Search Results (186)

Understanding how molecular structure governs the reactivity of organic amines with CO₂ is essential for the rational design of next-generation carbon-capture solvents. In this work, three representative series of amines, including linear aliphatic, cyclic aliphatic, and aromatic, were systematically conducted with substituents at different positions, and their reaction rate constants and equilibrium constants with CO₂ were calculated using transition state theory. A suite of electronic-structure and steric descriptors, including ALIE, Hirshfeld charge, Fukui functions, and ESP-derived parameters, was developed to quantify structure–reactivity relationships. Linear aliphatic amines were found to be most sensitive to steric hindrance, while cyclic and aromatic amines were predominantly governed by inductive and conjugation effects. Key descriptors such as N_ALIE and q(N) showed strong correlations with both kinetic and thermodynamic parameters, enabling quantitative interpretation of substituent effects. Notably, a positive linear correlation between ln(k) and ln(K) was observed across all amine classes, revealing an intrinsic coupling between reaction rate and equilibrium. These findings deepen the mechanistic understanding of CO₂–amine chemistry and provide a theoretical foundation for the targeted design and optimization of high-performance CO₂-capture solvents. Full article

Wastewater-derived microplastics (WW-MPs) are increasingly recognised as reactive vectors for aromatic organic contaminants (AOCs), yet their role in contaminant fate remains insufficiently constrained. This review synthesises current knowledge on the transformation of microplastics in wastewater treatment plants, including fragmentation, oxidative ageing, additive leaching, and biofilm formation, and links these processes to changes in sorption capacity toward phenols, PAHs and their derivatives, and organochlorine pesticides (OCPs). We summarise the dominant adsorption mechanisms-hydrophobic partitioning, π-π interactions, hydrogen bonding, and electrostatic and, in some cases, halogen bonding-and critically evaluate how wastewater-relevant parameters (pH, ionic strength, dissolved organic matter, temperature, and biofilms) can modulate these interactions. Evidence in the literature consistently shows that ageing and biofouling enhance WW-MP affinity for many AOCs, reinforcing their function as mobile carriers. However, major gaps persist, including limited data on real wastewater-aged MPs, lack of methodological standardisation, and incomplete representation of ageing, competitive sorption, and non-equilibrium diffusion in existing isotherm and kinetic models. We propose key descriptors that should be incorporated into future sorption and fate frameworks and discuss how WW-MP-AOC interactions may influence ecological exposure, bioavailability, and risk assessment. This critical analysis supports more realistic predictions of AOC behaviour in wastewater environments. Full article

Understanding the molecular determinants of antioxidant activity in natural phenolic compounds is essential for explaining their biological performance and designing new radical scavengers. In this work, the radical-scavenging mechanisms of three major ginger phenolics—6-gingerol (GIN), 6-shogaol (SHO), and 6-paradol (PAR)—were systematically investigated using density functional theory (DFT) thermochemistry at the M06-2X/6-31+G(d,p) level in the gas phase, benzene, and water. Three canonical pathways—hydrogen atom transfer (HAT), single-electron transfer followed by proton transfer (SET–PT), and sequential proton loss–electron transfer (SPLET)—were evaluated through full optimization and frequency calculations at 298.15 K, combined with the SMD solvation model. Frontier molecular orbital (FMO), molecular electrostatic potential (MEP), and quantum theory of atoms in molecules (QTAIM) analyses were employed to correlate electronic structure with reactivity. The results reveal a distinct solvent-dependent mechanistic crossover. In the gas phase and benzene, the low dielectric constant suppresses charge separation, making HAT the thermodynamically dominant pathway. In water, strong stabilization of ionic species lowers both the ionization and deprotonation barriers, allowing SPLET and SET–PT to become competitive or even preferred. Across all media, the phenolic O–H group is the principal reactive site, while the aliphatic O–H of GIN remains inactive. SHO exhibits the most versatile redox profile, combining a highly conjugated α,β-unsaturated chain with favorable charge delocalization; PAR is somewhat less redox-active, while GIN shows intermediate performance governed by intramolecular hydrogen bonding. The assembled thermodynamics for HOO• scavenging confirm that all three phenolics are thermodynamically competent antioxidants (ΔG° ≈ −4 kcal mol⁻¹ in water), with comparable driving forces; electronic descriptors indicate SHO is the most redox-flexible, GIN(phenolic) is moderately and PAR is somewhat less charge-transfer-prone, while GIN(aliphatic) remains inactive. These findings provide a comprehensive structure-to-mechanism correlation for ginger phenolics and establish a predictive framework for solvent-controlled antioxidant behavior in phenolic systems. Full article

