Molecular electrostatic potential analysis: A powerful tool to interpret and predict chemical reactivity

Role of Intermolecular Interactions in Deep Eutectic Solvents for CO2 Capture: Vibrational Spectroscopy and Quantum Chemical Studies

Recent research and reviews on CO2 capture methods, along with advancements in industry, have highlighted high costs and energy-intensive nature as the primary limitations of conventional direct air capture and storage (DACS) methods. In response to these challenges, deep eutectic solvents (DESs) have emerged as promising absorbents due to their scalability, selectivity, and lower environmental impact compared to other absorbents. However, the molecular origins of their enhanced thermal stability and selectivity for DAC applications have not been explored before. Therefore, the current study focuses on a comprehensive investigation into the molecular interactions within an alkaline DES composed of potassium hydroxide (KOH) and ethylene glycol (EG). Combining Fourier transform infrared (FT-IR) and quantum chemical calculations, the study reports structural changes and intermolecular interactions induced in EG upon addition of KOH and its implications on CO2 capture. Experimental and computational spectroscopic studies confirm the presence of noncovalent interactions (hydrogen bonds) within both EG and the KOH-EG system and point to the aggregation of ions at higher KOH concentrations. Additionally, molecular electrostatic potential (MESP) surface analysis, natural bond orbital (NBO) analysis, quantum theory of atoms-in-molecules (QTAIM) analysis, and reduced density gradient-noncovalent interaction (RDG-NCI) plot analysis elucidate changes in polarizability, charge distribution, hydrogen bond types, noncovalent interactions, and interaction strengths, respectively. Evaluation of explicit and hybrid models assesses their effectiveness in representing intermolecular interactions. This research enhances our understanding of molecular interactions in the KOH-EG system, which are essential for both the absorption and desorption of CO2. The study also aids in predicting and selecting DES components, optimizing their ratios with salts, and fine-tuning the properties of similar solvents and salts for enhanced CO2 capture efficiency.

Quantum chemical treatment, electronic energy in various solvents, spectroscopic, molecular docking and dynamic simulation studies of 2-amino-N-(2-chloro-6-methylphenyl)thiazole-5-carboxamide: A core of anticancer drug

The titled molecule 2-Amino-N-(2-chloro-6-methylphenyl)thiazole-5-carboxamide (ANMC) is a core of anticancer drug dasatinib (leukemia). Its derivatives exhibited bioactivity against breast cancer. Experimentally, the titled compound was described using NMR (1H NMR and 13C NMR), FTIR and UV-visible spectroscopy. The results were compared with the theoretical predictions, showing good agreement such as theoretical NH vibrations showed symmetric stretching and asymmetric stretching at 3429 and 3440 cm-1 respectively, λmax values appear at 305 nm for experimental and 307.75 nm for theoretical observations in acetone medium. Hirshfeld surface analysis well described the secondary internal and external interactions obtained like dnorm and di ranges -1.8551 to 1.4590 and 0.0918 to 2.6756 respectively. Comparing UV-visible spectra obtained in various solvents with the calculated TD-DFT results revealed minimal solvent effects. Molecular electrostatic potential (MEP) map and Fukui functions were employed, which indicated reactive sites of the molecule and the obtained order of nucleophilic reactivity was C16 > C2 > C8 > Cl1 > C22 > C21. The bioactivity profile probability of ANMC was theoretically explored by calculation of electrophilicity index and drug-likeness. Molecular docking of the ANMC molecule was performed with ten receptors to obtain the best ligand-protein interaction and the minimum binding energy obtained was -8.0 kcal/mol. Biomolecular stability of ANMC was investigated by Molecular Dynamic Simulation (MDS). And also the analysis of free energies showed strong interactions between the ligand and the protein.

Self-healable, stimuli-responsive bio-ionic liquid and sodium alginate conjugated hydrogel with tunable Injectability and mechanical properties for the treatment of breast cancer

Designing stimuli-responsive drug delivery vehicles with higher drug loading capacity, sustained and targeted release of anti-cancer drugs and able to mitigate the shortcomings of traditional systems is need of hour. Herein, we designed stimuli-responsive, self-healable, and adhesive hydrogel through synergetic interaction between [Cho][Gly] (Choline-Glycine) and sodium alginate (SA). The hydrogel was formed as a result of non-covalent interaction between the components of the mixture forming the fibre kind morphology; confirmed through FTIR/computational analysis and SEM/AFM images. The hydrogel exhibited excellent mechanical strength, self-healing ability, adhesive character and most importantly; adjustable injectability. In vitro biocompatibility of the hydrogel was tested on HaCaT and MCF-7 cells, showing >92 % cell viability after 48 h. The hemolysis ratio (<4 %) of the hydrogel confirmed the blood compatibility of the hydrogel. When tested for drug-loading capacity, the hydrogel show 1500 times drug loading for the 5-fluorouracil (5-FU) against the SA based hydrogel. In vitro release data indicated that 5-FU have more preference towards the cancerous cell condition, i.e. acidic pH (>85 %), whereas the drug-loaded hydrogel successfully killed the MCF-7 and HeLa cell with a Collapse

Key Words

• Bio-ionic liquid
• Injectable-hydrogel
• Sodium alginate

Collapse

MESH Headings

• Alginates/chemistry
• Humans
• Breast Neoplasms/drug therapy
• Breast Neoplasms/pathology
• Hydrogels/chemistry
• MCF-7 Cells
• Female
• Drug Liberation
• Drug Carriers/chemistry
• Fluorouracil/pharmacology
• Fluorouracil/chemistry
• Cell Survival/drug effects
• Hemolysis/drug effects
• Drug Delivery Systems
• Antineoplastic Agents/pharmacology
• Antineoplastic Agents/chemistry

Collapse

Grants Collapse

Affiliation(s)

Raviraj Pansuriya Ionic Liquids Research Laboratory, Department of Chemistry, Sardar Vallabhbhai National Institute of Technology, Surat 395007, Gujarat, India
Tapas Patel Ionic Liquids Research Laboratory, Department of Chemistry, Sardar Vallabhbhai National Institute of Technology, Surat 395007, Gujarat, India
Kuldeep Singh Salt and Marine Chemicals Division, CSIR-Central Salt and Marine Chemicals Research Institute, Council of Scientific and Industrial Research, G. B. Marg, Bhavnagar 364002, India
Azza Al Ghamdi Department of Chemistry, College of Science, Imam Abdul Rahman Bin Faisal University, P.O. Box 1982, Dammam 31441, Saudi Arabia; Basic & Applied Scientific Research Center (BASRC), Water Treatment Unit, Imam Abdulrahman Bin Faisal University, P.O. Box 1982, Dammam 31441, Saudi Arabia
Naresh Kasoju Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum 695011, Kerala, India
Arvind Kumar Salt and Marine Chemicals Division, CSIR-Central Salt and Marine Chemicals Research Institute, Council of Scientific and Industrial Research, G. B. Marg, Bhavnagar 364002, India
Suresh Kumar Kailasa Ionic Liquids Research Laboratory, Department of Chemistry, Sardar Vallabhbhai National Institute of Technology, Surat 395007, Gujarat, India
Naved I Malek Ionic Liquids Research Laboratory, Department of Chemistry, Sardar Vallabhbhai National Institute of Technology, Surat 395007, Gujarat, India.

