Stacking Interactions Research Articles

Understanding the Adsorption and Diffusion Behaviors of PBUT in Biocompatible MOFs.

With the increasing incidence of chronic kidney disease, the effective control of protein-bound uremic toxins (PBUTs), which are difficult to remove through dialysis, has become a priority. In this study, the adsorption and diffusion behaviors of several metal-organic frameworks (MOFs) for PBUTs (indoxyl sulfate and p-cresyl sulfate) were studied by molecular dynamics (MD) simulations and umbrella sampling. For the NU series of MOFs, good correlations between the Gibbs free energy (ΔG) and the experimental clearance rates of PBUTs are found. For the adsorption behaviors, in terms of ΔG, DAJWET exhibits the best adsorption effect for indoxyl sulfate (IS), whereas NU-1000 shows the best effect for p-cresyl sulfate (pCS). Similar trends observed in the radial distribution function and mean square displacement results suggest that the π-π stacking interactions play a crucial role in the adsorption and diffusion of PBUTs by MOFs. Furthermore, it can be concluded that MOFs with highly conjugated groups (porphyrin rings and pyrene groups) tend to generate more PBUT attraction, and provide design principles for potential MOF candidates in the removal of PBUTs.

The design of molecularly dispersed tungstovanadate catalyst via ionic liquid linkers for oxidative desulfurization

The sulfur removal process in diesel is one of the key technologies to produce clean energy using polyoxometalate (POM)-based catalyst with excellent catalytic active sites. Herein, a molecularly dispersed POM supported catalyst CNT@(C4mim)4VW12O40 (CNT@C4VW12) was designed by introducing imidazole ionic liquids (IL) [C4mim]Br as counterionic linkers for oxidation desulfurization (ODS). For the model oil, 100 % desulfurization rate and product selectivity can be achieved within 30 min, and it can be recycled for 5 times without obviously decrease. Moreover, CNT@C4VW12 also displayed excellent performance in real hydrotreated diesel with a removal rate of 97.4 %. Overall, a stable and molecularly dispersed catalyst was constructed by the cooperative effect of π-π stacking, hydrogen bonding and electrostatic force interaction among the CNT, [C4mim]+ and [VW12O40]4−, which would provide new inspirations for design of heterogeneous catalyst towards excellent ODS process.

On the flexibility of 1,4-bis(phenylethynyl)benzene butyl ester organic crystal featuring mobile components

The quest for organic materials with compliant mechanical properties has significantly increased in the past few years in materials science and engineering. Crystalline organic compounds are excellent candidates for exploring and developing those long-lasting properties in the solid state since their fine structural functionalization may provide them with unique flexible behaviors. This study describes the 1,4-bis(phenylethynyl)benzene butyl ester synthesized in four steps and whose crystal can display elastic and elasto-plastic responses upon action with an external stimulus. A detailed characterization by single crystal X-ray diffraction revealed a layered crystal array that results from π-π stacking interactions, C–H⋯O and C-H⋯π bonds. Complementarily, variable temperature solid-state 13C and 2H NMR studies were carried out to probe the motion of the different components of the molecule and explore their possible association with the mechanical features. The compiled evidence indicates that the central phenylenes and the butyl groups experience molecular motion at different timescales, which, combined with the crystal array, facilitate the observed elastic and elasto-plastic flexibility. The results presented here not only contribute to advancing our understanding of flexible behavior but also could inspire potential applications such as flexible electronics.

A polymeric Co(II) oxalate salt containing pyridinium type cations: Synthesis, structure, spectroscopy, thermal behavior and magnetism

A Co(II) oxalate coordination polymer, (C7H11N2)2[Co(C2O4)2]·5H2O (1) (C7H11N2+ = 2-amino-4,6-dimethylpyridinium cation), has been synthesized and characterized by elemental and thermal analyses, FT-IR and UV/Vis spectroscopies, powder X-ray diffraction (PXRD), single-crystal X-ray diffraction and variable temperature magnetic susceptibility measurements. Compound 1 is a polymerized organic–inorganic hybrid salt, the asymmetric unit of which consists of one Co(II) ion, one bidentate C2O42− ligand, two halves of bidentate C2O42− ligands, two 2-amino-4,6-dimethylpyridinium C7H11N2+ cations and five crystal water molecules. Each CoII center is six-coordinated in a distorted octahedral geometry fulfilled by six oxygen atoms from three chelating C2O42− ligands. The [Co(C2O4)2]2− ions act as complex ligands and efficiently bridge neighboring Co2+ ions, forming chains of complex anions linked by hydrogen bonded water molecules. Hydrogen bonding interactions of the type OH∙∙∙O and NH∙∙∙O along with π–π stacking interactions between pyridine rings contribute to the stabilization of the 3D supramolecular framework. Temperature-dependence magnetic moment (µ) collected under zero-field cooled (ZFC) and field-cooled (FC) conditions revealed weak antiferromagnetic ordering at low temperatures.

