Molecular electrostatic potentials and noncovalent interactions

The superiority of isomeric, fluorination and curtailed π-conjunction on A-D-A type acceptors for organic photovoltaics

The performance of organic solar cell (OSC) devices has been significantly enhanced by the dramatic evolution of A-D-A type non-fullerene acceptors (NFAs). Nevertheless, the structure-property-performance relationship of NFAs in the OSC device is unclear. Here, the intrinsic design factors of isomeric, fluorination and π-conjunction curtailing on the photophysical properties of benzodi (thienopyran) (BDTP) (named NBDTP-M, NBDTTP-M, NBDTP-Fin, and NBDTP-Fout)-based NFAs are discussed. The results show that fluorination on the terminal group of NBDTP-Fout could effectively decrease the highest occupied orbital (HOMO) energy level and the lowest unoccupied orbital (LUMO) energy level. And the long π-conjugated donor unit for NBDTTP-M could increase the HOMO energy level and bring a small HOMO-LUMO energy bandgap. Meanwhile, the substitution of external oxygen atoms and the fluorine atoms in the terminal group could introduce positive changes to the electrostatic potential of the NBDTP-Fout, favouring the charge separation at the donor/acceptor interface. Moreover, the structural design of external oxygen atom substitution, fluorination on the terminal group and curtailed π-conjugated donor unit could decrease the electron vibration-coupling of exciton diffusion, exciton dissociation and electronic transfer processes. The suppression of the exciton decay and charge recombination in those high-performance NFAs indicate that the investigated molecular designs could be effective for further improvement of OSCs.

Description of changes in chemical bonding along the pathways of chemical reactions by deformation of the molecular electrostatic potential

CONTEXT

The analysis of the changes in the electronic structure along intrinsic reaction coordinate (IRC) paths for model reactions: (i) ethylene + butadiene cycloaddition, (ii) prototype SN2 reaction Cl- + CH3Cl, (iii) HCN/CNH isomerization assisted by water, (iv) CO + HF → C(O)HF was performed, in terms of changes in the deformation density (Δr) and the deformation of MEP (ΔMEP). The main goal was to further examine the utility of the ΔMEP as a descriptor of chemical bonding, and to compare the pictures resulting from Δr and ΔMEP. Both approaches clearly show that the main changes in the electronic structure occur in the TS region. The ΔMEP picture is fully consistent with that based on Δρ for the reactions of the neutral species leading to the neutral products without large charge transfer between the fragments. In the case of reactions with large electron density displacements, the ΔMEP picture is dominated by charge transfer leading to more clear indication of charge shifts than the analysis of Δr.

METHODS

All the calculations were performed using the ADF package. The Becke-Perdew exchange-correlation functional was used with the Grimme's dispersion correction (D3 version) with Becke-Johnson damping. The Slater TZP basis sets defined within the ADF program were applied. For the analysed reactions, the stationary points were determined and verified by frequency calculations, and the IRC was determined. Further analysis was performed for the structures of reactants, TS, products, and the points corresponding to the minimum and maximum of the reaction force. For each point, two fragments, A and B, corresponding to the reactants were considered. The deformation density was calculated as the difference between the electron density of the system AB and the sum of densities of A and B, Δ ρ r = ρ AB r - ρ A r - ρ B r , with the same fragment definition as in the ETS-NOCV method. Correspondingly, deformation in MEP was determined as Δ V r = V AB r - V A r - V B r .

A short-time, low-dosage chemicals dyeing of polyester/cotton blended fabric with benzothiazole dyes in water-less, salt-free dyeing system

Non-aqueous media dyeing technology has highly innovative as it reduces pollution without increasing cost in polyester/cotton blended fabric dyeing. However, disperse dyes can stain in cotton component of the polyester/cotton blended fabric during dyeing process, resulting poor quality of dyed products. In this study, a groundbreaking comprehensive investigation was conducted on the dyeing behavior of C.I. Disperse Red 177 and C.I. Disperse Red 145 in non-aqueous media. The results revealed that the dyes' uptake rates on polyester components in non-aqueous medium were comparable to those in traditional water dyeing baths. Conversely, the staining rate of disperse dye on cotton fiber surface was relatively high. Interestingly, the migration of dyes from polyester surface to cotton surface after dyeing had minimal impact on staining. Thermodynamic analysis in non-aqueous media showed that the Gibbs free energy of C.I. Disperse Red 145 adsorption on cotton was higher than that of C.I. Disperse Red 177. Computational chemistry simulations showed that the terminal group of C.I. Disperse Red 177 (N-acetoxyethyl) led to stronger electrostatic interaction with cotton compared to C.I. Disperse Red 145. Therefore, disperse dyes with N-ethyl end groups have a weak interaction with the cotton and stain less on the cotton fiber surface.

Illuminating the Performance of Electron Withdrawing Groups in Halogen Bonding

Throughout the halogen bonding literature, electron withdrawing groups are relied upon heavily for tuning the interaction strength between the halogen bond donor and acceptor; however, the interplay of electronic effects associated with various substituents is less of a focus. This work utilizes computational techniques to study the degree of σ- and π-electron donating/accepting character of electron withdrawing groups in a prescribed set of halo-alkyne, halo-benzene, and halo-ethynyl benzene halogen bond donors. We examine how these factors affect the σ-hole magnitude of the donors as well as the binding strength of the corresponding complexes with an ammonia acceptor. Statistical analyses aid the interpretation of how these substituents influence the properties of the halogen bond donors and complexes, and show that the electron withdrawing groups that are both σ- and π-electron accepting form the strongest halogen bond complexes.

High-Fidelity Supramolecular Chirality Transportation Enabled Through Chalcogen Bonding

The formation of asymmetric microenvironments in proteins benefits from precise transportation of chirality across multiple levels through weak bonds in the folding and assembly process, which inspires the rational design and fabrication of artificial chiral materials. Herein, the chalcogen bonding-directed precise transportation of supramolecular chirality toward multiple levels is reported to aid the fabrication of chiroptical materials. Benzochalcogenadiazole (O, S, Se) motifs are conjugated to amino acid residues, and the solid-state assemblies afforded selective supramolecular chirality with handedness depending on the kinds of chalcogen atoms and amino acids. The chalcogen-N sequence assisted by hydrogen bonding synergistically allows for the complexation with pyrene conjugated aryl carboxylic acids to give macroscopic helical structures with active circular dichroism and circularly polarized luminescence, of which handedness is precisely determined by the pristine chiral species. Then the further application of chiral benzochalcogenadiazole motifs as seeds in directing handedness of benzamide via symmetry breaking is realized. Behaving as the dopants, embedding into the matrix of benzophenone induces the room temperature phosphorescence, whereby the thermal chiroptical switch is fabricated with color-tunable phosphorescent circularly polarized luminescence. This work utilized benzochalcogenadiazole-based chiral building units to accomplish precise transportation of supramolecular chirality in coassemblies with high-fidelity, achieving flexible manipulation of chiroptical properties and macroscopic helical sense.

Molecular Engineering Chemical Pre-lithiation Reagent with Low Redox Potential for Graphite Anode Enables High Coulombic Efficiency

Graphite (Gr) is a low-cost and high-stability anode for lithium-ion batteries (LIBs). However, Gr anode exhibits an obstinate drawback of low initial Coulombic efficiency (ICE), owing to the active lithium loss for the solid electrolyte interphase (SEI) layer. Herein, a straightforward and effective chemical pre-lithiation strategy is proposed to compensate for the lithium loss. A molecular engineering phenanthrene-based lithium-arene complex (Ph-based LAC) reagent is designed by density functional theory (DFT) calculations. The engineering Ph-based reagent enhances the stability of the π-electron system and the electron-donating capacity, resulting in a reduced redox potential to facilitate lithium transfer. The electrochemical distinct of the Ph-based reagent is illustrated, the prelithiation process in a low Li-insertion platform, and the lithiation degree is controllable with the dipping time (ICE = 102%, 3 min). Notably, a denser and homogeneous SEI layer has pre-formed to enhance the Li+ transport and interface stability. Moreover, the lithium-ion full batteries assemble with LiFePO4 and NCM811 cathode, which exhibits high ICE (96.5% and 90.3%) and energy density (310 and 333 Wh kg-1). These findings present a facile and controllable pre-lithiation strategy to compensate for the lithium of LIBs, providing new valuable insights into the design and optimization of battery manufacture.