Collapse

Investigating the electronic properties of edge glycine/biopolymer/graphene quantum dots

This study systematically investigated four types of graphene quantum dots (GQDs) AHEX, ZTRI, ZHEX, and ATRI, and their interactions with glycine to form GQD-glycine complexes. Utilizing density functional theory (DFT) and the PM6 semiempirical method, the study analyzed electronic properties and structure-activity relationships. Global reactivity indices were calculated using Koopmans' theorem, and quantitative structure-activity relationship (QSAR) parameters were assessed via SCIGRESS 0.3. The study further explored interactions using density of states (DOS) and quantum theory of atoms in molecules (QTAIM) analyses. Key findings revealed that glycine interaction significantly increased the total dipole moment (TDM) and decreased the HOMO/LUMO energy gap (ΔE) for the GQD-glycine complexes. Notably, ZTRI/glycine showed a TDM of 4.535 Debye and a reduced ΔE of 0.323 eV, indicating enhanced reactivity. Further interactions with cellulose, chitosan, and sodium alginate identified the ZTRI/glycine/sodium alginate composite as the most reactive, with a TDM of 8.020 Debye and the lowest ΔE of 0.200 eV. This composite also exhibited the highest electrophilicity index (56.421) and lowest chemical hardness (0.145 eV), underscoring its superior reactivity and stability. DOS analysis revealed that biomolecules contributed the most to molecular orbitals, with carbon atoms contributing the least. QTAIM analysis confirmed the greater stability of the ZTRI/glycine/sodium alginate complex compared to other studied composites. These results highlight the enhanced reactivity and stability of GQDs when interacting with glycine and sodium alginate.

Gold(I) Catalysis in Alkyne-Alkene Reactions: A Systematic Exploration through Molecular Electrostatic Potential Analysis

Gold catalysis enables selective chemical transformations with catalytic activity tunable through ligand selection. This study uses the density functional theory (DFT) to explore the impact of phosphine ligands (PR3) on gold(I)-catalyzed alkyne-alkene cyclobutene formation. We analyze the following key steps: (i) PR3-Au+ complexation, (ii) alkyne binding, (iii) alkene binding, (iv) C-C coupling transition state, (v) cyclobutene formation transition state, and (vi) cyclobutene dissociation. Molecular electrostatic potential (MESP) analysis provided a deeper understanding of electronic effects and revealed a strong correlation between the change in MESP at the gold nucleus (ΔNVAu+) upon complex formation with various ligands and the corresponding complexation energy, as well as between the change in MESP at the alkyne carbon (ΔVC) and the C-C coupling step activation barrier. This establishes MESP as a powerful tool for understanding ligand influence on catalysis. Our findings suggest that electron-donating phosphine ligands, combined with electron-withdrawing alkyne substituents, enhance catalyst turnover, promote cyclobutene product dissociation from the gold(I) complex, and facilitate catalyst regeneration. Solvent effects also play a crucial role. Bulky XPhos, JohnPhos, and CyJohnPhos ligands enhance gold(I) catalysis via steric protection, electron donation, and catalyst regeneration efficiency. In conclusion, this study provides insights into ligand effects in gold(I)-catalyzed cyclobutene formation, guiding future catalyst design.

Shedding light into the biological activity of aminopterin, via molecular structural, docking, and molecular dynamics analyses

In this study, the structural and anticancer properties of aminopterin, as well as its antiviral characteristics, were elucidated. The preferred conformations of the title molecule were investigated with semiempirical AM1 method, and the obtained the lowest energy conformer was then optimized by using density functional (DFT/B3LYP) method with 6-311++G(d,p) as basis set. The vibrational frequencies of the optimized structure were calculated by the same level of theory and were compared with the experimental values. The vibrational assignments were performed based on the computed potential energy distribution (PED) of the vibrational modes. The molecular electrostatic potential (MEP) and frontier molecular orbitals (HOMO, LUMO) analyses were carried out for the optimized structure and the chemical reactivity has been scrutinized. To enlighten the biological activity of aminopterin as anticancer and anti-COVID-19 agents, aminopterin was docked into DNA, αIIBβ3 and α5β1integrins, human dihydrofolate reductase, main protease (Mpro) of SARS-CoV-2 and SARS-CoV-2/ACE2 complex receptor. The binding mechanisms of aminopterin with the receptors were clarified. The molecular docking results revealed the strong interaction of the aminopterin with DNA (-8.2 kcal/mol), αIIBβ3 and α5β1 integrins (-9.0 and -10.8 kcal/mol, respectively), human dihydrofolate reductase (-9.7 kcal/mol), Mpro of SARS-CoV-2 (-6.7 kcal/mol), and SARS-CoV-2/ACE2 complex receptor (-8.1 kcal/mol). Moreover, after molecular docking calculations, top-scoring ligand-receptor complexes of the aminopterin with SARS-CoV-2 enzymes (6M03 and 6M0J) were subjected to 50 ns all-atom MD simulations to investigate the ligand-receptor interactions in more detail, and to determine the binding free energies accurately. The predicted results indicate that the aminopterin may significantly inhibit SARS-CoV-2 infection. Thus, in this study, as both anticancer and anti-COVID-19 agents, the versatility of the biological activity of aminopterin was shown.Communicated by Ramaswamy H. Sarma.

Monohydrides of the Group 13 Elements M=B, Al and Ga: Axial Bi-Nucleophilicity and the Propensity to Form Both H-M⋅⋅⋅HX and M-H⋅⋅⋅HX Hydrogen Bonds (X=F, Cl, Br, I, CN, CCH, CP)

Equilibrium dissociation energies De of the hydrogen-bonded complexes HAl⋅⋅⋅HX and HGa⋅⋅⋅HX (X=F, Cl, Br, I, CN, CCH, and CP) were calculated ab initio at the CCSD(T)-(F12c)/cc-pVDZ-F12 level of theory. The gradients of graphs of De versus the electrophilicity EHX of the Lewis acids HX yielded the nucleophilicities NM-X of the Group 13 atoms M in these diatomic molecules. Molecular electrostatic surfaces potentials reveal that H-Al and H-Ga are bi-nucleophilic and that the H ends of these H-M molecules are more nucleophilic than the M ends for M=Al and Ga, but not when M=boron. Therefore, the complexes M-H⋅⋅⋅HX were investigated using the same approach. It was concluded for M=Al and Ga that, for a given X, the M-H⋅⋅⋅HX complexes were more strongly bound than the corresponding H-M⋅⋅⋅HX complexes for both M=Al and Ga but the reverse order applies for M = boron. The effects of substituting the H atoms in the M-H molecules by F atoms and by methyl groups were investigated to measure the -I and +I inductive effects relative to H, respectively, on the nucleophilicities of the molecules M-H when M is acting as hydrogen-bond acceptor in complexes H-M⋅⋅⋅H-X.