RNA binding tunes the conformational plasticity and intradomain stability of TDP-43 tandem RNA recognition motifs

TAR DNA binding protein 43 (TDP-43) is a nuclear RNA/DNA-binding protein with pivotal roles in RNA-related processes such as splicing, transcription, transport, and stability. The high binding affinity and specificity of TDP-43 toward its cognate RNA sequences (GU-rich) is mediated by highly conserved residues in its tandem RNA recognition motif (RRM) domains (aa: 104–263). Importantly, the loss of RNA binding to the tandem RRMs caused by physiological stressors and chemical modifications promotes cytoplasmic mislocalization and pathological aggregation of TDP-43. Despite the substantial implications of RNA binding in TDP-43 function and pathology, its precise effects on the intradomain stability, and conformational dynamics of the tandem RRMs is not properly understood. Here, we employed all-atom molecular dynamics (MD) simulations to assess the effect of RNA binding on the conformational landscape and intradomain stability of TDP-43 tandem RRMs. RNA limits the overall conformational space of the tandem RRMs and promotes intradomain stability through a combination of specific base stacking interactions and transient electrostatic interactions. In contrast, tandem RRMs exhibit a high intrinsic conformational plasticity in the absence of RNA, which, surprisingly, is accompanied by a tendency of RRM1 to adopt partially unfolded conformations. Overall, our simulations reveal how RNA binding dynamically tunes the structural and conformational landscape of TDP-43 tandem RRMs, contributing to physiological function and mitigating pathological aggregation.

Constructing binuclear sites to modulate the charge distribution of MIL-101 for enhanced toluene adsorption performance: experimental and theoretical studies

Toluene is a class of volatile organic compounds (VOCs) in the air that harm environmental quality and human health. To enhance the adsorption performance of adsorbents for toluene, based on the principle that unsaturated metal sites in MOFs can be replaced, nanoscale M@MIL-101(M represents Mg, Ca, Sr) with binuclear sites was prepared by a one-step solvothermal method. The second metal was successfully introduced into the topology of MIL-101 by partially substituting Cr sites. The results of the dynamic adsorption experiments showed that 20%Sr@MIL-101 exhibited the highest toluene adsorption capacity, which was about 60% higher than that of the undoped MIL-101. Analysis using a monolayer and multilayer model based on statistical physics theory indicated that the Sr/Cr binuclear sites could enhance the interaction strength of the adsorption system, promoting the adsorption of more layers of toluene molecules on the surface of MIL-101. Characterization and simulation together confirmed that constructing Sr/Cr binuclear sites in MIL-101 can cause significant redistribution of charge within the pores, enhancing the van der Waals interactions, π-π stacking interactions, hydrogen bonding, and Lewis acid-base interactions between the pore interior and the adsorbate molecules. Additionally, density functional theory (DFT) revealed that the adsorption sites of toluene in MIL-101 were distributed in a trigonal prism arrangement and were symmetrically aligned with a 180° rotation of the MIL-101 triangular cage.

Monte Carlo QM/MM simulation studies of the Cannizzaro reaction in ionic liquids for improved biofuel production.

