Search Results (490)

Metal-free aminobenzoic acid-derived Schiff bases are attractive antimicrobial leads because their azomethine (–C=N–) functionality enables tunable electronic properties and target engagement. We investigated whether halogenation on the phenolic ring would modulate the redox behavior and enhance antibacterial potency, and hypothesized that heavier halogens would favorably tune physicochemical and electronic descriptors. We synthesized three derivatives (SB-3/Cl, SB-4/Br, and SB-5/I) and confirmed their structures using FTIR, ¹H- and ¹³C-NMR, UV-Vis, and HRMS. For SB-5, single-crystal X-ray diffraction and Hirshfeld analysis verified the intramolecular O–H⋯N hydrogen bond and key packing contacts. Cyclic voltammetry revealed an irreversible oxidation (aminobenzoic ring) and, for the halogenated series, a reversible reduction associated with the imine; peak positions and reversibility trends are consistent with halogen electronic effects and DFT-based MEP/LHS descriptors. Antimicrobial testing showed that SB-5 was selectively potent against Gram-positive aerobes, with low-to-mid micromolar MICs across the panel. Among anaerobes, activity was more substantial: Clostridioides difficile was inhibited at 0.1 µM, and SB-3/SB-5 reduced its sporulation at sub-MICs, while Blautia coccoides was highly susceptible (MIC 0.01 µM). No activity was detected against Gram-negative bacteria at the tested concentrations. In the fungal assay, Botrytis cinerea displayed only a transient fungistatic response without complete growth inhibition. In mammalian cells (HeLa), the compounds displayed clear concentration-dependent behavior. Overall, halogenation, particularly iodination, emerges as a powerful tool to couple redox tuning with selective Gram-positive activity and a favorable cellular tolerance window, nominating SB-5 as a promising scaffold for further antimicrobial optimization. Full article

The development of halogen-free flame-retardant formulations for wood-based panels is a promising strategy to improve both fire safety and environmental performance. In this study, oriented strand boards (OSB) were impregnated with aqueous solutions of sodium borate (SBo) and sodium bicarbonate (SBi) to evaluate their combined effects on fire resistance and mechanical properties. Fire performance was assessed using the ASTM D3806 small-scale tunnel test, while mechanical and physical properties were measured according to ASTM D1037. Significant improvements in fire performance were observed: mass loss (ML) during flammability testing decreased by 38% (from 6.9% to 4.3%), flame spread speed (FSS) was reduced by more than 50% (from 6.8 to 3.3 mm/s), and after-flame times (AFT) dropped from 17.2 s to 0 s. Thermogravimetric analysis (TGA) further confirmed enhanced thermal stability, with increased char residue (from 16.9% in untreated boards to 31.5% in treated ones). Mechanical testing revealed a 16% increase in internal bond (IB) strength (from 0.44 to 0.51 MPa), while modulus of rupture (MOR) and modulus of elasticity (MOE) were only slightly affected (decreased by up to 4.2% and 3.6%, respectively). Interestingly, the two additives exerted contrasting effects: SBo reduced strength and bonding performance, whereas SBi improved internal bond strength and dimensional stability. The optimal balance was obtained with treatment P250-50 (250 g SBi and 50 g SBo), which combined enhanced fire resistance with acceptable mechanical integrity. Overall, the results demonstrate that the synergistic use of SBo and SBi offers an effective halogen-free approach to simultaneously enhance the fire resistance and mechanical performance of OSB panels, highlighting its potential for industrial applications. Full article

The rising resistance of bacterial and fungal strains, particularly in biofilm form, is diminishing the efficacy of available therapies and poses a major threat to human health. This highlights the need for new antimicrobial agents. A review of biological studies has shown that 2,7-naphthyridine derivatives exhibit a wide spectrum of pharmacological properties, including antimicrobial activity, which has contributed to the development of new compounds containing this scaffold. In this work, the obtained compounds were tested to assess their ability to eradicate biofilm formed by selected reference strains of opportunistic pathogens: Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans as well as towards normal microbiota representative, referred to as the Lactobacillus crispatus. The tested 2,7-naphthyridine derivatives showed selective antimicrobial activity, exclusively against S. aureus. 10j demonstrated the highest, among tested compounds, activity on this pathogen (MIC = 8 mg/L), while compound 10f exhibited ~100-fold stronger activity (MIC = 31 mg/L) than the majority of the library compounds. The in vitro assessment on fibroblast cell lines demonstrated low cytotoxicity of both compounds 10f and 10j, which was subsequently confirmed in vivo using the Galleria mellonella larval model, where no signs of systemic toxicity were observed during the 5-day observation period. Due to the structural similarity of the compounds 10f and 10j to typical gyrase/topoisomerase IV inhibitors, molecular dynamics simulations were performed on a ternary complex containing protein, DNAds, and a 1,5-naphthyridine inhibitor (PDB ID: 6Z1A). Molecular dynamics of the gyrase–DNA ternary complex supported stable binding of both hydrazone derivatives, with 10j showing slightly more favorable MM/GBSA energetics driven by electrostatics and halogen bonding, consistent with its ~4-fold lower MIC versus 10f. Taken together, our data highlight compound 10j as a promising microbiota-sparing antibacterial candidate, particularly suitable for selective interventions against S. aureus, for instance in vaginal infections, where targeted eradication of the pathogen without disturbing protective commensals is highly desirable. Full article