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.

(-)-Epicatechin metabolites as a GPER ligands: a theoretical perspective

Diet habits and nutrition quality significantly impact health and disease. Here is delve into the intricate relationship between diet habits, nutrition quality, and their direct impact on health and homeostasis. Focusing on (-)-Epicatechin, a natural flavanol found in various foods like green tea and cocoa, known for its positive effects on cardiovascular health and diabetes prevention. The investigation encompasses the absorption, metabolism, and distribution of (-)-Epicatechin in the human body, revealing a diverse array of metabolites in the circulatory system. Notably, (-)-Epicatechin demonstrates an ability to activate nitric oxide synthase (eNOS) through the G protein-coupled estrogen receptor (GPER). While the precise role of GPER and its interaction with classical estrogen receptors (ERs) remains under scrutiny, the study employs computational methods, including density functional theory, molecular docking, and molecular dynamics simulations, to assess the physicochemical properties and binding affinities of key (-)-Epicatechin metabolites with GPER. DFT analysis revealed distinct physicochemical properties among metabolites, influencing their reactivity and stability. Rigid and flexible molecular docking demonstrated varying binding affinities, with some metabolites surpassing (-)-Epicatechin. Molecular dynamics simulations highlighted potential binding pose variations, while MMGBSA analysis provided insights into the energetics of GPER-metabolite interactions. The outcomes elucidate distinct interactions, providing insights into potential molecular mechanisms underlying the effects of (-)-Epicatechin across varied biological contexts.

Crystal structure and characterization of monascin from the extracts of Monascus purpureus-fermented rice

We present a novel solid form of monascin, an azaphilonoid derivative extracted from Monascus purpureus-fermented rice. The crystal structure, C21H26O5, was characterized by single-crystal X-ray diffraction and belongs to the orthorhombic space group P212121. To gain insight into the electronic properties of the short contacts in the crystalline state of monascin, we utilized the Experimental Library of Multipolar Atom Model 2 (ELMAM2) database to transfer the electron density of monascin in its crystalline state. Hirshfeld surface analysis, fingerprint analysis, electronic properties and energetic characterization reveal that intermolecular C-H...O hydrogen bonds play a crucial role in the noncovalent bonding interactions by connecting molecules into two- and three-dimensional networks. The molecular electrostatic potential (MEP) map of the monascin molecule demonstrates that negatively charged regions located at four O atoms are favoured binding sites for more positively charged amino acid residues during molecular recognition. In addition, powder X-ray diffraction confirms that no transformation occurs during the crystallization of monascin.

Unraveling the Isotropic Hyperfine Coupling Constants of Nitroxide Radicals via Molecular Electrostatic Potential Analysis

Nitroxide radicals have wide and promising applications as organic magnetic materials. Modulating the isotropic hyperfine coupling constants (HFCCs) of these radicals through proper structural design is an effective strategy for their application as spin probes and spin labels. In the present work, density functional theory calculations were carried out to develop a robust descriptor based on the molecular electrostatic potential for nitrogen HFCCs of nitroxide radicals. Forty nitroxide radicals from five distinct classes, namely, derivatives of cyclic, acyclic, imino, nitronyl, and benzimidazole nitronyl nitroxides, were selected, and the molecular electrostatic potential (MESP) at the nitrogen atom (VN) of the NO moiety was calculated. The VN values efficiently capture the electronic changes associated with the steric and electronic nature of these systems. A significant correlation between VN values and the experimental HFCCs of nitrogen nuclei demonstrates the applicability of VN as a simple and efficient descriptor for monitoring HFCCs. Furthermore, a good correlation between VN and experimental nitrogen HFCCs for each class of nitroxide radicals indicates the use of VN in the evaluation of the magnetic nature of the nitroxide radicals. The findings in this work are expected to facilitate the design of novel nitroxide radicals with desirable magnetic properties based on MESP topology analysis.

Density functional theory study of doped coronene and circumcoronene as anode materials in lithium-ion batteries

Density functional theory calculations are carried out to investigate the adsorption properties of Li+ and Li on twenty-four adsorbents obtained by replacement of C atoms of coronene (C24H12) and circumcoronene (C54H18) by Si/N/BN/AlN units. The molecular electrostatic potential (MESP) analysis show that such replacements lead to an increase of the electron-rich environments in the molecules. Li+ is relatively strongly adsorbed on all adsorbents. The adsorption energy of Li+ (Eads-1) on all adsorbents is in the range of - 42.47 (B12H12N12) to - 66.26 kcal/mol (m-C22H12BN). Our results indicate a stronger interaction between Li+ and the nanoflakes as the deepest MESP minimum of the nanoflakes becomes more negative. A stronger interaction between Li+ and the nanoflakes pushes more electron density toward Li+. Li is weakly adsorbed on all adsorbents when compared to Li+. The adsorption energy of Li (Eads-2) on all adsorbents is in the range of - 3.07 (B27H18N27) to - 47.79 kcal/mol (C53H18Si). Assuming the nanoflakes to be an anode for the lithium-ion batteries, the cell voltage (Vcell) is predicted to be relatively high (> 1.54 V) for C24H12, C12H12Si12, B12H12N12, C27H18Si27, and B27H18N27. The Eads-1 data show only a small variation compared to Eads-2, and therefore, Eads-2 has a strong effect on the changes in Vcell.

Synthesis and Regioselective Functionalization of Tetrafluorobenzo-[α]-Fused BOPYPY Dyes

The synthesis of a new bis-BF2 tetrafluorobenzo-[α]-fused BOPYPY dye from 4,5,6,7-tetrafluoroisoindole and 2-hydrazinopyrazine is reported. The regioselectivity of nucleophilic substitution reactions at the periphery of the tetrafluorinated BOPYPY and its α-bromo derivative were investigated using N-, O-, S-, and C-based nucleophiles. Among the aromatic fluorine atoms, the F2 atom is consistently regioselectively substituted, except when the α-position contains a thiophenol group; in this case, F4 is substituted instead due to stabilizing π-π-stacking between the two aromatic groups. The α-bromo BOPYPY derivative also reacts under Stille cross-coupling reaction conditions to produce the corresponding α-substituted product. The spectroscopic properties of these new fluorinated BOPYPYs were investigated and compared with nonfluorinated analogs.

Triple-Dearomative Photocycloaddition: A Strategy to Construct Caged Molecular Frameworks

An unprecedented caged 2H-benzo-dioxo-pentacycloundecane framework was serendipitously obtained in a single transformation via triple-dearomative photocycloaddition of chromone esters with furans. This caged structure was generated as part of an effort to access a tricyclic, oxygen-bridged intermediate enroute to the dihydroxanthone natural product nidulalin A. Reaction scope and limitations were thoroughly investigated, revealing the ability to access a multitude of synthetically challenging caged scaffolds in a two-step sequence. Photophysical studies provided key mechanistic insights on the process for formation of the novel caged scaffold.