The conversion of biomass to 5-hydroxymethylfurfural (HMF) holds substantial promise as a renewable energy source. Notably, HMF can be transformed into 2,5-bis(hydroxymethyl)furan (BHMF), a crucial reactant in biofuel production, but requires harsh operating conditions, H2, and precious metal catalysts. A recently reported Cannizzaro reaction of HMF to BHMF, characterized by its efficiency, mild conditions, and eco-friendliness, instead employed ionic liquids (ILs) to achieve high yields. In this study, combined quantum mechanical and molecular mechanical (QM/MM) simulations in conjunction with Metropolis Monte Carlo statistical mechanics and free-energy perturbation theory utilized M06-2X/6-31+G(d), PDDG/PM3, and the OPLS-VSIL force field to uncover important solute-solvent interactions present in the HMF to BHMF reaction pathway. The Cannizzaro reaction was examined in water and in five ILs composed of the 1-butyl-3-methylimidazolium [BMIM] cation coupled to hexafluorophosphate, tetrafluoroborate, thiocyanate, chloride, and bromide. Energetic and structural analysis of the rate-determining hydride transfer between HMF and the hydride-donor anion HMFOH- attributed the enhanced reactivity to highly organized solvent interactions featuring (1) hydrogen bonding between the ring protons of [BMIM] and the negatively charged carbonyl oxygen atoms on the transition structure, (2) favorable electrostatic interactions between the IL anions and solute hydroxyl groups, and (3) beneficial π-π stacking interactions between [BMIM] and the two aromatic rings present in HMF and HMFOH-.

Valorizing Moroccan crab shells to purify water from Orange G dye: Exploring equilibrium, kinetics, and thermodynamics

A successful approach has been taken to develop a biomaterial derived from fish waste, using Moroccan fish processing by-products from crab shells. Moroccan crab (Portunus pelagicus) shell-derived biomaterial has been developed for wastewater treatment, using marine crustacean waste and addressing the challenges of solid fish waste management. The crab shell powder (CSP) was calcined at 800 °C for three hours and characterized using SEM, EDS, FTIR, and XRD, revealing a predominantly crystalline structure. The CSP's effectiveness as a biosorbent for the removal of the anionic dye Orange G (OG) was assessed under various conditions, including pH, biosorbent mass, temperature, and contact time. Optimal conditions achieved a 98.84 % dye removal rate within 60 min at an adsorbent dose of 0.09 g. The adsorption process adhered to the pseudo-second-order kinetic model and the Freundlich isotherm, indicating a spontaneous, endothermic surface reaction involving multilayer physisorption. The biosorption mechanism is thought to include electrostatic attractions, n-π stacking interactions, hydrogen bonding, and Yoshida hydrogen bonds. The study suggests that CSP is an efficient, eco-friendly adsorbent for industrial wastewater treatment, offering a promising solution for the valorization of fish waste by-products.

Ferrocene-functionalized magnetic core-shell nanoparticles based on hydrosilylation reaction for pH-responsive doxorubicin delivery system

This study describes the development of an innovative pH-sensitive drug delivery system (DDS) utilizing ferrocene (Fc) and magnetic nanoparticles (MNPs) for cancer therapy. One potential method for generating a diverse range of functional NPs involves attaching functional substances to MNPs. In this investigation, we display the successful modification of Fe3O4 NPs by an Fc derivative (4-Ferrocenylbutyl)dimethylsilane through a hydrosilylation reaction toward the synthesis of the Fe3O4@SiO2@VTES@Fc nanocarrier (NC). The doxorubicin (DOX) drug was loaded onto Fe3O4@SiO2@VTES@Fc NC with a drug loading capacity of about 80 % via π-π stacking interactions. Also, the prepared materials were thoroughly characterized using FT-IR, XRD, FE-SEM, EDX-MAP, VSM, DAPI, MTT, antioxidants, and CV techniques. In vitro studies on the release of DOX from Fe3O4@SiO2@VTES@Fc NC indicated a pH-responsive behavior with a lower release rate (< 10 %) at pH 7.4 compared to pH 5 (approximately 70 %) over a period of 96 h. Moreover, cytotoxicity assessments demonstrated notable cytotoxic effects of DOX-loaded Fe3O4@SiO2@VTES@Fc on MCF-7 cells (IC50 value: ∼8 µg/mL). The study findings suggest that the fabricated magnetic core-shell NC (Fe3O4@SiO2@VTES@Fc/DOX) exhibits stimulus-responsive behavior and holds promise as a sophisticated approach to specifically transport therapeutic agents into tumor sites while minimizing exposure to healthy tissues.

A Newly Identified Peripheral Duplex Anchors and Stabilizes the MALAT1 Triplex.

