Dispersion Interactions Research Articles

Theoretical insights into the diverse stabilizing effects of fenchyl alcohol/thymol eutectic solvent on carotenoids

Carotenoids, a class of vital natural pigments, are known for their antioxidant properties and are integral to various industrial applications. However, their instability during processing and storage has limited their broader utilization. This study investigated the stabilizing effects of a fenchyl alcohol/thymol-based deep eutectic solvent (DES) on a spectrum of carotenoids, including lutein, zeaxanthin, astaxanthin, and β-carotene. Through a combination of ab initio molecular dynamics (AIMD) simulations and quantum chemical calculations, we elucidated the molecular interactions and stabilization mechanisms within the DES environment (methanol as the benchmark). Our findings reveal that the DES could exert varying degrees of influence on the stability of different types of carotenoids. The temperature-dependent behavior of carotenoids in the DES suggested a complex interplay between hydrogen bonding, dispersion forces, and the inherent structural properties of carotenoids. AIMD simulations provided a detailed picture of the structural organization and hydrogen bond network topology within the DES, highlighting the role of temperature on the stability and orientation of solvent molecules around carotenoids. Energy decomposition analysis (EDA), Hirshfeld surface analysis, and visual study of interactions further dissected the non-covalent interactions, emphasizing the significance of electrostatic and dispersion forces-driven non-covalent interactions (van der Waals dispersion interactions) in stabilizing carotenoids within the DES matrix. In comparison to methanol, the interactions between components of the eutectic system and the target molecules demonstrate enhanced dynamism, increased complementarity, and a greater variety of interaction patterns. This research presented a novel perspective on the use of DESs for the stabilization of carotenoids, offering potential solutions to enhance their industrial applicability and performance. The insights gained from this study are crucial for the development of sustainable and eco-friendly solvent systems, aligning with the growing demand for green chemistry in the pharmaceutical, cosmetic, and food industries.

Role of finite-temperature dynamics and dispersion interactions on the phonon bandgap in thermoelectric SnSe

Role of finite-temperature dynamics and dispersion interactions on the phonon bandgap in thermoelectric SnSe

Effect of iron oxidation state on the catalytic performance of Fe/C in liquid phase flow hydrogenation of 2-butyne-1,4-diol

Cis-2-butene-1,4-diol and 1,4-butanediol are crucial precursors in producing bioplastics and biodegradable plastics. Moreover, cis-2-butene-1,4-diol is used in the production of vitamins A and B6, fungicides and insecticides. On an industrial scale, they are produced by hydrogenation of 2-butyne-1,4-diol with Ni Raney as catalyst at > 160 °C and > 15 MPa. Herein, the effect of mesoporous carbon, iron loading (2, 6, 10 and 14 wt%), and metal oxidation state on the activity and selectivity of iron catalysts in the liquid phase continuous flow 2-butyne-1,4-diol hydrogenation at mild conditions (at temperature range 10–65 °C and pressure range 1–20 bar) was performed. Catalytic investigations supported by statistical modeling and physicochemical characterization (TPR, H2-TPD, physisorption, TEM, XPS, and Mössbauer spectroscopy), showed that the activity of the Fe/C can be determined by the presence of functional groups in mesoporous support which are responsible for high metal dispersion and strong metal-support interaction, which boosts the catalytic activity of iron catalysts. Additionally, the formation of metastable iron carbides which are active in hydrogenation cannot be excluded. All of the catalysts showed 100% selectivity toward cis-2-butene-1,4-diol at the lowest temperature. However, the best compromise between selectivity and activity (TOF=336 h−1) was achieved with 2 wt% Fe at 1 bar and 25 °C.

