Crystal Structure Analysis Research Articles

Chalcogen Bonding in Selective Recognition and Liquid-Liquid Extraction of Perrhenate.

Efficient recognition and extraction of hazardous anionic pollutants from water medium is of great significance for environmental concerns, representing a challenging area of research in supramolecular chemistry. In this study, we present, for the first time, a comprehensive demonstration of the ability of chalcogen bonding (ChB) to recognize and remove the ReO4- from 100% water medium. The anion recognition ability is well elucidated through solution phase NMR and ITC studies, which clearly reveal the selective binding of ReO4- over other oxo-anions. Moreover, the selenoimidazolium scaffold effectively engages in Se•••O ChB interaction with ReO4- as confirmed by X-ray crystal structure and XPS analysis. More importantly, the binding of ReO4- with different prolongations of the σ-holes, along with Se•••Se chalcogen bonding interactions, lead to the formation of a 1D supramolecular assembly. Eventually, ChB receptor Se4Me-Br exhibits ~62% ReO4- extraction efficiency through precipitation as the extraction method. Furthermore, in efforts to enhance efficiency, a hydrophobic ChB receptor Se4Do-PF6 has been prepared, achieving an efficiency of up to ~93% at a very low concentration (~5ppm) by liquid-liquid extraction.

Structural basis of water-mediated cis Watson-Crick/Hoogsteen base-pair formation in non-CpG methylation.

Non-CpG methylation is associated with several cellular processes, especially neuronal development and cancer, while its effect on DNA structure remains unclear. We have determined the crystal structures of DNA duplexes containing -CGCCG- regions as CCG repeat motifs that comprise a non-CpG site with or without cytosine methylation. Crystal structure analyses have revealed that the mC:G base-pair can simultaneously form two alternative conformations arising from non-CpG methylation, including a unique water-mediated cis Watson-Crick/Hoogsteen, (w)cWH, and Watson-Crick (WC) geometries, with partial occupancies of 0.1 and 0.9, respectively. NMR studies showed that an alternative conformation of methylated mC:G base-pair at non-CpG step exhibits characteristics of cWH with a syn-guanosine conformation in solution. DNA duplexes complexed with the DNA binding drug echinomycin result in increased occupancy of the (w)cWH geometry in the methylated base-pair (from 0.1 to 0.3). Our structural results demonstrated that cytosine methylation at a non-CpG step leads to an anti→syntransition of its complementary guanosine residue toward the (w)cWH geometry as a partial population of WC, in both drug-bound and naked mC:G base pairs. This particular geometry is specific to non-CpG methylated dinucleotide sites in B-form DNA. Overall, the current study provides new insights into DNA conformation during epigenetic regulation.

Crystal structure and function analysis of 6-phosphogluconate dehydrogenase in Mycobacterium tuberculosis

6-phosphogluconate dehydrogenase (6PGDH) is an essential enzyme in energy metabolism and redox reactions, and represents a potential drug target for the development of therapies targeting trypanosomes, plasmodium, or other pathogens. Tuberculosis, caused by Mycobacterium tuberculosis, is a contagious disease that severely affects human health, with approximately one-third of the world's population infected. However, the protein structure, exact oligomeric state, and catalytic mechanism of 6PGDH in Mycobacterium tuberculosis (Mt6PGDH) have remained largely unknown. In this study, we successfully purified and determined the structure of Mt6PGDH, revealing its function as a tetramer in both solution and crystal states. Through structural comparisons, we clarified the tetramer formation mechanism and the oligomeric organization of short-chain 6PGDHs. Additionally, we identified key residues for coenzyme recognition and catalytic activity. This work not only deepens our understanding of the enzymatic function of Mt6PGDH but also lays a foundation for the development of drugs targeting this enzyme.

Surface-Functionalized Nano-Montmorillonite and Its Application as Crude Oil Flow Improver

In view of the problem of poor flowability in the production and transportation of high-wax crude oil and high-viscosity crude oil, crude oil flow improvers are commonly used to reduce their viscosity and pour point. Although polymer-based crude oil flow improvers are highly effective in improving crude oil flowability, there are still problems such as high cost and the need for a large amount of solvent dilution when used. In this work, highly dispersed organic modified nano-montmorillonite was prepared by using Na-based montmorillonite and quaternary ammonium salts, and the influencing factors on the viscosity of the crude oil were investigated. The most effective modified nano-montmorillonite (B@MMT) can reduce the viscosity by 96.7% (21 °C) and depress the pour point by 15 °C. Furthermore, it has shown a high improvement in flowability in the other four different sources of crude oil, with viscosity reduction rates of 52.2, 93.4, 79.1 and 67.4%, respectively. B@MMT was characterized by FTIR, SEM, zeta potential and contact angle. Based on DSC and wax crystal structure analysis, the mechanism of the influence of B@MMT on crude oil viscosity and pour point was explored. Finally, the cost of B@MMT was estimated, and the result shows that, compared with the crude oil flow improver in use, B@MMT has considerable commercial competitive advantages.

