Large Interaction Energy Research Articles

The Role of Hydrogen Bonds in Interactions between [PdCl4]2- Dianions in Crystal.

[PdCl4]2− dianions are oriented within a crystal in such a way that a Cl of one unit approaches the Pd of another from directly above. Quantum calculations find this interaction to be highly repulsive with a large positive interaction energy. The placement of neutral ligands in their vicinity reduces the repulsion, but the interaction remains highly endothermic. When the ligands acquire a unit positive charge, the electrostatic component and the full interaction energy become quite negative, signalling an exothermic association. Raising the charge on these counterions to +2 has little further stabilizing effect, and in fact reduces the electrostatic attraction. The ability of the counterions to promote the interaction is attributed in part to the H-bonds which they form with both dianions, acting as a sort of glue.

Highly accurate DFT investigation for triggering the ultra-strong static and dynamic nonlinear optical properties of superalkali doped aminated graphdiyne (NH2-GDY) donor-π-acceptor (D-π-A) quantum dots

Keeping in mind the desirability of novel two-dimensional materials with an ultra-high nonlinear optical (NLO) response for the fabrication of optoelectronic devices, we have investigated nine complexes by doping superalkalis (M2X; M = Li, Na, K and X = F, Cl, Br) onto the novel aminated graphdiyne (NH2-GDY) quantum dots. The geometric, electronic and NLO responses (static and dynamic) of the M2X doped aminated graphdiyne (M2X@NH2-GDY) complexes have been systematically investigated using density functional theory (DFT) computations. All the superalkalis are preferably oriented on the triangular large porous site of NH2-GDY containing extensive delocalized π-conjugated electrons and interact via an intermolecular π-electron donor–acceptor (D-π-A) process. The lithium and potassium-containing superalkali doped complexes exhibit high structural stability due to their large interaction energies. The change in the electronic properties of the M2X doped NH2-GDY quantum dots is investigated by analyzing the NBO charge transfer, vertical ionization energies (VIEs), HOMO-LUMO energy gaps and density of states spectra. TD-DFT calculations show ultra-high transparency of these complexes in the ultraviolet region. The strong NLO characteristics of the designed complexes are demonstrated by their high static and dynamic hyperpolarizability values. Among all the nine complexes, the K2F@NH2-GDY, K2Cl@NH2-GDY and K2Br@NH2-GDY complexes possess exceptionally high βo values: 1.16 × 104, 1.06 × 104 and 1.02 × 104 au, respectively, owing to the large atomic radius and high atomic number of the potassium metal atoms. The frequency-dependent NLO responses, Electro-Optical Pockels Effects (EOPE) and Second Harmonic Generation (SHG) are analyzed to investigate the dynamic NLO response. It is revealed that the K2X@NH2-GDY complexes also exhibit exceptionally high dynamic NLO responses (107 or 108 au) at 1064 nm wavelength. Our present research not only highlights the significance of superalkali doping on aminated graphdiyne quantum dots but also indicates that the K2X@NH2-GDY complexes are potentially important for next-generation optoelectronic devices.

Reaction of lithium hexamethyldisilazide (LiHMDS) with water at ultracold conditions.

Alkali metal amides are highly reactive reagents that are broadly applied as strong bases in organic synthesis. Here, we use a combined helium nanodroplet IR spectroscopic and theoretical (DFT calculation) study to show that the reaction of the model compound lithium hexamethyldisilazide (LiHMDS) with water is close to barrierless even at ultra-cold conditions. Upon complex formation of dimeric (LiHMDS)2 with water in helium nanodroplets as ultra-cold nano-reactors (0.37 K) we observed the reaction product (LiOH)2(HMDS)2. This can be rationalized as aggregation induced reation upon stepwise addition of water. With increasing water partial pressure, only the product (LiOH)2(HMDS)2 is observed experimentally. This implies that the large interaction energy (69 kJ mol-1) of (LiHMDS)2 with water is sufficient to overcome the follow-up reaction barriers, in spite of the rapid cooling rates in He nanodroplets.

Large interaction energy for the homodimer and the heterodimer extracted from the supramolecular chain of a bent trinuclear zinc(ii) complex with a reduced Schiff base ligand

The coordinated amino groups in a trinuclear zinc complex participate in strong H-bonding interactions that have been analysed. The dimerization energy is very large for both the homodimer and the heterodimer in the 1D supramolecular chain.

