Molecular Polarizability Research Articles

Normal Mode Analysis, Electronic Descriptors, NLO Properties 8 Molecular Docking of "Butein, 2',3,4,4'- Tetrahydroxychalcone: A DFT approach"

Study of modern medicine is a flourishing field with activity revolving around the identification, characterization and assessment of therapeutic potential of phytochemicals in various disease conditions. Chalconoids, being prominently present in various medicinal herbs are being widely studied to unravel the molecular mechanisms associated with their effects. This paper describes the molecular structure of well known compound “(Butein, 2',3,4,4'- Tetrahydroxychalcone [C15H12O5]”, which has been optimized and its structural parameters have been calculated by DFT/B3LYP method using 6-311++G(d,p) basis set. The fundamental vibrational wavenumbers and their intensities were calculated and a good agreement between the observed FTIR spectrum and scaled calculated wavenumbers has been achieved. The electronic properties of the compound are explained using HOMO-LUMO and MEPS descriptors. The Non-Linear Optical parameters (NLO) are discussed using electrical parameters like electric dipole moment, molecular polarizability and hyperpolarizability measurements. We have done the molecular docking analysis also, in order to get a better perception into its observed physiological effects which are a prerequisite for determining its therapeutic potential. We hereby report a strong interaction of butein with the protein 1OG6, an enzyme of cytochrome P450 series designated CYP2C9 which is intricately involved in oxidative metabolic pathways. This provides a plausible mechanism for anti-oxidant properties of butein.

Structure and microwave dielectric properties of (Zn1/3Nb2/3)4+ co-substituted MgTiO3 ceramic

In this work, MgTi1-x(Zn1/3Nb2/3)xO3 (0 ≤ x ≤ 0.3) ceramics were synthesized by a solid-state reaction method. MgTiO3 is identified as main phase, while MgTi2O5 is detected as secondary phase at 0 ≤ x ≤ 0.3, in association with a minor Mg2TiO4 phase at x = 0. The (Zn1/3Nb2/3)4+ co-substituted ions are responsible for the change of bond length and the TiO6 octahedral distortion. The quality factor (Q × f) depends on the electronegativity difference (Δe) and average covalency. The dielectric constant (εr) is related to molecular polarizability (αtheo) and tolerance factor (t). Besides, the temperature coefficient of resonance frequency (τf) strongly correlates with TiO6 octahedral distortion and the secondary phase. In comparison to pure MgTiO3, desirable microwave dielectric properties of εr = 17.59, Q × f = 211 600 GHz, and τf = −50 ppm/°C were obtained when x = 0.12 sintered at 1250 °C. The MgTi0.88(Zn1/3Nb2/3)0.12O3 ceramic is a candidate material for the wireless communication applications.

Microwave dielectric properties of Ca1-xBaxMgSi2O6 ceramics

Ca1-xBaxMgSi2O6(x = 0–0.4) ceramics were prepared through a traditional solid-state reaction sintering route with various sintering temperatures. The effects of substituting Ba2+ for Ca2+, the relative density, phase composition, crystal morphology, and microwave dielectric properties of Ca1-xBaxMgSi2O6 (x = 0–0.4) ceramics were thoroughly studied. X-ray diffraction patterns indicate a single phase was formed in the samples when x ≤ 0.2, and the second phase BaMg2Si2O7 appeared at x = 0.4. As the amount of Ba2+ substitution increases, the Q×f value first increases and then decreases due to the combined effects of FWHM of peak v11 and atomic packing density, and the εr value was increased continuously which was closely corrected with the relative density and molecular polarization. The τf value improved slightly with the substituting Ba2+ for Ca2+. Typically, the Ca0.88Ba0.12MgSi2O6 ceramic can be well sintered at 1275 °C for 4 h with a maximum relative density of 99.3%, and possesses optimal microwave dielectric properties: εr=7.49, Q×f=64310 GHz, τf=-44.02 ppm/°C.