Surface-Functionalized Nano-Montmorillonite and Its Application as Crude Oil Flow Improver

In view of the problem of poor flowability in the production and transportation of high-wax crude oil and high-viscosity crude oil, crude oil flow improvers are commonly used to reduce their viscosity and pour point. Although polymer-based crude oil flow improvers are highly effective in improving crude oil flowability, there are still problems such as high cost and the need for a large amount of solvent dilution when used. In this work, highly dispersed organic modified nano-montmorillonite was prepared by using Na-based montmorillonite and quaternary ammonium salts, and the influencing factors on the viscosity of the crude oil were investigated. The most effective modified nano-montmorillonite (B@MMT) can reduce the viscosity by 96.7% (21 °C) and depress the pour point by 15 °C. Furthermore, it has shown a high improvement in flowability in the other four different sources of crude oil, with viscosity reduction rates of 52.2, 93.4, 79.1 and 67.4%, respectively. B@MMT was characterized by FTIR, SEM, zeta potential and contact angle. Based on DSC and wax crystal structure analysis, the mechanism of the influence of B@MMT on crude oil viscosity and pour point was explored. Finally, the cost of B@MMT was estimated, and the result shows that, compared with the crude oil flow improver in use, B@MMT has considerable commercial competitive advantages.

Novel magnetic iron oxide-dextran sulphate nanocomposites as potential anticoagulants: Investigating interactions with blood components and assessing cytotoxicity

Examining the critical role of anticoagulants in medical practice, particularly their central function in preventing abnormal blood clotting, is of the utmost importance. However, the study of interactions between blood proteins and alternative anticoagulant nano-surfaces is still understood poorly. In this study, novel approach involving direct functionalisation of magnetic iron oxide nanoparticles (MNPs) as carriers with sulphated dextran (s-dext) is presented, with the aim of evaluating the potential of magnetically-responsive MNPs@s-dext as anticoagulants. The physicochemical characterisation of the synthesised MNPs@s-dext includes crystal structure analysis, morphology study, surface and electrokinetic properties, thermogravimetric analysis and magnetic properties` evaluation, which confirms the successful preparation of the nanocomposite with sulfonate groups. The anticoagulant potential of MNPs@s-dext was investigated using a standardised activated partial thromboplastin time (APTT) test and a modified APTT test with a quartz crystal microbalance with dissipation (QCM-D) which confirmed the anticoagulant effect. Time-resolved solid-liquid interactions between the MNPs@s-dext and model blood proteins bovine serum albumin and fibrinogen were also investigated, to gain insight into their hemocompatibility, and revealed protein-repellence of MNPs@s-dext against blood proteins. The study also addressed comprehensive cytotoxicity studies of prepared nanocomposites, and provided valuable insights into potential applicability of MNPs@s-dext as a promising magnetic anticoagulant in biomedical contexts.

Analysis of hardness, crystal structure and tensile strength by treatment with variations of welding current strength GTAW material SS 316L

This research occurred because problems arose, one of which was a leak in the tank from welding in the tank fabrication with the connecting material being Stainless Steel 316L. The welding process is very important to influence the results and function of the output product from this fabrication. There were leaks in 4 of the 8 tanks, namely at the welded joints. Variations in current strength in the welding machine are one of the factors that influence the welding results. In this study, we analyzed the welded joints with variations in current strength, including 60 A, 70 A, and 80 A. The analysis tests were tensile testing, hardness testing, and X-RD to find out what the deviation is for variations in current strength and to know the results of crystal structure and uniform current strength settings for maximum results and overcoming leakage problems.

