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• BVOCs emissions in a subtropical pristine forest of southern China were measured in situ by using dynamic branch enclosures. • Representative mature evergreen trees were measured at four altitudes. • Monoterpenes were the dominant BVOCs emitted by most broad-leaved trees. • Localized emission factors of speciated BVOCs were obtained. Emission characteristics of biogenic volatile organic compounds (BVOCs) from dominant tree species in the subtropical pristine forests of China are extremely limited. Here we conducted in situ field measurements of BVOCs emissions from representative mature evergreen trees by using dynamic branch enclosures at four altitude gradients (600–1690 m a.s.l.) in the Nanling Mountains of southern China. Composition characteristics as well as seasonal and altitudinal variations were analyzed. Standardized emission rates and canopy-scale emission factors were then calculated. Results showed that BVOCs emission intensities in the wet season were generally higher than those in the dry season. Monoterpenes were the dominant BVOCs emitted from most broad-leaved trees, accounting for over 70% of the total. Schima superba, Yushania basihirsuta and Altingia chinensis had relatively high emission intensities and secondary pollutant formation potentials. The localized emission factors of isoprene were comparable to the defaults in the Model of Emissions of Gases and Aerosols from Nature (MEGAN), while emission factors of monoterpenes and sesquiterpenes were 2 to 58 times of those in the model. Our results can be used to update the current BVOCs emission inventory in MEGAN, thereby reducing the uncertainties of BVOCs emission estimations in forested regions of southern China. [Display omitted] [ABSTRACT FROM AUTHOR]

Bioactive peptides are short amino acid sequences that play important roles in various physiological processes, including antioxidant and protective effects. These compounds can be obtained through protein hydrolysis and have a wide range of potential applications in a variety of areas. However, despite the potential of these compounds, more in-depth knowledge is still necessary to better understand details regarding their chemical reactivity and electronic properties. In this study, we used molecular modeling techniques to investigate the electronic structure of isolated amino acids (AA) and short peptide sequences. Details on the relative alignments between the frontier electronic levels, local chemical reactivity and donor–acceptor properties of the 20 primary amino acids and some di- and tripeptides were evaluated in the framework of the density functional theory (DFT). Our results suggest that the electronic properties of isolated amino acids can be used to interpret the reactivity of short sequences. We found that aromatic and charged amino acids, as well as Methionine, play a key role in determining the local reactivity of peptides, in agreement with experimental data. Our analyses also allowed us to identify the influence of the relative position of AA and terminations on the local reactivity of the sequences, which can guide experimental studies and help to propose/evaluate possible mechanisms of action. In summary, our data indicate that the position of active sites of polypeptides can be predicted from short sequences, providing a promising strategy for the synthesis and bioprospection of new optimized compounds. [ABSTRACT FROM AUTHOR]

Fukui functions are related to electron densities, and their interpretation permits the determination of reactivity of atomic centres. However, negative values cannot be interpreted by an "electron density based" model and represent a phenomenon that has been little investigated and understood. Previous works in the literature suggest that they are related to nodes in the wave function. In our investigations we can relate negative values to nitro groups and their position on aromatic systems, as it is a moiety with HOMO electron densities close to "0" related to "electron attracting" groups. This work can help us understand and predict this phenomenon and the associated chemical reactivities. We also pay attention to the influence of the nitro group angle vs. the aromatic ring. [ABSTRACT FROM AUTHOR]

In this work, we introduce the q-Rényi's divergence, which results from the conjunction of Rényi's divergence and Jackson's integral. The resultant equation can be employed as a measure of chemical similarity, which consists of comparing two or more chemical species with a set of molecules that have been characterized to find two or more molecules that could have similar chemical or physical properties. To carry out our study, we applied q-Rényi's divergence using a set of Tetrodotoxin variants and a set of 1641 organic molecules. Our results suggest that q-Rényi's divergence could be a valuable tool to complement chemical similarity studies. [ABSTRACT FROM AUTHOR]

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 . [ABSTRACT FROM AUTHOR]

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Density functional theory (DFT) was used to study the mechanism of Diels–Alder (DA) reaction between 2‐Methyl‐ 1,3 Butadiene (MBD) with B12N12, B6N6C12 and B6C12N6 fullerens in the gas phase. In this mechanism, B‐N bonds of four‐membered and six‐membered rings of nanocages were chosen to react with MBD. Due to the existence of two types of B‐N bonds, two competitive pathways (a and b) were investigated. The effect of the substitution of carbon atoms instead of boron and nitrogen atoms on the stability of the structures and the regioselectivity of the DA reaction was examined. The potential energy of all structures and the activation barrier for all reaction pathways was evaluated. The chemical reactivity of fullerens using the molecular quantum descriptors was assessed. To evaluate the global electron density transfer in transition states (TS) structures, the natural bond orbital (NBO) analysis was performed. [ABSTRACT FROM AUTHOR]

Silymarin has been utilized as a traditional, complementary, and integrative medicine for centuries, despite a poor molecular‐level understanding of its interactions with other medicinal compounds and enzyme structures. However, recent studies indicate that this supplement, as with many others, should be considered with caution because it has the potential to interact with many drugs, medical plants, and foods. Silymarin is composed of several compounds that are either enantiomeric or have similar structures. Thus, this study presents the electronic structure properties and reactivity characteristics of silymarin components and warfarin through density functional theory modeling at the M06‐2X/6–311 + G(d,p) level of theory. The ligand‐protein interactions of the compounds with human serum albumin, cytochrome P450 (CYP2C9, CYP2C19, CYP2D6, and CYP3A4) enzymes, and alanine transaminase were presented using molecular docking. The critical residue‐based interactions of silymarin components and warfarin were fingerprinted. Furthermore, their drug‐likeness and toxicity characteristics were compared to those of warfarin and the well‐known flavonoids, taxifolin, and quercetin. The possibility of inhibiting the target enzymes to reduce the effectiveness of warfarin has been highlighted. [ABSTRACT FROM AUTHOR]