Bowl-shaped PAHs as gas adsorbents: Hydrogen storage and binding of gaseous pollutants

Understanding the non-covalent interactions of various molecules with bowl-shaped carbon structures at a quantum-chemistry level is important for the design of new materials. In this work, adsorption of three important diatomic molecules (H2, CO, and HF) on a flat coronene molecule and bowl-shaped PAHs (corannulene, sumanene, and triazasumanene) was theoretically investigated. The considerable increase of the interaction energy (Eint) was found for all molecules inside the curved structures compared to coronene (the increase was up to 2 × ). It was shown that dispersion interactions play the main role in total attraction for H2 and CO molecules. For HF molecules, the importance of induction (Eind) and electrostatics (Eel) for adsorption was revealed. QTAIM and IGM analyses showed the existence of non-covalent interactions (H2, CO) and H-bonding (HF) between the adsorbate molecules and the adsorbents. The obtained results establish the potential use of the studied bowl-shaped carbon structures in gas adsorbent systems.

Genuine non-Gaussian entanglement of light and quantum coherence for an atom from noisy multiphoton spin-boson interactions

Harnessing entanglement and quantum coherence plays a central role in advancing quantum technologies. In quantum optical light-atom platforms, these two fundamental resources are often associated with a Jaynes-Cummings model description describing the coherent exchange of a photon between an optical resonator mode and a two-level spin. In a generic nonlinear spin-boson system, more photons and more modes will take part in the interactions. Here we consider such a generalization: the two-mode multiphoton Jaynes-Cummings (MPJC) model. We demonstrate how entanglement and quantum coherence can be optimally generated and subsequently manipulated in experimentally accessible parameter regimes. A detailed comparative analysis of this model reveals that nonlinearities within the MPJC interactions produce genuinely non-Gaussian entanglement, devoid of Gaussian contributions, from noisy resources. More specifically, strong coherent sources may be replaced by weaker, incoherent ones, significantly reducing the resource overhead, though at the expense of reduced efficiency. At the same time, increasing the multiphoton order of the MPJC interactions expedites the entanglement generation process, thus rendering the whole generation scheme again more efficient and robust. We further explore the use of additional dispersive spin-boson interactions and Kerr nonlinearities in order to create spin coherence solely from incoherent sources and to enhance the quantum correlations, respectively. As for the latter, somewhat unexpectedly, there is not necessarily an increase in quantum correlations due to the augmented nonlinearity. Towards possible applications of the MPJC model, we show how, with appropriately chosen experimental parameters, we can engineer arbitrary NOON states as well as the tripartite W state. Published by the American Physical Society 2024

Computational Design of Ligands for the Ir-Catalyzed C5-Borylation of Indoles through Tuning Dispersion Interactions.

The indole moiety is ubiquitous in natural products and pharmaceuticals. C-H borylation of the benzenoid moiety of indoles is a challenging task, especially at the C5 position. We have combined computational and experimental studies to introduce multiple noncovalent interactions, especially dispersion, between the substrate and catalytic ligand to realize C5-borylation of indoles with high reactivity and selectivity. The successful computational predictions of new ligands should be suitable for ligand design in other transition-metal catalyzed reactions.

Cyclometalated C^C* Platinum(IV) NHC Complexes.

We present a previously unknown series of cyclometalated platinum(IV) NHC complexes, obtained by oxidative addition of iodine, iodomethane, and different benzyl bromides to platinum(II) complexes with cyclometalated C^C* dibenzofuran, dibenzothiophene, and phenylimidazole ligands together with an acetylacetonate ligand. All compounds were characterized by standard techniques (1H, 13C, and 195Pt NMR and elemental analysis), and for three complexes, solid-state structures could be obtained. DFT calculations (B3LYP(d3)/def2-TZVPP including dispersion interactions in dichloromethane and acetone) were performed to investigate the mechanism of the oxidation and explain the exclusive formation of the observed trans products.

Copper-Catalyzed Asymmetric Hydrogenation of Unsymmetrical ortho-Br Substituted Benzophenones.