Analysis of hardness, crystal structure and tensile strength by treatment with variations of welding current strength GTAW material SS 316L

This research occurred because problems arose, one of which was a leak in the tank from welding in the tank fabrication with the connecting material being Stainless Steel 316L. The welding process is very important to influence the results and function of the output product from this fabrication. There were leaks in 4 of the 8 tanks, namely at the welded joints. Variations in current strength in the welding machine are one of the factors that influence the welding results. In this study, we analyzed the welded joints with variations in current strength, including 60 A, 70 A, and 80 A. The analysis tests were tensile testing, hardness testing, and X-RD to find out what the deviation is for variations in current strength and to know the results of crystal structure and uniform current strength settings for maximum results and overcoming leakage problems.

Effects of the ligand linkers on stability of mixed-valence Cu(I)Cu(II) and catalytic aerobic alcohol oxidation activity

We synthesized a class of ligands that feature single (L1) and dual amine-bis(triazole) chelates (L2 with a 1,3-phenylene linker and L3 with a 1,5-naphthalene linker). Our findings which were derived from UV–Vis titrations, crystal structure analysis of relevant copper complexes, and DFT calculations indicate the formation of both mononuclear CuBr(L1) and dinuclear (μ-Ln)(CuBr)2 (Ln = L2 and L3) complexes. The catalytic activities of CuBr/Ln, in combination with TEMPO (2,2,6,6-tetramethylpiperidin-1-yl)oxyl) co-catalyst and NMI (N-methylimidazole) for aerobic alcohol oxidation, reveal the following activity trend: CuBr/L3 > CuBr/L2 > CuBr/L1. Furthermore, electrochemical data from in-situ generated CuBr complexes suggest that the higher catalytic performance of CuBr/L3 is attributed to the presence of less stable mixed-valence and more reducible Cu(I)-L3-Cu(II) species compared to Cu(I)-L2-Cu(II). This difference is a result of weaker σ interactions between Cu–Namine, larger bridging π systems, and a longer Cu···Cu distance in the presence of L3. Additionally, the catalyst system, CuBr/L3/TEMPO/NMI, efficiently promotes the aerobic oxidation of benzyl alcohol to benzaldehyde at room temperature in CH3CN with a high turnover frequency (TOF) of 38 h−1 at 1 h.

Rational Design of the Spatial Effect in a Fe(II)/α‐Ketoglutarate‐Dependent Dioxygenase Reverses the Regioselectivity of C(sp3)−H Bond Hydroxylation in Aliphatic Amino Acids

AbstractThe hydroxylation of remote C(sp3)−H bonds in aliphatic amino acids yields crucial precursors for the synthesis of high‐value compounds. However, accurate regulation of the regioselectivity of remote C(sp3)−H bonds hydroxylation in aliphatic amino acids continues to be a common challenge in chemosynthesis and biosynthesis. In this study, the Fe(II)/α‐ketoglutarate‐dependent dioxygenase from Bacillus subtilis (BlAH) was mined and found to catalyze hydroxylation at the γ and δ sites of aliphatic amino acids. Crystal structure analysis, molecular dynamics simulations, and quantum chemical calculations revealed that regioselectivity was regulated by the spatial effect of BlAH. Based on these results, the spatial effect of BlAH was reconstructed to stabilize the transition state at the δ site of aliphatic amino acids, thereby successfully reversing the γ site regioselectivity to the δ site. For example, the regioselectivity of L‐Homoleucine (5 a) was reversed from the γ site (1 : 12) to the δ site (>99 : 1). The present study not only expands the toolbox of biocatalysts for the regioselective functionalization of remote C(sp3)−H bonds, but also provides a theoretical guidance for the precision‐driven modification of similarly remote C(sp3)−H bonds in complex molecules.

International Union of Basic and Clinical Pharmacology. CXV: The Class F of G Protein-Coupled Receptors.

The class F of G protein-coupled receptors (GPCRs) consists of ten Frizzleds (FZD1-10) and Smoothened (SMO). FZDs bind and are activated by secreted lipoglycoproteins of the Wingless/Int-1 (WNT) family and SMO is indirectly activated by the Hedgehog (Hh) family of morphogens acting on the transmembrane protein Patched (PTCH). The advance of our understanding of FZDs and SMO as dynamic transmembrane receptors and molecular machines, which emerged during the past 14 years since the first class F GPCR IUPHAR nomenclature report, justifies an update. This article focuses on the advances in molecular pharmacology and structural biology providing new mechanistic insight into ligand recognition, receptor activation mechanisms, signal initiation and signal specification. Furthermore, class F GPCRs continue to develop as drug targets, and novel technologies and tools such as genetically encoded biosensors and CRISP/Cas9 edited cell systems have contributed to refined functional analysis of these receptors. Also, advances in crystal structure analysis and cryogenic electron microscopy contribute to a rapid development of our knowledge about structure-function relationships providing a great starting point for drug development. Despite the progress questions and challenges remain to fully understand the complexity of the WNT/FZD and Hh/SMO signaling systems. Significance Statement The recent years of research have brought about substantial functional and structural insight into mechanisms of activation of Frizzleds and Smoothened. While the advance furthers our mechanistic understanding of ligand recognition, receptor activation, signal specification and initiation, broader opportunities emerge that allow targeting class F GPCRs for therapy and regenerative medicine employing both biologics and small molecule compounds.

