Van Der Waals Interactions Research Articles

Hydrogen bonding in the crystal structure of molnupiravir Form I, C13H19N3O7

Molnupiravir Form I crystallizes in space group C2 (#5) with a = 6.48110(17), b = 8.71848(19), c = 27.0607(19) Å, β = 91.920(4)°, V = 1528.22(12) Å3, and Z = 4 at 295 K. The crystal structure consists of supramolecular double layers of molecules parallel to the ab-plane. The layer centers consist of hydrogen-bonded rings forming a 2D network and the outer surfaces of isopropyl groups, with van der Waals interactions between the layers. Each O atom acts as an acceptor in at least one hydrogen bond. A strong O–H⋯O hydrogen bond forms between the hydroxyl group of the oxolane ring and the carbonyl group of the oxopyrimidine ring. The other oxolane hydroxyl group forms bifurcated intra- and intermolecular hydrogen bonds. The hydroxylamino group forms an intramolecular O–H⋯N hydrogen bond with an N atom of the oxopyrimidine ring. The amino group forms an intermolecular N–H⋯N hydrogen bond to the same N atom of the ring. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®).

Flexible framework of computing binding free energy using the energy representation theory of solution.

Host-guest binding plays a crucial role in the functionality of various systems, and its efficiency is often quantified using the binding free energy, which represents the free-energy difference between the bound and dissociated states. Here, we propose a methodology to compute the binding free energy based on the energy representation (ER) theory of solution, which enables us to evaluate the free-energy difference between the systems of interest with the molecular dynamics (MD) simulations. Unlike the other free-energy methods, such as the Bennett acceptance ratio (BAR), the ER theory does not require the MD simulations for hypothetical intermediate states connecting the systems of interest, leading to reduced computational costs. By constructing the thermodynamic cycle of the binding process that is suitable for the ER theory, a robust calculation of the binding free energy is realized. We apply the present method to the self-association of N-methylacetamide in different solvents and the binding of aspirin to β-cyclodextrin (CD) in water. In the former case, the present method estimates that the binding free energy decreases as the solvent polarity decreases. This trend is consistent with the experimental finding. For the latter system, the binding free energies for the two representative CD-aspirin bound complexes, primary (P) and secondary (S) complexes, are estimated to be -5.2 ± 0.1 and -5.03 ± 0.09kcalmol-1, respectively. These values are satisfactorily close to those from the BAR method [-4.2 ± 0.2 and -4.1 ± 0.2kcalmol-1 for P and S, respectively]. Furthermore, the interaction-energy component analysis reveals that the van der Waals interaction between aspirin and CD dominantly contributes to the stabilization of the bound complexes, which is in harmony with the well-known binding mechanism in the CD systems.

Study on Crack Resistance Mechanism of Helical Carbon Nanotubes in Nanocomposites

Helical carbon nanotubes (HCNTs) with different geometrical properties were constructed and incorporated into nanocomposites for the investigation of the anti-crack mechanism. The interfacial mechanical properties of the nanocomposites reinforced with straight carbon nanotubes and various types of HCNTs were investigated through the pullout of HCNTs in the crack propagation using molecular dynamics (MD). The results show that the pullout force of HCNTs is much higher than that of CNTs because the physical interlock between HCNTs and matrices is much stronger than the van der Waals (vdW) interactions between CNTs and matrices. Remarkably, HCNTs with a large pitch length can not only effectively prevent the initiation of breakages but also hinder the growth of cracks, while HCNTs with a small diameter and tube radius cannot even effectively prevent the initiation of cracks, which is similar to straight CNTs. Moreover, the shear resistance of HCNTs increases with the increase in the helix angle, which remains at a high level when the helix angle reaches the critical value. However, HCNTs with a small helix angle and large diameter can carry out more polymer chains, while snake-like HCNTs and HCNTs with a small diameter and helix angle can hardly carry out any polymer chain during the pullout process and show similar interfacial properties to the straight CNTs.

Donor-Interacting Arylated Carbazole Self-Assembled Monolayer Enables Highly Efficient and Stable Organic Photovoltaics.