As an eco-friendly flame-retardant additive, magnesium hydroxide (MH) is widely employed in low-smoking, halogen-free polymer materials due to its environmentally benign nature. In order to enhance flame retardancy performance, the modified MH was modified with tetrakis(hydroxymethyl)phosphonium sulfate (THPS) by a one-pot hydrothermal method. The resulting morphology was characterized using scanning electron microscopy (SEM), and it shows the dispersion of nanometer particles and almost no aggregation. The X-ray photoelectron spectroscopy (XPS) along with Raman spectroscopy show that the THPS is connected with the Mg(OH)₂ by chemical bond. The sample was incorporated into ethylene–vinyl acetate (EVA) to evaluate the flame retardancy was assessed via limiting oxygen index (LOI) and vertical burning tests (UL-94). The results show that THPS modified MH effectively enhanced the flame retardancy, achieving a V-0 rating and an LOI value of 31.3%. In addition, the composites retain good mechanical integrity. The thermal analysis with TGA and DTG shows the formation of the MgO decomposition product, along with water vapor and phosphorus-containing radicals released by modified MH in the combustion process, forming a strong flame-retardant protective layer. In addition, the maximum smoke density of EVA/MHP-3 composite was 155.4, lower than 411.3 for EVA/MH, with a 62.2% reduction in total smoke production. The result shows that THPS is effective for improving the flame-retardant efficiency of inorganic metal hydroxide in polymer composites. Full article

The controlled incorporation of halogens into carbon materials remains a challenge, particularly under mild and scalable conditions. In this work, we investigate the fixation of iodine on high-surface-area graphite (HSAG-100) using green solvents and moderate temperatures. Commercial HSAG was treated with iodine in aqueous and in organic media, with and without promoters, and characterized by XPS, LEIS, N₂ physisorption, TGA/TPD, and XRD. The results reveal that iodine contents up to ~0.6 at% can be achieved, with incorporation strongly influenced by solvent and reaction time. XPS and LEIS confirmed the presence of C–I bonds, while BET analysis showed only moderate decreases in surface area and unchanged mesopore size distribution. Thermogravimetric and TPD analyses demonstrated the high thermal stability of C–I species, and XRD patterns ruled out intercalation between graphene layers. Collectively, these findings demonstrate that iodine can be covalently anchored to HSAG under mild conditions, preserving the graphitic structure and generating stable edge functionalities, thus opening a route for the design of halogen-doped carbons for catalytic and electrochemical applications. Full article

The coordination chemistry of a hydrazinylpyrazine-derived Schiff base ligand (L1), formed in situ from salicylaldehyde and 2-hydrazinopyrazine, with Fe(III) salts has been systematically investigated under varied synthetic conditions. Six discrete Fe(III) complexes (1a–1e and 2) were isolated and structurally characterised via single-crystal X-ray diffraction, revealing diverse coordination geometries ranging from five-coordinate pseudo-trigonal bipyramidal to six-coordinate pseudo-octahedral environments. The supramolecular architectures are governed by a rich interplay of non-covalent interactions, including hydrogen bonding, halogen bonding, and π–π stacking, which significantly influence the crystallisation pathways and final solid-state structures. Continuous shape measure (CShM) analysis highlights substantial geometric distortion in the bis-tridentate complexes, attributed to the steric and electronic constraints imposed by the ligand. Powder X-ray diffraction and infrared spectroscopy confirm the presence of multiple phases in bulk samples, underscoring the kinetic competition between crystallisation and coordination. The results demonstrate that supramolecular stabilisation of monoligated species can kinetically inhibit bis-ligation, with ligand excess and solvent polarity serving as key parameters to direct complex speciation. These findings provide insight into the delicate balance between coordination geometry, ligand strain, and supramolecular assembly in Fe(III) Schiff base complexes. Full article