Constructing, in silico, molecular self-aggregates and micro-hydrated complexes of oxirene and thiirene

CONTEXT

Oxirene, surmised to exist in the interstellar medium, was synthesized in the laboratory only recently. The present study investigates theoretically to what extent the two exotic molecules, oxirene and its thia-analogue thiirene, are capable of forming molecular self-aggregates and undergo micro-hydration under cooperative hydrogen bonding as the tour de force. Cogent molecular descriptors, such as binding energies for cluster formation, molecular electrostatic potential (MESP), effective atomic charges, infrared spectroscopic response, criticality profiles from the quantum theory of atoms in molecules (QTAIM), hydrogen bond energies, and reduced density gradient (RDG) maps identifying non-covalent interactions (NCI), all in unison confirm theoretically the existence and characterize the aggregates. In particular, infrared spectra display frequency down-shifts for the hydrogen bonded C-H vibrations in aggregates and for O-H in hydrated complexes. This work carried out in silico, should furnish credible tenets toward identification of oxirene and thiirene self-aggregates and their micro-hydrated complexes that potentially exist in the interstellar medium.

METHOD

By means of a molecular modeling program AVOGADRO, a multitude of initial-guess clusters under universal force field (UFF) were generated, which were subsequently optimized employing the GAUSSIAN16 suite of programs with the tightest convergence criterion, at the ωB97xD level of density functional theory embodying long-range dispersion effects, in conjunction with a reliable basis set 6-311 ++ G(2d,2p). The versatile package GAUSSVIEW yields the structures, vibrational frequencies, and criticality information, respectively.

Toward the Rational Design of an OsM4 Center for Methane Activation: Gas-Phase Result-Derived Neural Network Model

Gas-phase reactions of [OsBx]+ (x = 1-4) with methane at ambient temperature have been studied by using quadrupole-ion trap mass spectrometry combined with quantum chemical calculations. The [OsBx]+ (x = 1-4) cluster ions can undergo dehydrogenation reactions with methane. Comprehensive analysis of the [OsBx]+/CH4 (x = 1-4) system with Os-complexes ([OsCy]+ (y = 1-3) and [OsOz]+ (z = 1-3)) shows that the large polarity of the cluster and the high sum of the pair energies between Os and the ligand in the ETS-NOCV combine to promote the ability of the cluster to activate methane. Cluster polarity may induce heterolytic cleavage of the C-H bond, and the sum of the pair energies of the fragments may reduce the cluster orbital energy to match the methane orbital and improve the cluster stability. The synergistic interplay of these two factors may offer a viable approach for the activation of methane in the condensed phase, which involves modulating the coordination environment of the active sites to enhance the stability and facilitate C-H bond cleavage and the degree of matching with methane orbitals. A nonlinear function is used to extract second-order characteristic features that have a significant impact on the energy difference based on the limited energy difference data of the OsBmCnOlHk units. A neural network model is next designed to predict the reaction barrier for methane conversion by OsM4+ (M = C, N, O, Al, Si, or P) with high accuracy.

From weak to strong interactions between halogen and noble gas atoms in halonium complexes

Halonium cations can interact through a halogen bond with individual noble gas atoms. These bonds can vary widely in strength from 1 to 25 kcal mol-1. Quantum chemical analyses consider X to be attached to a propyl group, pyridine N, or Xe atom, with X = Cl, Br, and I, interacting with Ar, Kr, and Xe atoms. The most weakly bound dyads are bound primarily by electrostatics, but charge transfer takes a larger role for the more tightly held complexes.

Theoretical investigation of potential energetic material CL-20/TNBP co-crystal explosive based on molecular dynamics method

CONTEXT

The exploration of CL-20 eutectic has been a subject of fervent interest within the realm of high-energy material modification. Through the utilization of density functional and molecular dynamics methods, an investigation into the characteristics of hexanitrohexaazaisowurtzitane (CL-20)/4,4',5,5'-tetranitro-2H,2'H-3,3'-bipyrazole (TNBP)within the molar ratio range of 4:1-1:4 was conducted. This inquiry encompassed the scrutiny of molecular interaction pathways, attachment force, initiating molecular distance, unified energy concentration, and physical characteristics. Furthermore, the EXPLO-5 was harnessed to prognosticate the explosion features and byproducts of unadulterated CL-20, TNBP, and CL-20/TNBP frameworks. The findings delineate a substantial differentiation in the electrostatic charge distribution on the surface between CL-20 and TNBP particles, signifying the preeminence of intermolecular interactions between disparate entities over those within similar entities, thus intimating the plausibility of the eutectic constitution. Remarkably, the identification of maximal attachment force at a molar ratio of 1:1 suggests the heightened likelihood of eutectic formation, propelled primarily by electrostatic and van der Waals forces. The resultant eutectic explosive evinces intermediate reactivity and exemplary mechanical attributes. Moreover, the detonation achievement of the eutectic with a molar proportion of 1:1 straddles that of CL-20 and TNBP, representing a new type of insensitive high-energy material.

METHODS

The testing method employs the Materials Studio software and utilizes the molecular dynamics (MD) method to predict the properties of CL-20/TNBP cocrystals with different ratios and crystal faces. The MD simulation time step is set to 1 fs, and the total MD simulation time is 2 ns. An isothermal-isobaric (NPT) ensemble is used for the 2 ns MD simulation. The COMPASS force field is employed, with the temperature set to 295 K. The prediction of detonation characteristics and products is conducted using the EXPLO-5 software.

The Inhibitory Impact of a Co-Assembly Gel with Natural Carrier-Free Binary Small Molecules, as Used in Traditional Chinese Medicine, on the Viability of SW1990 Cells

Chinese herbs are a huge treasure trove of natural products and an important source of many active molecules. The theory of traditional Chinese medicine compatibility (TCMC) is widely applied in clinical practice, but its mechanism is still ambiguous. This study aims to open a new window for this predicament by studying the interaction between the main active ingredients from a drug pair. Carrier-free assembly of natural products improves the shortcomings of traditional nanodelivery systems and opens a new path for the development of new nanomaterials. The drug pair "Pueraria and Hedyotis diffusa" has been commonly used in clinical practice, with a predominant therapeutic effect. This study is devoted to the study of the binary small molecule co-assembly of the main active molecules from the drug pair. In this study, we introduce a carrier-free composite gel, formed by the co-assembly of puerarin (PUE) and deacetylasperulosidic acid (DAA) via non-covalent bonds including π-π packing, intermolecular hydrogen bonding, and C=O π interactions. With a strain point 7-fold higher than that of P gel, the P - D gel exhibited favorable rheological properties. The survival rate of SW1990 cells in the P - D group was only 21.39% when the concentration of administration reached 200 μM. It thus demonstrated activity in inhibiting SW1990 cells' survival, suggesting potential in combating pancreatic cancer. Furthermore, this research offers a valuable concept for enhancing the mechanical properties and bioactivity of hydrogel materials through the utilization of a multi-component natural small molecule co-assembly approach. More importantly, this provides new ideas and methods for the treatment of pancreatic cancer and the analysis of traditional Chinese medicine compatibility theory.