Carbazole-derived self-assembled monolayers (SAMs) are promising materials for hole-extraction layer (HEL) in conventional organic photovoltaics (OPVs). Here, a SAM Cbz-2Ph derived from 3,6-diphenylcarbazole is demonstrated. The large molecular dipole moment of Cbz-2Ph allows the modulation of electrode work function to facilitate hole extraction and maximize photovoltage, thus improving the OPV performance. Additionally, the flanking aryls of Cbz-2Ph help establish CH-π interactions for forming a dense and well-organized SAM HEL and exhibit stronger van der Waals interactions with the donor PM6 than acceptor BTP-eC9. The stronger SAM-donor interactions modulate the PM6 distribution in PM6:BTP-eC9 bulk-heterojunction film, leading to PM6 enrichment near HEL to facilitate efficient hole extraction to the ITO anode in conventional p-i-n OPVs. Consequently, binary PM6:BTP-eC9-based devices incorporating the Cbz-2Ph HEL demonstrate an impressive efficiency of 19.18%. These cells also showcase excellent operational stability, with a T80 lifetime of ≈1260 h at the maximum power point, over 10 times longer than those using the traditional PEDOT:PSS HEL (T80 ≈96h). Furthermore, the universal applicability of Cbz-2Ph as a HEL is evident through its successful implementation in PM6:BTP-eC9:L8-BO-F-based ternary devices and PM6:BTP-eC9-based printed OPV devices, achieving a PCE of 19.30% and 16.96%, respectively.

Syntheses, crystal structures, Hirshfeld surface analyses and crystal voids of 1-(4-bromophenyl)-2,2-dichloroethan-1-one and 2,2-dibromo-1-(p-tolyl)ethan-1-one

The asymmetric units of the compounds, C8H5BrCl2O (I), and C9H8Br2O (II), contain two and one crystallographically independent molecules, respectively. In compound (I), the planar rings are oriented at a dihedral angle of 13.23 (8)°. In crystals of both compounds, intermolecular C—H...O hydrogen bonds link the molecules into infinite chains along the b-axis direction. In crystal of (I), there are π–π interactions between the centroids of the parallel rings with centroid-to-centroid distances of 3.5974 (14), 3.6178 (16) and 3.9387 (16) Å while neither π–π nor C—H... π(ring) interactions are present in (II). The Hirshfeld surface analyses of the crystal structures indicate that the most important contributions for the crystal packings are from H...Cl/Cl...H (27.5%), H...O/O...H (15.0%), H...Br/Br...H (10.2%) and H...H (9.0%) for (I) and H...Br/Br...H (36.1%), H...H (22.2%), H...O/O...H (14.1%) and H...C/C...H (13.9%) for (II). Hydrogen bonding and van der Waals interactions are the dominant interactions in the crystal packings. The volumes of the crystal voids and the percentages of free spaces in the unit cells were calculated to 111.55 Å3 and 12.27% for (I) and 63.37 Å and 6.69% for (II), showing that no large cavities are present in either structure.

2D MoS2 for detection of COVID-19 biomarkers – a first-principles study

Abstract This study investigates specific compounds in the breath that can indicate COVID-19 and lung cancer. Heptanal (C7H14O), acetone (C3H6O), propanol-1 (CH3CH2CH2OH), butanal (C3H7CHO), isopropanol (CH3CHOHCH3), acetaldehyde (CH3CHO), 2,4-octadiene (C8H14), and ethyl butyrate (C6H12O2) were studied. We analyze how these compounds interact using two-dimensional (2D) 2H and SV-MoS2 monolayers through first-principles calculations. Van der Waals forces bind all VOCs on the MoS2 surface in vacuum and humid conditions. The decrease in the band gap of the MoS2-VOC complex in these environments enhances sensitivity. The complexes of 2,4-octadiene, propanol-1, and ethyl butanoate are more conductive because their work function is lower, and their V(z) shift is more significant. The adsorption isotherm demonstrates the potential for surface reuse in sensing applications. The study confirms high sensitivity (>85%) and fast recovery time (up to 70 femtoseconds) for detecting in visible (VL) and ultraviolet (UV) regions. Mainly, 2,4-octadiene exhibits high sensitivity and selectivity. In conclusion, the 2H and SV MoS2 monolayers effectively detect COVID-19 and lung cancer markers in vacuum and humid conditions.

