661 and wR = 0.1850 for 3782 observed reflections with I 2σ（I）.

Poly(3-hexylthio) thiophene Field-effect Transistor Device Performance: Impact of the Content of Hexylthio Side Chain on Backbone

Regioregular poly(3-hexylthio)thiopene(P3HTT) has emerged tremendous potential in organic electronic applications due to the strong noncovalent interactions from the sulfur atom linked to thiophene. However, P3HTT generally exhibits low charge mobility mostly due to poor solution processability attributed to dense arrangement of hexylthio side chain in polymer, which led to strong noncovalent interactions among sulfur atoms. To balance the nonvalent interaction and aggregation for P3HTT, herein, we systematically study the effect of hexylthio side chain content in polymer backbone on the structure and properties. A series of regioregular P3HTT-based homopolymers(P3HTT, P3HTT-50,P3HTT-33 and P3HTT-25) were prepared via Kumada catalyst transfer polycondensation method from a set of mono-, bi-, ter-and quarterthiophenes containing different contents of hexylthio side chain. The DFT calculation shows the planarity of polymers backbone could be improved through reducing the density of hexylthio side chain in polymer mainchain. And significant changes in their crystallinity, aggregation and optical properties were observed with the content of hexylthio side chain reducing. The P3HTT-33 displayed the highest field-effect transistor hole mobility of 2.83×10^(-2) cm^(2)·V^(-1)·s^(-1) resulting from a balance between the crystallinity and planarity. This study demonstrates modulating the content of hexylthio side chain in P3HTT is an effective strategy to optimize the opto-electronic properties of polymer obtaining excellent semiconductor device performance.

Near-infrared non-fused electron acceptors for efficient organic photovoltaics

Developing narrow-bandgap organic semiconductors is important to facilitate the advancement of organic photovoltaics(OPVs). Herein, two near-infrared non-fused ring acceptors(NIR NFRAs), PTBFTT-F and PTBFTT-Cl have been developed with A-π_A-π_D-D-π_D-π_A-A non-fused structures. It is revealed that the introduction of electron deficient π-bridge(π_A) and multiple intramolecular noncovalent interactions effectively retained the structural planarity and intramolecular charge transfer of NFRAs, extending strong NIR photon absorption up to 950 nm. Further, the chlorinated acceptor, with the enlarged π-surface compared to the fluorinated counterpart, promoted not only molecular stacking in solid, but also the desirable photochemical stability in ambient, which are helpful to thereby improve the exciton and charge dynamics for the corresponding OPVs. Overall, this work provides valuable insights into the design of NIR organic semiconductors.

Unconventional Organic Low-Dimensional Crystals:Diversity and Potential Applications

Organic low-dimensional crystals have garnered escalating interests in the realms of miniaturized optoelectronics and integrated photonics.The continual expansion of molecular systems and improvement in experimental conditions have given rise to unconventional organic low-dimensional crystals,which showcase a variety of appealing structure-dependent properties in the realm of organic semiconductors,owing to their adaptable physicochemical characteristics and exceptional optoelectronics performance.Simultaneously,the development of unconventional low-dimensional crystals is filled with abundant possibilities due to their diverse application prospects.Herein,we present a comprehensive overview of advancements in research on representative cases of unconventional low-dimensional organic crystals,using a systematic and rational structural classification.Finally,we have also discussed the existing challenges and future directions,aspiring to deepen understanding and encourage further research exploration in this field.

A Noncovalently Fused-Ring Asymmetric Electron Acceptor Enables Efficient Organic Solar Cells

Main observation and conclusion Recently,the asymmetric nonfullerene acceptors(NFAs)with acceptor-donor-acceptor(A-D-A)structure have been developed rapidly,especially for the modification of asymmetric core,asymmetric side chains and asymmetric end groups.In this work,a novel asymmetric A-D-π-A type NFA with a noncovalently fused-ring core named PIST-4F is synthesized,containing an indacenodithieno[3,2-b]dithiophene(IDT),two strong electron-withdrawing end groups and an alkylthio-substituted thiopheneπ-bridge.Benefiting from the S···S noncovalent interaction between the sulfur atom onπ-bridge and the adjacent thiophene in IDT,the PIST-4F presents nearly planar geometry and extended conjugated area,resulting in the optimized electronic properties,charge transport,and film morphology compared to the symmetric NFA PI-4F.As a result,PM6:PIST-4F-based devices achieve a higher power conversion efficiency(PCE)of 13.8%,while the PM6:PI-4F-based devices only show a PCE of 7.1%.Notably,the PM6:PIST-4F-based devices processed with nonhalogen solvent toluene exhibit an excellent PCE as high as 13.1%.These results indicate that PIST-4F is an effective acceptor for high-efficiency organic solar cells.