The asymmetric hydrogenation of benzophenones, catalyzed by low-activity earth-abundant metal copper, has hitherto remained a challenge due to the substrates equipped with two indistinguishably similar aryl groups. In this study, we demonstrated that the prochiral carbon of the ortho-bromine substrate exhibits the highest electrophilicity and high reactivity among the ortho-halogen substituted benzophenones, as determined by the Fukui function (f+) analysis and hydrogenation reaction. Considering that the enantiodirecting functional bromine group can be easily derivatized and removed in the products, we successfully achieved a green copper-catalyzed asymmetric hydrogenation of ortho-bromine substituted benzophenones. This method yielded a series of chiral benzhydrols with excellent results. The utility of this protocol has been validated through a gram-scale reaction and subsequent product transformations. Hirshfeld partition (IGMH) and energy decomposition analysis (EDA) indicate that the CH···HC multiple attractive dispersion interactions (MADI) effect between the catalyst and substrate enhances the catalyst's activity.

CO2‐Hydrogenation to Methanol over CuO/ZnO Based Infiltration Composite Catalyst Spheres

AbstractMultiple active component catalysts for efficient conversion of CO2 to Methanol (MeOH) are synthesized through coating γ‐Al2O3 carrier spheres by incipient wetness impregnation method (IWI). The well‐known bimetallic Copper Oxide/Zinc Oxide (CuO/ZnO)is promoted in three steps, first by Cerium Oxide (CeO2), then additionally with Zirconium Oxide (ZrO2) and finally with Calcium Oxide (CaO) resulting in four carrier catalysts with high surface area and catalyst pore volume. Quaternary and quinary carrier catalysts promoted with moderate CeO2, ZrO2 in the quaternary (20 % CZCZ) and additionally with CaO (20 % CZCZC) in the quinary catalysts demonstrate high CO2‐conversion ratios (16.2 % and 18.7 %) and space time yields (0.51 and 0.47 gMeOH h−1 gCatalyst−1) at 5 MPa and 250 °C. The high conversion ratios (XCO2) and good methanol space‐time‐yields (STYMeOH) are attributed to enhanced copper dispersion and several multi metal oxide component interactions essential to enhance CO2‐activation and ‐conversion through the catalytic systems as well as very high overall surface area. Compared to related studies, the carrier catalysts show superior conversion rates, proving the effectiveness of the introduced multi‐component carrier catalyst and extending the understanding of infiltrate composites as possible large‐scale application alternatives to precipitated MeOH catalyst systems.

DFT Modeling of Polyethylene Chains Cross-linked by Selected ns1 and ns2 Metal Atoms.

We analyze the structures, stabilities, and thermochemical properties of polyethylene (PE) oligomer chains cross-linked by metal (M) atoms through C-M-C bonds. Representative PEn-Mm-PEn complexes contain between 7 and 15 carbon atoms in each oligomer and one to three Li, Be, Mg, Zn, Ag, or Au cross-linking metal elements. PEn-Mm-PEn complexes are quasiplanar with nearly parallel PE chains. Their stability is determined by covalent C-M-C bonds accompanied by noncovalent dispersion interactions between PEn chains. Using the CAM-B3LYP+D3BJ+ABC functional, the binding energies of PE15-M-PE15 with respect to two PE15 radicals and metal fragments are -225, -230, -322, -551, -289, and -303 kJ/mol for Li, Ag, Au, Be, Mg, and Zn atoms, respectively. Entropy contributions (109 to 121 kJ/mol at 298.15 K) destabilize all complexes significantly. With two cross-linking metal elements in PE15-M2-PE15 complexes, binding energies are about double. Complexes with several open-shell Li, Ag, or Au doublet atoms have spins located on separated C-M-C bonds. High-spin PE15-Mm1-PE15-Mm2-PE15 complexes of three PE oligomers cross-linked by up to five doublet metal atoms create parallel PE tubes, which are suggested as elementary cells for modeling magnetic polymer tubes.