Facile and green synthesis of reduced graphene oxide/loofah sponge for Streptomyces albulus immobilization and ε-poly-l-lysine production

Facile and green fabrication of reduced graphene oxide on loofah sponge (rGOLS) carrier was applied for cell immobilization of ε-Poly-l-lysine (ε-PL) production. Due to surface properties including large specific surface area, high polarity, and low interaction energy, rGOLS-1 was employed as the optimum rGOLS to enhance immobilization of Streptomyces albulus. Compared with raw LS, batch experiments showed rGOLS-1 facilitated superior cell vitality for ε-PL production due to the presence of reduced graphene oxide. In the sequential fed-batch cultivation of Streptomyces albulus using rGOLS-1 with an aerobic plant fibrous-bed bioreactor (rGOLS-1-AFPB), the maximum ε-PL concentration and productivity reached to 39.2 ± 0.63 g/L and 0.48 g/L/h. The cells immobilized in rGOLS-1 with high vitality and ε-PL production efficiency were reused six times over a period of 624 h. This research afforded an effective approach to enhance the fermentation performance of immobilized cells with the design of an advanced immobilization carrier.

Free Energy Trajectory for Escape of a Single Chain from a Diblock Copolymer Micelle.

We use umbrella sampling to compute the free energy trajectory of a single chain undergoing expulsion from an isolated diblock copolymer micelle. This approach elucidates the experimentally unobservable transition state, identifies the spatial position of the maximum free energy, and reveals the chain conformation of a single chain as it undergoes expulsion. Combining umbrella sampling with dissipative particle dynamics simulations of A4B8 micelles reveals that the core block (A) of the expelled chain remains partially stretched at the transition state, in contrast with the collapsed state assumed in some previous models. The free energy barrier increases linearly with the Flory-Huggins interaction parameter χ up to large interaction energies, where the structure of the otherwise spherical core apparently deforms near the transition state.

Benzoato bridged dinuclear Mn(II) and Cu(II) compounds involving guest chlorobenzoates and dimeric paddle wheel supramolecular assemblies: Antiproliferative evaluation and theoretical studies

Two new benzoato bridged Mn(II) and Cu(II) dinuclear coordination compounds viz. [Mn2(bipy)2(4-Clbz)2(H2O)4]2(4-Clbz) (1) and [Cu2(bz)4(2-MePy)2] (2) (bipy = 2,2́-bipyridine, 4-Clbz = 4-chlorobenzoate, bz = benzoate, 2-MePy = 2-methylpyridine) have been synthesized and characterized using elemental analysis, TGA, spectroscopic (FTIR, electronic, EPR) and single crystal X-ray diffraction techniques. Crystal structure analysis of compound 1 reveals the enclathration of guest 4-Clbz moiety in the supramolecular host tetramer which provides rigidity to the crystal structure. Further analysis reveals the presence of cooperative (π–π)2/(π–π)1/(π–π)2 ternary assemblies involving alternate coordinated and uncoordinated 4-Clbz moieties. In compound 2, intermolecular CH∙∙∙O, CH∙∙∙π and CH∙∙∙C contacts are involved in the formation of dimeric paddle wheel supramolecular assemblies which stabilizes the layered architecture. The cooperative interplay of H-bonding and π-stacked ternary assemblies of 1 has been studied theoretically using DFT calculations, MEP surface and NCI Plot computational tools. The large interaction energies along with the NCI plot index analysis confirm that the π-stacking assemblies in combination with the H-bonds are strong binding motifs. In vitro anticancer activity of the compounds considering cytotoxicity and apoptosis assays reveal significant concentration dependent cytotoxicity in Dalton's lymphoma (DL) cancer cell lines with nominal effects in normal healthy PBMC cells. Molecular docking study reveals the efficient interaction of the compounds with the antiapoptotic BCL family target proteins.