Plasma activated water (PAW) has been prepared using atmospheric pressure air dielectric barrier discharge with the bubbling method. This study aims to elucidate the crucial role of gas-liquid interface in determining the physicochemical properties and biological reactivity of PAW, as well as describe the process of mass transfer for reactive oxygen and nitrogen species (RONS) during the PAW generation. Gas-liquid interfacial area is regulated by varying the airflow rate. When the airflow rate increases from 0.5 to 16.0 SLM, the concentrations of , , and activated oxygen in PAW increase significantly, and the water-activated time for complete E. coli inactivation can be shortened from more than 320 s to 40 s. The numerical simulation result shows that when the airflow rate increases from 0.5 to 16.0 SLM, the gas-liquid interfacial area increases from 0.014 to 0.3 m2/600 mL. The analysis shows that the dependence of the chemical reactivity and the biological reactivity on the interface area is mainly attributed to the change of the mass flux with the interface area. [ABSTRACT FROM AUTHOR]

AbstractA novel heterocyclic compound named (Z)-5-(4-nitrobenzylidene)-3-N(3-chlorophenyl)-2-thioxothiazolidin-4-one (NCTh) was synthesized and analyzed using various techniques, including single crystal X-ray diffraction, FT-IR, UV-Vis, NMR spectroscopy, and mass spectral data methods. NCTh was observed to crystallize in the triclinic crystal system P-1 space group. To validate the experimental findings, density functional theory (DFT) calculations were performed using the B3LYP functional with the 6-311 G(d,p) basis set. The results indicated good agreement in geometrical parameters between the experimental and theoretical outcomes. The study also calculated HOMO-LUMO energies, molecular electrostatic potential (MEP), and global chemical reactivity descriptors to evaluate the compound’s reactivity. Additionally, the study conducted reduced density gradient and Hirshfeld surface analyses to reveal attractive, repulsive, and van der Waals strong and weak interactions. The calculation of thermodynamic parameters was also included. The study focused on investigating the nonlinear optical (NLO) properties of NCTh, which were characterized through key parameters such as the electric dipole moment (µ), polarizability (α), first-order hyperpolarizability (β), and second-order hyperpolarizability (γ). These properties provide insights into the material’s potential applications in optical and photonic technologies. Additionally, a molecular docking study was performed to further explore the structure-activity relationship, particularly in a biological context. The docking results revealed a strong ligand-protein interaction, with a binding energy of −10.3 kcal/mol, indicating significant affinity. Moreover, the inhibition constant (Ki) was calculated to be 0.0281 μM, suggesting a highly potent interaction, which could be relevant for drug design or biochemical applications. [ABSTRACT FROM AUTHOR]

The dissociation of methane is not only an important reaction step in catalytic processes, but also of fundamental interest. Dynamical effects during the dissociative chemisorption of methane on metal surfaces cause significant differences in computed reaction rates, compared to what is predicted by typical transition state theory (TST) models. It is clear that for a good understanding of the catalytic activation of methane dynamical simulations are required. In this paper, a general blueprint is provided for performing dynamical simulations of the dissociative chemisorption of methane on metal surfaces, by employing either the quasi-classical trajectory or ring polymer molecular dynamics approach. If the computational setup is constructed with great care-since results can be affected considerably by the setup - chemically accurate predictions are achievable. Although this paper concerns methane dissociation, the provided blueprint is, so far, applicable to the dissociative chemisorption of most molecules. [ABSTRACT FROM AUTHOR]

The pozzolanic reaction of fly ashes with calcium-based additives can be effectively used to solidify and chemically stabilize (S&S process) highly concentrated brines inside a cementitious matrix. However, complex interactions between the fly ash, the additive, and the brine typically affect the phases formed at equilibrium, and the resulting solid capacity to successfully encapsulate the brine and its contaminants. Here, the performances of two types of fly ash (a Class C and Class F fly ash) are assessed when combined with different additives (two types of cement, or lime with and without NaAlO2), and two types of brine (NaCl or CaCl2) over a range of concentrations (0 ≤ [Cl-] ≤ 2 M). The best performing matrices - i.e., the matrices with the highest Cl-containing phases content - were identified using XRD and TGA. The experimental results were then combined with thermodynamic modeling to dissociate the contribution of the fly ash from that of the additives. All results were implemented in a machine learning model that showed good accuracy at predicting the fly ash degree of reaction, allowing for the robust prediction of extended systems performance when combined with thermodynamic modeling.