Local-Field Effects in Linear Response Properties within a Polarizable Frozen Density Embedding Method

In this work, we present a polarizable frozen density embedding (FDE) method for calculating polarizabilities of coupled subsystems. The method (FDE-pol) combines a FDE method with an explicit polarization model such that the expensive freeze/thaw cycles can be bypassed, and approximate nonadditive kinetic potentials are avoided by enforcing external orthogonality between the subsystems. To describe the polarization of the frozen environment, we introduce a Hirshfeld partition-based density-dependent method for calculating the atomic polarizabilities of atoms in molecules, which alleviates the need to fit the atomic parameters to a specific system of interest or to a larger general set of molecules. We show that the Hirshfeld partition-based method predicts molecular polarizabilities close to the basis set limit, and thus, a single basis set-dependent scaling parameter can be introduced to improve the agreement against the reference polarizability data. To test the model, we characterized the uncoupled and coupled response of small interacting molecular complexes. Here, the coupled response properties include the perturbation of the frozen system due to the external perturbation which is ignored in the uncoupled response. We show that FDE-pol can accurately reproduce both the exact uncoupled polarizability and the coupled polarizabilities of the supermolecular systems. Using damped response theory, we also demonstrate that the coupled frequency-dependent polarizability can be described by including local field effects. The results emphasize the necessity of including local-field effects for describing the response properties of coupled subsystems, as well as the importance of accurate atomic polarizability models.

Evidence of a C60 /Co interface reconstruction and its influence on magnetic properties

By using grazing incidence x-ray diffraction and scanning tunneling microscopy experiments, we determine the interface structure of a ${\mathrm{C}}_{60}$ layer deposited on a Co(0001) surface. The room temperature deposition gives rise to a ($4\ifmmode\times\else\texttimes\fi{}4$) molecular structure with a 10% vertical relaxation of the underneath Co atoms. When annealed around 550 K, the interface undergoes a structural change with most of the buckyballs sitting in a seven Co vacancies nanohole. Ab initio calculations show that this interface reconstruction is stabilized by a strong C-Co hybridization and has a significant impact both on the interfacial magnetic anisotropy that is decreased and on the molecular spin polarization that it increased.

The Appeal of Small Molecules for Practical Nonlinear Optics.

Small organic molecules with a π-conjugated system that consists of only a few double or triple bonds can have significantly smaller optical excitation energies when equipped with donor and acceptor groups, which raises the quantum limits to the molecular polarizabilities. As a consequence, third-order nonlinear optical polarizabilities become orders of magnitude larger than those of molecules of similar size without donor-acceptor substitution. This enables strong third-order nonlinear optical effects (as high as 1000 times those of silica glass) in dense, amorphous monolithic assemblies. These properties, accompanied by the possibility of deposition from the vapor phase and of electric-field poling at higher temperatures, make the resulting materials competitive towards adding an active nonlinear optical or electro-optic functionality to state-of-the-art integrated photonics platforms.

Magnetic Fields in Massive Star-forming Regions (MagMaR). II. Tomography through Dust and Molecular Line Polarization in NGC 6334I(N)

Abstract Here, we report ALMA detections of polarized emission from dust, CS(J = 5 → 4), and C33S(J = 5 → 4) toward the high-mass star-forming region NGC 6334I(N). A clear “hourglass” magnetic field morphology was inferred from the polarized dust emission, which is also directly seen from the polarized CS emission across velocity, where the polarization appears to be parallel to the field. By considering previous findings, the field retains a pinched shape that can be traced to clump length scales from the envelope scales traced by ALMA, suggesting that the field is dynamically important across multiple length scales in this region. The CS total intensity emission is found to be optically thick (τ CS = 32 ± 12) while the C33S emission appears to be optically thin ( τ C 33 S = 0.1 ± 0.01 ). This suggests that sources of anisotropy other than large velocity gradients, i.e., anisotropies in the radiation field, are required to explain the polarized emission from CS seen by ALMA. By using four variants of the Davis–Chandrasekhar–Fermi technique and the angle dispersion function methods (ADF), we obtain an average of the estimates for the magnetic field strength on the plane of the sky of B pos = 16 mG from the dust and B pos ∼ 2 mG from the CS emission, where each emission traces different molecular hydrogen number densities. This effectively enables a tomographic view of the magnetic field within a single ALMA observation.

Substrate-Dependent Trans-Stimulation of Organic Cation Transporter 2 Activity.