Supramolecular self-assembly strategy for the enhanced solubility/dissolution rate and anti-cancer efficacy of osimertinib: Insights from multi-component crystals to drug chemistry

Multi-component crystal based on supramolecular self-assembly is an effective strategy to modify the physicochemical properties of poorly water-soluble drugs. In this study, eight novel multi-component crystals of Osimertinib (AZD) were firstly synthesized under the guidance of theoretical analysis. Five single crystals were successfully obtained, and the AZD-FMS cocrystal shows a distinctive structure wherein free FMS filled in the skeleton, which may be crucial for maintaining morphology. Analysis of crystal structures and Hirshfeld surfaces indicated the involvement of N−H···O and N···H−O hydrogen bonds in the multi-component crystals. Owing to robust intermolecular interactions, multi-component crystals exhibited improved solubility/dissolution rate compared to pure AZD. Multivariate analysis revealed coformers and strong solute–solvent interactions determined the solubility/dissolution rate. Multi-component crystals showed superior stability in solution and low humidity. Moreover, AZD-FSM increased 5.2-fold anti-tumor activity over AZD, which is anticipated to enhance efficacy, reduce drug toxicity, combat drug resistance, and transition from laboratory to clinical application.

Taming of Trinitromethyl-Oxadiazole to access high density and high oxygen balance via a dual modulation strategy

Energetic compounds bearing the trinitromethyl group are garnering broad attraction as potential candidates for a new generation of high energy dense oxidizers. In this work, an effective dual modulation strategy involving both molecular isomerization and crystal morphology control was employed to design and optimize trinitromethyl-oxadiazole with improved comprehensive performance. Utilizing this dual strategy, 3,5-bis(trinitromethyl)-1,2,4-oxadiazole (3) was synthesized, resulting in the formation of two distinct crystal morphologies (needle and sheet) corresponding to two crystal forms (3-a and 3-b). Encouragingly, while maintaining ultra-high oxygen balance (21.73%), 3 achieves impressive densities (1.97–1.98 g/cm3). To our knowledge, the density of 1.98 g/cm3 for 3-a sets a new record among that of nitrogen-rich monocyclic compounds. Notably, practical crystal morphology prediction was creatively introduced to guide the experimental crystallization conditions of 3, increasing the impact sensitivity and friction sensitivity from 1 J and 80 N (3-a) to 10 J and 240 N (3-b), respectively. Additionally, the crystal structural analyses and theoretical calculations were conducted to elucidate the reasons of differences between 3-a and 3-b in density and stability. This work provides an efficient strategy to enhance performance of trinitromethyl derivatives, broadening the path and expanding the toolbox for energetic materials.

Synthesis and application of the AIE-ESIPT fluorescent probe for Cystiene detection: Crystal structure analysis and DFT calculation

Accurate detection of Cysteine (Cys) in cells is critical for clinical diagnosis and pathogen detection. It was of practical significance to develop fluorescent probes with specific recognition and rapid detection of Cys. Therefore, based on the nucleophile reaction and intramolecular cyclization reaction between biothiols and acrylates (AAS), a fluorescence probe, BTY-TPE-AAS, was designed and synthesized by combining the advantages of the Aggregation-Induced Emission (AIE) and Excited-State Intramolecular Proton Transfer (ESIPT) mechanisms. BTY-TPE-AAS could specifically detect Cys with a short detection time and strong anti-interference, which had important application value in the monitoring of Cys in the biomedical field. It provided some reference values for the design of a specific fluorescent probe for Cys detection.