Basic magnesium sulfate@TiO2 composite for efficient adsorption and photocatalytic degradation of 4-dodecylmorpholine in brine

More than 70% of the potash fertilizer globally is produced by the froth flotation process, in which 4-dodecylmorpholine (DMP) serves as a reverse flotation agent. As the potash fertilizer production rapidly rises, the increased DMP levels in discharged brine pose a threat to the production of high-value chemicals. In this paper, composite particles of basic magnesium sulfate@TiO2 (BMS@TiO2) were prepared using a simple and mild loading method. These particles were utilized for the adsorption and photocatalytic degradation of DMP in brine. Compared with normal powdered materials, the granular BMS@TiO2 in this study can be easily separated from liquid, and the degradation intermediates will not enter the brine without causing secondary pollution. BMS@TiO2 consists of 5·1·7 phase (5Mg(OH)2·MgSO4·7H2O) whisker clusters embedding 2.3% TiO2. The adsorption equilibrium of DMP on BMS@TiO2 particles was achieved through hydrogen bonding and pore interception with the adsorption capacity of approximately 5 mg g-1 after 6 h. The photodegradation efficiency of DMP adsorbed on BMS@TiO2 reached about 92% within 16 h, which is compared with that of pure TiO2 nanoparticles. Additionally, excellent stability and recyclability of BMS@TiO2 were also observed in five cycle tests of adsorption and photocatalytic degradation of DMP, and the possible photocatalytic degradation pathways and mechanism of DMP are proposed following molecular electrostatic potential analysis. This work provides a sustainable and environmentally friendly approach for eliminating organic micropollutants from water environments.

Interaction of zincite, alpha-terpineol, geranyl acetate, linalool, myrcenol, terpinolene, and thymol with virulence factors of Escherichia coli, Mycobacterium tuberculosis, Pseudomonas aeruginosa, and Staphylococcus aureus

BACKGROUND

Based on gas chromatography - mass spectrometry (GC-MS) results of a previous study, six metabolites including alpha-terpineol, geranyl acetate, linalool, myrcenol, terpinolene, and thymol showed significantly higher amounts relative to other metabolites.

METHODS

A continuation of the previous study, the interaction of these metabolites with the main virulence factors of P. aeruginosa (pseudomonas elastase and exotoxin A), Staphylococcus aureus (alpha-hemolysin and protein 2a), Mycobacterium tuberculosis (ESX-secreted protein B and the serine/threonine protein kinase), and Escherichia coli (heat-labile enterotoxin and Shiga toxin) were evaluated by molecular docking study and molecular simulation.

RESULTS

In the case of Shiga toxin, higher and lower binding affinities were related to alpha-terpinolene and zincite with values of -5.8 and -2.6 kcal/mol, respectively. For alpha-hemolysin, terpinolene and alpha-terpinolene demonstrated higher binding affinities with similar energies of -5.9 kcal/mol. Thymol and geranyl acetate showed lower binding energy of -5.7 kcal/mol toward protein 2a. Furthermore, thymol had a higher binding affinity toward heat-labile enterotoxin and ESX-secreted protein B with values of -5.9 and -6.1 kcal/mol, respectively.

CONCLUSIONS

It is concluded that the availability of secondary metabolites of A. haussknechtii surrounding zinc oxide (ZnO) NPs can hinder P. aeruginosa by inactivating Pseudomonas elastase and exotoxin.

Insight into the interaction of host-guest structures for pyrrole-based metal compounds and C70

This study focuses on the recognition and isolation of fullerenes, which are crucial for further exploration of their physical and chemical properties. Our goal is to investigate the potential recognition of the D5h-C70 fullerene using crown-shaped metal compositions through density functional theory calculations. We assess the effectiveness of fullerene C70 recognition by studying the binding energy. Additionally, various analyses were conducted, including natural bond order charge analysis and reduced density gradient analysis, to understand the interaction mechanism between the host and guest molecules. These investigations provide valuable insights into the nature of the interaction and the stability of the host-guest system. To facilitate the release of the fullerene guest molecule, the vis-NIR spectra were simulated for the host-guest structures. This analysis offers guidance on the specific wavelengths that can be utilized to release the fullerene guest from the host-guest structures. Overall, this work proposes a new strategy for the effective recognition of various fullerene molecules and their subsequent release from host-guest systems. These findings could potentially be applied in assemblies involving fullerenes, advancing their practical applications.

Thiophene Stability in Photodynamic Therapy: A Mathematical Model Approach

Thiophene-containing photosensitizers are gaining recognition for their role in photodynamic therapy (PDT). However, the inherent reactivity of the thiophene moiety toward singlet oxygen threatens the stability and efficiency of these photosensitizers. This study presents a novel mathematical model capable of predicting the reactivity of thiophene toward singlet oxygen in PDT, using Conceptual Density Functional Theory (CDFT) and genetic programming. The research combines advanced computational methods, including various DFT techniques and symbolic regression, and is validated with experimental data. The findings underscore the capacity of the model to classify photosensitizers based on their photodynamic efficiency and safety, particularly noting that photosensitizers with a constant rate 1000 times lower than that of unmodified thiophene retain their photodynamic performance without substantial singlet oxygen quenching. Additionally, the research offers insights into the impact of electronic effects on thiophene reactivity. Finally, this study significantly advances thiophene-based photosensitizer design, paving the way for therapeutic agents that achieve a desirable balance between efficiency and safety in PDT.

Bond Strength and Interaction Energies in Togni Reagents: Insights from Molecular Electrostatic Potential-Based Parameters

Togni reagents and their analogs, classified as hypervalent iodine(III) complexes, serve as potent trifluoromethylation agents. The interplay of cis and trans factors plays a pivotal role in shaping their performance, affecting aspects such as bond strength, interaction energies, stability, and subsequent nucleophilic reactions. In this context, we propose the utilization of the molecular electrostatic potential (MESP) at the carbon atom (VC) of the I-CF3 moiety as a sensitive parameter to quantify the cis and trans influences in Togni-type reagents. Our study has shown that VC serves as a convenient probe for determining the heterolytic bond dissociation energy (BDE) and, consequently, assessing the reactivity of these reagents. Moreover, these parameters have been successfully applied to evaluate the strength of the σ-hole interactions with nucleophiles (Cl- and NMe3). Additionally, we provide insights into interactions of Togni reagents with Brønsted acids such as HCl and HSO3F, elucidating them in terms of MESP topological parameters. These findings yield valuable information about the electronic properties of hypervalent iodine reagents, particularly Togni-type reagents, offering the potential for optimizing structurally modified reagents with enhanced activity and stability.