The accumulation of the 8-kb oncogenic long noncoding MALAT1 RNA in cells is dependent on the presence of a protective triple helix structure at the 3' terminus. While recent studies have examined the functional importance of numerous base triples within the triplex and its immediately adjacent base pairs, the functional importance of peripheral duplex elements has not been thoroughly investigated. To investigate the functional importance of a peripheral linker region that was previously described as unstructured, we employed a variety of assays including thermal melting, protection from exonucleolytic degradation by RNase R, small-angle X-ray scattering, biochemical ligation and binding assays, and computational modeling. Our results demonstrate the presence of a duplex within this linker that enhances the functional stability of the triplex in vitro, despite its location more than 40 Å from the 3' terminus. We present a full-length model of the MALAT1 triple helix-containing RNA having an extended rod-like structure and comprising 33 layers of coaxial stacking interactions. Taken together with recent research on a homologous triplex, our results demonstrate that peripheral elements anchor and stabilize triplexes in vitro. Such peripheral elements may also contribute to the formation and stability of some triple helices in vivo.

Boosting of Redox-Active Polyimide Porous Organic Polymers with Multi-Walled Carbon Nanotubes towards Pseudocapacitive Energy Storage.

Redox-active porous organic polymers (POPs) demonstrate significant potential in supercapacitors. However, their intrinsic low electrical conductivity and stacking tendencies often lead to low utilization rates of redox-active sites within their structural units. Herein, polyimide POPs (donated as PMTA) are synthesized in situ on multi-walled carbon nanotubes (MWCNTs) from tetramino-benzoquinone (TABQ) and 1,4,5,8-naphthalene tetracarboxylic dianhydride (PMDA) monomers. The strong π-π stacking interactions drive the PMTA POPs and the MWCNTs together to form a PMTA/MWCNT composite. With the assistance of MWCNTs, the stacking issue and low conductivity of PMTA POPs are well addressed, leading to the obvious activation and enhanced utilization of the redox-active groups in the PMTA POPs. PMTA/MWCNT then achieves a high capacitance of 375.2 F g-1 at 1 A g-1 as compared to the pristine PMTA POPs (5.7 F g-1) and excellent cycling stability of 89.7% after 8000 cycles at 5 A g-1. Cyclic voltammetry (CV) and in situ Fourier-Transform Infrared (FT-IR) results reveal that the electrode reactions involve the reversible structural evolution of carbonyl groups, which are activated to provide rich pseudocapacitance. Asymmetric supercapacitors (ASCs) assembled with PMTA/MWCNTs and activated carbon (AC) offer a high energy density of 15.4 Wh kg-1 at 980.4 W kg-1 and maintain a capacitance retention of 125% after 10,000 cycles at 5 A g-1, indicating their good potential for practical applications.

Synthesis, crystals structures, DFT, and anticancer activities of polycyclic heterocyclic quinones

In this work, we synthesized six polycyclic heterocyclic quinones (PHQs) and one unexpected product (compound 6). We verified all of their structures by 1HNMR, 13CNMR, and HRMS and obtained four crystal structures of the seven products. At first, we compared the crystal structures with crystal structures similar to those reported in the literature and explained their differences by conjugative effect, hyperconjugative effect, and electrostatic effect. Then, we compared the crystal structure of compound 6 with the calculated structure of compound 6. The natural bond orbital analysis showed that the calculated structure formed intramolecular hydrogen bonds, whereas the crystal structure formed intermolecular hydrogen bonds but not intramolecular hydrogen bonds. The main reason for this difference was not due to the atomic charge or the interatomic distance, but rather the energy levels of the orbitals of the lone-pair electrons. In crystal structures, the intermolecular interactions contained many weak interactions, and we used the hydrogen atom substitution (HAS) method to divide the total intermolecular interactions as several independent weak interactions and to calculate their energies. The HAS method was often successful if the substituted group did not have a strong effect on the electronic structure of the entire molecule, and we found examples in the calculations of energies of weak interactions of crystal structure of compound 6 and compound 3a. An unsuccessful example of the HAS method was the substitution of C = O group with CH2 group to eliminate the O…H-N hydrogen bond interaction from the total interaction. According to the HAS method, our calculations showed that the strength order of the weak interactions was as follows: π-π stacking > hydrogen bond > n-π stacking > σ-π stacking. For the hydrogen bond, the strength order was as follows: C = O…H-N > CCl…H-N > C-F…H-N. For n-π stacking interaction, the strength order was as follows: Cl-π > N-π > F-π. Finally, we selected five synthesized PHQs to test anticancer activities and some of them showed better anticancer activities than the positive control drugs.