Abstract Synthetic accessibility prediction is a task to estimate how easily a given molecule might be synthesizable in the laboratory, playing a crucial role in computer-aided molecular design. Although synthesis planning programs can determine synthesis routes, their slow processing times make them impractical for large-scale molecule screening. On the other hand, existing rapid synthesis accessibility estimation methods offer speed but typically lack integration with actual synthesis routes and building block information. In this work, we introduce BR-SAScore, an enhanced version of SAScore that integrates the available building block information (B) and reaction knowledge (R) from synthesis planning programs into the scoring process. In particular, we differentiate fragments inherent in building blocks and fragments to be derived from synthesis (reactions) when scoring synthetic accessibility. Compared to existing methods, our experimental findings demonstrate that BR-SAScore offers more accurate and precise identification of a molecule's synthetic accessibility by the synthesis planning program with a fast calculation time. Moreover, we illustrate how BR-SAScore provides chemically interpretable results, aligning with the capability of the synthesis planning program embedded with the same reaction knowledge and available building blocks. Scientific contribution We introduce BR-SAScore, an extension of SAScore, to estimate the synthetic accessibility of molecules by leveraging known building-block and reactivity information. In our experiments, BR-SAScore shows superior prediction performance on predicting molecule synthetic accessibility compared to previous methods, including SAScore and deep-learning models, while requiring significantly less computation time. In addition, we show that BR-SAScore is able to precisely identify the chemical fragment contributing to the synthetic infeasibility, holding great potential for future molecule synthesizability optimization.

Context: Constrained methods in electronic structure methodologies add terms to the variational equations and generate solutions that represent distorted electronic distributions. In some cases, the new solutions can be used to study the chemical reactivity of parts of the molecule. Additionally, this contribution presents the use of population constraints to define pseudo atoms in a molecule. The effects of the pseudo atom on the molecular properties are analyzed. The pseudo atoms are used to simulate the inductive effect of the substituent in a group of carbonyl molecules and their effect on the stability of the complexes between these organic species and one molecule of water. A discussion on the assumptions involved in the present definition of pseudo atoms is also included. Method: The constrained RHF computations are done in a modified Hartree-Fock code for Gaussian basis sets. The selected basis set is STO-6 G. [ABSTRACT FROM AUTHOR]

Catalytic performance of zirconyl hydrogen tellurate (ZrOHTe) and hafnium hydrogen tellurate (HfHTe) was studied for the first time. A process of butyl acetate synthesis was used as a test reaction. A number of physicochemical techniques (XRD, SEM, TGA/DSC and XPS) was applied for catalyst characterization. Using molecular electrostatic potential and net atomic charges, both the electronic structure and the chemical reactivity of ZrOHTe and HfHTe were considered. Kinetic (activation energy, pre-exponential factor) and thermodynamic (enthalpy, entropy, Gibbs free energy barrier) parameters were calculated. A plausible reaction mechanism for esterification was offered. Particles of a low crystallinity degree or small-sized crystallites were found to form ZrOHTe and HfHTe. The fragments in ZrOHTe/HfHTe are prismatic/layered in shape with an average size around 160 μm. XPS exposed that HTeO 4 - managed the surface phenomena for ZrOHTe and HfHTe. A higher butyl acetate yield using ZrOHTe than HfHTe due to higher surface acidity of the former was generated. [ABSTRACT FROM AUTHOR]

Synthetic accessibility prediction is a task to estimate how easily a given molecule might be synthesizable in the laboratory, playing a crucial role in computer-aided molecular design. Although synthesis planning programs can determine synthesis routes, their slow processing times make them impractical for large-scale molecule screening. On the other hand, existing rapid synthesis accessibility estimation methods offer speed but typically lack integration with actual synthesis routes and building block information. In this work, we introduce BR-SAScore, an enhanced version of SAScore that integrates the available building block information (B) and reaction knowledge (R) from synthesis planning programs into the scoring process. In particular, we differentiate fragments inherent in building blocks and fragments to be derived from synthesis (reactions) when scoring synthetic accessibility. Compared to existing methods, our experimental findings demonstrate that BR-SAScore offers more accurate and precise identification of a molecule's synthetic accessibility by the synthesis planning program with a fast calculation time. Moreover, we illustrate how BR-SAScore provides chemically interpretable results, aligning with the capability of the synthesis planning program embedded with the same reaction knowledge and available building blocks. Scientific contribution We introduce BR-SAScore, an extension of SAScore, to estimate the synthetic accessibility of molecules by leveraging known building-block and reactivity information. In our experiments, BR-SAScore shows superior prediction performance on predicting molecule synthetic accessibility compared to previous methods, including SAScore and deep-learning models, while requiring significantly less computation time. In addition, we show that BR-SAScore is able to precisely identify the chemical fragment contributing to the synthetic infeasibility, holding great potential for future molecule synthesizability optimization. [ABSTRACT FROM AUTHOR]

Recent advances in machine learning offer powerful tools for exploring complex reaction mechanisms in condensed phases via reactive simulations. In this tutorial review, we describe the key challenges associated with simulating reactions in condensed phases, we introduce neural network potentials and detail how they can be trained. We emphasize the importance of active learning to construct the training set, and show how these reactive force fields can be integrated with enhanced sampling techniques, including transition path sampling. We illustrate the capabilities of these new methods with a selection of applications to chemical reaction mechanisms in solution and at interfaces.