A thiazole–thiophene derivative, (E)-4-(2-(2-(1-(5-chlorothiophen-2-yl)ethylidene)hydrazinyl)thiazol-4-yl)benzonitrile (CTHTBN), was synthesized via a one-pot multicomponent reaction involving 5-chloro-2-acetylthiophene, thiosemicarbazide, and 4-(2-bromoacetyl)benzonitrile. The synthesized compound was characterized by FT-IR, ¹H NMR, and ¹³C NMR spectroscopy, confirming the formation of the title compound. Density Functional Theory (DFT) calculations at the B3LYP/6-311G(d,p) level were performed to explore the electronic structure and reactivity of CTHTBN. The HOMO and LUMO energies were found to be −5.75 eV and −2.03 eV, respectively, with an energy gap (E_g) of 3.72 eV, suggesting a balanced chemical stability and reactivity. The dipole moment of 7.9381 Debye indicated substantial polarity, favorable for biological interactions. Global reactivity descriptors, including chemical hardness (η = 1.86 eV), chemical softness (σ = 0.5376 eV⁻¹), electronegativity (χ = 3.89 eV), electrophilicity index (ω = 4.07 eV), and maximum charge transfer capacity (ΔN_max = 2.09), further supported the molecule’s electronic competence. Molecular docking against M. tuberculosis CYP51 revealed a strong binding affinity (−8.8 kcal/mol), stabilized by π–sulfur contacts with MET79 and PHE83, π–π stacking with TYR76, and π–π T-shaped interactions with PHE83 and the heme cofactor. Additional π–alkyl interactions with LEU321, ALA325, and the heme group reinforced hydrophobic complementarity, confirming efficient accommodation of CTHTBN in the active site. These findings suggest that CTHTBN holds promising potential as an antimycobacterial agent targeting CYP51 and may be explored in future biological studies. Full article

Polycyclic aromatic hydrocarbons (PAHs) play a central role in materials science due to their extended π-conjugated systems, with their stability and reactivity depending critically on their aromatic character. In this work, we systematically investigated the aromaticity and stability of a broad range of linear (acenes, phenacenes, biphenylenes, and cyclobuta-acenes) and belt-like (cyclacenes, cyclophenacenes, and cyclobiphenylenes) PAHs containing five to twelve benzene rings. A diverse set of aromaticity descriptors was employed, including geometric (HOMA), electronic (MCI, FLU) and magnetic (NICS) descriptors, plus the recently developed ${\mathit{Q}}_2$ indices, based on the components of the distributed multipole analysis (DMA) electric quadrupole tensor. These data were complemented by stability analyses using singlet–triplet energy splitting (ΔE_S–T) and fractional occupation number-weighted densities (N_FOD) values. Our results indicate that acenes and phenacenes follow a comparable aromatic trend, with inner rings possessing lower aromaticity and the edge rings showing a more pronounced aromatic character. A subtle difference is observed in the position of the most aromatic ring, which lies slightly closer to the interior in acenes. Phenacenes, however, exhibit greater overall stability, attributed to their armchair edges. For biphenylenes and cyclobuta-acenes, the antiaromatic cyclobutadiene moiety perturbs the aromaticity only in its direct neighborhood and preserves the aromaticity in the remaining chains. In belt-like systems, cyclacenes exhibit strong radical character and low stability, consistent with longstanding synthetic challenges, whereas cyclophenacenes display enhanced aromaticity and stability with extending size. Cyclobiphenylenes combine localized antiaromatic centers with preserved benzene-like aromaticity in rings distant from the cyclobutadiene unit. Full article

A comprehensive analysis of key findings derived from density functional theory (DFT) studies reveals that current theoretical data on curcumin remain incomplete, underscoring the need for further computational investigation to achieve a more thorough understanding of its chemical and biological reactivity. This study addresses these gaps through four primary objectives: (i) determination of a complete set of thermodynamic descriptors and elucidation of the multi-step anti-radical mechanisms of the neutral, radical, anionic, and radical–anionic forms of curcumin; (ii) calculation of global chemical reactivity descriptors of curcumin in various solvent environments; (iii) theoretical reproduction of experimentally determined pK_a values for all active sites within the molecule; and (iv) examination of the effects of dispersion interactions and solvent polarity on the reactivity descriptors of keto–enol forms of curcumin. The results obtained provide enhanced insight into the molecular behavior of curcumin, facilitating improved predictions of its reactivity under diverse conditions. Moreover, the findings indicate a potential structural modification of the keto form of curcumin, involving the attachment of two 4-hydroxy-3-methoxyphenyl-prop-1-en-2-one moieties to the methylene group. The resulting modeled compound, referred to as di-curcumin, exhibits enhanced chemical reactivity and increased anti-radical potential. Full article