Effect of mixing ratio on the adsorption behavior of low-rank coal surface using mixed collectors: Experimental and molecular dynamics simulation study

ABSTRACT The effect mechanism of mixing ratio on the adsorption behavior of low-rank coal surface using mixed collectors has not been systematically studied. In this study, dodecane (D) and n-valeric acid (N) were mixed into different collectors in different ratios, and their adsorption mechanism on the surface of LRC was studied by experiment and simulation calculation. The flotation results indicated that the sequence of the flotation clean coal yield was 8:2 > 6:4 > 5:5 > 7:3 > 9:1. The measurement results of the heat of adsorption, total organic carbon, and liquid phase contact angle all responded to the flotation results as a whole. The molecular dynamics simulation results revealed that when an appropriate ratio was used to form a mixed collector, the N molecules could make the D molecules form oil molecular layer thicken, thus increasing the hydrophobicity of the surface of the LRC molecules. The optimal mixing ratio could also create a large interaction energy between the mixed collector and LRC. Therefore, D and N need to be mixed at a proper ratio to maximize the LRC flotation efficiency.

Study of nonlinear optical properties of superhalogen and superalkali doped phosphorene

Herein, nonlinear optical properties of superhalogen and superalkali doped phosphorene are investigated by utilizing the density functional theory. Large interaction energies revealed that these complexes are satisfactory stable. Doping materials reduce the bandgap and enhance electronic conduction. Density of states analysis provides a better understanding of the electronic transition from HOMO to LUMO of doped compounds. The dipole and transition dipole moment of all doped molecules is changed. These doped molecules have small transition energies (ΔE) which leads to increase in their hyperpolarizabilities. Doping of superalkali enhances the second hyperpolarizability from 51.99 × 104 to 138.25 × 104 au Electron density difference map analysis provides information on the electronic distribution of doped compounds. TD-DFT analysis reveals that these molecules have absorption in the UV region. All these results have proven that doping of phosphorene is an effective approach in designing efficient nonlinear optical materials.

On the adsorption affinity of graphene and white graphene sheets by dioxin‐like pollutants

AbstractThe affinity of graphene and white graphene sheets by dioxin‐like pollutants was compared by means of high‐level quantum chemical calculations. 2,3,7,8‐tetrachloro‐p‐dibenzodioxin (TCDD) and 2,3,7,8‐tetrachlorodibenzofuran (TCDF) were chosen as prototypes of dioxin‐like pollutants with high toxicological activity. Large interaction energies were obtained both in graphene and white graphene surfaces, contrary to other previous works using the graphene surface only. The interactions clearly differed in the relative weight of inductive and dispersion forces, being the former more important in white graphene. Leaving thermal effects out, the stacking adsorption was energetically favored over the perpendicular in graphene whereas no difference was found in white graphene. Due to the low water solubility of dioxin‐like pollutants very small differences were obtained between gas phase and solution adsorption enthalpies. Including thermal effects, perpendicular adsorption was found to be both energetically and entropically favored over stacking at 298 K. The adsorption free energies reflected a larger affinity by white graphene than graphene by around 2–5 kcal·mol−1. Therefore, boron nitride 2D surfaces are expected to perform better than carbon 2D surfaces as adsorbents for dioxin‐like pollutants in line with recent experimental works on water contaminants.

Redox Modulation of the Reactivity and Regioselectivity in Diels–Alder Reaction of Metallofullerene La@C82 with Cyclopentadiene

AbstractModulation of the reactivity of metallofullerenes is critical for production of metallofullerene derivatives with desired properties and functionalities. In this study, we investigate the effects of reduction and oxidation on the reactivity and regioselectivity in Diels–Alder reaction of metallofullerene La@C82 by means of density functional theory calculations. Because of the enhanced electron‐deficiency characteristic upon oxidation, the oxidized metallofullerene exhibits higher thermodynamic and kinetic reactivity as compared with neutral La@C82. The regioselectivity in the reaction of La@C82 with cylcopentadiene is remarkably changed after oxidation of the metallofullerene, which is explained in terms of the changes in the geometrical structure and the electronic structure of the metallofullerene. Quantitative analysis based on the activation‐strain model demonstrates that the low activation energy barrier for the reaction of the cation La@C82+ with cyclopentadiene originates from small strain energy and large interaction energy between the reactants. Energy decomposition analysis on the transition states of the reactions reveals that the exchange‐repulsion interaction energy is one of the critical factors that determine the kinetic reactivity of the metallofullerene. This study not only provides new theoretical insights on how to modulate the reactivity of metallofullerenes, but also offers guideline for future experimental synthesis of new metallofullerene derivatives.

