Search Results (510)

Highly polar M-mol-X (M = alkali metal, mol = molecule, X = halogen) insertion complexes have been predicted to offer potential practical applications, including molecular interactions with light, ion-pair induced isomerization, etc. In the present work, the insertion complexes of the seven-membered, fused bicyclic norcaradiene and its monocyclic isomer trapped in Li-I, Na-I, and K-I counterion pairs were investigated using ab initio methods. The structures, stability, polarities, and simulated infrared spectra are analyzed and the effects of the insertion on the norcaradiene to cycloheptatriene isomerization process are examined. Furthermore, an uncommon bond between iodine and a fully substituted carbon atom is reported upon and hypothesized to be catalyzed by the presence of the cation in the insertion complexes. Full article

Two novel cocrystals of zwitterionic trimethylglycine (TMG) with 2,6-dichlorophenol [TMG•2,6-dichlorophenol] (1:1) and 2,6-dibromophenol [TMG•2,6-dibromophenol] (1:2) are synthesized and structurally characterized using single crystal X-ray diffraction. To estimate the energy of various intermolecular interactions, periodic DFT calculations were performed followed by Bader analysis of the crystalline electron density. TMG molecules form dimers in [TMG•2,6-dichlorophenol] (1:1). Its supramolecular structure is governed by the primary charge-assisted H-bonds (~60 kJ/mol) and supported by C–H∙∙∙O contacts (~12 kJ/mol). Cl/Br substitution introduces a more potent halogen-bonding donor. The Br∙∙∙O⁻ interaction (~10 kJ/mol) is strong enough to reorganize the packing into a catemeric motif. As a result, TMG molecules form infinite chains in [TMG•2,6-dibromophenol] (1:2). This illustrates that “fine tuning” is not merely about changing distances, but about shifting the entire energy hierarchy of the crystal. Two-dimensional fingerprint diagrams (2D diagrams) obtained from the Hirshfeld surface and Bader’s analysis of the crystalline electron density give significantly different values of the contributions of the H∙∙∙H contacts, 28% vs. 5% respectively. The main reason for this discrepancy is the large number of relatively short intermolecular H∙∙∙H contacts without a critical bond point in trimethylglycine cocrystals. Full article

This paper systematically studied the structural, mechanical, electronic, and optical characteristics of cubic KZnX₃ (X = F, Cl, Br, and I) perovskites through the density functional theory (DFT) in the Quantum Espresso framework. Structural optimization and stability analyses confirm that all compounds crystallize in the cubic Pm-3m phase and are thermodynamically, mechanically, and dynamically stable. Elastic constants indicate that the materials are anisotropic and ductile in nature. Calculations of Debye temperatures show a systematic decrease of 402 K (KZnF₃) to 158 K (KZnI₃), which is related to the increasing mass of halogen and its impact on the rigidity of the lattice. Electronic structure calculations show that all compounds are indirect bandgap semiconductors, with bandgaps systematically decreasing from 4.24 eV (KZnF₃) to 0.86 eV (KZnI₃) at the HSE06 level, enabling tunable semiconducting characteristics for optoelectronic applications. The analysis of the density of states and charge density indicates that the bonding between Zn and X is mixed ionic and covalent and that the bonding between K and X is mostly ionic. Calculations of optical properties show an increase in polarizability, absorption, refractive index and plasmonic response when heavier halogen is used, highlighting the potential of KZnX₃ perovskites for photovoltaic and optoelectronic devices. Overall, halogen substitution in KZnX₃ provides an effective strategy for tailoring electronic and optical properties. Full article

Phenothiazine is a heteroaromatic molecule capable of various noncovalent interactions, including halogen bonding and π-stacked association. Despite its broad use in functional materials and pharmaceutical ingredients, a systematic comparison of these interaction modes has been lacking. Here, we report a combined experimental and computational study of intermolecular interactions of phenothiazine with a prototypical halogen-bond (HaB) donor (tetrabromomethane), planar π-electron acceptors (tetracyanopyrazine and tetrafluoro-p-benzoquinone), and multifunctional species capable of both interaction types (iodo- and bromo-3,5-dinitrobenzenes). X-ray structural analysis revealed that CBr₄ forms exclusively C–Br···π halogen bonds with the aromatic rings of phenothiazine, whereas all π-acceptors yield alternating donor–acceptor stacks characterized by multiple short contacts indicative of multicenter interactions. Notably, co-crystals of iodo- and bromodinitrobenzenes with phenothiazine display only π-stacked architectures. Density-functional calculations showed that isolated HaB complexes involving N, S, or π sites of phenothiazine possess comparable binding energies (≈−3 kcal mol⁻¹), whereas π-stacked complexes are substantially stronger (≈−9–12 kcal mol⁻¹). QTAIM, NCI, NBO, and energy-decomposition analyses indicated that while amounts of charge transfer in halogen-bonded and π-stacked complexes are comparable, the enhanced stability of the latter originates primarily from a large dispersion contribution. These results rationalize the solid-state preference for π-stacking over halogen bonding in systems where both motifs are accessible and clarify the hierarchy and physical origin of noncovalent interactions involving phenothiazine, providing guidance for the design of supramolecular assemblies and functional materials based on this versatile electron donor. Full article