Resin bound gold nanocomposites assisted SE/ATR-FTIR spectroscopy for detection of pymetrozine insecticide in vegetable samples

The goal of this work was to assess the competence of organic hydrophobic resin bound gold nanocomposites (OH/R-AuNCs) for detection of pymetrozine insecticide from vegetable samples employing surface-enhanced/attenuated total reflectance-Fourier transform infrared (SE/ATR-FTIR) spectroscopy. The adsorption isotherm models, including the Langmuir, Freundlich and Temkin, are tested to reveal the interactive behaviour between the OH/R-AuNCs and pesticide. The adsorption occurs principally by London–Van der Waals dispersion interactions and hydrogen bonding interactions between the surface of OH/R-AuNCs materials and the hydrophobic part of pesticide molecule. The characteristic absorption band obtained at 3019.94 cm−1 was utilized for the quantitative analysis of pymetrozine insecticide in vegetable samples. The method was found to be accurate and precise, with mean recovery values in the range of 94.5–110 %, correlation coefficient of 0.992 %, and detection limit of 2.65 μg mL−1. The adsorption efficiency of the designed OH/R-AuNCs significantly influences the SE/ATR-FTIR response of the pymetrozine around 90 %. The optimized and validated method was applied to determine the residual concentrations of the pymetrozine that had been applied to vegetable samples.

Simple fabrication of green nanocellulose-reinforced sugarcane (S. officinarum) bagasse film with improved water barrier properties

This study reports a simple fabrication of green sugarcane (Saccharum officinarum) bagasse nanocomposite-based films with improved water barrier properties. In this work, cellulose nanofibers derived from sugarcane bagasse (SB-CNF) were employed as reinforcing agents. The reinforcing effects of varying SB-CNF concentrations, ranging from 10 to 40 wt%, on the characteristics and functionalities of nanocomposite films were measured. Our results demonstrated that the film incorporating 30 % SB-CNF into the SB matrix exhibited optimal characteristics and was chosen for further evaluation of its water barrier properties. To enhance the water barrier properties of the resulting films, different concentrations of lysozyme (0, 3.5, 7, 10.5, and 14 wt%) were incorporated into the film matrix. With the addition of 3.5 % LZ, the film exhibited enhanced water barrier properties, yielding a water contact angle of 97.60 ± 0.79°, a water solubility of 18.64 ± 0.79 %, and a water vapour permeability of 0.65 ± 0.04 g mm/m2 d kPa. The film also showcased its ability to retain water over the course of 120 minutes, with a swelling ratio of 430 %. An increase in mechanical strength (67.28 ± 0.58 MPa) and transparency (88.70 ± 0.39 %) of the film was also noted. The observed findings were attributed to the good dispersion and excellent intermolecular interactions between the lysozyme and the SB/30 %SB-CNF. These results offer a promising prospect for utilization in food packaging applications, with an emphasis on food preservation.

The carbonyl-sulfur chalcogen bonding interaction: Rotational spectroscopic study of the 2,2,4,4-tetrafluoro-1,3-dithietane···formaldehyde complex

The rotational spectrum of a binary molecular cluster consisting of 2,2,4,4-tetrafluoro-1,3-dithietane (C2S2F4) and formaldehyde (H2CO) was studied by means of high-resolution Fourier transform microwave spectroscopy in conjunction with quantum chemical calculations. One of the three isomers predicted at the B3LYP-D3(BJ)/def2-TZVP level of theory was successfully detected in the supersonic expansion. Theoretical analyses using the non-covalent interactions and natural bond orbital methods reveal that the observed isomer is primarily stabilized by one C=O⋯S chalcogen bond and two C−H⋯F hydrogen bonds. The distance between the oxygen atom of H2CO and the nearest sulfur atom of C2S2F4 within the observed isomer is 2.9260(1) Å and the angle ∠O⋯S−C is 161.83(1)°. The analysis utilizing the symmetry-adapted perturbation theory approach demonstrates that electrostatic interactions play a significant role in stabilizing the studied complex, with the contribution of dispersion interactions being comparable to that of electrostatic ones.