The search of substrates for solute carriers (SLCs) constitutes a major issue, owing notably to the role played by some SLCs, such as the renal electrogenic organic cation transporter (OCT) 2 (SLC22A2), in pharmacokinetics, drug–drug interactions and drug toxicity. For this purpose, substrates have been proposed to be identified by their cis-inhibition and trans-stimulation properties towards transporter activity. To get insights on the sensitivity of this approach for identifying SLC substrates, 15 various exogenous and endogenous OCT2 substrates were analysed in the present study, using 4-(4-(dimethylamino)styryl)-N-methylpyridinium iodide (DiASP) as a fluorescent OCT2 tracer substrate. All OCT2 substrates cis-inhibited DiASP uptake in OCT2-overexpressing HEK293 cells, with IC50 values ranging from 0.24 µM (for ipratropium) to 2.39 mM (for dopamine). By contrast, only 4/15 substrates, i.e., acetylcholine, agmatine, choline and metformin, trans-stimulated DiASP uptake, with a full suppression of the trans-stimulating effect of metformin by the reference OCT2 inhibitor amitriptyline. An analysis of molecular descriptors next indicated that trans-stimulating OCT2 substrates exhibit lower molecular weight, volume, polarizability and lipophilicity than non-trans-stimulating counterparts. Overall, these data indicated a rather low sensitivity (26.7%) of the trans-stimulation assay for identifying OCT2 substrates, and caution with respect to the use of such assay may therefore be considered.

Influence of geometry on positron binding to molecules

Annihilation studies have established that positrons bind to most molecules. They also provide measurements of the positron-molecule binding energies, which are found to vary widely and depend upon molecular size and composition. Trends of binding energy with global parameters such as molecular polarizability and dipole moment have been discussed previously. In this paper, the dependence of binding energy on molecular geometry is investigated by studying resonant positron annihilation on selected pairs of isomers. It is found that molecular geometry can play a significant role in determining the binding energies even for isomers with very similar polarizabilities and dipole moments. The possible origins of this dependence are discussed.

Understanding gas absorption in multivalent ionic liquids via solute-solvent interaction analyses

Solute-solvent interactions are often evaluated to understand and explain gas solubilities. This information is regularly used to interpret gas solubility and separation within ionic liquids (ILs). Here, we use several different quantum chemical and previous molecular dynamics simulation results to show that strong solute–solvent interactions neither lead to high solubility nor to high selectivity, with respect to other solutes. Instead, the solute–solvent interaction strength with different isolated IL ions is affected by the electrostatic extremes. Also, the solute–solvent interaction with different IL molecules is strongly correlated to the molecular volumes or polarizabilities (within a series of same-anion based ILs).

Doubly Polarized QM/MM with Machine Learning Chaperone Polarizability.

A major shortcoming of semiempirical (SE) molecular orbital methods is their severe underestimation of molecular polarizability compared with experimental and ab initio (AI) benchmark data. In a combined quantum mechanical and molecular mechanical (QM/MM) treatment of solution-phase reactions, solute described by SE methods therefore tends to generate inadequate electronic polarization response to solvent electric fields, which often leads to large errors in free energy profiles. To address this problem, here we present a hybrid framework that improves the response property of SE/MM methods through high-level molecular-polarizability fitting. Specifically, we place on QM atoms a set of corrective polarizabilities (referred to as chaperone polarizabilities), whose magnitudes are determined from machine learning (ML) to reproduce the condensed-phase AI molecular polarizability along the minimum free energy path. These chaperone polarizabilities are then used in a machinery similar to a polarizable force field calculation to compensate for the missing polarization energy in the conventional SE/MM simulations. Because QM atoms in this treatment host SE wave functions as well as classical polarizabilities, both polarized by MM electric fields, we name this method doubly polarized QM/MM (dp-QM/MM). We demonstrate the new method on the free energy simulations of the Menshutkin reaction in water. Using AM1/MM as a base method, we show that ML chaperones greatly reduce the error in the solute molecular polarizability from 6.78 to 0.03 Å3 with respect to the density functional theory benchmark. The chaperone correction leads to ∼10 kcal/mol of additional polarization energy in the product region, bringing the simulated free energy profiles to closer agreement with the experimental results. Furthermore, the solute-solvent radial distribution functions show that the chaperone polarizabilities modify the free energy profiles through enhanced solvation corrections when the system evolves from the charge-neutral reactant state to the charge-separated transition and product states. These results suggest that the dp-QM/MM method, enabled by ML chaperone polarizabilities, provides a very physical remedy for the underpolarization problem in SE/MM-based free energy simulations.