This study investigates the rational design of a dinuclear zinc(II) coordination polymer, (C₃₆H₃₄Br₂N₈O₄S₂Zn₂), to explore how halogen substitution and ligand choice modulate structural architecture, contributing to the development of functional coordination polymers with tailored properties. The complex was synthesized from a bromo-substituted semicarbazone Schiff base ligand (L1) and a rigid bipyridine linker (L2) under solvothermal conditions, and its structure was elucidated using single-crystal X-ray diffraction (SCXRD), complemented by characterization via powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), and infrared (IR) spectroscopy. Crystallographic analysis reveals that the complex crystallizes in the triclinic space group P-1, forming discrete dinuclear units where each Zn(II) center adopts a distorted square–pyramidal geometry; these units are extended into one-dimensional chains by bridging L2 ligands and further assembled into a three-dimensional supramolecular network through hydrogen-bonding interactions. PXRD confirms the high phase purity of the bulk material, TGA indicates notable thermal stability up to 130 °C, and IR spectroscopy validates the coordination modes and hydrogen-bonding network. This work elucidates the critical role of the bromo substituent and rigid ancillary ligands in modulating the solid-state structure of the zinc(II) complex. The revealed structure-directing principles provide a valuable reference for the rational design of functional coordination polymers. Full article

Pirimicarb is a carbamate insecticide, widely used due to its specific control effect on aphid populations. However, the European Food Safety Authority conducted a risk assessment and proposed regulatory endpoints for it in October 2024. Therefore, there is an urgent need to develop rapid, sensitive, and convenient rapid detection technologies for pirimicarb. Thus, this study proposes an enzyme-free rapid detection method: using 4,5,6,7-tetrabromo-2′,4′,5′,7′-tetraiodofluorescein (RB2) as a detection probe, since the synergistic effect of halogen and hydrogen bonding between RB2 and pirimicarb (PIB) in acidic aqueous solution induces charge transfer and leads to a distinct color change in RB2, thereby enabling the rapid detection of PIB. This method has good selectivity, and a limit of detection (LOD) of 0.0321 mg·L⁻¹ in aqueous solution is achieved with a visual detection time of less than 60 s for PIB. And the LODs for PIB in cucumber and tomato peel samples are 0.0536 mg·L⁻¹ and 0.0243 mg·L⁻¹, respectively. Importantly, this method does not require enzymes as a vehicle in the detection process; it solely relies on the synergistic effect of halogen and hydrogen bonding between RB2 and PIB to achieve visual identification and detection of PIB, providing a reference method for the rapid detection of PIB. Full article

Water pollution from phenols remains a critical concern due to their persistence, toxicity, and industrial prevalence. Graphene oxide (GOx), with its functional groups and large surface area, offers strong adsorption potential. Using density functional theory (DFT), reduced density gradient (RDG), and quantitative structure–activity relationship (QSAR), we examined how protonation and substituents influence phenol adsorption. Deprotonated phenolates bind more strongly to GO than neutral species via electrostatics and H-bonding. Substituents alter affinity: halogens enhance it, bulky alkyls hinder it, and nitro groups show electron-withdrawing effects. Bisphenolate A displayed multidentate binding. QSAR models reproduced DFT energies with R² > 0.99, enabling fast prediction. These results highlight how pH speciation and substituents govern adsorption on GO, guiding the design of efficient water treatment materials. Full article

The title compound 2-iodopyridin-3-yl acetate was obtained by acetylation of the OH group of 2-iodo-3-hydroxypyridine. Knowing that the hydroxyl group, as a strong H-bond donor in halogenated hydroxypyridines, usually directs supramolecular packing and might enforce possible halogen–halogen contacts, we crystallized 2-iodo-3-acetoxypyridine with the aim of disrupting the most important H-bond donor and assessing the propensity of the iodine for halogen bond formation. Indeed, in the compound 2-iodopyridin-3-yl acetate, the crystal packing is characterized by infinite 3D chains bonded through I···O=C and C-H···I contacts between adjacent molecules. These chains are interconnected by weak C-H···O contacts, implying the presence of oxygen in the ester. The I···H contact with the C-H axis perpendicular to the electron belt of the iodine atom can enhance the σ-hole of the iodine and act cooperatively in crystal cohesion. No halogen–halogen contacts were present. Full article