Theoretical study of potential energetic material CL-20/DNAN eutectic explosive based on molecular dynamics method

CONTEXT

The exploration of CL-20 eutectic has been a subject of fervent interest within the realm of high-energy material modification. Through the utilization of density functional and molecular dynamics methods, an investigation into the characteristics of hexanitrohexaazaisowurtzitane (CL-20)/2,4-dinitroanisole (DNAN) within the molar ratio range of 9:1-1:9 was conducted. This inquiry encompassed the scrutiny of molecular interaction pathway, attachment force, initiating molecular distance, unified energy concentration, and physical characteristics. Furthermore, EXPLO-5 was harnessed to prognosticate the explosion features and byproducts of unadulterated CL-20, DNAN, and CL-20/DNAN frameworks. The findings delineate a substantial differentiation in the electrostatic charge distribution on the surface between CL-20 and DNAN particles, signifying the preeminence of intermolecular interactions between disparate entities over those within similar entities, thus intimating the plausibility of eutectic constitution. Remarkably, the identification of maximal attachment force at a molar ratio of 4:6 suggests the heightened likelihood of eutectic formation, propelled primarily by electrostatic and van der Waals forces. The resultant eutectic explosive evinces intermediate reactivity and exemplary mechanical attributes. Moreover, the detonation achievement of the eutectic with a molar proportion of 4:6 straddles that of CL-20 and DNAN, representing a new type of insensitive high-energy material.

METHODS

The testing method employs the Materials Studio software and utilizes the molecular dynamics (MD) method to predict the properties of CL-20/DNAN co-crystals with different ratios and crystal faces. The MD simulation time step is set to 1 fs, and the total MD simulation time is 2 ns. An isothermal-isobaric (NPT) ensemble is used for the 2-ns MD simulation. The COMPASS force field is employed, with the temperature set to 295 K. The prediction of detonation characteristics and products is conducted using the EXPLO-5 software.

A weakly coordinating-intervention strategy for modulating Na+ solvation sheathes and constructing robust interphase in sodium-metal batteries

Constructing powerful anode/cathode interphases by modulate ion solvation structure is the principle of electrolyte design. However, the methodological and theoretical design principles of electrolyte/solvation structure and their effect on electrochemical performance are still vague. Here, we propose a cationic weakly coordinating-intervention strategy for modulating the Na+ solvation sheathes and constructing robust anode/cathode interphases in sodium-metal batteries. Unlike the local highly concentrated electrolytes, 1,2-difluorobenzene can weakly coordinate with Na+ thus transforming the solvation structure into Na+-anion-incorporated structures and strengthening anode/cathode interphases formation by combining with salt decomposition. Furthermore, the correlations between the electrode interface properties and solvation structure are revealed, which can be tuned by the weakly coordination. Ultimately, the modulated electrolyte achieves 97.5% Coulombic efficiency for 600 cycles in Na‖Cu cells at 1 mA cm-2 and a beneficial lifetime (2500 h) in Na‖Na cells. Meanwhile, Na‖PB cells have achieved long-term operation at 4.8 V, along with operation at wide temperatures.

Chalcogen Noncovalent Interactions between Diazines and Sulfur Oxides in Supramolecular Circular Chains

The noncovalent chalcogen interaction between SO2/SO3 and diazines was studied through a dispersion-corrected DFT Kohn-Sham molecular orbital together with quantitative energy decomposition analyses. For this, supramolecular circular chains of up to 12 molecules were built with the aim of checking the capability of diazine molecules to detect SO2/SO3 compounds within the atmosphere. Trends in the interaction energies with the increasing number of molecules are mainly determined by the Pauli steric repulsion involved in these σ-hole/π-hole interactions. But more importantly, despite the assumed electrostatic nature of the involved interactions, the covalent component also plays a determinant role in its strength in the involved chalcogen bonds. Noticeably, π-hole interactions are supported by the charge transfer from diazines to SO2/SO3 molecules. Interaction energies in these supramolecular complexes are not only determined by the S···N bond lengths but attractive electrostatic and orbital interactions also determine the trends. These results should allow us to establish the fundamental characteristics of chalcogen bonding based on its strength and nature, which is of relevance for the capture of sulfur oxides.

Sensitivity-Enhancing Modified Holographic Photopolymer of PQ/PMMA

Phenanthrenequinone-doped poly(methyl methacrylate) (PQ/PMMA) photopolymers are potential holographic storage media owing to their high-density storage capacities, low costs, high stability, and negligible shrinkage in volume holographic permanent memory. However, because of the limitations of the substrate, conventional Plexiglas materials do not exhibit a good performance in terms of photosensitivity and molding. In this study, the crosslinked structure of PMMA was modified by introducing a dendrimer monomer, pentaerythritol tetraacrylate (PETA), which increases the photosensitivity of the material 2 times (from ~0.58 cm/J to ~1.18 cm/J), and the diffraction efficiency is increased 1.6 times (from ~50% to ~80%). In addition, the modified material has a superior ability to mold compared to conventional materials. Moreover, the holographic performance enhancement was evaluated in conjunction with a quantum chemical analysis. The doping of PETA resulted in an overall decrease in the energy required for the reaction system of the material, and the activation energy decreased by ~0.5 KJ/mol in the photoreaction stage.

Unique solvation structure induced by anionic Cl in aqueous zinc ion batteries

Aqueous zinc ion batteries (AZIBs) have garnered significant attention in large-scale static energy storage battery systems due to their low cost, high safety and environmental friendliness. However, it has some inherent problems during operation, such as the occurrence of side reactions (hydrogen evolution reaction, HER) and anode corrosion, formation of by-products and growth of metal dendrites. To analyze the mechanism of generation from aspect of the electrolyte solvation structure and make cell efficiency further improvements based on it, so we use DFT calculations to find the most stable solvation structure in AZIBs with ZnCl2 as the electrolyte and analyze it. We define the relative concentration C r , and calculate different groups metal cation cluster structures such as [ Zn ( H 2 O ) n ] 2 + , [ ZnCl ( H 2 O ) n ] + , [ ZnCl 2 ( H 2 O ) n ] and [ ZnCl 3 ( H 2 O ) n ] - that exist at different C r . We discuss the effect of different clusters formed due to the C r variations on the battery performance in terms of three aspects: the structural conformation, the cluster characteristics (including the hydrogen bonding network, bond lengths, bond angles, as well as the electrostatic potential ESP) and the cluster performance (including the adsorption energy Ea, binding energy Eb, and desolvation energy Edes). The results shows that the electrolyte metal cation Zn2+ can be coordinated with up to six H2O molecules in first shell, and this metal cation solvation structure contributes to the occurrence and formation of side reactions and by-products, which reduces the battery efficiency. Increasing the electrolyte anion Cl- concentration by appropriately increasing the C r helps to desolvate the metal cation cluster structure, which greatly improves the battery efficiency and suppresses the side reactions and by-products. Yet the improvement effect was not obviously further improved by further increasing the Cl- concentration.

Investigation of cathinone analogs targeting human dopamine transporter using molecular modeling

In a step towards understanding the structure-property relationship among Synthetic Cathinones (SCs), a combined methodology based on Density Functional Theory (DFT), Administration, Distribution, Metabolism, Excretion, and Toxicity (ADMET) predictions, docking and molecular dynamics simulations have been applied to correlate physicochemical descriptors of various SCs to their biological activity. The results from DFT and molecular docking studies correlate well with each other explaining the biological activity trends of the studied SCs. Quantum mechanical descriptors viz. polarizability, electron affinity, ionization potential, chemical hardness, electronegativity, molecular electrostatic potential, and ion interaction studies unravel the distinguishingly reactive nature of Group D (pyrrolidine substituted) and Group E (methylenedioxy and pyrrolidine substituted) compounds. According to ADMET analysis, Group D and Group E molecules have a higher probability of permeating through the blood-brain barrier. Molecular docking results indicate that Phe76, Ala77, Asp79, Val152, Tyr156, Phe320, and Phe326 constitute the binding pocket residues of hDAT in which the most active ligands MDPV, MDPBP, and MDPPP are bound. Finally, to validate the derived quantum chemical descriptors and docking results, Molecular Dynamics (MD) simulations are performed with homology-modelled hDAT (human dopamine transporter). The MD simulation results revealed that the majority of SCs remain stable within the hDAT protein's active sites via non-bonded interactions after 100 ns long simulations. The findings from DFT, ADMET analysis, molecular docking, and molecular dynamics simulation studies complement each other suggesting that pyrrolidine-substituted SCs (Group D and E), specifically, MPBP and PVN are proven potent SCs along with MDPV, validating various experimental observations.Communicated by Ramaswamy H. Sarma.