The Role of Antisolvents with Different Functional Groups in the Formation of Cs4PbBr6 and CsPbBr3 Particles

Compared to the high-temperature hot injection (HI) technique, the room-temperature supersaturated recrystallization (SR) approach is more hopeful to realize the industrialized production of CsPbX3 (X = Cl, Br, and I) nanomaterials. However, accurate compositional control of the product is still difficult, and the role and underlying mechanism of antisolvents in the reprecipitation process remain unclear. Herein, CsPbBr3 particles and CsPbBr3/Cs4PbBr6 composites with certain proportions are synthesized using different antisolvents with the SR method. By adjustment of the polarity or functional group of antisolvents, it is found that the functional groups of antisolvents have a major impact on the composition of the products. Furthermore, the influential mechanism of different antisolvents on the compositions of products is investigated by combining electrostatic potential calculations and ultraviolet-visible absorption spectroscopy. It suggests that the interaction between functional groups of antisolvents and organic ligands influences the coordination status of the intermediate Pb-complex and further affects the separating rate of the Pb(II)-intermediate, leading to the formation of products with different compositions. A physicochemical mechanism is proposed to explain the formation of Cs4PbBr6 and CsPbBr3. This work deepens the understanding of the formation mechanism of all-inorganic metal halide perovskite-related materials based on the SR method and provides new routes to achieve their controllable preparation.

Unraveling the Push-Pull Effect in Acenes, Polyenes and Polyynes

Substituent effects (SEs) are fundamental for predicting molecular reactivity, while polyene, polyyne and acene derivatives are precursors to compounds with diverse applications. Computations were performed for Y-R-X systems, where reaction sites Y=NO2 and O- , substituents X=NO2 , CN, Cl, H, OH, NH2 , and spacers R=polyene, polyyne (n=1-5, 10 repeating units) and acene (up to tetracene). The cSAR (charge of the substituent active region) approach allowed to present, for the first time, quantitative relations describing the spacer's electron-donating and withdrawing properties as a function of n and the spacer type. The electronic properties of the X substituents depend on the type of spacer, its length and the Y group, which is an example of the reverse SE. To describe how the SE between Y and X weakens with n, two approaches were compared: cSAR and SESE (SE stabilization energy). The EDDB (electron density of delocalized bonds) characterize changes in electron delocalization in spacers due to the SE. A new approach - EDDB differential maps - allow to extract the effect of X substitution on the electron delocalization. The charges at spacer's C atoms correlate with cSAR; changes in the slopes confirm the charge transfer by resonance.

DFT Exploration of Metal Ion-Ligand Binding: Toward Rational Design of Chelating Agent in Semiconductor Manufacturing

Chelating agents are commonly employed in microelectronic processes to prevent metal ion contamination. The ligand fragments of a chelating agent largely determine its binding strength to metal ions. Identification of ligands with suitable characteristics will facilitate the design of chelating agents to enhance the capture and removal of metal ions from the substrate in microelectronic processes. This study employed quantum chemical calculations to simulate the binding process between eleven ligands and the hydrated forms of Ni2+, Cu2+, Al3+, and Fe3+ ions. The binding strength between the metal ions and ligands was quantified using binding energy and binding enthalpy. Additionally, we explored the binding interaction mechanisms and explained the differences in binding abilities of the eleven ligands using frontier molecular orbitals, nucleophilic indexes, electrostatic potentials, and energy decomposition calculations based on molecular force fields. Based on our computational results, promising chelating agent structures are proposed, aiming to guide the design of new chelating agents to address metal ion contamination issues in integrated circuit processes.

A Nanoporous Polymer Modified with Hexafluoroisopropanol to Detect Dimethyl Methylphosphonate

The increasing threat of nerve agents has prompted the need for gas sensors with fast response, high sensitivity, and good stability. In this work, the hexafluoroisopropanol functional group was modified on a porous aromatic framework material, which served as a sensitive material for detecting dimethyl methylphosphonate. A nerve agent sensor was made by coating sensitive materials on a surface acoustic wave device. Lots of pores in sensitive materials effectively increase the specific surface area and provide channels for diffusion of gas molecules. The introduction of hexafluoroisopropanols enables the sensor to specifically adsorb dimethyl methylphosphonate and improves the selectivity of the sensor. As a result, the developed gas sensor was able to detect dimethyl methylphosphonate at 0.8 ppm with response/recovery times of 29.8/43.8 s, and the detection limit of the gas sensor is about 0.11 ppm. The effects of temperature and humidity on the sensor were studied. The results show that the baseline of the sensor has a linear relationship with temperature and humidity, and the temperature and humidity have a significant effect on the response of the sensor. Furthermore, a device for real-time detection of nerve agent is reported. This work provides a new strategy for developing a gas sensor for detecting nerve agents.

Comprehensive Structural and Electronic Properties of 2-Azaadamantane N-Oxyl Derivatives Correlated with Their Catalytic Ability

Herein, a comprehensive kinetic study is performed to compare the catalytic efficiency of 2-azaadamantane N-oxyl (AZADO) derivatives with that of 2,2,6,6-tetramethylpiperidine N-oxyl (TEMPO) used as radical catalysts in the aerobic oxidation of l-menthol. Furthermore, the correlation between the catalytic activity and structural/electronic parameters of AZADOs and TEMPO is elucidated. The reaction rate constants achieved with several AZADO derivatives exhibit moderate relationships with spectroscopic parameters, such as the hyperfine coupling constant of the N atom (AN) and NO stretching vibration frequency (νNO) observed in electron spin resonance and infrared spectra, respectively. The planarity C-(NO)-C angle (φ) at the N atom, determined by density functional theory (DFT) calculations, also strongly correlates with the AN and νNO. Moreover, the bond order of NO, which strongly depends on the structural and electronic properties of NO radicals, correlates with radical activity; thus, the radical activity can be predicted by DFT calculations, thereby accelerating the synthesis of new AZADO derivatives without requiring alcohol oxidation experiments.

Copper(I) Complexes of Amide Functionalized Bisphosphine: Proximity Enhanced Metal-Ligand Cooperativity and Its Catalytic Advantage in C(sp3)-H Bond Activation of Unactivated Cycloalkanes in Dehydrogenative Carboxylation Reactions

The reactions of amide functionalized bisphosphine, o-Ph2PC6H4C-(O)N(H)C6H4PPh2-o (1) (BalaHariPhos), with copper salts is described. Treatment of 1 with CuX in a 1:1 molar ratio yielded chelate complexes of the type [CuX{(o-Ph2PC6H4C(O)N(H)C6H4PPh2-o)}-κ2-P,P] (X = Cl, 2; Br, 3; and I, 4), which on subsequent treatment with KOtBu resulted in a dimeric complex [Cu(o-Ph2PC6H4C(O)(N)C6H4PPh2-o)]2 (5). Interestingly, complexes 2-4 showed weak N-H···Cu interactions. These weak H-bonding interactions are studied in detail both experimentally and computationally. Also, CuI complexes 2-5 were employed in the oxidative dehydrogenative carboxylation (ODC) of unactivated cycloalkanes in the presence of carboxylic acids to form the corresponding allylic esters. Among complexes 2-5, halide-free dimeric CuI complex 5 showed excellent metal-ligand cooperativity in the oxidative dehydrogenative carboxylation (ODC) in the presence of carboxylic acids to form the corresponding allylic esters through C(sp3)-H bond activation of unactivated cycloalkanes. Mechanistic details of the catalytic process were established by isolating the precatalyst [Cu{(o-Ph2PC6H4C(O)(NH)C6H4PPh2-o)-κ2-P,P}(OOCPh)] (6) and fully characterized by mass spectrometry, NMR data, and single-crystal X-ray analysis. Density functional theory-based calculations further provided a quantitative understanding of the energetics of a series of H atom transfer steps occurring in the catalytic cycle.