Objective: Based on our previous findings, we designed new molecules by extending functionalized pyrazole derivatives containing iodine atoms, which are linked via an amino bond to halogen-substituted phenyl groups. In addition, these newly developed pyrazole compounds exhibit anti-tumor, antibacterial, and anti-biofilm activities. Methods: Three new series of pyrazole compounds were designed. Fifteen novel pyrazole derivatives, distributed across three series (4a–d, 5a–d, and 6a–g), were synthesized and structurally characterized by ¹H-NMR, ¹³C-NMR, FTIR, UV-Vis spectroscopy, and elemental analysis. Results: Among them, compound 4c, which exhibited notable anti-tumor activity, crystallized in a monoclinic system and was further analyzed via single-crystal X-ray diffraction. All synthesized compounds were evaluated in vitro on NCTC normal fibroblast cells and HEp-2 tumor epithelial cells. Compound 4c demonstrated significant anti-tumor activity while displaying no cytotoxic effects on normal cells. The antibacterial and anti-biofilm activities of the compounds were also assessed against four bacterial strains. Compounds 5a and 5c exhibited the highest antibacterial activity against Staphylococcus aureus ATCC 25923, both with a minimum inhibitory concentration (MIC) of 0.023 μg/mL. Additionally, compounds 4a, 5a, 6a, 6e, and 6f showed the strongest anti-biofilm effects, each presenting a minimum biofilm inhibition concentration (MBIC) of 0.023 μg/mL. ADME and ADMET in silico predictions indicated that all compounds exhibit generally favorable, drug-like physicochemical properties. Conclusions: The study reinforces the applicability of these compounds as promising anticancer, antibacterial, and anti-biofilm drugs. Full article

By the reaction of AgNO₃, 2-methyl-2-propanethiol (HStBu), with various-sized halogen ions as templates, three multi-nuclear silver-thiolate cluster-based chain-like coordination polymers, [Ag₆(μ-SBu)₆]_n (USC-CP-2), [Ag₆(μ-StBu)₅Br]_n (USC-CP-4) and [Ag₁₄(μ-StBu)₁₂I₂]_n (USC-CP-3) constructed by different Ag(I)-nanocages, have been synthesized and characterized by X-ray diffraction analyses. With F⁻, Cl⁻ or without template, USC-CP-2 exhibits a one-dimensional structure composed of detached Ag₆-cages, absent of fluoride or chloridion. While with Br⁻ and I⁻, USC-CP-4 and USC-CP-3, two distinct halogen-templating multi-sliver cages-based chain-like polymeric structures have been observed, which are a mono-Br⁻ encapsulated Ag₈-cage, or a dual-I⁻ embedded Ag₁₆-cage, respectively. In these three compounds, the multi-Ag(I) cages were self-assembled by Ag-S bonds through bridged μ₂-StBu ligands, and stabilized argentophilic interactions between neighboring silver atoms. This study demonstrates that the halide anions of varying sizes play a critical role in inducing the nucleation and structural evolution of the silver-thiolate clusters. Full article

Per- and polyfluoroalkyl substances (PFASs), as a class of “permanent chemicals” with high environmental persistence and bioaccumulation, have attracted much attention. In this study, we focused on the molecular mechanism of the interaction between perfluoroalkyl acids (PFAAs) and peroxisome proliferator-activated receptor δ (PPARδ). Using molecular docking, binding free energy calculation, and structural analysis, we systematically investigated the binding modes, key amino acid residues, and binding energies of 20 structurally diverse PFAAs with PPARδ. The results showed that the binding energies of PFAAs with PPARδ were significantly affected by the molecular weight, the number of hydrogen bond donors, and the melting point of PFAAs. PFAAs with smaller molecular weights and fewer hydrogen bond donors showed stronger binding affinity. The binding sites were concentrated in high-frequency amino acid residues such as TRP-256, ASN-269, and GLY-270, and the interaction forces were dominated by hydrogen and halogen bonds. PFAAs with branched structure of larger molecular weight (e.g., 3m-PFOA, binding energy of −2.92 kcal·mol⁻¹; 3,3m₂-PFOA, binding energy of −2.45 kcal·mol⁻¹) had weaker binding energies than their straight-chain counterparts due to spatial site-blocking effect. In addition, validation group experiments further confirmed the regulation law of binding strength by physicochemical properties. In order to verify the binding stability of the key complexes predicted by molecular docking, and to investigate the dynamic behavior under the conditions of solvation and protein flexibility, molecular dynamics simulations were conducted on PFBA, PFOA, 3,3m₂-PFOA, and PFHxA. The results confirmed the dynamic stability of the binding of the high-affinity ligands selected through docking to PPARδ. Moreover, the influence of molecular weight and branched structure on the binding strength was quantitatively verified from the perspectives of energy and RMSD trajectories. The present study revealed the molecular mechanism of PFAAs interfering with metabolic homeostasis through the PPARδ pathway, providing a theoretical basis for assessing its ecological and health risks. Full article