Quantification of CH and NH/π-Stacking Interactions in Cells Using Nuclear Magnetic Resonance Spectroscopy.

π-Stacking, a type of noncovalent interactions involving aromatic residues, plays an important role in protein folding and function. In this work, an attempt has been made to measure CH/π and NH/π stacking interactions in a protein in Escherichia coli cells using a combined double-mutant cycle and nuclear magnetic resonance spectroscopy method. The results show that the CH/π and NH/π stacking interactions are generally weaker in cells than those in the buffer. The transient intermolecular noncovalent interactions between the protein and the complex cellular environment may compete with and thus weaken the stacking interactions in the protein. The weakening of stacking interactions can enhance the local conformational opening of proteins in E. coli cells. This is evident from the faster rates of amide hydrogen/deuterium exchange observed in cells than in the buffer, for residues that undergo local conformational opening. This study highlights the influence of the cellular environment on π-stacking and the conformational dynamics of proteins.

Evaluating larvicidal, ovicidal and growth inhibiting activity of five medicinal plant extracts on Culex pipiens (Diptera: Culicidae), the West Nile virus vector

Mosquitoes, one of the deadliest animals on the planet, cause millions of fatalities each year by transmitting several human illnesses. Synthetic pesticides were previously used to prevent the spread of diseases by mosquitoes, which was effective in protecting humans but caused serious human health problems, environmental damage, and developed mosquito pesticide resistance. This research focuses on exploring new, more effective, safer, and environmentally friendly compounds to improve mosquito vector management. Phytochemicals are possible biological agents for controlling pests and many are target-specific, rapidly biodegradable, and eco-friendly. The potential of extracts of Lantana camara, Melia azedarach, Nerium oleander, Ricinus communis, and Withania somnifera against 3rd instar Culex pipiens (Common house mosquito) larvae was evaluated. Methanol extracts had more toxic effects against Cx. pipiens larvae (95–100%, 24 h post-treatment) than aqueous extracts (63–91%, 24 h post-treatment). The methanol extracts of Nerium oleander (LC50 = 158.92 ppm) and Ricinus communis (LC50 = 175.04 ppm) were very effective at killing mosquito larvae, 24 h after treatment. N. oleander (LC50 = 373.29 ppm) showed high efficacy in aqueous plant extracts. Among the different extracts of the five plants screened, the methanol extract of R. communis recorded the highest ovicidal activity of 5% at 800 ppm concentration. Total developmental duration and growth index were highly affected by R. communis and M. azedarach methanol extracts. In field tests it was clear that plant extracts decreased mosquito larval density, especially when mixed with mosquito Bti briquette, with stability up to seven days for N. oleander. GC–MS results showed that the methanol extract had a higher number of chemical compounds, particularly with more terpene compounds. A high-performance liquid chromatography (HPLC) technique was used to detect the existence of non-volatile polyphenols and flavonoids. All five methanol extracts showed high concentrations of active ingredients such as gallic acid, chlorogenic acid (more than 100 μg/ml) and the rosmarinic acid was also found in all the five extracts in addition to 17 active polyphenols and flavonoids presented at moderate to low concentrations. Molecular modeling of 18 active ingredients detected by the HPLC were performed to the vicinity of one of the fatty acid binding proteins of lm-FABP (PDB code: 2FLJ). Rutin, Caffeic acid, coumaric acid and rosmarinic acid which presented densely in R. communis and N. oleander showed multiple and stable intermolecular hydrogen bonding and π–π stacking interactions. The inhibition ability of the fatty acid binding protein, FABP4, was evaluated with remarkable receptor inhibition evident, especially with R. communis and N. oleander having inhibitory concentrations of IC50 = 0.425 and 0.599 µg/mL, respectively. The active phytochemical compounds in the plants suggest promising larvicidal and ovicidal activity, and have potential as a safe and effective alternative to synthetic insecticides.