Enhanced H2S gas sensing utilizing UV-assisted In2O3@ZnO nanosheets

In the realm of environmental protection, there is a growing demand for efficient and environmentally friendly gas sensors. In this study, we employed a simple hydrothermal method to synthesize nanosheets composed of zinc oxide (ZnO)-doped indium oxide (In2O3), utilizing zeolitic imidazolate framework-8 (ZIF-8) as a precursor. These nanosheets demonstrated exceptional sensitivity and selectivity in detecting hydrogen sulfide (H2S) gas. A comprehensive analysis of crystal structure, chemical states, elemental composition, surface area, and morphology was conducted. Brunauer–Emmett–Teller (BET) surface area measurements to assess the materials' textural properties revealed that the nanosheets labeled In2O3/0.1ZnO possessed a high specific surface area of 49.02 m2/g, greater than the 45.65 m2/g of pure In2O3 nanosheets, a crucial factor contributing to the observed exceptional sensitivity and selectivity in detecting H2S gas. Particularly noteworthy is the substantial improvement in gas detection response from 109.9 to 146.2 (approximately 24.7 %) observed in the In2O3/0.1ZnO material under UV irradiation at the optimal temperature of 250 °C. This enhancement emphasizes the material's potential for superior gas detection. The incorporation of ZIF-8-derived ZnO nanostructures played a crucial role in creating additional active sites, further enhancing the gas-sensing capabilities. Importantly, this innovative synthesis technique ensures the production of clean, non-toxic materials, aligning with environmental conservation objectives, and holds promise for achieving heightened sensitivity and selectivity in the detection of environmentally harmful gases.

Novel magnetic iron oxide-dextran sulphate nanocomposites as potential anticoagulants: Investigating interactions with blood components and assessing cytotoxicity

Examining the critical role of anticoagulants in medical practice, particularly their central function in preventing abnormal blood clotting, is of the utmost importance. However, the study of interactions between blood proteins and alternative anticoagulant nano-surfaces is still understood poorly. In this study, novel approach involving direct functionalisation of magnetic iron oxide nanoparticles (MNPs) as carriers with sulphated dextran (s-dext) is presented, with the aim of evaluating the potential of magnetically-responsive MNPs@s-dext as anticoagulants. The physicochemical characterisation of the synthesised MNPs@s-dext includes crystal structure analysis, morphology study, surface and electrokinetic properties, thermogravimetric analysis and magnetic properties` evaluation, which confirms the successful preparation of the nanocomposite with sulfonate groups. The anticoagulant potential of MNPs@s-dext was investigated using a standardised activated partial thromboplastin time (APTT) test and a modified APTT test with a quartz crystal microbalance with dissipation (QCM-D) which confirmed the anticoagulant effect. Time-resolved solid-liquid interactions between the MNPs@s-dext and model blood proteins bovine serum albumin and fibrinogen were also investigated, to gain insight into their hemocompatibility, and revealed protein-repellence of MNPs@s-dext against blood proteins. The study also addressed comprehensive cytotoxicity studies of prepared nanocomposites, and provided valuable insights into potential applicability of MNPs@s-dext as a promising magnetic anticoagulant in biomedical contexts.

Unexpected tunable photoluminescence and emission mechanism during the gradual increase of cyclic glucose units

Excitation-dependent (λex-dependent) emission is one of the most common emission characteristics of nonconventional luminophores. Previously, we have reported D-xylose crystals has an obvious λex-dependent color tunable persistent room temperature phosphorescence (p-RTP) from blue to green, but its p-RTP emission at long wavelength is very weak. To further explore this attractive multicolor p-RTP behavior, and to enhance its tunability, the photoluminescence (PL) behavior of three common cyclodextrins (CDs), namely α-CD, β-CD and γ-CD, including solution and single crystals, were studied. Their single crystals demonstrate λex-dependent multicolor p-RTP properties in the order of β-CD>αγ-CD>γα-CD, rather than the strongest with the least glucose units (γα-CD). Among them, the λex-dependent tunable p-RTP of β-CD and α-CD is superior to that of D-(+)-xylose single crystal. The above unexpected phenomena could be explained reasonably through detailed single crystal structure analysis and theoretical calculations. The emission behavior of solution and single crystals of CDs can be reasonably explained by the clustering-triggered emission (CTE) mechanism. Furthermore, CD-based covalent organic frameworks (COF) and supramolecules are readily fabricated, which own significantly enhanced p-RTP emission. Due to the intriguing PL property as well as hydrophilic rim and low biotoxicity of CDs, successful imaging of HCT116 cells and encryption applications were demonstrated. It is believed that the intrinsic PL properties of CDs, especially their regularly adjustable multicolor p-RTP that varies with the number of glucose units, have significant guidance for the development of a series of multicolor luminescent materials.