Haloketoesters are synthetic intermediates in various cyclization reactions that facilitate the production of biologically active compounds. Nonetheless, the selective synthesis of dihaloketoesters and trihaloketoesters, which are expected to be highly versatile, presents significant challenges. In this study, we designed a new synthetic approach that selectively and efficiently produces haloketoesters through the halogenative C–C bond cleavage and ring-opening reactions of cyclic 1,3-diketones. This convenient method enables the direct synthesis of di- and trichloro-functionalized ketoesters from 1,3-cyclohexadiones under mild conditions. Na₂HPO₄, employed as a buffer salt, proved to be effective in facilitating the alcoholytic ring-opening reaction of 2,2-dichloro-1,3-cyclohexadiones, which were generated as synthetic intermediates. Full article

Classical chemical bonding is typically categorized into primary, strong interactions, such as covalent, ionic, and metallic bonds, and secondary, weak interactions, such as van der Waals forces, the hydrogen bond, and their likes (halogen bond, chalcogen bond, etc.). However, other not-so-known bonding mechanisms also play a crucial role in chemical systems. Particularly important are the charge-shift bond (CSB) and the multicenter bonds, i.e., the electron-rich multicenter bond (ERMB), also known as hypervalent or three-center-four-electron (3c-4e) bond, and the electron-deficient multicenter bond (EDMB), also known as the three-center-two-electron (3c-2e) bond in molecules and, more recently, as the two-center-one-electron (2c-1e) bond in extended solids. We consider that these latter interactions have not yet received the proper attention of the scientific community, even though multicenter interactions were proposed in the early days of Quantum Mechanics. In this work, we aim at providing: (i) a concise historical overview of the two types of multicenter bonds; (ii) a short introduction to the recently proposed unified theory of multicenter bonding (UTMB), which elucidates the origin and mechanisms of formation of both ERMBs and EDMBs; and (iii) an extension of the UTMB to include CSBs, due to the strong relationship between ERMBs and CSBs. We hope that the integrated perspective of chemical bonding, the heartland of chemistry, offered by the UTMB (beyond traditional and historical assumptions) will help researchers to understand materials properties and will provide a framework allowing the development of advanced materials for enhanced technological applications. Full article

Four benzyltrimethylammonium (BTMA) salts were successfully prepared: bis(benzyltrimethylammonium) hexachloroplatinate (1), benzyltrimethylammonium tetrachloroaurate (2), bis(benzyltrimethylammonium) tetrachlorocuprate (3), and bis(benzyltrimethylammonium) tetrabromocuprate (4) from benzyltrimethylammonium hydroxide (Triton B). Their crystal structures were determined by single-crystal X-ray diffraction, and the supramolecular architectures were characterized hierarchically. Extended Hirshfeld surface analysis, including enrichment ratio calculations, was performed to evaluate intermolecular interactions. Nonclassical hydrogen bonds, such as C–H^…Cl(Br), involving the anions, contribute to the formation of self-assembled architectures. Additional stabilization arises from π^…π and Cu–Br^…π interactions, particularly in crystals 2 and 4, respectively. Hirshfeld surface analysis showed that H^…H and C^…H/H^…C interactions are the dominant contributors in all crystals. According to enrichment ratio calculations, C^…H/H^…C interactions in 1, 3, and 4; Cl^…H/H^…Cl in 1 and 3; Cu^…H/H^…Cu in 3 and 4; and Br^…H/H^…Br and Br^…C/C^…Br in 4 are statistically favored in the crystal packing. Halogen bonding Cl^…Cl was observed in 1 but does not significantly influence packing. Energy framework calculations indicated that dispersive interactions are favorable in the analyzed crystals. A library of H-bonding supramolecular patterns, including interchangeable synthons, is provided and may guide the rational design of new derivatives with controllable features. Finally, the topology of intermolecular connections and the electronic structure of the benzyltrimethylammonium cation, investigated by quantum-chemical calculations, provide insights into its reactivity. 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