Equilibrium solubility of kojic acid in four binary solvents: Determination, model evaluation, Hansen solubility parameter, thermodynamic properties and quantum chemical calculations

Using the laser monitoring method, the solubility of kojic acid (KA) in the four binary solvents {[(N, N-dimethylformamide) DMF, (N, N-dimethylacetamide) DMAC, (dimethyl sulfoxide) DMSO and (N-methylpyrrolidone) NMP] + ethyl acetate} was measured at various temperatures. The results revealed that the experimental solubility values of KA have positive correlations with mass fraction of co-solvents and temperature in investigated four binary solvents. The solubility order of KA with mass fraction of co-solvents being w1 = 0.2000, 0.4000 and 0.6000 is: DMSO + ethyl acetate > NMP + ethyl acetate > DMAC+ ethyl acetate > DMF + ethyl acetate, respectively. However, in DMAC (w1 = 0.8005) + ethyl acetate, the solubility values of KA overtook that in NMP (w1 = 0.8004) + ethyl acetate at the higher temperature. The miscibility behaviors of KA with tested four binary solvents was revealed by the Hansen Solubility Parameters (HSPs). According to the calculated interaction energy, KA can be more easily dissolved in the solvent which has larger interaction energy with KA. Additionally, the measurement solubility data was mathematically correlated by the NRTL, Three-Suffix Margules, UNIQUAC models and Apelblat equation. The thermodynamic parameters (ΔdisGo, ΔdisHo, ΔdisSo, ζH, ζTS) of KA dissolution processes in investigated four binary solvents were evaluated utilizing the van't Hoff equation. The positive ΔdisHo and ΔdisSo, indicate that the dissolution processes of KA are endothermic and entropy-driven in all chosen binary solvents. And the main contributor of ΔdisGo is positive enthalpy.

Scale-invariant magnetic anisotropy in RuCl3 at high magnetic fields

In RuCl$_3$, inelastic neutron scattering and Raman spectroscopy reveal a continuum of non-spin-wave excitations that persists to high temperature, suggesting the presence of a spin liquid state on a honeycomb lattice. In the context of the Kitaev model, magnetic fields introduce finite interactions between the elementary excitations, and thus the effects of high magnetic fields - comparable to the spin exchange energy scale - must be explored. Here we report measurements of the magnetotropic coefficient - the second derivative of the free energy with respect to magnetic field orientation - over a wide range of magnetic fields and temperatures. We find that magnetic field and temperature compete to determine the magnetic response in a way that is independent of the large intrinsic exchange interaction energy. This emergent scale-invariant magnetic anisotropy provides evidence for a high degree of exchange frustration that favors the formation of a spin liquid state in RuCl$_3$.

Activation of the Unreactive Bond in C70 Fullerene toward Diels-Alder Reaction by Encapsulation of a Lithium Atom.

Diels-Alder cycloaddition reaction is useful for generation of covalent derivatives of fullerenes. Diels-Alder reactions of C70 and dienes usually take place at the carbon-carbon bond that has a short bond length in C70 , while the bonds with long lengths are generally unreactive. In this paper, we investigated the reactivities of Li+ @C70 and Li@C70 toward Diels-Alder reactions with cyclohexadiene by means of density functional theory calculations. We found that the thermodynamic and kinetic reactivities of the fullerene cage are changed significantly after the encapsulation of the lithium ion or atom. The encapsulated lithium ion causes a remarkable decrease of the activation barrier for the cycloaddition reaction, which can be ascribed to the enhanced orbital interaction between cyclohexadiene and the fullerene cage. The unreactive bond with a long length in C70 is activated efficiently after the encapsulation of the lithium atom. According to the activation-strain model analysis, the improved reactivity of the long bond is associated with the small deformation energy and large interaction energy of the reactants. Unlike conventional Diels-Alder reactions that proceed through concerted mechanism, the reaction of Li@C70 and cyclohexadiene undergoes an unusual stepwise mechanism because of the open-shell electronic structure of Li@C70 .