Interplay of Hydrogen, Pnicogen, and Chalcogen Bonding in X(H2O)n=1-5 (X = NO, NO+, and NO-) Complexes: Energetics Insights via a Molecular Tailoring Approach

Nitric oxide (NO) and its redox congeners (NO+ and NO-), designated as X, play vital roles in various atmospheric and biological events. Understanding the interaction between X and water is inevitable to explain the different reactions that occur during these events. The present study is a unified attempt to explore the noncovalent interactions in microhydrated networks of X using the MP2/aug-cc-pVTZ//MP2/6-311++G(d,p) level of theory. The interactions between X and water have been probed by the molecular electrostatic potential (MESP) by exploiting the features of the most positive (Vmax) and most negative potential (Vmin) sites. The individual energy and cooperativity contributions of various types of noncovalent interactions present in X(H2O)n=1-5 complexes are estimated with the help of a molecular tailoring-based approach (MTA-based). The MTA-based analysis reveals that among various possible interactions in NO(H2O)n complexes, the water···water hydrogen bonds (HBs) are the strongest. Neutral NO can form hydrogen and pnicogen bonds (PBs) with water depending on the orientation; however, such HBs and PBs are the weakest. On the other hand, in the NO+(H2O)n complexes, the NO+···water interactions that occur through PBs are the strongest; the next one is the chalcogen bonding (CB), and the water···water HBs are the weakest. In the case of the NO-(H2O)n complexes, the HB interactions via both N and O atoms of NO- and water molecules are the strongest ones. The strength of water···water HB interactions is also seen to increase with the increase in the number of water molecules in NO-(H2O)n. The present study exemplifies the applicability of MTA-based calculations for quantifying various types of individual noncovalent interactions and their interplay in microhydrated networks of NO and its related ions.

Cadmium-chelating ability of the siderophore DHBS secreted by Leclercia adecarboxylata FCH-CR2 and its action mechanism

As one of the most accumulative toxic heavy metals, cadmium (Cd) poses a major threat to human health. Bacterial siderophores, as small molecules with metal-absorbing ability, have great potential activity for Cd-reduction. In this study, the siderophore-producing bacterialstrain FCH-CR2 was isolated from a high-Cd contaminated soil using the CAS method. Leclercia adecarboxylata was identified through 16S rRNA sequence, homology analysis, colony morphology, physiological and biochemical tests. A siderophore, catechol type 2,3-dihydroxy-N-benzoyl-l-serine (DHBS) secreted by FCH-CR2, was purified using RP-HPLC and identified by LC-MS/MS. Intraperitoneal injection of DHBS significantly increased fecal Cd levels, and reduced Cd accumulation in organs. In density flooding theory (DFT) analysis, DHBS may bind to Cd via the hydroxyl site on the benzene ring. Besides, the isothermal titration calorimetry (ITC) assay revealed that the formation of Cd-DHBS is a spontaneous and endothermic reaction with ΔG = -21.4 kJ/mol and ΔH = 1.51 ± 0.142 kJ/mol.

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.

Molecular simulation of Cu, Ag, and Au-decorated Si-doped graphene quantum dots (Si@QD) nanostructured as sensors for SO2 trapping

In view of the numerous environmental hazards and health challenges linked to sulfur (iv) oxide (SO2), an indirect greenhouse gas, and the resultant need to develop efficient gas nanosensor devices, this research had as its principal focus on the theoretical evaluation of the gas sensing potential of metals: Ag, Au and Cu functionalized silicon-doped quantum dots (Si@QD) for the detection and adsorption of SO2 gas investigated using the first-principles density functional theory (DFT) computation at the B3LYP-D3(BJ)/def2-SVP level of theory. Eight (8) possible adsorption modes: SO2_O_Si@QD, SO2_O_Ag_Si@QD, SO2_O_Au_Si@QD, SO2_O_Cu_Si@QD, SO2_S_Si@QD, SO2_S_Ag_Si@QD, SO2_S_Au_Si@QD, and SO2_S_Cu_Si@QD were considered based on SO2 interactions with the studied materials at the -S and -O sites of the SO2 molecule. The counterpoise correction (BSSE) showed that five of the eight interactions had favorable Ead + BSSE values ranging from -0.31 to -1.98 eV. All the eight interactions were observed to be thermodynamically favorable with ΔG and ΔH ranging from -129.01 to -200.24 kcal/mol and -158.26 to -229.73 kcal/mol respectively. Results from the topology analysis reveal that van der Waals forces occurred the greatest at the gas-sensor interphase while SO2_S_ Cu_Si@QD is predicted to have the highest sensing potency based on the conductivity and recovery time estimations. These results confirm the potential efficient feasibility of real-world device application of the metals (Ag, Au, Cu) functionalized Si-doped QDs.

Reduced bacterial resistance antibiotics with improved microbiota tolerance in human intestinal: Molecular design and mechanism analysis

Antibiotic selectivity and bacterial resistance are critical global public health issues. We constructed a multi-class machine learning model to study antibiotic effects on human intestinal microbiota abundance and identified key features. Binding energies of β-lactam antibiotics with Escherichia coli PBP3 mutant protein were calculated, and a 2D-QSAR model for bacterial resistance was established. Sensitivity analysis identified key features affecting bacterial resistance. By coupling key features from the machine learning model and 2D-QSAR model, we designed ten flucloxacillin (FLU) substitutes that improved intestinal microbiota tolerance and reduced antibiotic bacterial resistance. Concurrently, the substitutes exhibited superior degradability in soil, aquatic environments, and under photolytic conditions, coupled with a reduced environmental toxicity compared to the FLU. Evaluations under combined medication revealed significant improvements in functionality and bacterial resistance for 80% of FLU substitutes, with 50% showing more than a twofold increase. Mechanistic analysis demonstrated enhanced binding to target proteins and increased biodegradability for FLU substitutes due to more concentrated surface charges. Reduced solvent hindrance and increased cell membrane permeability of FLU substitutes, mainly due to enhanced interactions with phospholipid bilayers, contributed to their functional selectivity. This study aims to address poor antibiotic selectivity and strong bacterial resistance, providing guidance for designing antibiotic substitutes.