Synergizing Steric Hindrance and Stacking Interactions To Facilitate the Controlled Assembly of Multiple 41 Metalla‐Knots and Pseudo‐Solomon Links

AbstractIn this work, a noncoplanar terphenyl served as a building block to synthesize a novel 3,3′‐substituted bipyridyl ligand (L1) which further reacted with binuclear half‐sandwich units A/B, giving rise to two aesthetic 41 metalla‐knots in high yields via a coordination‐driven self‐assembly strategy. Furthermore, given the inherent compactness of the 41 metalla‐knots, it creates favorable conditions for the emergence of steric repulsion. We focused on progressively introducing nitrogen atoms featuring a lone pair of electrons (LPEs) into ligand L1 to manipulate the balance of H⋅⋅⋅H/LPEs⋅⋅⋅LPEs steric repulsion during the assembly process, ultimately achieving controlled assembly from 41 metalla‐knots to the pseudo‐Solomon link and then to molecular tweezer‐like assembly facilitated by stacking interactions. All the assemblies were well characterized by solution‐state NMR techniques, ESI‐TOF/MS, and single‐crystal X‐ray diffraction. The evolutionary process of the topological architectures is equivalent to visualizing the synergistic effect of steric hindrance and stacking interactions on structural assembly, providing a new avenue for achieving the controlled synthesis of different topologies.

Synergizing Steric Hindrance and Stacking Interactions To Facilitate the Controlled Assembly of Multiple 41 Metalla-Knots and Pseudo-Solomon Links.

In this work, a noncoplanar terphenyl served as a building block to synthesize a novel 3,3'-substituted bipyridyl ligand (L1) which further reacted with binuclear half-sandwich units A/B, giving rise to two aesthetic 41 metalla-knots in high yields via a coordination-driven self-assembly strategy. Furthermore, given the inherent compactness of the 41 metalla-knots, it creates favorable conditions for the emergence of steric repulsion. We focused on progressively introducing nitrogen atoms featuring a lone pair of electrons (LPEs) into ligand L1 to manipulate the balance of H⋅⋅⋅H/LPEs⋅⋅⋅LPEs steric repulsion during the assembly process, ultimately achieving controlled assembly from 41 metalla-knots to the pseudo-Solomon link and then to molecular tweezer-like assembly facilitated by stacking interactions. All the assemblies were well characterized by solution-state NMR techniques, ESI-TOF/MS, and single-crystal X-ray diffraction. The evolutionary process of the topological architectures is equivalent to visualizing the synergistic effect of steric hindrance and stacking interactions on structural assembly, providing a new avenue for achieving the controlled synthesis of different topologies.

Deeply Reduced Chiral MoIV6-Polyoxometalates with Highly Enhanced Electronic Conductivity.

A series of deeply reduced MoIV6-polyoxometalates (POMs), [MoIV6(bpy)6MoVI2O16S2]·10H2O (1) (bpy = 2,2'-bipyridine), [MoIV6(bpy)4(L-TrA)2MoV4(bpy)2O14S4]2·36.5H2O (2), and [MoIV6(bpy)4(D-TrA)2MoV4(bpy)2O14S4]2 (3) (TrA = tartaric acid), were obtained from one-pot hydrothermal syntheses. They feature the bioxo-bridged [MoIV3O3S]4+ incomplete cuboidal cores stabilized by strong triangular metal-metal bonds and datively chelated bpy π-ligands. The two apical MoVIO4 in 12e-Mo8 (1) and two [MoV2O3STrAbpy] in 16e-Mo10 (2, 3) complete the octahedral coordination geometry of the deeply reduced MoIV, not counting the MoIV-MoIV d2-d2 bonds. The aromatic planar bpy π ligands form a two-dimensional face-to-face π stacking supramolecular structure, which are further strengthened by point-to-face C-H···π interactions in the π stacked layers. 16e-Mo10 (2, 3) has stronger intramolecular face-to-face π stacking interactions, which are interconnected by intermolecular C-H···π into a three-dimensional framework structure. These structural features account for their highly enhanced electronic conductivities (1, 6.19 × 10-8 S cm-1; 2, 2.18 × 10-7 S cm-1), providing a new way of thinking to improve electronic conductivity of POMs. 1-3 have been described by first-principles density function theory (DFT) calculations and also characterized by elemental analyses, powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), solid UV-visible spectra, and circular dichroic (CD) spectra.