1,2,3,4-Tetrafluorobiphenylene: A Prototype Janus-Headed Scaffold for Ambipolar Materials

The title compound was synthesized by Ullmann cross-coupling in low yield as the first representative of [n]phenylene containing hydrocarbon and fluorocarbon rings. Stille/Suzuki-Miyaura cross-coupling reactions, as well as substitution of fluorine in suitable starting compounds, failed to give the same product. The geometric and electronic structures of the title compound were studied by X-ray diffraction, cyclic voltammetry and density functional theory calculations, together with Hirshfeld surface and reduced density gradient analyses. The crystal structure features head-to-tail π-stacking and other fluorine-related secondary bonding interactions. From the nucleus-independent chemical shifts descriptor, the four-membered ring of the title compound is antiaromatic, and the six-membered rings are aromatic. The Janus molecule is highly polarized; and the six-membered fluoro- and hydrocarbon rings are Lewis π-acidic and π-basic, respectively. The electrochemically-generated radical cation of the title compound is long-lived as characterized by electron paramagnetic resonance, whereas the radical anion is unstable in solution. The title compound reveals electrical properties of an insulator. On expanding its molecular scaffold towards partially fluorinated [n]phenylenes (n≥2), the properties presumably can be transformed into those of semiconductors. In this context, the title compound is suggested as a prototype scaffold for ambipolar materials for organic electronics and spintronics.

Binding Strengths and Orientations in CO2 Adsorption on Cationic Scandium Oxides: Governing Factor Revealed by a Combined Infrared Spectroscopy and Theoretical Study

Carbon dioxide (CO2) adsorption is a critical step to curbing carbon emissions from fossil fuel combustion. Among various options, transition metal oxides have received extensive attention as promising CO2 adsorbents due to their affordability and sustainability for large-scale use. Here, the nature of binding interactions between CO2 molecules and cationic scandium oxides of different sizes, i.e., ScO+, Sc2O2+, and Sc3O4+, is investigated by mass-selective infrared photodissociation spectroscopy combined with quantum chemical calculations. The well-accepted electrostatic considerations failed to provide explanations for the trend in the binding strengths and variations in the binding orientations between CO2 and metal sites of cationic scandium oxides. The importance of orbital interactions in the driving forces for CO2 adsorption on cationic scandium oxides was revealed by energy decomposition analyses. A molecular surface property, known as the local electron attachment energy, is introduced to elucidate the binding affinity and orientation-specific reactivity of cationic scandium oxides upon the CO2 attachment. This study not only reveals the governing factor in the binding behaviors of CO2 adsorption on cationic scandium oxides but also serves as an archetype for predicting and rationalizing favorable binding sites and orientations in extended surface-adsorbate systems.

Probing intramolecular interactions using molecular electrostatic potentials: changing electron density contours to unveil both attractive and repulsive interactions

We focus on intramolecular interactions, using the electrostatic potential plotted on iso-density surfaces to lead the way. We show that plotting the electrostatic potential on varying iso-density envelopes much closer to the nuclei than the commonly used 0.001 a.u. contour can reveal the driving forces for such interactions, whether they be stabilizing or destabilizing. Our approach involves optimizing the structures of molecules exhibiting intramolecular interactions and then finding the contour of the electronic density which allows the interacting atoms to be separated; we call this the nearly-touching contour. The electrostatic potential allows then to identify the intramolecular interactions as either attractive or repulsive. The discussed 1,5- and 1,6-intramolecular interactions in o-bromophenol and o-nitrophenol are attractive, while the interactions between terminal methyl hydrogens in diethyl disulfides (as shown recently) and those between the closest hydrogens in planar biphenyl and phenanthrene are clearly repulsive in nature. For the attractive 1,4-interactions in trinitromethane and chlorotrinitromethane, and the 1,3-S⋯N and the 1,4-Si⋯N interactions in the ClH2Si(CH2)nNH2 series, the lack of (3,-1) bond critical points has often been cited as reason to not identify such interactions as attractive in nature. Here, by looking at the nearly-touching contours we see that bond critical points are neither necessary nor sufficient for attractive interactions, as others have pointed out, and in some instances also pointing to repulsive interactions, as the examples of planar biphenyl and phenanthrene discussed in this work show.

Anisotropies in electronic densities and electrostatic potentials of Halonium Ions: focus on Chlorine, Bromine and Iodine

CONTEXT

Why are the halonium cations so effective in forming strongly-bound complexes? We directed our research to address this question and we present electrostatic potential data for the valence-state halogen atoms X and halonium cations X+, where X = Cl, Br, I. The electron densities and electrostatic potentials of the halonium cations show considerably greater anisotropy than do the valence state halogens. The distances from the electrostatic potential surface maxima to the halogen nuclei are about 0.5 Å smaller than the distances from the electrostatic potential surface minima to the nuclei, giving the halonium cations each a more disk-like shape than the corresponding neutral valence state halogens. Their surface electrostatic potentials are totally consistent with the directionalities of halonium cations in complexes and the strengths of their interactions. To add perspective to this brief report, we have included calculations of the isotropic cation K+ and noble gas Kr.

METHODS

The calculations of the electrostatic potentials of the valence states of the halogen atoms Cl, Br and I and the halonium cations Cl+, Br+ and I+, as well as K+ and Kr, on 0.001 au contours of their electronic densities were carried out with Gaussian O9 and the Wave Function Analysis - Surface Analysis Suite (WFA-SAS) at the M06-2X/6-31 + G(d,p) and M06-2X/3-21G* levels.

Experimental and theoretical study to control the heavy metals in solid waste and sludge during pyrolysis using modified expanded vermiculite

Na+/K+/Mg2+/Ca2+ expansion-modified vermiculite and calcination expansion (700 °C, 800 °C and 900 °C)-modified vermiculite (700-Mg-V, 800-Mg-V and 900-Mg-V) were prepared as additives to control the emission of five heavy metals (Zn, Cr, Cu, Pb, and Cd) during the pyrolysis of municipal sewage sludge, paper mill sludge, municipal domestic waste, and aged refuse. Mg2+-Modified vermiculite obtained via thermally activated calcination at 800 °C retained 65% of heavy metals from all raw materials at 450 °C. Zn, Cr, and Cu retained nearly 90%. Although modified vermiculite could reduce the ecological risk, Cd had an ecological risk level higher than Zn, Cr, Cu, and Pb. The fine textural properties, laminated morphology, and expansion capacity of modified vermiculite were positively correlated with its retention of heavy metals. Heavy metals interacted with the (002) surface of vermiculite, and the reactions were mainly concentrated near the 17-O and surrounding atoms. The heavy-metal monomers were less capable of binding to the (002) surface of vermiculite than the oxides and chlorides of heavy metals. The effect of heavy-metal oxides and chlorides binding to the (002) surface of vermiculite was related to heavy metals.