Starch-ZnCr/LDH Composite and ZnCr-LDH: Synthesis, Characterization, and Adsorption Efficiency to Remove Congo Red from Aqueous Solution

Background: To bring new materials with high performance, a large number of composites, among others, such as starch-laminated double hydroxides (starch/ZnCr-LDH), have been produced, which have shown significant adsorption predisposition to remove heavy metals and dyes. These LDHs display great adsorption potential due to their high anion exchange capacity, large surface area, and good thermal stability. Objective: This study aimed to develop starch-ZnCr-hydroxide composite (S/ZnCr-LDH) as a new material and investigate its performance in removing various anionic dyes compared to ZnCr- LDH. Methods: The starch-ZnCr-laminated double hydroxides (S/ZnCr-LDH) and ZnCr-LDH composites were prepared by the co-precipitation method and their structures were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential thermogravimetric/ thermal analysis (TG/DTA) Scanning electron microscopy (SEM), and Energy Dispersive Xrays Spectroscopy (EDX). Results: The effects of different operating parameters, such as pH, initial CR concentration, contact time, and adsorbent dose, on CR removal were studied. The results showed that the S/ZnCr- LDH composite is more efficient for CR removal, reaching 99% at pH 3, while ZnCr-LDH presented a removal efficiency of 90%. Isothermal data were processed according to the Langmuir, Freundlich, and Temkin models. According to the results, Langmuir's isothermal model best matched the experimental data, with a maximum adsorption capacity of 252. 92 and 236. 98 mg/g for S/ZnCr-LDH and ZnCr-LDH, respectively. The adsorption kinetics corresponded to the PSO model. CR dye molecules were adsorbed to different sites on the S/ZnCr-LDH composite based on various interactions, such as electrostatic interactions, hydrogen bonds, and Van der Waals forces. Conclusions: S/ZnCr-LDH composite displays the highest capacity to remove CR dye molecules compared to ZnCr-LDH.

Anisotropic Shock Response of 3,4-Dinitropyrazole Revealed by First-Principles Calculations.

DNP (3,4-dinitropyrazole) has attracted much interest due to its promising melting characteristics and high detonation performances, such as low melting point, high density, high detonation velocity, and low sensitivity. In this work, first-principles molecular dynamics (MD) simulations were performed to investigate the anisotropic shock response of DNP in conjunction with the multiscale shock technique (MSST). The initial decomposition mechanism was revealed through the evolution of the chemical reaction and product analysis. Independent gradients based on the Hirshfeld partition (IGMH) method showed that van der Waals forces mainly exist between the layered structures. Chemical reaction analyses revealed four major initial decomposition reactions for the DNP molecule. At different shock velocities, the molecules in were more inclined to undergo H dissociation reactions, whereas the molecules in were more inclined to undergo nitro-dissociation reactions. Product analysis showed that the faster the shock velocities, the earlier the DNP molecules completely disappeared. Furthermore, N2 and CO2 were mainly produced by the ring-opening reaction, and their numbers in were higher than in , indicating that the ring-opening reaction was more easy to occur in . The ring-opening reaction mainly occurred in , suggesting that was more decomposable than . The fitting results of the state equation showed that the theoretical detonation pressures for and are close to the experimental value. These results could help to increase the understanding of shock-induced anisotropy in energetic materials.

Photoinduced Long-Distance Charge Transfer in Silicanes: The Stacking Matters.