LQFM289: Electrochemical and Computational Studies of a New Trimetozine Analogue for Anxiety Treatment

This study employs electrochemical and Density Functional Theory (DFT) calculation approaches to investigate the potential of a novel analogue of trimetozine (TMZ) antioxidant profile. The correlation between oxidative stress and psychological disorders indicates that antioxidants may be an effective alternative treatment option. Butylatedhydroxytoluene (BHT) is a synthetic antioxidant widely used in industry. The BHT-TMZ compound derived from molecular hybridization, known as LQFM289, has shown promising results in early trials, and this study aims to elucidate its electrochemical properties to further support its potential as a therapeutic agent. The electrochemical behavior of LQFM289 was investigated using voltammetry and a mechanism for the redox process was proposed based on the compound's behavior. LQFM289 exhibits two distinct oxidation peaks: the first peak, Ep1a ≈ 0.49, corresponds to the oxidation of the phenolic fraction (BHT), and the second peak, Ep2a ≈ 1.2 V (vs. Ag/AgCl/KClsat), denotes the oxidation of the amino group from morpholine. Electroanalysis was used to identify the redox potentials of the compound, providing insight into its reactivity and stability in different environments. A redox mechanism was proposed based on the resulting peak potentials. The DFT calculation elucidates the electronic structure of LQFM289, resembling the precursors of molecular hybridization (BHT and TMZ), which may also dictate the pharmacophoric performance.

Computational Exploration of Phenolic Compounds in Corrosion Inhibition: A Case Study of Hydroxytyrosol and Tyrosol

The corrosion of materials remains a critical challenge with significant economic and infrastructural impacts. A comprehensive understanding of adsorption characteristics of phytochemicals can facilitate the effective design of high-performing environmentally friendly inhibitors. This study conducted a computational exploration of hydroxytyrosol (HTR) and tyrosol (TRS) (potent phenolic compounds found in olive leaf extracts), focusing on their adsorption and reactivity on iron surfaces. Utilizing self-consistent-charge density-functional tight-binding (SCC-DFTB) simulations, molecular dynamics (MD) simulations, and quantum chemical calculations (QCCs), we investigated the molecules' structural and electronic attributes and interactions with iron surfaces. The SCC-DFTB results highlighted that HTR and TRS coordinated with iron atoms when adsorbed individually, but only HTR maintained bonding when adsorbed alongside TRS. At their individual adsorption, HTR and TRS had interaction energies of -1.874 and -1.598 eV, which became more negative when put together (-1.976 eV). The MD simulations revealed parallel adsorption under aqueous and vacuum conditions, with HTR demonstrating higher adsorption energy. The analysis of quantum chemical parameters, including global and local reactivity descriptors, offered crucial insights into molecular reactivity, stability, and interaction-prone atomic sites. QCCs revealed that the fraction of transferred electron ∆N aligned with SCC-DFTB results, while other parameters of purely isolated molecules failed to predict the same. These findings pave the way for potential advancements in anticorrosion strategies leveraging phenolic compounds.

Selective confinement of potassium, rubidium, or caesium ions in a non-covalent hydroxyproline octamer cage stabilized by cis-hydroxyl locks

While numerous studies have focused on the impact of chirality on some magic amino acid clusters, this article investigates the effects of steric isomerization using 4-hydroxyproline octamers as a model system. Through mass spectrometry, infrared photodissociation spectroscopy, and theoretical calculation, it was demonstrated that the cis-4-hydroxy-L-proline octamer can selectively cage potassium, rubidium, or caesium ions through stable cis-hydroxyl locks, while the trans-form cannot. The results highlight the importance of hydroxyl group orientation in designing biocompatible membrane transporters with high ion-selectivity.

Methylammonium Tetrel Halide Perovskite Ion Pairs and Their Dimers: The Interplay between the Hydrogen-, Pnictogen- and Tetrel-Bonding Interactions

The structural stability of the extensively studied organic-inorganic hybrid methylammonium tetrel halide perovskite semiconductors, MATtX₃ (MA = CH₃NH₃⁺; Tt = Ge, Sn, Pb; X = Cl, Br, I), arises as a result of non-covalent interactions between an organic cation (CH₃NH₃⁺) and an inorganic anion (TtX₃^-). However, the basic understanding of the underlying chemical bonding interactions in these systems that link the ionic moieties together in complex configurations is still limited. In this study, ion pair models constituting the organic and inorganic ions were regarded as the repeating units of periodic crystal systems and density functional theory simulations were performed to elucidate the nature of the non-covalent interactions between them. It is demonstrated that not only the charge-assisted N-H···X and C-H···X hydrogen bonds but also the C-N···X pnictogen bonds interact to stabilize the ion pairs and to define their geometries in the gas phase. Similar interactions are also responsible for the formation of crystalline MATtX₃ in the low-temperature phase, some of which have been delineated in previous studies. In contrast, the Tt···X tetrel bonding interactions, which are hidden as coordinate bonds in the crystals, play a vital role in holding the inorganic anionic moieties (TtX₃^-) together. We have demonstrated that each Tt in each [CH₃NH₃⁺•TtX₃^-] ion pair has the capacity to donate three tetrel (σ-hole) bonds to the halides of three nearest neighbor TtX₃^- units, thus causing the emergence of an infinite array of 3D TtX₆^4- octahedra in the crystalline phase. The TtX₄^4- octahedra are corner-shared to form cage-like inorganic frameworks that host the organic cation, leading to the formation of functional tetrel halide perovskite materials that have outstanding optoelectronic properties in the solid state. We harnessed the results using the quantum theory of atoms in molecules, natural bond orbital, molecular electrostatic surface potential and independent gradient models to validate these conclusions.

Substituent Effects from the Point of View of Energetics and Molecular Geometry in Acene, Polyene, and Polyyne Derivatives

The substituent effect (SE) is one of the most important topics in organic chemistry and related fields, and Hammett constants (σ) are commonly used to describe it. The results of the computational studies carried out for Y-R-X systems (reaction sites Y = NO₂, O^-; substituents X = NO₂, CN, Cl, H, OH, NH₂; spacers R = polyene, polyyne, acene with n = 1-5 repeatable units) show that the substituent properties depend significantly on n, the type of R, and Y. Results of the analysis of the substituent effect stabilization energy and geometrical parameters of the Y-R-X systems reveal that (i) the SE strength and its inductive and resonance components decay with the increase in spacer length, its weakening depends on the Y and R type; quantitative relations describing decay are presented; (ii) the ratio between inductive and resonance effect strength changes with n and depends on Y; (iii) differences in the substituents' properties are examples of reverse SE; (iv) in general, structural parameters are mutually well correlated as well as with the SE descriptors; (v) due to the strong O^- resonance effect, the changes in π-electron delocalization within R are well correlated with the SE strength only for Y = O^- systems.