Strengthening of halogen bond in XCl∙∙∙FH∙∙∙F− through cooperativity with a strong hydrogen bond and proton transfer

A theoretical calculation has been performed for the ternary complexes XCl∙∙∙FH∙∙∙F− (X = CCH, CN, OH, NC, and F) and the corresponding binary complexes. The halogen bond in the dyad is very weak with the interaction energy less than 2.5 kcal/mol. Interestingly, the halogen bond gets a big enhancement when it combines with a very strong hydrogen bond in FH∙∙∙F−, and the largest interaction energy is up to ∼25.6 kcal/mol in FCl∙∙∙FH∙∙∙F−. The enhancement of halogen bond not only results in a larger elongation of X–Cl bond and a bigger redshift of the bond stretch vibration but also makes the blue-shifting halogen bond in NCCl∙∙∙FH be a red-shifting one in NCCl∙∙∙FH∙∙∙F−. The halogen bond belongs to a purely close-shell interaction in the dyad, while it becomes a partially covalent interaction in XCl∙∙∙FH∙∙∙F− (X = OH, NC, and F) with negative energy density. In FH∙∙∙F−, the proton is shared between the two F atoms, however, this proton transfers towards the F− end in XCl∙∙∙FH∙∙∙F−.

Theoretical insights into the spectral properties of a salicylideneaniline-based fluorescence chemosensor (SB1) and its sensing mechanism for cyanide anion

The sensing mechanism of a salicylideneaniline-based fluorescence chemosensor (SB1) for the cyanide anion (CN−) has been investigated by nonadiabatic dynamics and transition state (TS) theory. The intramolecular hydrogen bonds in SB1 and the product SB1-CN are strengthened after photoexcitation, which induce the intramolecular proton transfer in 114 fs and 167 fs by the results of nonadiabatic dynamics. The fluorescence (626 nm) of SB1 emits from the proton-transfer tautomer rather than the excited state intramolecular charge transfer (ICT) state. The new appeared emission peak (523 nm) after the addition of CN− is attributed to the proton-transfer tautomer of SB1-CN, which has a large blue shift (103 nm) compared to that of SB1. The TS calculations demonstrate the occurrence of reaction from SB1to SB1-CN after overcoming an energy barrier of 10.52 kcal/mol and there is a large interaction energy (95.92 kJ/mol) between SB1 and CN−, both of which confirm that SB1 has high sensitivity and selectivity to CN−. The nucleophilic addition reaction of CN− interrupts the π-conjugation structure of SB1, resulting in an inefficient ICT, which in turn destroys the excited state intramolecular charge/proton transfer (ESICT-ESIPT) coupled system and causes the blue shift of the spectral peak. The work gives a complete explanation about ESICT-ESIPT coupling switching behavior and the sensing mechanism of SB1 for CN−.

Synthesis & characterization of ion imprinted polymer for arsenic removal from water: A value addition to the groundwater resources

In this study, ion imprinted polymer (As(III)-IIP) was synthesized using allylthiourea as a functional monomer and As(III) as a template in removing As from water. The synthesis of As(III)-IIP as a sorbent was prepared via bulk polymerization. The characterization study has been conducted included pre-polymerization study by using Proton Nuclear Magnetic Resonance (1H NMR); Fourier Transform Infrared (FTIR) analysis, saturation study and pH effects with Inductively Couple Plasma-Mass Spectrometer (ICP-MS) as an instrumental detection. FTIR analysis was done to differentiate spectra between As(III)-IIP; and NIP as a control. From pre-polymerization study, the nature of bonding complexation was selective towards sulphur atoms and hydrogen atoms. A moiety of amino acid at functional sites of As(III)-IIP contributes to the selective properties between sulphur atoms and arsenite. In addition, reduction process occurred during adsorption and change from arsenite to arsenate which produce less toxic compounds. From 1H NMR spectra, AT has the largest interaction energy towards the As(III) as a template in a mixture of 0.5 M AT. Downfield chemical shifts occurred from 6.68 ppm to 7.01 ppm and from 6.13 ppm to 6.32 ppm respectively. The formation of thioarsenic complex was obtained from this study. In the saturation study, the total capacity loaded reached until 0.0679 mmol/g for 25 mg/L of initial arsenite. The specialty of As(III)-IIP among other sorbents, As(III)-IIP able to recover the arsenite from aqueous media. At pH 7, As(III)-IIP works as a good sorbent at high percentage of removal (90%). In the FTIR spectra, there is no significant differences in NIP and As(III)-IIP as a sorbent. As a conclusion, As(III)-IIP would be a great alternative methods for As removal from water.