Hypersaline brines can be solidified and stabilized via the hydraulic and pozzolanic reactions between fly ash(es) and calcium-based additives. Although recent work has examined fly ash reactivity in single-salt ("simple") hypersaline brines (ionic strength, Im > 1 mol/L), the effects of mixed-salt solutions on fly ash reactivity remain unclear. Herein, the reactivity of a Class C (calcium oxide [CaO]-rich) or Class F (CaO-poor) fly ash mixture with calcium hydroxide is reacted in solutions bearing sodium chloride (NaCl), calcium chloride (CaCl2), magnesium chloride (MgCl2), sodium sulfate (Na2SO4), or combinations thereof for 1.5 ≤ Im ≤ 2.25 mol/L, from 1 week until 24 weeks. Expectedly, sulfate anions promote the formation of sulfate phases (i.e., ettringite, monosulfoaluminate, U-phase), while chloride anions induce the formation of Cl-AFm compounds (i.e., Kuzel's and Friedel's salt). Although the Class C fly ash's reactivity is similar across different anions (for a fixed cation and Im), Class F fly ash shows a small change in reactivity depending on the anion present. NaCl suppresses (Class C and Class F) fly ash reactivity by up to 30 % as compared to neat CaCl2 and MgCl2-based brines. Thermodynamic modeling reveals that NaCl induces a considerable increase in pH-up to 13.7, where many hydrated phases of interest cease to be the major phase expected-as compared to CaCl2 and MgCl2 brines (pH < 13). In mixed-salt brines, anion immobilization is competitive: Sulfate achieves a greater level of incorporation into the hydrates, as compared to chloride. These results offer new understanding of how the brine composition affects solidification and stabilization and thereby yield new insight into improved approaches for wastewater disposal.

Benzophenone and its derivatives are widely used as UV filters and UV‐ink photoinitiators. The photoinitiating properties of benzophenones depend on their degree of conjugation and delocalization within the molecule. By understanding how conjugation, delocalization, and different substituents affect these properties, benzophenone derivatives can be customized for specific applications. Using quantum mechanical calculations based on B3LYP/6‐311++G(d, p) density functional theory (DFT), chemical reactivity, stability, and photoinitiating capabilities of 4‐(4‐methylphenylthio)benzophenone are analyzed. This includes studying its physical and chemical properties in the gas phase, as well as its excited state electronic transitions, vibrational characteristics, and spectroscopic properties both in gas phase and in various solvents. The DFT‐computed infrared spectra match experimental results. The UV/Visible spectra shows absorption towards longer wavelengths due to extended delocalization of π‐electrons. In different solvents with varying polarity, the absorption spectra exhibit high‐intensity peaks, shift in excitation energy and wavelengths based on the polarity of the solvent. This knowledge allows for the development of novel initiators with customized light absorption, excited state lifetimes, and reaction selectivities, which can enhance processes like UV‐curing, photopolymerization, and other light‐driven reactions. [ABSTRACT FROM AUTHOR]

The reactivity of 22 unsaturated molecules undergoing attack by a methyl radical (⋅CH3) have been elucidated using the condensed radical general‐purpose reactivity indicator (condensed radical GPRI) appropriate for relatively nucleophilic or electrophilic molecules. Using the appropriate radical GPRI equation for electrophilic attack or nucleophilic radical attack, seven different population schemes were used to assign the most reactive atoms in each of the 22 molecules. The results show that the condensed radical GPRI is sensitive to the population scheme chosen, but less sensitive than the radical Fukui function. Therefore, the reliability of these methods depends on the population scheme. Our investigation indicates that the condensed radical GPRI is most accurate in predicting the dominant products of the methyl radical addition reactions on a variety of unsaturated molecules when the Hirshfeld, Merz–Singh–Kollman, or Voronoi deformation density population schemes are used. Furthermore, for all populations schemes in the majority of instances where the radical Fukui function failed the radical GPRI was able to identify the most reactive atom under certain reactivity conditions. [ABSTRACT FROM AUTHOR]

The antimicrobial activity and molecular reactivity of two phenylthiosemicarbazone ligands containing the thiophenyl nuclues (L1 & L2) with their Cu(II) complexes have been investigated. The thiosemicarbazone ligands 1 2 were obtained by condensing 4-phenylthiosemicarbazone with 2-thiophene carboxaldehyde and 3-methyl-2-thiophene carboxaldehyde respectively. The antimicrobial activity of the ligands and the metal complexes were evaluated using gram-positive and gram-negative bacterial strains. In addition the compounds were further characterised with various global molecular reactivity descriptors using DFT calculations. The compounds exhibited mild inhibition against the bacterial strains, especially Staphylococus aureus and Escherichiia coli. In addition, the activity of the uncomplexed thiosemicarbazones became enhanced upon chelation with Cu(II) ions. The DFT studies showed that ligand L is more reactive than L and the energy gaps for the complexes were 1 2 0.936 eV and 1.103 eV for [CuL1] and [CuL2] respectively. Furthermore, the results showed that the copper(II) 1 2 complexes are soft molecules having higher molecular reactivity, high electro-optic responses and low kinetic stability than their respective ligands. [ABSTRACT FROM AUTHOR]