The Formation of σ-Hole Bonds: A Physical Interpretation

This paper discusses two quite different computational experiments relating to the formation of σ-hole bonds A···B. The first involves looking at the complex at equilibrium and finding the contour X of the electronic density which allows the iso-density envelopes of A and B to be nearly touching. This contour increases, becoming closer to the nuclei, as the strength of the interaction increases. The second experiment involves allowing A and B to approach each other, with the aim of finding the distance at which their 0.001 a.u. iso-density envelopes are nearly merging into one envelope. What is found in the second experiment may be somewhat surprising, in that the ratio of the distance between interacting atoms at this nearly merging point-divided by the sum of the van der Waals radii of these atoms-covers a narrow range, typically between 1.2 and 1.3. It is intriguing to note that for the dataset presented, approaching molecules attracted to each other appear to do so unknowing of the strength of their ultimate interaction. This second experiment also supports the notion that one should expect favorable interactions, in some instances, to have close contacts significantly greater than the sums of the van der Waals radii.

Recent developments in molecular modeling tools and applications related to pharmaceutical and biomedical research

In modern pharmaceutical and biomedical research, molecular modeling represents a useful tool to explore processes and their mechanistic bases at the molecular level. Integrating experimental and virtual analysis is a fruitful approach to study ligand-receptor interaction in chemical, biochemical and biological environments. In these fields, molecular docking and molecular dynamics are considered privileged techniques for modeling (bio)macromolecules and related complexes. This review aims to present the current landscape of molecular modeling in pharmaceutical and biomedical research by examining selected representative applications published in the last years and highlighting current topics and trends of this field. Thus, a systematic compilation of all published literature has not been attempted herein. After a brief overview of the main theoretical and computational tools used to investigate mechanisms at molecular level, recent applications of molecular modeling in drug discovery, ligand binding and for studying protein conformation and function will be discussed. Furthermore, specific sections will be devoted to the application of molecular modeling for unravelling enantioselective mechanisms underlying the enantioseparation of chiral compounds of pharmaceutical and biomedical interest as well as for studying new forms of noncovalent interactivity identified in biochemical and biological environments. The general aim of this review is to provide the reader with a modern overview of the topic, highlighting advancements and outlooks as well as drawbacks and pitfalls still affecting the applicability of theoretical and computational methods in the field of pharmaceutical and biomedical research.

Comprehensive quantum chemical study of the associative complex of para-aminobenzoic acid and 7-diethylamino 4-methyl coumarin by adsorption and aromatic bridges

CONTEXT

The present study accounts for the quantum chemical and nonlinear optical properties of the combination of para-aminobenzoic acid and 7-diethylamino 4-methyl coumarin. Three different complexes were designed, surface interaction (adsorption) and two by connecting both molecules with π-bridge benzene and biphenyl. The amino and carboxyl groups were observed to behave as strong donor and acceptor sites in all the complexes. The band gap of the adsorbed complex was found more suitable. The absorption wavelength and intensity both were seen to increase with the increase in the number of benzene rings in the π-bridge. The values of first- and second-order hyperpolarizability suggest the improved nonlinear optical responses of the introduced complexes. Additionally, the negative value of second-order hyperpolarizability suggests the possibility of the occurrence of reverse saturable absorption in these combinations. The reported work gives theoretical insights into the nonlinear optical properties of the combination of para-aminobenzoic acid and 7-diethylamino 4-methyl coumarin.

METHODS

The molecular modeling and the quantum chemical studies were performed with Gaussian software packages. The standard B3LYP-6-311++G(d,p) basis functionals were used for energy minimization and other spectral calculations. All the surface analyses reported here are obtained by employing Multiwfn software. The chemical reactivity was established by the global reactivity descriptors. The intramolecular interactions and charge localization were stated using inter-fragment charge transfer analysis.

Regulating Electrostatic Interaction between Hydrofluoroethers and Carbonyl Cathodes toward Highly Stable Lithium-Organic Batteries

Organic carbonyl electrode materials have shown great promise for high-performance lithium batteries due to their high capacity, renewability, and environmental friendliness. However, their practical application is hindered by the high solubility of these materials in traditional electrolytes, leading to poor cycling stability and serious shuttle effects. Here, we develop a series of hydrofluoroethers (HFEs) with weak electrostatic interaction toward organic carbonyl cathode materials, aiming to address the dissolution issue and achieve high cycling stability in lithium batteries. Theoretical calculations reveal that the electrostatic interactions between HFEs and pyrene-4,5,9,10-tetraone (PTO) are significantly weaker compared with common solvents such as 1,2-dimethoxyethane. Consequently, the dissolution of PTO in the HFE-based electrolyte is remarkably reduced, as observed by in situ ultraviolet-visible spectra. Notably, when using the electrolyte based on 1,1,1,3,3,3-hexafluoro-2-methoxypropane with a certain coordination ability, PTO exhibits excellent cycling stability with a high capacity retention of 78% after 1000 cycles. This work proposes the regulation of electrostatic interactions to inhibit the dissolution of organic carbonyl cathode materials and significantly enhance their cycle life.

Molecular level investigation of interactions between pharmaceuticals and β-cyclodextrin (β-CD) functionalized adsorption sites for removal of pharmaceutical contaminants from water

This study describes a novel application of the use of molecular modeling tools for investigating the adsorption of organic micropollutants (OMPs) from water by nanocomposites. The partitioning of pharmaceuticals onto β-Cyclodextrin (β-CD) functionalized adsorbents was investigated at the molecular level to explore the atomistic interactions of pharmaceutical contaminants in water systems with β-CD and to provide insight into possible approaches for removal of pharmaceuticals from water. Molecular electrostatic surface potential mapping of β-CD derivatives was employed to examine the impact of substitution degree of β-CD and type of grafting agent on host-guest complexation. The stability of the complexes of selected pharmaceuticals and β-CD derivatives were assessed via molecular dynamics simulations to evaluate competitive adsorption between organic micropollutants (OMPs) and between OMPs and fulvic acid, a representative natural organic material (NOM) component found in water systems. Molecular electrostatic surface potential maps showed that grafting agents with aromatic and amine functional groups were found to provide attractive interactions for negatively charged OMPs. In addition, optimization of substitution degree of β-CD is necessary to enhance adsorption of target OMPs. Furthermore, it was found that aromatic ring bearing grafting agents can provide additional electrostatic attractions by π-π interactions with the aromatic ring of the OMPs. The impact of common water quality characteristics on adsorption was assessed and it was revealed that the effect of pH and calcium on adsorption depends on the ionizable functional groups present on the grafting agent. Molecular dynamics simulations showed that adsorption of target OMPs does not solely depend on hydrophobicity but is affected by electrostatic interactions. The simulations revealed that fulvic acid which is commonly present in environmental waters can be a competitor with ibuprofen for the β-CD cavity. Ultimately, this study showed that molecular level simulation can be effectively employed to investigate adsorption of OMPs by β-CD functionalized adsorbents and could be employed to enhance their design and subsequent environmental applications.

Exploring the electron donor-acceptor duality of B3N3 in noncovalent interactions

Boron nitrides are very important and are used as lubricants, insulating agents, etc. Interactions of such systems with small molecules are important. This study examined the potential of B3N3 (triboron trinitride) to act as both an electron acceptor and an electron donor in the formation of noncovalent interactions. The anisotropic electronic distribution observed in the electrostatic potential map supported the B3N3's ability to exhibit the predicted electron donor-acceptor duality. Further computational investigations on optimized gas-phase complexes of B3N3:(NH3)n=1-3, B3N3:(NCH)n=1-6, B3N3:(N2H2)n=1-3 and (B3N3)2 confirmed that the B3N3 molecule can participate in B⋯N triel bonding interactions and H···N hydrogen bonding interactions. These energetically stable complexes are primarily governed by electrostatic and polarization interactions.