Ultraviolet Photoactivated Room Temperature NO2 Gas Sensor of ZnO Hemitubes and Nanotubes Covered with TiO2 Nanoparticles.

Prolonged exposure to NO2 can cause lung tissue inflammation, bronchiolitis fibrosa obliterans, and silo filler’s disease. In recent years, nanostructured semiconducting metal oxides have been widely used to fabricate gas sensors because of their unique structure and surface-to-volume ratio compared to layered materials. In particular, the different morphologies of ZnO-based nanostructures significantly affect the detection property of NO2 gas sensors. However, because of the large interaction energy of chemisorption (1–10 eV), metal oxide-based gas sensors are typically operated above 100 °C, overcoming the energy limits to attain high sensitivity and fast reaction. High operating temperature negatively affects the reliability and durability of semiconductor-based sensors; at high temperature, the diffusion and sintering effects at the metal oxide grain boundaries are major factors causing undesirable long-term drift problems and preventing stability improvements. Therefore, we demonstrate NO2 gas sensors consisting of ZnO hemitubes (HTs) and nanotubes (NTs) covered with TiO2 nanoparticles (NPs). To operate the gas sensor at room temperature (RT), we measured the gas-sensing properties with ultraviolet illumination onto the active region of the gas sensor for photoactivation instead of conventional thermal activation by heating. The performance of these gas sensors was enhanced by the change of barrier potential at the ZnO/TiO2 interfaces, and their depletion layer was expanded by the NPs formation. The gas sensor based on ZnO HTs showed 1.2 times higher detection property than those consisting of ZnO NTs at the 25 ppm NO2 gas.

Regular/abnormal variation in the strength and nature of the halogen bond between H2Te and the dihalogens: Prominent effect of methyl substituents

The halogen‐bonded complexes between H2Te/Me2Te and the dihalogen molecules XY (XY = F2, Cl2, Br2, I2, ClF, ClBr, BrF, BrCl, BrI, IF, ICl, IBr) have been studied to investigate the dependence of its strength and nature on the halogen donor X and its adjoining atom Y, as well as the methyl groups in the electron donor. The interaction energy varies between −1.7 and − 43.5 kcal/mol, indicating that the Te atom in H2Te/Me2Te has a strong affinity for the dihalogen molecules. For the H2Te‐XY complex, the halogen bond is stronger for the heavier halogen donor X atom and the strong electron‐withdrawing group Y. However, for Me2Te‐XY, the halogen bond is stronger for the lighter halogen donor X atom. The H2Te/Me2Te‐F2 complex has the largest interaction energy, although the σ‐hole on F2 is the smallest in magnitude. In most of the complexes, the electrostatic and polarization contributions to the binding strength are similar in magnitude. However, for H2Te/Me2Te‐F2, the polarization contribution is much larger than the electrostatic contribution, with a significant contribution from charge transfer.

Valine adsorption on pristine and N-doped graphenes: DFT, AIM, and IGM study

Deep insight into interactions of various biomolecules with nanomaterials is very important to design novel materials for different applications. The present work studies physical adsorption of valine, an amino acid, on the surfaces of graphene and N-doped graphenes using density functional theory (DFT). Atoms-in-molecules (AIM) and independent gradient model (IGM) analyses have been implemented to reveal the features of interactions in studied complexes. The SAPT0 method has been used to decompose total interaction energy into constituents, which allows one to carry out the complete analysis of the valine/adsorbent interactions. Dispersion forces have been found to play major roles in attractive interactions for the considered complexes. They are followed by electrostatic components. Studies of N-doping effects reveal that valine binds more strongly to the N-doped graphene surfaces in comparison with pristine graphene. The total interaction energy reaches—0.82 eV, which is ∼65% larger than that for pristine graphene. Our results demonstrate that N-doped graphenes with the large interaction energy would be of importance for technical realization of the targeted delivery of valine.