It would be very beneficial to have a method for joining of ceramics to titanium reliably. Although several techniques have been developed and tested to prevent extensive interfacial chemical reactions in titanium‐ceramic systems, the main problem of the inherent brittleness of interfaces was still unsolved. To overcome this problem also in dental applications, we decided to make use of an interlayer material that needs to meet the following requirements: First, it has to be biocompatible, second, it should not melt below the bonding temperatures, and third, it should not react too strongly with titanium, so that its plasticity will be maintained. Considering possible material options only the metals: gold, platinum, palladium, and silver, fulfill the first and second requirements. To find out—without an extensive experimental testing program—which of the four metals fulfills the third requirement best, the combined thermodynamic and reaction kinetic modeling was employed to evaluate how many and how thick reaction layers are formed between the interlayer metals and titanium. With the help of theoretical modeling, it was shown that silver fulfills the last requirement best. However, before starting to test experimentally the effect of the silver layer on the mechanical integrity of dental ceramic/Ag/Ti joints it was decided to make use of mechanical analysis of the three‐point bending test, the result of which indicated that the silver layer increases significantly the bond strength of the joints. This result encouraged us to develop a new technique for plating silver on titanium. Subsequently, we executed numerous three‐point bending tests, which demonstrated that silver‐plated titanium‐ceramic joints are much stronger than conventional titanium‐ceramic joints. Hence, it can be concluded that the combined thermodynamic, reaction kinetic, and mechanical modeling method can also be a very valuable tool in medical research and development work. [ABSTRACT FROM AUTHOR]

In this study, we introduce a novel definition for the electrophilic descriptor. Following the proposal of other researchers, the foundation of our approach lies in expanding the change in the energy of an electronic system using a third‐order Taylor series, leading to the integration of hyperhardness into the formulation of the electrophilic descriptor. To validate our results, we conducted a comparative analysis of reactivity sequences among 35 electrophilic systems with known reactivities, as reported in external experimental studies. The electrophilic descriptor demonstrated a remarkable ability to accurately replicate the relative reactivities of the compounds under consideration, surpassing predictions based solely on the electrophilicity index. These findings underscore the significance of incorporating hyperhardness as a crucial reactivity descriptor. Additionally, our study provides interesting insights into the interpretation of this concept. [ABSTRACT FROM AUTHOR]

Employing the formalism of the joint density functional theory (JDFT) in the grand canonical ensemble, this paper studies the electronic structure and relative reactivity of an hydroxyl radical adsorbed on the surface of three different metal oxides that share the rutile-type structure and the (110) crystal plane; these materials are electrodes used in electrochemical advanced oxidation processes which consist in the generation of hydroxyl radicals, highly reactive species, that are able to oxidize organic compounds to CO 2 , making these anodes efficient for wastewater treatment. By analyzing the changes in the average number of electrons as a function of the applied chemical potential at fixed external potential, we studied two reactivity indices from conceptual density functional theory: global and local softness, to help us understand the differences between these materials, additionally we propose a new scheme to approximate the redox properties of clean surfaces or surfaces in contact with different adsorbed molecules so that these values can be arranged in a relative potential scale which would allow direct comparison with experimental results. [ABSTRACT FROM AUTHOR]

Context Finding catalysts that do not rely on the use of expensive metals is one of the requirements to achieve sustainable production. The reactivity of graphene doped with 3d transition metals was studied. All dopants enhanced the reactivity of graphene and performed better than Stone–Wales defects and divacancies, but were inferior to monovacancies. For hydrogenation of doped-monovacancies, Sc, Ti, Cr, Co, and Ni induced more prominent reactivity on the carbon atoms. However, the metals were the most reactive center for V, Mn, and Fe-doped graphene. Cu and Zn turned the four neighboring carbon atoms into the preferred sites for hydrogenation. The addition of oxygen to doped graphene with Ti, V, Cr, Mn, Fe, Co, and Ni on a monovacancy revealed a more uniform pattern since the metal, preferred to react with oxygen. However, Sc induced a larger reactivity on the carbon atoms. The afnity of the 3d metal-doped graphene systems towards oxygen was inferior to that observed for single-vacancies. Therefore, vacancy engineering is the most favorable and least expensive method to enhance the reactivity of graphene. Methods We applied Truhlar’s M06-L method accompanied by the 6-31G* basis sets to perform periodic boundary conditions calculations as implemented in Gaussian 09. The ultrafne grid was employed and the unit cells were sampled employing 100 k-points. Results were visualized employing Gaussview 5.0.1 [ABSTRACT FROM AUTHOR]

Plenty of traditional and novel sintering techniques have been utilized to enhance the performance of perovskite materials. Among several sintering methods, electric field-assisted spark plasma sintering (SPS) is a modern category and has been effective for the excellent functionalities of perovskite compounds. The state-of-the-art SPS systems, perovskite materials development, and corresponding design are focused. This article will highlight the parameters of this technique, the advanced procedure of sintering, and their respective effects on the densification and dielectric performance of ABO3 perovskite materials. No such work has been reported to relate the crystalline nature of the various functional perovskites with the spark plasma sintering procedures. This review illustrates a good compilation of recently reported few perovskite materials processed by spark plasma sintering and relationships between thermal effects, density, and dielectric performance. The enhanced density, high dielectric permittivity, and low dielectric loss were achieved due to SPS.

The investigation into a prospective pharmaceutical chalcone derivative employs a comprehensive methodology, integrating theoretical and empirical analyses. Rigorous scrutiny of the compound's distinct attributes is conducted through FT-IR, NMR and UV–Vis spectroscopy. Utilizing Density Functional Theory (DFT), specifically B3LYP/6–311++G(d,p), yields crucial insights into the potential energy surface, molecular structure optimization, vibrational properties, and electronic configuration stability. The study establishes correlations between simulated and actual spectra, and Frontier Orbital Theory (FMOs) explores the compound's chemical properties and electron-hole excitation across various solvents. The lowest energy gaps are observed in UV–visible and HOMO-LUMO analyses for various solvent effects between 3.7 to 3.8 eV Intra-molecular analysis through Natural Bond Orbitals (NBO) is complemented by the calculation and molecular electrostatic potential (MEP) and local descriptors like Fukui functions (f+, f−, f0), alongside topological analyses. Molecular docking is performed for different antifungal protein receptors (6EYY, 3DD4, 7YQP and 3WIX). The lowest binding energies of -8.89, -7.95 and -7.85 Kcal/mol were observed for the receptors 6EYY, 3DD4 and 7YQP. This facet of the research suggests promising pharmaceutical applications for the compound.