The generation of interlayer charge transfer excitons upon photoexcitation is strongly desirable for two-dimensional (2D) materials stacked through van der Waals interactions. In this work, we investigate photoinduced charge transfer in silicanes (SiH) with three typical stackings. A concept of the regional natural hole orbital and its conjugated particle orbital is developed to characterize excited states in solids. This method delivers bonding information about excited states and explains the formation of certain types of states in nanomaterials. Utilizing this tool, we demonstrate that SiH in the 1H and 6R stackings exhibits an interlayer charge transfer distance that reaches ∼10 Å under violet and near-ultraviolet radiation. The charge transfer is attributed to the interlayer overlap between orbitals at the conduction band minimum, which is disfavored by the 3R stacking. Our findings suggest a new and feasible approach for tuning the optoelectronic properties of Group 14 2D materials by altering their stackings.

Study on the modulation mechanism of the optoelectronic properties based on common electrode metal atom adsorption on graphene/MoTe2.

The two-dimensional graphene/MoTe2 heterostructure holds extensive potential applications in optoelectronic devices, sensors, and catalysts. To expand its optical applications, this study systematically investigates the adsorption stability of metal atoms (Au, Pt, Pd, and Fe) on the graphene/MoTe2 and their influence on its optoelectronic properties employing first-principles methods. The findings indicate that after the adsorption of Au and Pd, the structure retains its direct bandgap properties, while the adsorption of Pt and Fe exhibits indirect bandgap characteristics. The work functions for all adsorbed structures are lower compared to the pristine graphene/MoTe2. The total density of states is primarily derived from the C-2p, Mo-4d, Te-5p orbitals, as well as the d and s orbitals of the adsorbed atoms. The pristine graphene/MoTe2 exhibits significant absorption in the ultraviolet range. Once graphene/MoTe2 is adsorbed by metal atoms, it can significantly enhance the optical absorption across the spectrum from infrared to ultraviolet light. These findings provide important theoretical guidance for regulating the application of graphene/MoTe2 in optoelectronics and related fields. All analyses are grounded in density functional theory first principles and computed using CASTEP. Graphene/MoTe2 consists of 4 × 4 × 1 single-layer, graphene single layer, and 3 × 3 × 1 single-layer MoTe2. To prevent interactions between neighboring unit cells, a 20Å vacuum space in the z-direction is employed. The electronic exchange-correlation interactions are treated using the Perdew-Burke-Ernzerhof functional within the framework of the generalized gradient approximation. Van der Waals (vdW) interactions are incorporated using the vdW correction function proposed by Grimme, which effectively describes vdW interactions. During the simulation, the cutoff energy for plane wave expansion is set to 420eV, and the k-point grid is set to 4 × 4 × 1. The atomic displacement convergence standard is 0.002Å, the internal stress convergence standard is 0.1GPa, and the interaction force convergence standard between atoms is 0.05eV/Å. The convergence threshold for the iteration precision is set to ensure that the total energy for each atom is not less than 2 × 10-5eV/atom.

Formation of Rydberg crystals induced by quantum melting in one dimension

Quantum fluctuations in frustrated systems can lead to the emergence of complex many-body phases. However, the role of quantum fluctuations in frustration-free lattices is less explored and could provide an interesting avenue for exploring new physics, and perhaps is easier to realize compared to frustrated lattice systems. Using Rydberg atoms with tunable interactions as a platform, we leverage strong van der Waals interactions and obtain a constrained model in one dimension with nonlocal fluctuations given by dipolar interactions alongside local fluctuations. The combined effect of such processes leads to intrinsically quantum-ordered Rydberg crystals through the order-by-disorder mechanism. Finite-size analyses indicate that combined fluctuations drive the transition from disordered to ordered phases, contrary to the expected direction. We provide a theoretical description to understand the physics of order-by-disorder in one-dimensional systems, which are typically seen only in higher dimensions. Published by the American Physical Society 2025

Alignment, Rising, Sticking, and Phototaxis: Modulating the Behavior of Hematite Micropeanuts