Unraveling Bonding Mechanisms and Electronic Structure of Pyridine Oximes on Fe(110) Surface: Deeper Insights from DFT, Molecular Dynamics and SCC-DFT Tight Binding Simulations

The development of corrosion inhibitors with outstanding performance is a never-ending and complex process engaged in by researchers, engineers and practitioners. The computational assessment of organic corrosion inhibitors' performance is a crucial step towards the design of new task-specific materials. Herein, the electronic features, adsorption characteristics and bonding mechanisms of two pyridine oximes, namely 2-pyridylaldoxime (2POH) and 3-pyridylaldoxime (3POH), with the iron surface were investigated using molecular dynamics (MD), and self-consistent-charge density-functional tight-binding (SCC-DFTB) simulations. SCC-DFTB simulations revealed that the 3POH molecule can form covalent bonds with iron atoms in its neutral and protonated states, while the 2POH molecule can only bond with iron through its protonated form, resulting in interaction energies of -2.534, -2.007, -1.897, and -0.007 eV for 3POH, 3POH⁺, 2POH⁺, and 2POH, respectively. Projected density of states (PDOSs) analysis of pyridines-Fe(110) interactions indicated that pyridine molecules were chemically adsorbed on the iron surface. Quantum chemical calculations (QCCs) revealed that the energy gap and Hard and Soft Acids and Bases (HSAB) principles were efficient in predicting the bonding trend of the molecules investigated with an iron surface. 3POH had the lowest energy gap of 1.706 eV, followed by 3POH⁺ (2.806 eV), 2POH⁺ (3.121 eV), and 2POH (3.431 eV). In the presence of a simulated solution, MD simulation showed that the neutral and protonated forms of molecules exhibited a parallel adsorption mode on an iron surface. The excellent adsorption properties and corrosion inhibition performance of 3POH may be attributed to its low stability compared to 2POH molecules.

The Tetrel Bond and Tetrel Halide Perovskite Semiconductors

The ion pairs [Cs+•TtX3-] (Tt = Pb, Sn, Ge; X = I, Br, Cl) are the building blocks of all-inorganic cesium tetrel halide perovskites in 3D, CsTtX3, that are widely regarded as blockbuster materials for optoelectronic applications such as in solar cells. The 3D structures consist of an anionic inorganic tetrel halide framework stabilized by the cesium cations (Cs+). We use computational methods to show that the geometrical connectivity between the inorganic monoanions, [TtX3-]∞, that leads to the formation of the TtX64- octahedra and the 3D inorganic perovskite architecture is the result of the joint effect of polarization and coulombic forces driven by alkali and tetrel bonds. Depending on the nature and temperature phase of these perovskite systems, the Tt···X tetrel bonds are either indistinguishable or somehow distinguishable from Tt-X coordinate bonds. The calculation of the potential on the electrostatic surface of the Tt atom in molecular [Cs+•TtX3-] provides physical insight into why the negative anions [TtX3-] attract each other when in close proximity, leading to the formation of the CsTtX3 tetrel halide perovskites in the solid state. The inter-molecular (and inter-ionic) geometries, binding energies, and charge density-based topological properties of sixteen [Cs+•TtX3-] ion pairs, as well as some selected oligomers [Cs+•PbI3-]n (n = 2, 3, 4), are discussed.

Polycyclic Aromatic Hydrocarbons as Anode Materials in Lithium-Ion Batteries: A DFT Study

The structure and energetics of the interactive behavior of Li⁺ and Li with polycyclic aromatic hydrocarbons (PAHs) have been studied at the wB97XD/6-311G(d,p) level of DFT. The electron distribution in the PAHs, analyzed using the topology of the molecular electrostatic potential (MESP), led to the categorization of their aromatic rings into five types, viz R_s, R_n, R_d, R_b, and R_e. Among the different rings, sextet-type R_s and naphthalene-type R_n rings showed the highest interaction with Li⁺. The change in MESP at the nucleus of Li⁺ (ΔV_Li⁺) due to the formation of the complex Li⁺...PAH is found to be proportional to the adsorption energy (E₁). In Li...PAH, the spin density on Li is close to zero, suggesting the formation of Li⁺...PAH^•- due to the electron transfer from Li to PAH. The adsorption energy (E₂) for Li...PAH does not correlate with the change in MESP at the nucleus of Li, whereas the dissociation energy (E₃) of Li⁺...PAH^•- to yield Li⁺ and PAH^•- correlates well with the MESP data, ΔV_Li. The study confirms that the change in MESP at the nucleus of Li⁺ due to complex formation gives a quantitative measure of the electronic effect of the cation-π binding. The cell potential (V_cell) is predicted for the lithium ion battery (LIB) using the Li⁺...PAH and Li...PAH adsorption energies. On the basis of the V_cell data, "carbon nanoflake"-type systems, viz coronene, circumbiphenyl, C₄₂H₁₆, and C₅₀H₁₈ are suggested as good anode materials for LIBs.

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.

A density fitting scheme for the fast evaluation of molecular electrostatic potential

Molecular electrostatic potential (MEP) is a significant and crucial physical quantity that can be applied to a large number of scenarios, such as the prediction of nucleophilic or electrophilic attacks, fitting atomic charges, σ-hole, and so forth. The computational cost for the MEP has an O(N² ) scaling with the increase of atoms, which is intractable and laborious for macromolecules. Herein, a density fitting molecular electrostatic potential (DF-MEP) is used to reduce the computational costs for the macromolecular MEP. It is found that the accuracy of DF-MEP is almost identical to the conventional molecular electrostatic potential (Conv-MEP), while the computational costs can be reduced to an O(N) scaling, for example, the computational time of 699,200 grids for the Trp-cage molecule (304 atoms) only takes 16.6 s at the B3LYP-D3(BJ)/def2-SVP level of theory with 16 CPU cores compared with 3060.2 s for the Conv-MEP method.

Definition of the Pnictogen Bond: A Perspective

This article proposes a definition for the term “pnictogen bond” and lists its donors, acceptors, and characteristic features. These may be invoked to identify this specific subset of the inter- and intramolecular interactions formed by elements of Group 15 which possess an electrophilic site in a molecular entity.

Manifesting Direction-Specific Complexation in [HFIP-H·H2O2]-: Exclusive Formation of a High-Lying Conformation

Size-selective, negative ion photoelectron spectroscopy in conjunction with quantum chemical calculations is employed to investigate the geometric and electronic structures of a protype system in catalytic olefin epoxidation research, that is, deprotonated hexafluoroisopropanol ([HFIP_-H]^-) complexed with hydrogen peroxide (H₂O₂). Spectral assignments and molecular electrostatic surface analyses unveil a surprising prevalent existence of a high-lying isomer with asymmetric dual hydrogen-bonding configuration that is preferably formed driven by influential direction-specific electrostatic interactions upon H₂O₂ approaching [HFIP_-H]^- anion. Subsequent inspections of molecular orbitals, charge, and spin density distributions indicate the occurrence of partial charge transfer from [HFIP_-H]^- to H₂O₂ upon hydrogen-bonding interactions. Accompanied with electron detachment, a proton transfer occurs to form the neutral complex of [HFIP·HOO^•] structure. This work conspicuously illustrates the importance of directionality encoded in intermolecular interactions involving asymmetric and complex molecules, while the produced hydroperoxyl radical HOO^• offers a possible new pathway in olefin epoxidation chemistry.