Halide Complexes of 5,6-Dicyano-2,1,3-Benzoselenadiazole with 1 : 4 Stoichiometry: Cooperativity between Chalcogen and Hydrogen Bonding

The [M4 -Hal]- (M=the title compound; Hal=Cl, Br, and I) complexes were isolated in the form of salts of [Et4 N]+ cation and characterized by XRD, NMR, UV-Vis, DFT, QTAIM, EDD, and EDA. Their stoichiometry is caused by a cooperative interplay of σ-hole-driven chalcogen (ChB) and hydrogen (HB) bondings. In the crystal, [M4 -Hal]- are connected by the π-hole-driven ChB; overall, each [Hal]- is six-coordinated. In the ChB, the electrostatic interaction dominates over orbital and dispersion interactions. In UV-Vis spectra of the M+[Hal]- solutions, ChB-typical and [Hal]- -dependent charge-transfer bands are present; they reflect orbital interactions and allow identification of the individual [Hal]- . However, the structural situation in the solutions is not entirely clear. Particularly, the UV-Vis spectra of the solutions are different from the solid-state spectra of the [Et4 N]+ [M4 -Hal]- ; very tentatively, species in the solutions are assigned [M-Hal]- . It is supposed that the formation of the [M4 -Hal]- proceeds during the crystallization of the [Et4 N]+ [M4 -Hal]- . Overall, M can be considered as a chromogenic receptor and prototype sensor of [Hal]- . The findings are also useful for crystal engineering and supramolecular chemistry.

Direct glyphosate soil monitoring at the triazine-based covalent organic framework with the theoretical study of sensing principle

Covalent organic frameworks (COFs) are emerging as promising sensing materials due to their controllable structure and function properties, as well as excellent physicochemical characteristics. Here, specific interactions between a triazine-based COF and a mass-used herbicide - glyphosate (GLY) have been utilized to design a disposable sensing platform for GLY detection. This herbicide has been extensively used for decades, however, its harmful environmental impact and toxicity to humans have been recently proven, conditioning the necessity for the strict control and monitoring of its use and its presence in soil, water, and food. Glyphosate is an organophosphorus compound, and its detection in complex matrices usually requires laborious pretreatment. Here, we developed a direct, miniaturized, robust, and green approach for disposable electrochemical sensing of glyphosate, utilizing COF's ability to selectively capture and concentrate negatively charged glyphosate molecules inside its nanopores. This process generates the concentration gradient of GLY, accelerating its diffusion towards the electrode surface. Simultaneously, specific COF-glyphosate binding catalyses the oxidative cleavage of the C-P bond and, together with pore nanoconfinement, enables sensitive glyphosate detection. Detailed sensing principles and selectiveness were scrutinized using DFT-based modelling. The proposed electrochemical method has a linear working range from 0.1 μM to 10 μM, a low limit of detection of 96 nM, and a limit of quantification of 320 nM. The elaborated sensing approach is viable for use in real sample matrices and tested for GLY determination in soil and water samples, without pretreatment, preparation, or purification. The results showed the practical usefulness of the sensor in the real sample analysis and suggested its suitability for possible out-of-laboratory sensing.

MgO-mediated activation of active carbon as an affordable strategy to "in situ" degradation of lindane in contaminated soils

The accumulation in soil landfills of toxic and persistent lindane, widely used as an insecticide, triggers the risk of leaching with the concomitant contamination of surrounding rivers. Thus, viable remediation to eliminate in situ high concentrations of lindane in soil and water becomes an urgent demand. In this line, a simple and cost-effective composite is proposed, including the use of industrial wastes. It includes reductive and non-reductive base-catalyzed strategies to remove lindane in the media. A mixture of magnesium oxide (MgO) and activated carbon (AC) was selected for that purpose. The use of MgO provides a basic pH. In addition, the specific selected MgO forms double-layered hydroxides in water which permits the total adsorption of the main heavy metals in contaminated soils. AC provides adsorption microsites to hold the lindane and a reductive atmosphere that was increased when combined with the MgO. These properties trigger highly efficient remediation of the composite. It permits a complete elimination of lindane in the solution. In soils doped with lindane and heavy metals, it produces a rapid, complete, and stable elimination of lindane and immobilization of the metals. Finally, the composite tested in lindane-highly contaminated soils permits the "in situ" degradation of nearly 70% of the initial lindane. The proposed strategy opens a promising way to face this environmental issue with a simple, cost-effective composite to degrade lindane and fix heavy metals in contaminated soils.

Ultralow-background SERS substrates for reliable identification of organic pollutants and degradation intermediates

Chemical methods for preparing SERS substrates have the advantages of low cost and high productivity, but the strong background signals from the substrate greatly limit their applications in characterization and identification of organic compounds. Herein, we developed a one-step synthesis method to prepare silver nanoparticle substrates with ultralow SERS background using anionic ligands as stabilizing agents and applied the SERS substrate for the reliable and reproducible identification of typical organic pollutants and corresponding degradation intermediates. The synthesis method shows excellent universality to different reducing agents cooperating with different anionic ligands (Cl-, Br-, I-, SCN-). As model applications, the machine learning algorithm can realize the precise prediction of six organophosphorus pesticides and eight sulfonamide antibiotics with 100% accuracy based on SERS training data. More importantly, the ultralow-background SERS substrate enables one to detect and identify the time-dependent degradation intermediates of organophosphorus pesticides by combining them with density functional theory (DFT) calculations. All the results indicate that the ultralow-background SERS substrate will greatly push the development of SERS characterization applications.

A drug design strategy based on molecular docking and molecular dynamics simulations applied to development of inhibitor against triple-negative breast cancer by Scutellarein derivatives

Triple-negative breast cancer (TNBC), accounting for 10-15% of all breast malignancies, is more prevalent in women under 40, particularly in those of African descent or carrying the BRCA1 mutation. TNBC is characterized by the absence of estrogen and progesterone receptors (ER, PR) and low or elevated HER2 expression. It represents a particularly aggressive form of breast cancer with limited therapeutic options and a poorer prognosis. In our study, we utilized the protein of TNBC collected from the Protein Data Bank (PDB) with the most stable configuration. We selected Scutellarein, a bioactive molecule renowned for its anti-cancer properties, and used its derivatives to design potential anti-cancer drugs employing computational tools. We applied and modified structural activity relationship methods to these derivatives and evaluated the probability of active (Pa) and inactive (Pi) outcomes using pass prediction scores. Furthermore, we employed in-silico approaches such as the assessment of absorption, distribution, metabolism, excretion, and toxicity (ADMET) parameters, and quantum calculations through density functional theory (DFT). Within the DFT calculations, we analyzed Frontier Molecular Orbitals, specifically the Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO). We then conducted molecular docking and dynamics against TNBC to ascertain binding affinity and stability. Our findings indicated that Scutellarein derivatives, specifically DM03 with a binding energy of -10.7 kcal/mol and DM04 with -11.0 kcal/mol, exhibited the maximum binding tendency against Human CK2 alpha kinase (PDB ID 7L1X). Molecular dynamic simulations were performed for 100 ns, and stability was assessed using root-mean-square deviation (RMSD) and root-mean-square fluctuation (RMSF) parameters, suggesting significant stability for our chosen compounds. Furthermore, these molecules met the pharmacokinetics requirements for potential therapeutic candidates, displaying non-carcinogenicity, minimal aquatic and non-aquatic toxicity, and greater aqueous solubility. Collectively, our computational data suggest that Scutellarein derivatives may serve as potential therapeutic agents for TNBC. However, further experimental investigations are needed to validate these findings.

Intramolecular Repulsion Visible Through the Electrostatic Potential in Disulfides: Analysis via Varying Iso-density Envelopes

For a series of diethyl disulfide conformations, the nearly touching contours of the electrostatic potential plotted on iso-density molecular surfaces allow the assessment of intramolecular repulsion. The electrostatic potential is plotted on varying iso-density envelopes to find the nearly touching contours for which (a) the surface electrostatic potential does not show overlap between atoms or functional groups and (b) the typical features are visible (σ-hole, lone pair, hydrogen VS,max). When these nearly touching contours X are closer to the nuclei, the more electron density is excluded from the iso-density envelopes and the smaller are the volumes corresponding to these envelopes. Both the contours X and the corresponding volumes are found to correlate with relative conformational energy, reflecting the degree of intramolecular repulsion present in the various diethyl disulfides. Quantitative estimates of intramolecular repulsion can be made based on relationships between the nearly touching contour X vs relative energy and volume (of the nearly touching contour X) vs relative energy, obtained for series of diethyl disulfide conformers. These relations were used to analyze intramolecular repulsion in a set of disulfides broader than diethyl disulfide conformers. We have shown that the approach of varying electronic density contours can be used in the study of repulsive intramolecular interactions, hereby extending earlier work involving attractive intermolecular interactions.