As work continues unabated in the study of noncovalent bonding, particularly σ-hole bonds, new challenges have emerged as the participation of transition metals in interactions of this sort is fast becoming appreciated. While there are certain similarities with the halogen, chalcogen, etc, bonds, in which the main group elements participate, there are certain unique properties of these metal atoms that must be analyzed before a complete understanding can be attained. As one example, these atoms tend to act simultaneously as both electron donors and acceptors, a synergistic action that amplifies the overall bond strength. Ideas are expressed in this paper to hopefully guide future work in this exciting new arena. Full article

The reaction of rhodanine vinyl bithiophene (BTR) with molecular dibromine (Br₂) resulted in the formation of compound 1. Single-crystal X-ray diffraction analysis revealed bromination of the terminal thiophenyl ring and the formation of a 1:1 CT “spoke” adduct between the rhodanine thiocarbonyl group and a neutral dibromine (Br₂) molecule. Full article

Hormone-dependent breast cancer, particularly in its treatment-resistant forms, remains a significant therapeutic challenge. In this study, we applied a fully computational strategy to design steroid-based compounds capable of simultaneously targeting three key receptors involved in disease progression: progesterone receptor (PR), estrogen receptor alpha (ER-α), and HER2. Using a robust 3D-QSAR model (R² = 0.86; Q²_LOO = 0.86) built from 52 steroidal structures, we identified molecular features associated with high anticancer potential, specifically increased polarizability and reduced electronegativity. From a virtual library of 271 DFT-optimized analogs, 31 compounds were selected based on predicted potency (pIC₅₀ > 7.0) and screened via molecular docking against PR (PDB 2W8Y), HER2 (PDB 7JXH), and ER-α (PDB 6VJD). Seven candidates showed strong binding affinities (ΔG ≤ −9 kcal/mol for at least two targets), with Estero-255 emerging as the most promising. This compound demonstrated excellent conformational stability, a robust hydrogen-bonding network, and consistent multitarget engagement. Molecular dynamics simulations over 100 nanoseconds confirmed the structural integrity of the top ligands, with low RMSD values, compact radii of gyration, and stable binding energy profiles. Key interactions included hydrophobic contacts, π–π stacking, halogen–π interactions, and classical hydrogen bonds with conserved residues across all three targets. These findings highlight Estero-255, alongside Estero-261 and Estero-264, as strong multitarget candidates for further development. By potentially disrupting the PI3K/AKT/mTOR signaling pathway, these compounds offer a promising strategy for overcoming resistance in hormone-driven breast cancer. Experimental validation, including cytotoxicity assays and ADME/Tox profiling, is recommended to confirm their therapeutic potential. Full article

The crystal structures of the 2-amino-5-halogenopyridines (halogen = Cl (1), Br (2)) and 2,3-diamino-5-halogenopyridines (halogen = Cl (3), Br (4)) were compared with respect to their intermolecular interactions. An ab-initio-based method for evaluating the interaction energies between molecules was employed to estimate the driving forces of crystal formation. As a result, regularities in crystal structure organization were identified. For compounds 1 and 2, a dimeric building unit is formed by two N–H…N_pyr hydrogen bonds. These dimers are further connected to neighboring units by C–H…π, C–H…N, N…X (X = Cl, Br), and non-specific interactions. The aforementioned intermolecular interactions give rise to layered structures that are similar but not isotypical. No significant contributions from π–π or N–H…N(H₂) interactions are observed in 1 and 2. The structures of 3 and 4 are isotypical and crystallize in the non-centrosymmetric space group P2₁2₁2₁. The most important intermolecular interactions are N–H…N_pyr, N–H…N(H₂), and stacking interactions. These interactions lead to identical columnar-layered structures in both 3 and 4. No significant contributions from halogen bonds of the type N…X (X = Cl, Br) are found in 3 and 4. Full article