Unravelling large-scale patterns and drivers of biodiversity in dry rivers

More than half of the world’s rivers dry up periodically, but our understanding of the biological communities in dry riverbeds remains limited. Specifically, the roles of dispersal, environmental filtering and biotic interactions in driving biodiversity in dry rivers are poorly understood. Here, we conduct a large-scale coordinated survey of patterns and drivers of biodiversity in dry riverbeds. We focus on eight major taxa, including microorganisms, invertebrates and plants: Algae, Archaea, Bacteria, Fungi, Protozoa, Arthropods, Nematodes and Streptophyta. We use environmental DNA metabarcoding to assess biodiversity in dry sediments collected over a 1-year period from 84 non-perennial rivers across 19 countries on four continents. Both direct factors, such as nutrient and carbon availability, and indirect factors such as climate influence the local biodiversity of most taxa. Limited resource availability and prolonged dry phases favor oligotrophic microbial taxa. Co-variation among taxa, particularly Bacteria, Fungi, Algae and Protozoa, explain more spatial variation in community composition than dispersal or environmental gradients. This finding suggests that biotic interactions or unmeasured ecological and evolutionary factors may strongly influence communities during dry phases, altering biodiversity responses to global changes.

The relative importance of local versus regional habitat structure variation on the abundance of two generalist mutualists along a forest disturbance gradient

Mutualistic interactions are key to biodiversity generation and maintenance, being pollination and seed dispersal interactions essential for plant reproduction. However, anthropogenic habitat disturbance can alter these interactions. We studied the regional and local effects of habitat disturbance on two generalist mutualist animals of southern Chile temperate rainforests: the hummingbird Sephanoides sephaniodes and the marsupial Dromiciops gliroides, which perform key roles as pollinator and seed disperser, respectively. We sampled 12 sites corresponding to four disturbance conditions (mature native forest, secondary forest, native forest under selective logging, and exotic forest plantations) in which we estimated the number of S. sephaniodes and D. gliroides records (as a proxy of relative abundance) using camera traps. We measured seven habitat structure variables at each site, known to influence their occurrence. Specifically, we examined S. sephaniodes and D. gliroides abundance variation at (i) a regional scale (among disturbance conditions) and (ii) at a local scale (among sampling sites). Dromiciops gliroides abundance decreased as disturbance increased, but S. sephaniodes abundance was highly variable. At the local scale, S. sephaniodes and D. gliroides abundances were largely variable among sites, influenced by habitat structural features, such as bamboo and shrub cover and woody debris. Our results show that although habitat disturbance may influence mutualist abundances, they can tolerate disturbance if minimum structure and resource requirements are met, but respond idiosyncratically to local conditions. Examining local-scale variability may provide valuable information on ecological processes, which often goes unnoticed when local sites are considered as replicates in landscape-level studies.

Quantitative analysis of intermolecular forces in cellulose microfibrils and hemicellulose with AFM nano-colloidal probes

It is an interesting research topic to study the interfacial interactions between hemicellulose and cellulose, specifically how hemicellulose's structure affects its binding to cellulose nanofibers. Our research proposes that dispersion interaction play an important role in this interfacial interaction, more so than electrostatic forces when considering the adherence of cellulose to xylan. To quantify these interactions, the Atomic Force Microscope (AFM) colloidal probe technique is applied to measure the intermolecular forces between cellulose nanofibers, which are attached to the probe and xylan. These measured forces are then analyzed in relation to the length, diameter and functional groups of the nanocellulose, as well as the molecular weight and side chains of the xylan. Moreover, the predominance of dispersion forces by contrasting the adhesive forces before and after the grafting of a large nonpolar group onto xylan. This modification significantly reduces contact between the cellulose and xylan backbone, thereby markedly diminishing the dispersion interactions. Parallel to the AFM experiments, molecular dynamics (MD) simulations corroborate the experimental results and support our hypotheses. Collectively, these findings contribute to a deeper understanding of polysaccharide interactions within lignocellulose.