How Mutations Affecting the Ligand-receptor Interactions： a Combined MD and QM/MM Calculation on CYP2E1 and Its Two Mutants

Cytochrome P450（CYP） 2El is a dual function monoxygenase with a crucial role in the metabolism of 6% of drugs on the market at present. The enzyme is of tremendous interest for its association with alcohol consumption, diabetes, obesity and fasting. Despite the abundant experimental mutagenesis data, the molecular origin and the structural motifs for the enzymatic activity deficiencies have not been rationalized at the atomic level. In this regard, we have investigated the effects of mutation on the structural and energetic characteristics upon single point mutations in CYP2E1, N219D and $366C. The molecular dynamics（MD） simulation combined with quantum mechanics/molecular mechanics（QM/MM） and noncovalent interaction（NCI） analysis was carried out on CYP2EI and its two mutants. The results highlight the critical role of Phe207, which is responsible for both structural flexibility and energetic variation, shortening the gap between the theory and the experimentally observed results of enzymatic activity decrease, The underlying molecular mechanism of the enzymatic activity deficiencies for mutants may be attributed to the changes of spatial position of Phe207 in the two mutants. This work provides particular explanations to how mutations affect ligand-receptor interactions based on combined MD and QM/MM calculations. Furthermore, the mutational effects on the activity of CYP2E1 obtained in the present study are beneficial to both the experimental and the computational works of CYPs and may allow researchers to achieve desirable changes in enzymatic activity.

Host-Guest Chemistry and Nonlinear Optical Behaviors of Aluminum Molecular Rings

Macrocyclic compounds are of great interest for their ability to capture guest molecules into their cavities.In particular,host-guest interaction plays a crucial role in the formation of supramolecular compounds.Herein,two host-guest supramolecular compounds,[Al_(8)(OH)_(8)(L)_(16)]·2HL(HL@AlOC-166,HL=4-Iodobenzoic acid)and[Al_(8)(OH)_(8)(L)_(8)(L1)_(8)]·2DMF(DMF@AlOC-166,HL1=isoamyl alcohol),are acquired by introducing different types of guest components based on the internal pore cavities of the aluminum molecular ring[Al_(8)(OH)_(8)(L)_(16)](AlOC-166).The inclusion of these guests is attributed to the presence of abundant hydrophilic OH serving as the hydrogen bond donors inward the ring cavity.Host-guest compounds usually exhibit superior nonlinear optical(NLO)response due to the existence of guest molecules that could change symmetry,dipole moments,charge distributions,etc.Unexpectedly,the AlOC-166 achieved the best NLO results,although it had no guest molecules inside its molecular ring,which breaks the traditional concept.The reason for this trend can be explained by the difference in intermolecular force rather than intramolecular interaction,mainly related to the amount and strength ofπ···πand C—I···πinteractions in different compounds.This work investigates the effect of host-guest interaction on NLO,representing a new perspective for designing optical limiting materials.

New Insights into the Ion-Specific Behaviors and Design Strategies for Ion–πInteractions

Ion–πinteractions play a critical role in many important biological processes,such as gene expression,nicotine addiction,ion channel function,and so on,through recognizing specific ions by the receptors.However,widely used models,such as electrostatic potential and quadrupole moment,either treat ions as point charges or consider arenes only such that the key role of the information carried by ions is rarely discussed.Here,we shed light on the ion specificities in ion–πinteractions by correlating binding energies to a new model,namely the orbital electrostatic energy(OEE),which describes the electrostatic properties of both ions and theπsystems in detail via electron density distributions on orbitals.With this more detailed descriptor of electrostatics,new insights behind several important experimental and theoretical behaviors of ion–πinteractions are revealed,which will provide a deeper understanding of molecular recognition and communication through ion–πinteractions.On top of the OEE model,an ion-specific design strategy is proposed.