The present work focuses on the structural properties, spectroscopic signatures, intermolecular hydrogen bonding interactions, chemical and biological activity of nicotinamide (NIC) based on its monomeric and trimeric models using density functional theory and vibrational spectroscopy. FT-IR and FT-Raman spectra were obtained using the double-side forward-backward acquisition mode under vacuum. UV-Vis absorption spectra were recorded in methanol and compared with the calculated values. Geometry optimization and vibrational wavenumbers were obtained with the aid of Gaussian 09 program packages. The structural analysis of NIC revealed that the trimeric model was in better agreement with the experimental values than the monomer due to the incorporation of nearest hydrogen bond interactions. Spectroscopic results showed that NH2 and C = O groups of NIC were involved in intermolecular interactions in the trimeric model. The natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) analyses determined the presence, strength as well as nature of the hydrogen bonds were partially covalent. The lesser value of the HOMO-LUMO energy gap for the trimeric model indicated higher reactivity than monomer. Moreover, chemical reactivity was calculated using molecular electrostatic potential surface (MESP) and reactivity descriptors. The docking studies for NIC with several targets explored its biological activity. [ABSTRACT FROM AUTHOR]

Compartmentalization and binding‐triggered conformational change regulate many metabolic processes in living matter. Here, we have synergistically combined these two biorelevant processes to tune the Diels‐Alder (DA) reactivity of a synthetic self‐complexing host‐guest molecular switch CBPQT4+‐Fu, consisting of an electron‐rich furan unit covalently attached to the electron‐deficient cyclobis(paraquat‐p‐phenylene) tetrachloride (CBPQT4+, 4Cl−) host. This design allows CBPQT4+‐Fu to efficiently compartmentalize the furan ring inside its host cavity in water, thereby protecting it from the DA reaction with maleimide. Remarkably, the self‐complexed CBPQT4+‐Fu can undergo a conformational change through intramolecular decomplexation upon the addition of a stronger binding molecular naphthalene derivative as a competitive guest, triggering the DA reaction upon addition of a chemical regulator. Remarkably, connecting the guest to a thermoresponsive lower critical solution temperature (LCST) copolymer regulator controls the DA reaction on command upon heating and cooling the reaction media beyond and below the cloud point temperature of the copolymer, representing a rare example of decreased reactivity upon increasing temperature. Altogether, this work opens up new avenues towards combined topological and supramolecular control over reactivity in synthetic constructs, enabling control over reactivity through molecular regulators or even mild temperature variations. [ABSTRACT FROM AUTHOR]

A new series of liquid crystals consisting of biphenyl unit connected to phenyl core system have been successfully prepared wherein various substituents X= OCH3, F, Cl, Br and I were introduced in the para position of the imine fragment while the length of terminal alkoxy chain of seven carbon atoms was intact. The mesomorphic and thermal studies by POM and DSC exhibit dominant enantiotropic nematic (N) phase. A relatively weak magnetism was detected with vibrating sample magnetometer (VSM) for compounds 3F and 3I at room temperature, wherein the magnetic strength of fluoro-substituted compound appeared stronger than the iodo-substituted compound. The connectivity between the substituents X and their kinetic stability associated with the changes in HOMO-LUMO energy gap value (ΔEgap) supports that the terminal substituents X have great influence on the ΔEgap which can be ascribed to the chemical activity of the compounds. Present study shows an increase in the ΔEgap from OCH3 < I < Br < Cl < F, where the largest ΔEgap indicates high molecular kinetic stability and low chemical reactivity because adding electrons to high-lying LUMO is energetically unfavourable, resulting in disruption of the molecular packing and reduction of nematogenic, which were validated by DSC and POM. [ABSTRACT FROM AUTHOR]

Important biological compounds, namely, methyl 3-amino-4-(4-bromophenyl)thiophene-2-carboxylate (BPTC) and methyl 3-amino-4-(4-chlorophenyl)thiophene-2-carboxylate (CPTC), were characterized using complementary techniques of Fourier transform infrared (FT-IR), Raman spectroscopy. Nuclear magnetic resonance spectroscopy (NMR) confirmed the structural features, while Ultra Violet–Visible Spectroscopy was used to investigate the electronic properties of both compounds. The quantum chemical calculations for both compounds were performed using the DFT/B3LYP functional with the 6-311++G(d,p) basis set. This study computes electrostatic potential observation, electron localization function (ELF) assessment, and atoms-in-molecules (AIM) analysis. In the present investigation, the global hardness, chemical softness, electrophilicity, nucleophilicity indices, and dipole moment of both compounds were calculated. In addition, a molecular docking analysis was conducted to determine the binding potential of target molecules with protein tyrosine phosphatase. A 200-ns molecular dynamics (MDs) simulation had been performed to assess the compound's binding stability. [ABSTRACT FROM AUTHOR]