Achieving a highly efficient chitosan-based triboelectric nanogenerator via adding organic proteins: Influence of morphology and molecular structure

The utilization of biodegradable materials for the triboelectric nanogenerator (TENG) has provoked intensive interest since the growth of electronic devices tended to operate in proximity of the human body. This work proposed highly efficient biopolymer, based on a chitosan (CS) TENG, by incorporating protein-based compounds as fillers. The effect of different types of protein; albumin, egg-shell membrane (ESM) and silk fiber (SF), with the loaded content on the output performance of TENG was explored. It was found that the output signal can be maintained and even enhanced by embedding interlaced-fiber and making a gauze-like structure inside the CS matrix. Morphologies not only have different types of amino acid side chains, but also affect triboelectric output performance. High content of glycine, alanine and serine consequently increases the output signal by providing additional charges from molecular polarizations. Mixing glycine amino acid in the presence of alanine and serine reduces the centrosymmetric structure of the host amino acid and creates polar domains. Adding SF in CS, therefore, achieves the best output voltage ( V OC ) and current ( I SC ) as compared to other additives. The CS/SF TENG, with 10 wt% SF added, can reach ~ 77 V and ~ 13 µA of V OC and I SC , respectively. Its maximum output power of ~ 202 μW, with power density of 22.4 μW/cm 2 , is 6 times higher than that from pristine CS TENG, which can easily light up 59 light emitting diodes (LEDs) connected in series. Finally, the biodegradability was confirmed at various weeks related to the output measurement of V OC and I SC . After 9 weeks of the soil burial test, the CS/SF still generated ~ 20 V V OC and ~ 2.5 µA I SC with 30% weight loss. • The highly efficient chitosan-based TENG is fabricate by adding organic proteins as fillers. • Molecular polarizations in organic proteins boost the powder density. • The amino acid types and their concentration were proven to have the crucial role in triboelectric performance. • The biodegradability was confirmed at various weeks related to the output measurement of V OC and I SC .

Principle component analysis for nonlinear optical properties of thiophene-based metal complexes.

The simulation of molecular descriptors of thiophene-based metal complexes has been performed using Gaussian 03 and Atomistic toolkit Virtual Nanolab (ATK-VNL) software. It is found that with respect to the obtained molecular descriptors, the molecules show distinct properties. The dimensions of the data set being large, the principal components (PC1 and PC2) have been obtained using principal component analysis (PCA). Analysis has been done for the Linear regression of principal components with first hyperpolarizability and second hyperpolarizability of the molecules. The results indicate that, of all the calculated molecular descriptors of thiophene-based metal complexes, the molecular energy (E), ionization energy (EI), and molecular dipole moment (D) plays a dominant role in determining their nonlinear optical properties i.e., the hyperpolarizability value, of the studied molecules. Also, the molecular descriptors, polarizability (P) and molar refractivity (MR), show considerable impact on the nonlinear optical properties of the studied molecules.

Synthesis, characterisation, and effects of molecular structure on phase behaviour of 4-chloro-1,3-diazobenzene bent-core liquid crystals with high photosensitivity

ABSTRACT A series of new compounds were synthesised by adding azo functional groups and chlorine substituent to the central bent-cores to form a 4-chloro-1,3-dizaophenylene bent-core. The structure, mesogenic properties, and photosensitivity of these compounds were characterised. The results show these synthesised compounds exhibit a broad temperature window up to 63.8°C for nematic phase and the rapid rate of trans – cis photoisomerisation. For instance, at 95°C, compound 4c in nematic phase became an isotropic liquid under UV-irradiation in 3 s and could be restored to nematic under natural visible light in 5 s. Quantum mechanics calculation confirms that using azos instead of esters as the central linkages can effectively reduce the molecular dipole moment, which appears to promote favourable mesogenic and photonic characteristics. Moreover, varying the carbon number in the terminal alkyl chains can alter molecular dipole moment and polarisability anisotropy, which are strongly correlated with the phase transition temperature and temperature range of the nematic phase. These findings suggest that 1) changing azo group position can effectively alter the intermolecular interactions by varying molecular polarity and polarisability; 2) reducing long-range electrostatic interactions can promote favourable mesogenic and possibly photonic properties of azobenzene bent-core liquid crystal.