AbstractArtificial active colloids are an active area of research in the field of active matter and microrobotic systems. In particular, light‐driven semiconductor particles are shown to display interesting behaviors ranging from phototaxis (movement toward or away from a light source), rising from the substrate, interparticle attraction, attraction to the substrate, or other phenomena. However, these observations involve using multiple different designs of particles in varying conditions, making it unclear how the experimental parameters, such as pH, peroxide concentration, and light intensity, affect the outcomes. In this work, a peanut‐shaped hematite semiconductor particle is shown to exhibit a rich range of behavior as a function of the experimental conditions. The particles show rising, sticking, phototaxis, and in‐plane alignment of their long axes perpendicular to a magnetic field. A theoretical model accounting for gravity, van der Waals forces, electric double layer interactions with the glass surface, and self‐diffusiophoresis is formulated to describe the system. Using experimental data on the dependence of particle behavior on pH and ionic concentrations, the model captures the interplay of competing effects and explains many of the observed behaviors, providing insight into the relevant physical phenomena and how different environmental conditions can lead to such a rich diversity of behavior.

Dissecting the Binding Affinity of Anti-SARS-CoV-2 Compounds to Human Transmembrane Protease, Serine 2: A Computational Study

The human transmembrane protease, serine 2 (TMPRSS2), essential for SARS-CoV-2 entry, is a key antiviral target. Here, we computationally profiled the TMPRSS2-binding affinities of 15 antiviral compounds. Molecular dynamics (MD) simulations for the docked complexes revealed that three compounds exited the substrate-binding cavity (SBC), suggesting noncompetitive inhibition. Of the remaining compounds, five charged ones exhibited reduced binding stability due to competing electrostatic interactions and increased solvent exposure, while seven neutral compounds showed stronger binding affinity driven by van der Waals (vdW) interactions compensating for unfavorable electrostatic effects (including electrostatic interactions and desolvation penalties). Positive and negative hotspot residues were identified as uncharged and charged, respectively, both lining the SBC. Despite forming diverse interactions with compounds, the burial of positive hotspots led to strong vdW interactions that overcompensated for unfavorable electrostatic effects, whereas negative hotspots incurred high desolvation penalties, negating any favorable contributions. Charged residues at the SBC’s outer rim can reduce binding affinity significantly when forming hydrogen bonds or salt bridges. These findings underscore the importance of enhancing vdW interactions with uncharged residues and minimizing the unfavorable electrostatic effects of charged residues, providing valuable insights for designing effective TMPRSS2 inhibitors.

Degradation of naphthalene in aqueous solution using a microbial symbiotic system founded by degrading and ureolytic bacteria.

Although single bacteria have been applied to the Polycyclic Aromatic Hydrocarbons (PAHs) remediation, its efficacy is severely restricted by long degradation periods and low efficacy. A microbial symbiotic system founded by two or more bacterial strains may be an alternative to traditional remediation approaches. Its construction is, however, hampered by antagonistic interactions and remains challenging. The present work proposed a microbial symbiotic system consisting of the naphthalene degrading bacteria and the non-PAHs degrading bacteria and improved their interspecies interactions by using sequential inoculation. The non-PAHs degrading bacteria were inoculated after the inoculation of the naphthalene degrading bacteria. The sequential inoculation not only promoted the non-PAHs degrading bacteria to use the metabolites of the naphthalene degrading bacteria as an energy source but developed a resistance of the two bacterial strains to naphthalene. Vaterite and aragonite were identified following urea hydrolysis by the non-PAHs degrading bacteria. The faster precipitation rate in naphthalene degradation by the symbiotic system elevated the proportion of vaterite, allowing more naphthalene and its metabolites to be wrapped in or attached to minerals with the bacteria through the physisorption (Van der Waals force) and chemisorption (Ca-π interaction with aromatic rings) and promoting the formation of aggregates. The formation of aggregates further reduced the mobility of naphthalene. Results indicate that 40% of naphthalene in the non-inoculated sterile control group was quickly released into the atmosphere, causing serious public concerns regarding health safety. According to the thermogravimetry-gas chromatography mass spectrometry (TG-GC/MS) analysis, no trace of naphthalene was found in the samples, indicating that the degrading bacteria fully degraded naphthalene after its adsorption. As a result, the degradation efficiency of 100% was attained using the symbiotic system even at 200 mg/L naphthalene. The findings underscore the relative merits of the symbiotic system applied to the remediation of naphthalene in an aqueous solution.