Highly Hazardous Pesticides (HHPs) pose severe risks to human health and the environment, making it essential to understand their molecular stability and degradation pathways. In this study, the Quantum Theory of Atoms in Molecules (QTAIM) was applied to four representative organophosphate pesticides, allowing the identification of electronically weak bonds as intrinsic sites of lability. These findings are consistent with reported hydrolytic, oxidative, enzymatic, and microbial degradation routes. Importantly, QTAIM descriptors proved largely insensitive to solvation, confirming their intrinsic character within the molecular electronic structure. To complement QTAIM, conceptual DFT (Density Functional Theory) reactivity indices were analyzed, revealing that solvent effects induce more noticeable variations in global and local descriptors than in topological parameters. In addition, a Topological Analysis of the Fukui Function (TAFF) was performed, which mapped nucleophilic, electrophilic, and radical susceptibilities directly onto QTAIM basins. The TAFF analysis confirmed that bonds identified as weak by QTAIM (notably P–O, P–S, and P–N linkages) also coincide with the most reactive sites, thereby reinforcing their mechanistic role in degradation pathways. This integrated framework highlights the robustness of QTAIM, the sensitivity of global and local reactivity descriptors to solvation revealed by conceptual DFT, and the complementary insights provided by TAFF, contributing to risk assessment, remediation strategies, and the rational design of safer pesticides. Full article

A chemical platform for post-polymerization methods was developed, starting from the ecodesign and enzymatic synthesis of safe and sustainable bio-based polyesters containing discrete units of itaconic acid. This unsaturated bio-based monomer enables the covalent linkage of molecules that can impart desired properties such as hydrophilicity, flexibility, permeability, or affinity for biological targets. Molecular descriptor-based computational methods, which are generally used for modeling the pharmacokinetic properties of drugs (ADME), were employed to predict in silico the hydrophobicity (LogP), permeability, and flexibility of virtual terpolymers composed of different polyols (1,4-butanediol, glycerol, 1,3-propanediol, and 1,2-ethanediol) with adipic acid and itaconic acid. Itaconic acid, with its reactive vinyl group, acts as a chemical platform for various post-polymerization functionalizations. Poly(glycerol adipate itaconate) was selected because of its higher hydrophilicity and synthetized via solvent-free enzymatic polycondensation at 50 °C to prevent the isomerization or crosslinking of itaconic acid. The ecotoxicity and marine biodegradability of the resulting oligoester were assessed experimentally in order to verify its compliance with safety and sustainability criteria. Finally, the viability of the covalent linkage of biomolecules via Michael addition to the vinyl pendant of the oligoesters was verified using four molecules bearing thiol and amine nucleophilic groups: N-acetylcysteine, N-Ac-Phe-ε-Lys-OtBu, Lys-Lys-Lys, and glucosamine. Full article

In this article, the 1,3-dipolar cycloaddition (1,3-DC) reactions between 4-acyl-1H-pyrrole-2,3-diones fused at the [e]-side with a heterocyclic moiety (FPDs) and diphenylnitrone are studied using Molecular Electron Density Theory (MEDT) at different computational levels. An analysis of the global reactivity descriptors has determined the role of the reagents. FPDs will act as electrophiles, while diphenylnitrone will be a nucleophile. It was found that the reactions proceed according to a one-step but asynchronous mechanism. Additionally, based on the Bonding Evolution Theory (BET) analysis of the model 1,3-DC reaction between FPDs 1b and diphenylnitrone 2, we can distinguish eight different phases. The formation of the first C1-O5 single bond takes place in phase VII through the disappearance of the V(C1) monosynaptic basin and the depopulation of the V″(O5) monosynaptic basin, while the formation of the second C2-C3 single bond begins at the last phase of the reaction through the connection of two V(C2) and V(C3) monosynaptic basins. Based on this, we can classify this reaction as a “one-step two-stage” process. Furthermore, molecular dynamics (MD) simulation analysis up to 100 ns demonstrated the stability of both the 2P3B–Ligand1 and 2P3B–Zidovudine complexes. An enhancer of shape compression was generated for ligand1, whereas Zidovudine generated a more packed and stable hydrogen bond network that would allow a better occupancy of the active site. Full article