Berberine analog of chloramphenicol exhibits a distinct mode of action and unveils ribosome plasticity.

Chloramphenicol (CHL) is an antibiotic targeting the peptidyl transferase center in bacterial ribosomes. We synthesized a new analog, CAM-BER, by substituting the dichloroacetyl moiety of CHL with a positively charged aromatic berberine group. CAM-BER suppresses bacterial cell growth, inhibits protein synthesis invitro, and binds tightly to the 70S ribosome. Crystal structure analysis reveals that the bulky berberine group folds into the P site of the peptidyl transferase center (PTC), where it competes with the formyl-methionine residue of the initiator tRNA. Our toe-printing data confirm that CAM-BER acts as a translation initiation inhibitor in stark contrast to CHL, a translation elongation inhibitor. Moreover, CAM-BER induces a distinct rearrangement of conformationally restrained nucleotide A2059, suggesting that the 23S rRNA plasticity is significantly higher than previously thought. CAM-BER shows potential in avoiding CHL resistance and presents opportunities for developing novel berberine derivatives of CHL through medicinal chemistry exploration.

Enhanced Marine Biodegradation of Polycaprolactone through Incorporation of Mucus Bubble Powder from Violet Sea Snail as Protein Fillers.

Microplastics' spreading in the ocean is currently causing significant damage to organisms and ecosystems around the world. To address this oceanic issue, there is a current focus on marine degradable plastics. Polycaprolactone (PCL) is a marine degradable plastic that is attracting attention. To further improve the biodegradability of PCL, we selected a completely new protein that has not been used before as a functional filler to incorporate it into PCL, aiming to develop an environmentally friendly biocomposite material. This novel protein is derived from the mucus bubbles of the violet sea snail (VSS, Janthina globosa), which is a strong bio-derived material that is 100% degradable in the sea environment by microorganisms. Two types of PCL/bubble composites, PCL/b1 and PCL/b5, were prepared with mass ratios of PCL to bubble powder of 99:1 and 95:5, respectively. We investigated the thermal properties, mechanical properties, biodegradability, surface structure, and crystal structure of the developed PCL/bubble composites. The maximum biochemical oxygen demand (BOD) degradation for PCL/b5 reached 96%, 1.74 times that of pure PCL (≈55%), clearly indicating that the addition of protein fillers significantly enhanced the biodegradability of PCL. The surface morphology observation results through scanning electron microscopy (SEM) definitely confirmed the occurrence of degradation, and it was found that PCL/b5 underwent more significant degradation compared to pure PCL. The water contact angle measurement results exhibited that all sheets were hydrophobic (water contact angle > 90°) before the BOD test and showed the changes in surface structure after the BOD test due to the newly generated indentations on the surface, which led to an increase in surface toughness and, consequently, an increase in surface hydrophobility. A crystal structure analysis by wide-angle X-ray scattering (WAXS) discovered that the amorphous regions were decomposed first during the BOD test, and more amorphous regions were decomposed in PCL/b5 than in PCL, owing to the addition of the bubble protein fillers from the VSS. The differential scanning calorimeter (DSC) and thermal gravimetric analysis (TGA) results suggested that the addition of mucus bubble protein fillers had only a slight impact on the thermal properties of PCL. In terms of mechanical properties, compared to pure PCL, the mucus-bubble-filler-added composites PCL/b1 and PCL/b5 exhibited slightly decreased values. Although the biodegradability of PCL was significantly improved by adding the protein fillers from mucus bubbles of the VSS, enhancing the mechanical properties at the same time poses the next challenging issue.

Crystal structure and Hirshfeld surface analysis of a halogen bond between 2-(allyl-thio)-pyridine and 1,2,4,5-tetra-fluoro-3,6-di-iodo-benzene.

The crystal structure of the title 2:1 mol-ecular complex between 2-(allyl-thio)-pyridine and 1,2,4,5-tetra-fluoro-3,6-di-iodo-benzene, C6F4I2·2C8H9NS, at 100 K has been determined in the monoclinic space group P21/c. The most noteworthy characteristic of the complex is the halogen bond between iodine and the pyridine ring with a short N⋯I contact [2.8628 (12) Å]. The Hirshfeld surface analysis shows that the hydrogen⋯hydrogen contacts dominate the crystal packing with a contribution of 32.1%.