Enthalpy-Driven Interaction between Bovine Serum Albumin and Biomass-Derived Low-Melting Mixture Solvents (LoMMSs) for Efficient and Green Purification of Protein.

Green separation of protein (e.g., bovine serum albumin (BSA)) by low-melting mixture solvents (LoMMSs) depends on the underlying mechanism between BSA and LoMMSs. Here, we for the first time find that eco-friendly biomass-derived LoMMSs could be potentially used for the efficient and green purification of BSA protein by enthalpy-driven interactions. Biomass-derived LoMMSs possess the merits of high biocompatibility, high degradability, high abundance, and low cost. A single high-affinity binding site via hydrogen bonding and van der Waals forces is observed between BSA and LoMMSs by fluorescence and thermodynamic analysis. Experimental results from circular dichroism and infrared spectra demonstrate that the addition of LoMMSs stabilizes the secondary structure of the BSA protein. This work provides a valuable indication for the design of eco-friendly and cost-effective LoMMSs for the purification of protein.

G-C3N4 S-Scheme Homojunction through van der Waals Interface Regulation by Intrinsic Polymerization Tailoringfor Enhanced Photocatalytic H2 Evolution and CO2 Reduction.

The effective S-scheme homojunction relies on the precise regulation of band structure and construction of advantaged charge migration interfaces. Here, the electronic structural properties of g-C3N4 were modulated through meticulous polymerization of self-assembled supramolecular precursors. Experimental and DFT results indicate that both the intrinsic bandgap and surface electronic characteristics were adjusted, leading to the formation of an in-situ reconstructed homojunction interface facilitated by intrinsic van der Waals forces. The homojunction catalyst, composed of g-C3N4 nanodots and ultra-thin g-C3N4 nanoflakes, exhibited a significant S-scheme carrier separation mechanism, which enhances the utilization of electrons and holes. Consequently, under AM 1.5 light irradiation (~100 mW/cm2), the g-C3N4 homojunction photocatalyst achieved a remarkable hydrogen evolution rate of 580 μmol h-1. Furthermore, a reversed CH4 selectivity in CO2 reduction was observed, yielding 80.30 μmol g-1 h-1 with a selectivity of 96.86%, in contrast to the performance of bulk g-C3N4, which produced only 2.22 μmol g-1 h-1 with the 15.69% CH4 selectivity. These findings not only highlight the significant potential of the g-C3N4 homojunction photocatalyst for hydrogen production and CO2 reduction but also propose a superior and effective strategy for optimizing the structural properties of g-C3N4, which are crucial for the design of photocatalytic reactions.

Construction of Multiple Nonpolar SF6 Nano-Traps by Highly Stable Pyrazole-Based MOFs for SF6 Recovery.

Sulfur hexafluoride (SF6), widely used in electric power systems, is one of the most potent greenhouse gases. Efficient separation of SF6/N2 by adsorptive separation technology based on porous materials is of great significance in the industry yet remains a daunting challenge. Herein, a novel strategy is introduced to construct unique pore channels with multiple SF6 nano-traps by precisely selecting bipyrazole ligands to design the nonpolar surface of microporous metal-organic frameworks (MOFs), which significantly enhances the material's affinity for SF6. A series of ultra-stable bipyrazole-based MOFs, M(BPZ) (M═Co, Ni, Zn), are synthesized and investigated. Among these three materials, Co(BPZ) and Zn(BPZ) show excellent SF6 uptakes of 2.47 and 2.39mmol g-1 at 298 K and 0.1bar while Co(BPZ) exhibits the highest SF6/N2 (10/90, v/v) IAST selectivity of 748. Breakthrough experiments reveal that SF6/N2 mixtures can be efficiently separated by Co(BPZ) with a high SF6(≥99.5 %) productivity of 46.1 L kg-1. Theoretical calculations suggest that SF6 preferably adsorbs in the channels through multiple S-F···π (pyrazole rings) van der Waals interactions. This work provides a straightforward approach for exploring adsorbents in efficient SF6/N2 separation.