Identifying the most reactive conformation of a molecule is a central challenge in computational chemistry, particularly when reactivity depends on subtle conformational effects. While most conformation search tools aim to find the lowest-energy structure, they often overlook the electronic descriptors that govern chemical reactivity. In this work, we present GAELLE, a cheminformatics tool that combines conformer generation with quantum reactivity descriptors to identify the most reactive structure of a molecule in solution. GAELLE integrates an evolutionary algorithm with fast semiempirical quantum chemical calculations (xTB), enabling the automated ranking of conformers based on HOMO–LUMO gap minimization (Pearson’s principle of maximum hardness) and electrophilicity index (Parr’s electrophilicity scale). Solvent effects are accounted for via implicit solvation models (GBSA/ALPB) to ensure realistic evaluation of reactivity in solution. The method is fully SMILES-driven, open-source, and scalable to medium-sized drug-like molecules. Applications to reactive intermediates, bioactive conformations, and pre-reactive complexes demonstrate the method’s relevance for mechanism elucidation, molecular design, and in silico screening. GAELLE is publicly available and offers a reactivity-focused alternative to traditional energy-minimization tools in conformational analysis. Full article

Inhibitors of the tyrosine kinase Zap70 are actively searched to improve treatments of lymphoid malignancies and autoimmune diseases associated with an abnormal T-cell response. The natural product withaferin A (WFA) has been characterized as a covalent inhibitor of Zap70 capable of blocking the migration of human T-cells. By analogy, we postulated that other withanolides equipped with a thiol-reactive, α,β-unsaturated ketone may form covalent complexes with Zap70. The hypothesis was tested using a molecular modeling approach with a panel of 12 withanolides docked onto the kinase domain of Zap70. Seven natural products revealed a capability to form stable complexes with Zap70 comparable to that of WFA, including withangulatin A, 4β-hydroxywithanolide E, withaperuvin, and ixocarpalactone A. Withangulatin A surpassed all the other withanolides for its ability to engage an interaction with Zap70 kinase and to form covalent complexes via bonding to the Cys346 residue close to the enzyme active site. The physicochemical and ADMET properties of withangulatin A were analyzed via Density Functional Theory calculations and an analysis of its Fukui function descriptors. The C3 position of the enone moiety was identified as the most reactive (nucleophilic) site of the molecule. Withangulatin A revealed a satisfactory ADMET profile with no major toxicity anticipated. It represents a potential hit to guide the design of Zap70 inhibitors. Full article

A new Schiff base, (E)-2-(((1,10-phenanthrolin-5-yl)imino)methyl)-4,6-di-tert-butylphenol (Fen-IHB), was designed to incorporate an intramolecular hydrogen bond (IHB) between the phenolic OH and the azomethine nitrogen with the goal of modulating its physicochemical and biological properties. Fen-IHB was synthesized by condensation of 5-amino-1,10-phenanthroline with 3,5-di-tert-butyl-2-hydroxybenzaldehyde and exhaustively characterized by HR-ESI-MS, FTIR, 1D/2D NMR (¹H, ¹³C, DEPT-45, HH-COSY, CH-COSY, D₂O exchange), and UV–Vis spectroscopy. Cyclic voltammetry in anhydrous CH₃CN revealed a single irreversible cathodic peak at −1.43 V (vs. Ag/Ag⁺), which is consistent with the intramolecular reductive coupling of the azomethine moiety. Density functional theory (DFT) calculations, including MEP mapping, Fukui functions, dual descriptor analysis, and Fukui potentials with dual descriptor potential, identified the exocyclic azomethine carbon as the principal nucleophilic site and the phenolic ring (hydroxyl oxygen and adjacent carbons) as the main electrophilic region. Noncovalent interaction (NCI) analysis further confirmed the strength and geometry of the intramolecular hydrogen bond (IHB). In vitro antimicrobial assays indicated that Fen-IHB was inactive against Gram-negative facultative anaerobes (Salmonella enterica serovar Typhimurium and Typhi, Escherichia coli) and strictly anaerobic Gram-positive species (Clostridioides difficile, Roseburia inulinivorans, Blautia coccoides), as any growth inhibition was indistinguishable from the DMSO control. Conversely, Fen-IHB displayed measurable activity against Gram-positive aerobes and aerotolerant anaerobes, including Bacillus subtilis, Streptococcus pyogenes, Enterococcus faecalis, Staphylococcus aureus, and Staphylococcus haemolyticus. Overall, these comprehensive characterization results confirm the distinctive chemical and electronic properties of Fen-IHB, underlining the crucial role of the intramolecular hydrogen bond and electronic descriptors in defining its reactivity profile and selective biological activity. Full article