Disentangling the complexity of plant-bird relationships: From monolayer to multilayer network perspectives

Most plant-bird interaction research employing complex ecological networks focuses on pollination and seed dispersal interactions. However, birds and plants are immersed in a great variety and complexity of direct and indirect relationships. Therefore, the use of multilayer networks (i.e., species interaction networks involving different types of interactions) could provide new insights into the ecological and coevolutionary dynamics of plant-bird relationships. Here, we used a multilayer network approach to determine how a bird-plant interaction network involving different types of interactions (i.e., foraging for invertebrates on plants, frugivory, nectarivory, and perching) is organized in a peri-urban Mexican cloud forest. Moreover, we added information about the interactive roles of the winter migratory and resident birds in the multilayer network. In general, we found that the bird-plant multilayer network exhibits modular but a non-nested structure. We also observed that interactions involving perching and foraging for invertebrates on plants are more frequent than frugivory and nectarivory. Moreover, just a small proportion of birds and plant species were important to the network organization and for connecting different interaction types. In this case, we observed that only two bird species, Cardellina pusilla (Parulidae) and Dumetella carolinesis (Mimidae), and the plant species Telanthophora grandifolia (Asteraceae) and Platanus mexicanus (Platanaceae) presented higher centrality values (i.e., an interactive role). Finally, we found that betweenness values (i.e., the number of times a species acts as a bridge along the shortest path between two species) and network structure's contributions are similar for both migratory and resident bird species. Our results highlight the importance of key interacting species that connect other interacting species for the preservation of community cohesion and to the persistence of species-rich assemblages.

The variation of the temperature of maximum density of non-polar solutes in water: insights from the pressure change in a constant volume solution process

The effects of non-polar solutes on the temperature of maximum density (T MD) of water are revisited by means of a molecular dynamics study of TIP4P/2005 water and two examples of spherically symmetric non-polar solutes modelled by same size single Lennard-Jones sites, with weak and strong solute–water dispersive interactions. We have adopted a two-stage strategy to model the solution process at constant pressure to reduce the analysis to the description of the pressure variation in the solution process at constant volume. To this end, the Reaction Field treatment of the Coulombic forces was used so as to be able to decompose the different molecular components to the virial pressure and their spatial variation in terms of the distance to the solute molecule. In this way, we have been able to separate which factors induce the increase of water’s T MD observed for weakly interacting non-polar solutes and the decrease that occurs when the solute is strongly interacting.

Correcting Dispersion Corrections with Density-Corrected DFT.

Almost all empirical parametrizations of dispersion corrections in DFT use only energy errors, thereby mixing functional and density-driven errors. We introduce density and dispersion-corrected DFT (D2C-DFT), a dual-calibration approach that accounts for density delocalization errors when parametrizing dispersion interactions. We simply exclude density-sensitive reactions from the training data. We find a significant reduction in both errors and variation among several semilocal functionals and their global hybrids when tailored dispersion corrections are employed with Hartree-Fock densities.

Hydrogen bonding to the electron accepting group controls the absorption spectrum of a push–pull stilbene adsorbed on amorphous silica

The photophysical and photochemical properties of push–pull photoswitches, such as stilbene derivatives, are very sensitive to their surroundings, allowing, e.g., for the control of the spectral properties or alternatively for probing the molecular environment. Here, we investigate how various adsorption motifs of 4-(N, N-Dimethylamino)-4’-nitrostilbene (DANS) on an amorphous glass surface influence its absorption spectra. Particular attention is given to the prominent first bright charge transfer state and the factors governing these modifications. The absorption spectra is simulated using time-dependent density functional theory on a large set of adsorption geometries that exhibit different kinds of molecule–surface interactions. We find that C–H⋯O interactions of the methyl or phenyl moieties with the glass affect the spectrum only marginally, whereas the dispersion interaction of the π system with the surface tends to diminish the intensity of the first absorption band. Moreover, an enhancement of the push–pull properties of DANS and a significant redshift occur whenever O–H⋯O hydrogen bonds with the NO2 group are present, whereas a hydrogen bond O–H⋯N to the NMe2 group results in a blueshift.