In this study, plasma activated water (PAW) has been prepared by using atmospheric pressure air dielectric barrier discharge (DBD) at the PAW temperature of 3–90 °C. The effects of PAW temperature, pH values and O3 concentration on the E. coli inactivation have been studied, and the chemical reactivity of PAW has been analyzed by using the chemical probe. It is found that both the biological and chemical reactivities of PAW are strongly dependent on the PAW temperature, however, their dependences on temperature are not consistent. When the PAW temperature decreases from 90 to 3 °C, the chemical reactivity of PAW is significantly increased due to an increase in the concentration of activated oxygen in PAW. Decreasing the temperature from 30 to 3 °C or increasing the temperature from 45 to 90 °C leads to an obvious increase in the biological reactivity of PAW. Our analysis shows that an obvious increase in the biological reactivity of low-temperature (≤ 15 °C) PAW is due to the synergistic effect of acidic solutions and a high concentration of activated oxygen in PAW. The high biological reactivity of PAW at the temperature of ≥ 60 °C can be attributed to the synergistic effect of acidic solutions, heat and the activated oxygen, such as O3 and HOONO. [ABSTRACT FROM AUTHOR]

The petrochemical industry is one of the main sources of industrial volatile organic compounds (VOCs) emissions. In this study, typical petrochemical refining enterprises in Southeast China were selected, direct testing of VOCs in 18 petrochemical processes, and 87 samples were obtained using different on-site sampling methods, such as stack, fugitive, static and dynamic sealing point emissions sampling methods, based on the key process units, tank areas, loading and unloading areas, and plant boundaries of the petrochemical industry. Simultaneously, on-site concentration testing and laboratory analysis of 115 VOCs were conducted. Our findings reveal that, although the overall industry emission profile predominantly consists of low-carbon alkanes and alkenes, with relatively minimal halogenated hydrocarbon VOC emissions, there are substantial discrepancies in the primary species across different stages. The mass percentages of alkanes, alkenes, aromatics, halogenated hydrocarbons, and oxygenated VOCs in different process units of the petrochemical industry were 55 ± 27%, 8.5 ± 15%, 23 ± 27%, 3.9 ± 4.3%, and 10 ± 8.4%, respectively. The dominant species in the atmospheric vents of the depropanizer, light hydrocarbon recovery unit, continuous reforming unit, catalytic cracking unit, and sulfur recovery unit were n-butane (15%), n-hexane (13%), propane (21%), propylene (26%), and ethylene (28%), respectively. The dominant species in the gasoline tank top source profile was isopentane (48%), while that of the gasoline loading and unloading area was methyl tert-butyl ether (19%). High-carbon alkanes such as n-decane, n-octane, and n-heptane (>5% mass fractions) were prominent in kerosene tank tops. Furthermore, the results of the chemical reactivity assessment indicate that VOC emissions during the loading and unloading processes, as well as the ethylene production process, should be managed to mitigate ozone formation potential. According to the cancer risk assessments, benzene was the main factor that increased the risk, and its levels were far beyond the accepted cutoff point.

A simple composite scheme developed for the calculation of accurate reaction barriers, and benchmarked against small systems, is applied here to compute barriers in the BH28 data set published in 2019 by Karton. This set comprises more complex transition states, with up to 7 non‐hydrogen and 10 hydrogen atoms, which barriers calculated at the SVECV‐f12 level are compared to the accurate CCSDT(Q)/CBS values obtained by Karton. A mean absolute difference of 2.4 kJ mol−1 and a root mean square difference of 1.9 kJ mol−1 were obtained, underlying the chemical accuracy of the protocol. [ABSTRACT FROM AUTHOR]

Marine organisms have been found to produce compounds that have the potential to serve as templates for novel therapeutics. Among these compounds, peptides are of particular interest due to their intermediate size between amino acids and proteins. Kahalalides are a family of structurally complex cyclic peptides with potent cytotoxic and antitumor activities, making them promising candidates for cancer therapy. In this study, we investigate the chemical reactivity of Kahalalides A–F using Conceptual Density Functional Theory to gain insight into their bioactivity from a molecular perspective. Our investigation includes characterizing and isolating the peptides, determining their local and global properties and predicting the active reaction sites. We also calculate Bioactivity Scores to predict their biological targets. Overall, this study contributes to the discovery of new therapeutic peptides from natural sources by providing insights into their chemical reactivity and potential biological targets. [ABSTRACT FROM AUTHOR]

Molecular quantum mechanical modeling, accelerated by machine learning, has opened the door to high‐throughput screening campaigns of complex properties, such as the activation energies of chemical reactions and absorption/emission spectra of materials and molecules; in silico. Here, we present an overview of the main principles, concepts, and design considerations involved in such hybrid computational quantum chemistry/machine learning screening workflows, with a special emphasis on some recent examples of their successful application. We end with a brief outlook of further advances that will benefit the field. [ABSTRACT FROM AUTHOR]

We argue for an account of chemical reactivities as chancy propensities, in accordance with the 'complex nexus of chance' defended by one of us in the past. Reactivities are typically quantified as proportions, and an expression such as "A + B → C" does not entail that under the right conditions some given amounts of A and B react to give the mass of C that theoretically corresponds to the stoichiometry of the reaction. Instead, what is produced is a fraction α < 1 of this theoretical amount, and the corresponding percentage is usually known as the yield, which expresses the relative preponderance of its reaction. This is then routinely tested in a laboratory against the observed actual yields for the different reactions. Thus, on our account, reactivities ambiguously refer to three quantities at once. They first refer to the underlying propensities effectively acting in the reaction mechanisms, which in 'chemical chemistry' (Schummer in Hyle 4:129–162, 1998) are commonly represented by means of Lewis structures. Besides, reactivities represent the probabilities that these propensities give rise to, for any amount of the reactants to combine as prescribed. This last notion is hence best understood as a single case chance and corresponds to a theoretical stoichiometric yield. Finally, reactivities represent the actual yields observed in experimental runs, which account for and provide the requisite evidence for/against both the mechanisms and single case chances ascribed. [ABSTRACT FROM AUTHOR]