This study investigates the influence of vacancy engineering and nitrogen doping on the structural, electronic, and optical properties of T-graphene fragments (TFs) using density functional theory (DFT) and time-dependent DFT (TD-DFT). A central vacancy and five pyridinic nitrogen doping configurations are explored to modulate the optoelectronic behavior. All systems are thermodynamically stable, exhibiting tunable HOMO–LUMO gaps, orbital distributions, and charge transfer characteristics. Optical absorption spectra show redshifts and enhanced oscillator strengths in doped variants, notably v-NTF2 and v-NTF4. Nonlinear optical (NLO) analysis reveals significant enhancement in both static and frequency-dependent responses. v-NTF2 displays an exceptionally high first-order hyperpolarizability (⟨β⟩ = 1228.05 au), along with a strong electro-optic Pockels effect (β (−ω; ω, 0)) and second harmonic generation (β (−2ω; ω, ω)). Its third-order response, γ (−2ω; ω, ω, 0), also exceeds 1.2 × 10⁵ au under visible excitation. Conceptual DFT descriptors and energy decomposition analysis further supports the observed trends in reactivity, charge delocalization, and stability. These findings demonstrate that strategic nitrogen doping in vacancy-engineered TFs is a powerful route to tailor electronic excitation, optical absorption, and nonlinear susceptibility. The results offer valuable insight into the rational design of next-generation carbon-based materials for optoelectronic, photonic, and NLO device applications. Full article

This study examines the effect of oxygen concentration and sputtering power on the surface morphology of TiO₂ thin films deposited by DC reactive magnetron sputtering. Surface roughness parameters were obtained using MountainsMap^® software(10.2) from SEM images, while fractal dimensions and texture descriptors were extracted via Python-based image processing. Fractal dimension was calculated using the box-counting method applied to binarized images with multiple threshold levels, and texture analysis employed Gray-Level Co-occurrence Matrix (GLCM) statistics to capture local anisotropies and spatial heterogeneity. Four samples were analyzed, previously prepared with oxygen concentrations of 50% and 75%, and sputtering powers of 500 W and 1000 W. The results have shown that films deposited at higher oxygen levels and sputtering powers exhibited increased roughness, higher fractal dimensions, and stronger GLCM contrast, indicating more complex and heterogeneous surface structures. Conversely, films produced at lower oxygen and power settings showed smoother, more isotropic surfaces with lower complexity. This integrated analysis framework links deposition parameters with morphological characteristics, enhancing the understanding of surface evolution and enabling better control of TiO₂ thin film properties. Full article

Understanding the early-stage physical interactions between polymeric membranes and supersaturated salt solutions is crucial for advancing membrane-assisted crystallization (MCr) processes. In this study, we employed molecular dynamics (MD) simulations to investigate the short-term morphological response of an isotactic polypropylene (PP) membrane in contact with LiF solutions at different concentrations (5.8 M and 8.9 M) and temperatures (300–353 K), across multiple time points (0, 150, and 300 ns). These data were used as input for computational fluid dynamics (CFD) analysis to evaluate structural descriptors of the membrane, including tortuosity, connectivity, void fraction, anisotropy, and deviatoric anisotropy, under varying thermodynamic conditions. The results show subtle but consistent rearrangements of polymer chains upon exposure to the hypersaline environment, with a marked reduction in anisotropy and connectivity, indicating a more compact and isotropic local structure. Surface charge density analyses further suggest a temperature- and concentration-dependent modulation of chain mobility and terminal group orientation at the membrane–solution interface. Despite localized rearrangements, the membrane consistently maintains a net negative surface charge. This electrostatic feature may influence ion–membrane interactions during the crystallization process. While these non-reactive, short-timescale simulations do not capture long-term degradation or fouling mechanisms, they provide mechanistic insight into the initial physical response of PP membranes under MCr-relevant conditions. This study lays a computational foundation for future investigations bridging atomistic modeling and membrane performance in real-world applications. Full article