Valence Bond Theory Allows a Generalized Description of Hydrogen Bonding

This paper describes the nature of the hydrogen bond (HB), B:---H-A, using valence bond theory (VBT). Our analysis shows that the most important HB interactions are polarization and charge transfer, and their corresponding sum displays a pattern that is identical for a variety of energy decomposition analysis (EDA) methods. Furthermore, the sum terms obtained with the different EDA methods correlate linearly with the corresponding VB quantities. The VBT analysis demonstrates that the total covalent-ionic resonance energy (RECS) of the HB portion (B---H in B:---H-A) correlates linearly with the dissociation energy of the HB, ΔEdiss. In principle, therefore, RECS(HB) can be determined by experiment. The VBT wavefunction reveals that the contributions of ionic structures to the HB increase the positive charge on the hydrogen of the corresponding external/free O-H bonds in, for example, the water dimer compared with a free water molecule. This increases the electric field of the external O-H bonds of water clusters and contributes to bringing about catalysis of reactions by water droplets and in water-hydrophobic interfaces.

Halogen Bonding Involving Isomeric Isocyanide/Nitrile Groups

2,3,5,6-Tetramethyl-1,4-diisocyanobenzene (1), 1,4-diisocyanobenzene (2), and 1,4-dicyanobenzene (3) were co-crystallized with 1,3,5-triiodotrifluorobenzene (1,3,5-FIB) to give three cocrystals, 1·1,3,5-FIB, 2·2(1,3,5-FIB), and 3·2(1,3,5-FIB), which were studied by X-ray diffraction. A common feature of the three structures is the presence of I···Cisocyanide or I···Nnitrile halogen bonds (HaBs), which occurs between an iodine σ-hole and the isocyanide C-(or the nitrile N-) atom. The diisocyanide and dinitrile cocrystals 2·2(1,3,5-FIB) and 3·2(1,3,5-FIB) are isostructural, thus providing a basis for accurate comparison of the two types of noncovalent linkages of C≡N/N≡C groups in the composition of structurally similar entities and in one crystal environment. The bonding situation was studied by a set of theoretical methods. Diisocyanides are more nucleophilic than the dinitrile and they exhibit stronger binding to 1,3,5-FIB. In all structures, the HaBs are mostly determined by the electrostatic interactions, but the dispersion and induction components also provide a noticeable contribution and make the HaBs attractive. Charge transfer has a small contribution (<5%) to the HaB and it is higher for the diisocyanide than for the dinitrile systems. At the same time, diisocyanide and dinitrile structures exhibit typical electron-donor and π-acceptor properties in relation to the HaB donor.

Coordination-Promoted Bio-Catechol Electro-Reforming toward Sustainable Polymer Production

Sustainable polymer production is essential for a carbon-neutral society. cis,cis-Muconic acid is attracting growing interest as a biomass-derived platform molecule with direct access to adipic acid and terephthalic acid, prominent monomers of commercial polymers. Here, a sustainable route of electro-reforming biorenewable catechol to cis,cis-muconic acid with concurrent H2 production has been proposed. By using a CuO foam electrode, a high cis,cis-muconate yield of 90% and a high faradaic efficiency of 87% can be achieved under ambient conditions without external oxidant. Zn2+ coordination with the catechol is central to the yield and selectivity. In a combinatory analysis via steady-state electrochemical kinetics, in situ spectroscopy, and theoretical calculation, we revealed that the reaction ensemble of catechol electrooxidation involves three major processes of polymerization, ring cleavage, and depolymerization, in which Zn2+ coordination is highly effective in delaying polymerization and promoting ring cleavage toward cis,cis-muconate. The catecholate coordinated to the Zn2+ cations reallocated its electron density with partial structural deformation to accelerate the electron transfer and facilitate the OH- nucleophilic attack. A practical two-electrode system was eventually demonstrated to efficiently and stably electro-reform catechol into isolable cis,cis-muconic acid and hydrogen, providing solutions for polymer sustainability via utilizing alternative biomass resources and electrified processes.

Effect of the isotiazole adjuvants in combination with cisplatin in chemotherapy of neuroepithelial tumors: experimental results and modeling

Chemotherapy is one of the main treatment options for cancer, but it is usually accompanied with negative side effects. The classical drugs combination with synergistic adjuvants can be the solution to this problem, allowing reducing therapeutic dose. Elucidating the mechanism of adjuvant action is of key importance for the selection of the optimal agent. Here we examine the system drug-adjuvant to explain the observed effect in practice. We used the first line drug cisplatin. Morpholinium and 4-methylpiperazinium 4,5-dichloro isothiazol-3-carboxylates were selected as adjuvants. The study of the cisplatin-adjuvant system was carried out by quantum chemical modeling using DFT. It turned out that adjuvants form conjugates with cisplatin that lead to the relocation of frontier molecular orbitals as well as increase of conjugate's dipole moment. It resulted in change of the interaction character with DNA and increase of the bioactivity of the system. The data obtained are the basis for expanding the studies to include other drugs and adjuvants. Oncologists will have opportunity to use "classical" chemotherapy drugs in combination with synergists for those patients who have not been previously recommended to such a treatment because of pronounced toxic side effects.

Theoretical Appraisal of Cyclopropenone: Aggregation and Complexes with Water

Cyclopropenone (HCCOCH, "CPN") is an exotic quasi-aromatic cyclic carbene that abounds in the interstellar medium (ISM). Astronomical observations suggest that (i) stagnate CPN exhibits a tendency to polymerize and that (ii) interactions may occur between CPN and water that is also ubiquitous in the ISM. In this light, density functional theory investigations reveal cooperative hydrogen bonding, which leads to stable polymeric conformations of (CPN)_n, tracked up to n = 14. Stable agglomerations with water, however, constitute at best only two CPN and two water molecules, signifying that while CPN exhibits remarkable cooperativity for "cohesive" clustering via hydrogen bonding, this tendency is markedly diminished for "hetero"-interactions. Multifaceted data are employed to probe cogent molecular descriptors, such as structure and energetics of various conformers, vibrational spectroscopic response, molecular electrostatic potential (MESP), effective atomic charges: all these, in unison, describe the evolution of the characteristics upon cluster formation. Salient stretching frequency shifts, as well as charge redistribution gleaned from MESP morphology, have a direct bearing on variegated hydrogen bonding patterns: linear, nonlinear, as well as bifurcated. In particular, characteristic C-H, C═O stretching, and O-H vibrations in the water complexes reveal a "softening" (downshift) of frequencies. While small conformers have markedly distinct MESP variations, the differences become less pronounced with incremental clustering, an effect substantiated by corresponding emergent atomic charges.

Interaction of glycine with Li+ in the (H2O)n (n = 0-8) clusters

CONTEXT

We investigated the interaction between glycine and Li⁺ in water environment based on the Gly·Li⁺(H₂O)_n (n = 0-8) cluster. Our study shows that for Gly·Li⁺, Li⁺ binds to both carbonyl oxygen and amino nitrogen to form a bidentate structure, and the first three water molecules preferentially interact with Li⁺. For n = 0-5, the complexes of Gly·Li⁺(H₂O)_n exist in neutral form, and when the water number reached 6, the complex can coexist in neutral and zwitterionic form, then zwitterionic structures are dominant for n = 7, 8. The analyses by RDG, AIM, and ESP in conjunction with the calculated interaction energies show that the interaction between Li⁺ and Gly decreases gradually with the water molecules involved successively from n = 1 to 6 and then increases for n = 7-8. Additionally, the infrared spectra of Gly·Li⁺(H₂O)_n (n = 0-8) are also calculated.