Graphene Origami Amplifies Mechanical Properties of Polyethylene Nanocomposites.

Graphene and its derivatives have been widely used as reinforcing nanofillers for high-performance polymer nanocomposites. The effectiveness of the reinforcement largely depends on the properties of the nanofiller-matrix interface, which can be represented by the interfacial shear strength (IFSS). This work systematically investigates IFSS enhancements for polyethylene (PE) nanocomposites reinforced by graphene origami (GOri) through molecular dynamics pull-out simulations. When two-dimensional (2D) graphene is transformed into a three-dimensional (3D) origami structure, the resultant GOri/PE nanocomposite exhibits a higher IFSS due to the larger surface roughness of GOri and the associated higher van der Waals interaction strength between the filler and the matrix. Moreover, the incorporation of GOri into the PE matrix leads to more flexible and auxetic nanocomposites due to the unusual properties of GOri. The unique combination of high IFSS, high flexibility, and intrinsic auxeticity makes GOri/PE nanocomposites an ideal candidate for many practical applications, such as impact protection, flexible electronics, and soft robotics.

Stacking interactions in stabilizing supramolecular assembly of M[9C]2M complexes: dynamic stability with remarkable nonlinear optical features.

Continual attempts have been made to discover excellent nonlinear optical (NLO) materials. Here, we investigate the role of stacking interactions and van der Waals forces in the designed parallel stacked complexes M[9C]2M (where M = Li, Na, K, Be, Mg, and Ca) using various quantum chemical and molecular dynamics methods. The thermodynamic stability of the present complexes is also revealed by the computed interaction energy, enthalpy of formation, and Gibbs free energy of formation (ΔGf). Molecular dynamics simulations were performed at room temperature to determine the stability of the dimer formation and their complexes. Alkali metals act as a more prominent source of excess electrons at long-range interaction distances. Charge decomposition analysis (CDA) and natural bonding orbital (NBO) analyses suggest excellent charge transfer in the alkalide complexes. In this series, Li[9C]2Li exhibits an excellent hyperpolarizability response up to 2.3 × 106 a.u., while Ca[9C]2Ca performs well in alkaline-earth metal complexes. The NLO response is mostly influenced by the alkalide and earthide characteristics. Dynamic NLO features were computed at externally applied frequencies. Scattering first hyperpolarizability (βHRS) and its associated components were also measured. The effect of solvents on hyperpolarizability is also considered. The quantum theory of atoms in molecules (QTAIM) and NCI are employed to investigate the bonding nature and vdW forces in addition to stacking interactions. TD-DFT and vibrational studies are also performed. We aim for this research to pave the way for the innovative strategies in designing supramolecular assemblies tailored for NLO applications.

Mechanisms for translating chiral enantiomers separation research into macroscopic visualization.

Chirality is a common phenomenon in nature, including the dominance preference of small biomolecules, the special spatial conformation of biomolecules, and the biological and physiological processes triggered by chirality. The selective chiral recognition of molecules in nature from up-bottom or bottom-up is of great significance for living organisms. Such as the transcription of DNA, the recognition of membrane proteins, and the catalysis of enzymes all involve chiral recognition processes. The selective recognition between these macromolecules is mainly achieved through non covalent interactions such as hydrophobic interactions, ammonia bonding, electrostatic interactions, metal coordination, van der Waals forces, and π-π stacking. Researchers have been committed to studying how to convert this weak non covalent interaction into macroscopic visualization, which has further understood of the interactions between chiral molecules and is of great significance for simulating the interactions between molecules in living organisms. This article reviews several models of chiral recognition mechanisms, the interaction forces involved in the chiral recognition process, and the research progress of chiral recognition mechanisms. The outlook in this review points out that studying chiral recognition interactions provides an important bridge between chiral materials and the life sciences, providing an ideal platform for studying chiral phenomena in biological systems.