Amorphous Ni(OH)2 nanocages as efficient SERS substrates for selective recognition in mixtures

Surface-enhanced Raman scattering (SERS) technology has become one of the most powerful tools for identifying trace analytes due to its outstanding merit of fingerprint spectrum. It has been found that noble metal (Ag, Au) materials can produce obvious surface plasmon resonance under visible light illumination, which can bring out a strong SERS effect. However, due to poor stability and non-selectivity, its practical applications are seriously hindered, especially for the detection of polluted water contaminating mixture organic pollutants. Herein, we designed an amorphous Ni(OH)2 nanocages (a-Ni(OH)2 NCs) substrate that exhibits an excellent SERS performance with good spectral stability and selectivity, which is attributed to the strong interfacial photo-induced charge transfer (PICT) mechanism between a-Ni(OH)2 NCs and molecules. Due to the effective vibrational coupling of a-Ni(OH)2 NCs and molecule under laser irradiation, the PICT transitions between a-Ni(OH)2 NCs and molecules evidently increase the molecular polarizability tensor and magnify molecular Raman scattering cross-section, resulting in a remarkable SERS activity. Besides, in wastewater containing several nitrogen and phosphorus pollutants, we successfully identified methylene blue and crystal violet molecules by using a-Ni(OH)2 NCs due to their selective recognition function. This research points out a new application direction for SERS technology in water pollution detection based on non-metal substrates, which widely broadens application prospects of SERS spectroscopy.

Physical Mechanism Analysis of Conductivity and Relaxation Polarization Behavior of Oil-Paper Insulation Based on Broadband Frequency Domain Spectroscopy

This paper focuses on the in-depth analysis of the physical mechanism of the broadband frequency domain spectroscopy of oil-paper insulation. The complex permittivity shows two low-frequency dispersion phenomena, and the real part of the complex conductivity exhibits two slope changes under the synergistic effect of aging and moisture. The two slope changes are mainly attributed to the migration characteristics of water molecules and polar aging products with a degradation of the oil-paper insulation, resulting in the transition of the frequency dependence between the DC conductivity and AC conductivity. When the oil-paper insulation deteriorates seriously, the imaginary part of the dielectric modulus shows double relaxation peaks. Physical models of parasitic capacitance and molecular polarity interface polarization are proposed to reveal the physical mechanism of the double relaxation peaks. The left peak of the double relaxation peaks is caused by the accumulation of water molecules and polar aging products at the electrode/insulation interface, and the right peak is due to the charge disturbance of the cellulose molecular chain surface. This paper can provide theoretical support and technical guidance for the condition diagnosis and evaluation of oil-paper insulation.

2D GaN for Highly Reproducible Surface Enhanced Raman Scattering.

Surface-enhanced Raman scattering (SERS) based on 2D semiconductors has been rapidly developed due to their chemical stability and molecule-specific SERS activity. High signal reproducibility is urgently required towards practical SERS applications. 2D gallium nitride (GaN) with highly polar Ga-N bonds enables strong dipole-dipole interactions with the probe molecules, and abundant DOS (density of states) near its Fermi level increases the intermolecular charge transfer probability, making it a suitable SERS substrate. Herein, 2D micrometer-sized GaN crystals are demonstrated to be sensitive SERS platforms with excellent signal reproducibility and stability. Strong dipole-dipole interaction between the dye molecule and 2D GaN enhances the molecular polarizability. Furthermore, 2D GaN benefits its SERS enhancement by the combination of increased DOS and more efficient charge transfer resonances when compared with its bulk counterpart.