Type 2 diabetes mellitus (T2DM) demands safer and more effective therapies to control postprandial hyperglycemia. Here, we report the synthesis and in vitro evaluation of ten salicylic acid-derived Schiff base derivatives (4a–4j) as α-glucosidase inhibitors. Compounds 4e, 4g, 4i, and 4j exhibited potent enzyme inhibition, with IC₅₀ values ranging from 14.86 to 18.05 µM—substantially better than acarbose (IC₅₀ = 45.78 µM). Molecular docking and 500 ns molecular dynamics simulations revealed stable enzyme–ligand complexes driven by π–π stacking, halogen bonding, and hydrophobic interactions. Density Functional Theory (DFT) calculations and molecular electrostatic potential (MEP) maps highlighted key electronic factors, while ADMET analysis confirmed favorable drug-like properties and reduced nephrotoxicity. Structure–activity relationship (SAR) analysis emphasized the importance of halogenation and aromaticity in enhancing bioactivity. Full article

The radical-mediated intramolecular translocation of cyano groups has been recognized as a useful tool for the site-selective functionalization of organic molecules. The process is believed to proceed through the addition of an in situ-generated carbon-centered radical to the nitrile triple bond, followed by the β-scission of the resulting cyclic iminyl radical intermediate to relocate the cyano group and produce a more stable carbon radical for further elaboration. Beginning in the early 1960s and continuing for the next forty years, the research in this particular area has seen a surge of growth during the past two decades with advancements in radical chemistry and photocatalysis. The present article attempts to conduct a comprehensive review of existing studies on this topic by covering the literature from 1961 to 2025. The procedures developed for the purpose are grouped and discussed in four sections according to the strategies used to generate the initial carbon radicals, which include (i) hydrogen-atom transfer (HAT), (ii) radical addition to the π system, (iii) halogen-atom transfer (XAT), and (iv) the homolytic fission of a C-C single bond. In each section, a specific emphasis will be placed on reaction conditions, substrate scopes, and mechanisms. Full article

The pyrrolo[2,3-d]pyrimidine (7-deazapurine) scaffold is a unique heterocyclic system included in the composition of most nucleotides. In this study, series of the pyrrolo[2,3-d]pyrimidine-imines and 3-halo-substituted pyrrolo[2,3-d]pyrimidines were designed and prepared in high yields. Condensed pyrimidines are obtained via carbonyl-amine condensation and carbon-halogen bond formation. Pyrrolo[2,3-d]pyrimidine-imines containing a bromine substituent at position C-4 of the phenyl ring and azepine side-ring exhibited superior antitumor activity on the colon cancer HT-29 cell line; IC₅₀ values were 4.55 and 4.01 µM, respectively. These results revealed an interesting pattern, where condensed pyrimidinones containing an azepine ring demonstrated selective antitumor activity on the colon cancer cell line HT-29. In addition, the molecular docking results suggest that compound 8g provided a thorough understanding of its interactions with the DDR2 active site. This could pave the way for further development and optimization of DDR-targeting drugs, contributing to advancements in cancer therapeutics. This lead compound may serve as design templates for further studies. Full article

The photofragmentation of halothane (CF₃CHBrCl) was studied with synchrotron radiation by photoionization efficiency (PIE) measurements and photoelectron–photoion coincidence (PEPICO) experiments, as well as by a theoretical exploration of potential energy surfaces. Among the other fragments, the formation of the CHClF⁺ and CHBrF⁺ ions, which involves the transfer of a F atom between the two moieties of the parent molecule, was observed. To understand the mechanisms leading to the halogen migration, a detailed theoretical study of the production of CHClF⁺, m/z 67⁺, based on DFT calculations and natural bond orbital (NBO) analysis was conducted. The results contribute to the understanding of the photochemistry of halothane, its polluting behavior in the high atmosphere, and the formation of highly reactive species. Full article

Accurate determination of carbon core-electron binding energies (C1s CEBEs) is crucial for X-ray photoelectron spectroscopy (XPS) assignments and predictive computational modeling. This study evaluates density functional theory (DFT)-based methods for calculating C1s core-electron binding energies (CEBEs), comparing three functionals—PW86x-PW91c (DFTpw), mPW1PW, and PBE50—across 68 C1s cases in small hydrocarbons and halogenated molecules (alkyl halides), using the delta self-consistent field ΔSCF (or ΔDFT) method developed by one of the authors over the past decade. The PW86x-PW91c functional achieves a root mean square deviation (RMSD) of 0.1735 eV, with improved accuracy for polar C-X bonds (X=O, F) using mPW1PW and PBE50, reducing the average absolute deviation (AAD) to ~0.132 eV. The study emphasizes the role of Hartree–Fock (HF) exchange in refining CEBE predictions and highlights the synergy between theoretical and experimental approaches. These insights lay the groundwork for machine learning (ML)-driven spectral analysis, advancing materials characterization, and catalysis through more reliable automated XPS assignments. Full article