Self‐Assembled Hydrazide‐Based Nanochannels: Efficient Water Translocation and Salt Rejection

Nature has ingeniously developed specialized water transporters that effectively reject ions, including protons, while transporting water across membranes. These natural water channels, known as aquaporins (AQPs), have inspired the creation of Artificial Water Channels (AWCs). However, replicating superfast water transport with synthetic molecular structures that exclude salts and protons is a challenging task. This endeavor demands the coexistence of a suitable water‐binding site and a selective filter for precise water transportation. Here, we present small‐molecule hydrazides 1b−1d that self‐assemble into a rosette‐type nanochannel assembly through intermolecular hydrogen bonding and π‐π stacking interactions, and selectively transport water molecules across lipid bilayer membranes. The experimental analysis demonstrates notable permeability rates for the 1c derivative, enabling approximately 3.18 × 108 water molecules to traverse the channel per second. This permeability rate is about one order of magnitude lower than that of AQPs. Of particular significance, the 1c ensures exclusive passage of water molecules while effectively blocking salts and protons. MD simulation studies confirmed the stability and water transport properties of the water channel assembly inside the bilayer membranes at ambient conditions.

Self-Assembled Hydrazide-Based Nanochannels: Efficient Water Translocation and Salt Rejection.

Nature has ingeniously developed specialized water transporters that effectively reject ions, including protons, while transporting water across membranes. These natural water channels, known as aquaporins (AQPs), have inspired the creation of Artificial Water Channels (AWCs). However, replicating superfast water transport with synthetic molecular structures that exclude salts and protons is a challenging task. This endeavor demands the coexistence of a suitable water-binding site and a selective filter for precise water transportation. Here, we present small-molecule hydrazides 1b-1d that self-assemble into a rosette-type nanochannel assembly through intermolecular hydrogen bonding and π-π stacking interactions, and selectively transport water molecules across lipid bilayer membranes. The experimental analysis demonstrates notable permeability rates for the 1c derivative, enabling approximately 3.18 × 108 water molecules to traverse the channel per second. This permeability rate is about one order of magnitude lower than that of AQPs. Of particular significance, the 1c ensures exclusive passage of water molecules while effectively blocking salts and protons. MD simulation studies confirmed the stability and water transport properties of the water channel assembly inside the bilayer membranes at ambient conditions.

Material synthesis, crystal structure, Hirshfeld surface and physicochemical characteristics Novel Stilbazolium crystal of 4-(2-(3-ethoxy-4-hydroxy-phenyl)-vinyl)-1-methyl pyridinium iodide (MEMPI) single crystal for NLO activity

In this study, a novel cation donor group 3-ethoxy-4-hydroxy benzaldehyde has been incorporated in the Stilbazolium cation with iodide anion to generate a new NLO activity of a single crystal of 4-(2-(3-ethoxy-4-hydroxy-phenyl)-vinyl)-1-methyl pyridinium iodide (MEMPI). The MEMPI crystal was effectively formed via the solvent evaporation technique. The structure and hydrogen bond interactions found in the molecule were determined by employing single-crystal X-ray diffraction. The compound crystallizes in the space group P21/c and monoclinic crystal pattern. The crystal structures are stabilized via intramolecular, intermolecular hydrogen bond interactions, C‒H···π, cation‒π, anion‒π, π···π stacking and lone pair-π interaction. In addition, a variety of O‒H···O, O‒H···I and C‒H···O interactions are also responsible for crystal packing. The 3D Hirshfeld surface and 2D fingerprint plots were used to examine the nature of intermolecular interaction. The 2D fingerprint maps indicate that the interactions between H···H contribute to 48.9 % of the total crystal stability. The newly synthesized material was characterized by 1H NMR and 13C NMR. In addition, the vibrational study of the synthesized molecule was performed using FTIR analysis. The grown crystal in linear optical characteristics were examined via a UV–Visible-NIR study. The photoluminescence (PL) activity of a MEMPI was studied with respect to the visible area and green colour emission was observed at 536 nm. The estimated CIE coordinates on the RGB colour gamut show the MEMPI crystal's ability to emit green light. The chemical etching approach was used to analyse the etch pit density and the growth habitat of the MEMPI crystal. The closed and open aperture Z-scan tests were carried out to determine the nature of third-order NLO susceptibility of the MEMPI crystal.