Using density-based quantities to establish a qualitative or even quantitative framework to predict molecular reactivity in density functional theory is of considerable interest in the current literature. Recent developments in information-theoretic approach (ITA) represent such a trend. Traditionally, we represent ITA quantities in terms of the electron density, shape function, and atoms in molecules. In this contribution, we expand the theoretical framework of ITA by introducing a new representation. To that end, we make use of the first-order partial derivative of ITA quantities with respect to the number of total electrons and then approximate them in the finite difference approximation. The new representation has both local (three-dimensional) and global (condensed to atoms) versions. Its close relationship with Fukui function from conceptual density functional theory was derived analytically and confirmed numerically. Extensions of our present approach to include other types of derivatives are discussed. This work not only enriches the theoretical framework of ITA with a new representation but also provides opportunities to expand its territory as well as the scope of its applicability in dealing with molecular processes and chemical reactivity from a new perspective. [ABSTRACT FROM AUTHOR]

MK-1 molecule (C16H16O2), the simplest structure of vitamin K (VK) compound family, is an extract from traditional Chinese medicine Cymbopogon distans (Nees ex Steud.) Wats (Chinese name YunXiangCao), which has attracted a great deal of attention in recent years due to its antiasthmatic, antitussives and expectorant effects. To investigate the molecular structure and chemical reactivity of MK-1 molecule, computational investigations on six conformational minima structures were carried out at the MP2/6-311++G(2d,2p) level of theory. Several local reactivity descriptors including condensed Fukui function, average local ionization energy, and molecular electrostatic potential on each individual atom were determined to predict the intrinsic reactivity of MK-1 molecule. [ABSTRACT FROM AUTHOR]

To discover anti-acetylcholinesterase agents for the treatment of Alzheimer's disease (AD), a series of novel Schiff base-coumarin hybrids was rationally designed, synthesized successfully, and structurally characterized using Fourier transform infrared (FTIR), Nuclear magnetic resonance (NMR), and High-Resolution Mass Spectrometry (HRMS) analyses. These hybrids were evaluated for their potential inhibitory effect on acetylcholinesterase (AChE). All of them exhibited excellent inhibitory activity against AChE. The IC50 values ranged from 87.84 to 515.59 μg/mL; hybrids 13c and 13d with IC50 values of 0.232 ± 0.011 and 0.190 ± 0.004 µM, respectively, showed the most potent activity as acetylcholinesterase inhibitors (AChEIs). The reference drug, Galantamine, yielded an IC50 of 1.142 ± 0.027 µM. Reactivity descriptors, including chemical potential (μ), chemical hardness (η), electrophilicity (ω), condensed Fukui function, and dual descriptors are calculated at wB97XD/6-311++ G (d,p) to identify reactivity changes of the designed compounds. An in-depth investigation of the natural charge pattern of the studied compounds led to a deep understanding of the important interaction centers between these compounds and the biological receptors of AChE. The molecular electrostatic surface potential (MESP) of the most active site in these derivatives was determined using high-quality information and visualization. Molecular docking analysis was performed to predict binding sites and binding energies. The structure-activity-property relationship studies indicated that the proposed compounds exhibit good oral bioavailability properties. To explore the stability and dynamic behavior of the ligand-receptor complexes, molecular dynamics simulations (MDS) were performed for 100 ns on the two best docked derivatives, 13c and 13d, with the AChE (4EY7) receptor. A popular method for determining the free binding energies (MM/GBSA) is performed using snapshots taken from the systems' trajectories at 100 ns. These results revealed that the complex system of compound 13d acquired a relatively more stable conformation and exhibited better descriptors than the complex system of compound 13c and the Galantamine drug, suggesting its potential as an effective inhibiting drug. The binding free energy analysis revealed that the 13d-4EY7 complex exhibited greater stability with AChE receptors compared to other complexes. [ABSTRACT FROM AUTHOR]

The infrastructure features of the spent mushroom substrate (SMS) were detected and explored based on experimental data acquired from Fourier Transform Infrared Spectroscopy, Pyrolysis–Gas Chromatography/Mass Spectrometry as well as Thermogravimetric Analysis. Further, molecular simulation methods were combined with diverse testing technologies to build the 2D and associated 3D models from cellulose, hemicellulose, and lignin. Eventually, a rational 3D model was constructed for SMS using geometry optimization calculations and annealing dynamics simulations. According to the Mulliken population analysis and electron density analysis, the π-π conjugation effect of the aromatic ring structures was influenced by the oxygen atoms, thus, resulting in the electron accumulation on these oxygen atoms. At the same time, oxygen exhibited a greater electronic charge density and reactivity in the Furan ring and pyran ring structures in contrast to other atoms. Furthermore, the molecular orbitals for HOMO and LUMO were computed to check the chemical reaction characteristics of the SMS. According to the HOMO–LUMO energy gap, the structure of the polycyclic aromatic hydrocarbons provided reaction sites for the reaction and played a key role in chemical bond breaking. [ABSTRACT FROM AUTHOR]