METHODS

The initial structures were optimized using Gaussian 09 program package in B3LYP-D3 (BJ)/6-311G(d, p) method, and the frequency was calculated with 6-311 + G(2d, p) basis set. GaussView5.0.9 was used to view simulation infrared spectra. The noncovalent interaction method (NCl), energy decomposition (EDA), atoms in molecules (AIM) analysis, and electrostatic potential (ESP) analyses were conducted using Multiwfn software to gain a deeper understanding of the interaction properties of Gly, Li⁺, and water.

A Wide Bandgap Acceptor with Large Dielectric Constant and High Electrostatic Potential Values for Efficient Organic Photovoltaic Cells

Low-bandgap materials have achieved rapid development and promoted the enhancement of power conversion efficiencies (PCEs) of organic photovoltaic (OPV) cells. However, the design of wide-bandgap non-fullerene acceptors (WBG-NFAs), required by indoor applications and tandem cells, has been lagging far behind the development of OPV technologies. Here, we designed and synthesized two NFAs named ITCC-Cl and TIDC-Cl by finely optimizing ITCC. In contrast with ITCC and ITCC-Cl, TIDC-Cl can maintain a wider bandgap and a higher electrostatic potential simultaneously. When blending with the donor PB2, the highest dielectric constant is also obtained in TIDC-Cl-based films, enabling efficient charge generation. Therefore, the PB2:TIDC-Cl-based cell possessed a high PCE of 13.8% with an excellent fill factor (FF) of 78.2% under the air mass 1.5G (AM 1.5G) condition. Furthermore, an exciting PCE of 27.1% can be accomplished in the PB2:TIDC-Cl system under the illumination of 500 lux (2700 K light-emitting diode). Combined with the theoretical simulation, the tandem OPV cell based on TIDC-Cl was fabricated and exhibited an excellent PCE of 20.0%.

Halogen bonds, chalcogen bonds, pnictogen bonds, tetrel bonds and other σ-hole interactions: a snapshot of current progress

We report here on the status of research on halogen bonds and other σ-hole interactions involving p-block elements in Lewis acidic roles, such as chalcogen bonds, pnictogen bonds and tetrel bonds. A brief overview of the available literature in this area is provided via a survey of the many review articles that address this field. Our focus has been to collect together most review articles published since 2013 to provide an easy entry into the extensive literature in this area. A snapshot of current research in the area is provided by an introduction to the virtual special issue compiled in this journal, comprising 11 articles and entitled `Halogen, chalcogen, pnictogen and tetrel bonds: structural chemistry and beyond.'

Efficient Synthesis, Spectroscopic Characterization, and Nonlinear Optical Properties of Novel Salicylaldehyde-Based Thiosemicarbazones: Experimental and Theoretical Studies

Currently, we reported the synthesis of six novel salicylaldehyde-based thiosemicarbazones (BHCT1-HBCT6) via condensation of salicylaldehyde with respective thiosemicarbazide. Through various spectroscopic methods, UV-visible and NMR, the chemical structures of BHCT1-HBCT6 compounds were determined. Along with synthesis, a computational study was also performed at the M06/6-31G(d,p) functional. Various analyses such as natural bond orbital (NBO) analysis, natural population analysis, frontier molecular orbital (FMO) analysis, and molecular electrostatic potential surfaces were carried out to understand the nonlinear optical (NLO) characteristics of the synthesized compounds. Additionally, a comparative study was carried out between DFT and experimental results (UV-vis study), and a good agreement was observed in the results. The energy gap calculated through FMOs was found to be in decreasing order as 4.505 (FHCT2) > 4.499 (HBCT6) > 4.497 (BHCT1) = 4.497(HMCT5) > 4.386 (CHCT3) > 4.241(AHCT4) in eV. The global reactivity parameters (GRPs) were attained through E _HOMO and E _LUMO, which described the stability and hardness of novel compounds. The NBO approach confirmed the charge delocalization and stability of the molecules. Among all the investigated compounds, a larger value (557.085 a.u.) of first hyperpolarizability (β_tot) was possessed by CHCT3. The NLO response (β_tot) of BHCT1-HBCT6 was found to be 9.145, 9.33, 13.33, 5.43, 5.68, and 10.13 a.u. times larger than that of the standard para-nitroaniline molecule. These findings ascertained the potential of entitled ligands as best NLO materials for a variety of applications in modern technology.

Cocrystallization of Antifungal Compounds Mediated by Halogen Bonding

The application of halogen bonding in pharmaceutical chemistry remains a challenge. In this work, novel halogen-bonded cocrystals based on azole antifungal active pharmaceutical ingredients (APIs) and the ditopic molecule 1,4-diiodotetrafluorobenzene are reported. Their crystal structural features, spectroscopic properties, and thermal stability were studied. The components are bound through I···N from the triazole moieties present in all of the compounds. The molecular electrostatic potential (MEP) surfaces and quantum theory of atoms in molecules (QTAIM) calculations are used to rationalize the presence of hydrogen and halogen bonds in the resulting structures and their energetic analysis. The relative halogen bond ability of the different groups of voriconazole, fluconazole, and itraconazole was analyzed using MEP surfaces, demonstrating this approach to be an interesting tool to predict halogen-bonding preferences.

Metal Atoms (Li, Na, and K) Tuning the Configuration of Pyrrole for the Selective Recognition of C60

Host-guest structure assembly is significant in the recognition of molecules, and the fullerene-based host-guest structure is a convenient method to determine the structures of fullerenes of which recognition is with many difficulties in experiments. Here, with density functional theory calculations, we designed several crown-shaped pyrrole-based hosts tuned by doping metal atoms (Li, Na, and K) for the effective recognition of C₆₀ with modest interaction between the host and guest. Binding energy calculations showed an enhanced interaction of the concave-convex host-guest system with the doped metal atoms, enabling the selective recognition of C₆₀. The electrostatic interaction between the host and guest was studied by the natural bond order charge analysis, reduced density gradient, and electrostatic potential. Furthermore, the UV-vis-NIR spectra of host-guest structures were simulated to give guidance on the release of the fullerene guest. With much expectation, this work would give a new strategy to design new hosts for effectively recognizing much more fullerene molecules with modest interaction and would be useful for the assembly involving fullerenes.

Activation of metal-involved halogen bonds and classical halogen bonds in gold(I) catalysis

In gold(I) catalysis, the activation of Au(I) chloride catalysts via chloride abstraction and noncovalent interactions has become a research focus in organometallic catalysis. In this work, taking halogen bond donors (C₄H₂INO₂, C₆F₅I, C₈H₉O₂I) as activators for a Au(I) chloride catalyst (Ph₃PAuCl), the mechanism of the cyclization reaction of propargylic amide was investigated. It was found that there are two activation modes as design principles to obtain the catalytically active species Ph₃PAu⁺: the halogen bond donors activate the Cl atoms of Ph₃PAuCl to form X-I⋯Cl (X = C, N) classical halogen bonds and activate the Au atoms of Ph₃PAuCl to form X-I⋯Au (X = C, N) metal-involved halogen bonds. For the two activation modes, the mechanism of the cyclization reaction of propargylic amide has pathways: the chloride abstraction process of the first step and the 5-exo/6-endo cyclization process of the second step. Both activation modes show good activity for the cyclization reaction with the activation ability of classical halogen bonds being slightly stronger than that of the metal-involved halogen bonds, which is consistent with the strength of the X-I⋯Cl halogen bonds being slightly stronger than that of the X-I⋯Au halogen bonds. Therefore, both metal-involved halogen bonds and classical halogen bonds have important development prospects for the activation of catalysts in gold(I) catalysis.