Property-optimized Gaussian basis sets for lanthanides

Property-optimized Gaussian basis sets of split-valence, triple-zeta valence, and quadruple-zeta valence quality are developed for the lanthanides Ce-Lu for use with small-core relativistic effective core potentials. They are constructed in a systematic fashion by augmenting def2 orbital basis sets with diffuse basis functions and minimizing negative static isotropic polarizabilities of lanthanide atoms with respect to basis set exponents within the unrestricted Hartree-Fock method. The basis set quality is assessed using a test set of 70 molecules containing the lanthanides in their common oxidation states and f electron occupations. 5d orbital occupation turns out to be the determining factor for the basis set convergence of polarizabilities in lanthanide atoms and the molecular test set. Therefore, two series of property-optimized basis sets are defined. The augmented def2-SVPD, def2-TZVPPD, and def2-QZVPPD basis sets balance the accuracy of polarizabilities across lanthanide oxidation states. The relative errors in atomic and molecular polarizability calculations are ≤8% for augmented split-valence basis sets, ≤ 2.5% for augmented triple-zeta valence basis sets, and ≤1% for augmented quadruple-zeta valence basis sets. In addition, extended def2-TZVPPDD and def2-QZVPPDD are provided for accurate calculations of lanthanide atoms and neutral clusters. The property-optimized basis sets developed in this work are shown to accurately reproduce electronic absorption spectra of a series of LnCp3 '- complexes (Cp' = C5H4SiMe3, Ln = Ce-Nd, Sm) with time-dependent density functional theory.

Acute toxicity of polychlorinated diphenyl ethers (PCDEs) in three model aquatic organisms (Scenedesmus obliquus, Daphnia magna, and Danio rerio) of different trophic levels

The frequent detection of polychlorinated diphenyl ethers (PCDEs) in aquatic systems has aroused widespread concerns, however, their potential hazard to aquatic ecosystems has been poorly understood. Here the acute toxicity of 12 PCDE congeners was evaluated in three model aquatic organisms representing different trophic levels following OECD test guidelines, including green algae (Scenedesmus obliquus), water flea (Daphnia magna), and zebrafish (Danio rerio). Dose-dependent increases in growth inhibition and mortality were observed for all tested PCDE congeners. Most of the PCDE congeners, in particular 3,3′,4,4′-tetra-CDE, were highly toxic to the three aquatic organisms with EC50 or LC50 values below 1 mg L-1. Their toxicities were generally comparable with those of certain polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). Moreover, D. magna was the most sensitive species among the three aquatic organisms. In addition, the EC50 or LC50 values had an extremely significant correlation with the n-octanol-water partition coefficient (logKow) of the PCDE congeners. The established quantitative structure-property relationship (QSPR) models indicated that the molecular polarizability (α) could significantly influence the acute toxicity of PCDEs on Daphnia magna and Danio rerio, and the energy of the lowest unoccupied molecular orbital (ELUMO) is the key factor of the acute toxicity of PCDEs in Scenedesmus obliquus. In addition, even at environmental levels, 3,3′,4,4′-tetra-CDE could induced seveve oxidative damages in the three aquactic species. These findings would contribute to the understanding of adverse effects of PCDEs in aquatic organisms.

A novel low-dielectric nanocomposite with hydrophobicity property: Fluorinated MOFs modified bismaleimide-triazine resin

A fluorine-functionalized zirconium-based metal organic framework (F4-UiO-66) was successfully synthesized via the reflux method, and the F4-UiO-66/BT nanocomposites of F4-UiO-66 modified bismaleimide-triazine resin (BT resin) were prepared. The effects of F4-UiO-66 on the crosslinking structure and properties of BT resin were evaluated for the first time. The investigations showed that the active H in F4-UiO-66 effectively catalyzed the self-polymerization of cyanate ester and promoted the formation of more rigid triazine rings which increased the initial storage modulus of nanocomposites. But the steric hindrance effect of F4-UiO-66 reduced the crosslinking density, which increased the free volume of nanocomposites. So, the dielectric constants of the nanocomposites were significantly reduced with the increase of F4-UiO-66 for the reduction of molecular polarization due to triazine rings and C–F bonds, and the decrease of polarization density caused by the nanopores and free volume. In addition, F4-UiO-66 was evenly dispersed in BT resin. On the basis of maintaining the thermal stability, the toughness and hydrophobic properties of nanocomposites were also enhanced. This study provided a novel approach for low-dielectric materials with hydrophobic property through the synergy between the nanopores and the C–F bonds.