Change In Dipole Moment Research Articles

Computational study of phosphate adsorption on Mg/Ca modified biochar structure in aqueous solution

Phosphate removal in water using biochar is widely investigated. Density functional theory was used to study the adsorption of phosphate (H2PO4−) on biochar in water after metal modification. Two types of metals, Mg and Ca, were used to modify the biochar structure, and the edge and metal adsorptions of H2PO4− were investigated on the modified biochar structure. Results were analyzed from the aspects of structural stability, adsorption energy, change in dipole moment, density of electronic states, and atoms in molecules analysis. The overall effect of metal-modified biochar materials on phosphate adsorption was stronger than that of unmodified biochar materials in terms of molecular level. The stability of the metal-modified structure by adding metal was low, and adsorption was prone to occur in this situation. The Ca-modified biochar showed better phosphate adsorption than the Mg-modified structure. Metal adsorption performed better than edge adsorption, proving that the modified metal in the biochar structure played a leading role in H2PO4− adsorption. Metal adsorption was mainly caused by electrostatic attraction, and edge adsorption was mainly caused by covalent bonding.

Isoenergetic two-photon excitation enhances solvent-to-solute excited-state proton transfer.

Two-photon excitation (TPE) is an attractive means for controlling chemistry in both space and time. Since isoenergetic one- and two-photon excitations (OPE and TPE) in non-centrosymmetric molecules are allowed to reach the same excited state, it is usually assumed that they produce similar excited-state reactivity. We compare the solvent-to-solute excited-state proton transfer of the super photobase FR0-SB following isoenergetic OPE and TPE. We find up to 62% increased reactivity following TPE compared to OPE. From steady-state spectroscopy, we rule out the involvement of different excited states and find that OPE and TPE spectra are identical in non-polar solvents but not in polar ones. We propose that differences in the matrix elements that contribute to the two-photon absorption cross sections lead to the observed enhanced isoenergetic reactivity, consistent with the predictions of our high-level coupled-cluster-based computational protocol. We find that polar solvent configurations favor greater dipole moment change between ground and excited states, which enters the probability for TPE as the absolute value squared. This, in turn, causes a difference in the Franck-Condon region reached via TPE compared to OPE. We conclude that a new method has been found for controlling chemical reactivity via the matrix elements that affect two-photon cross sections, which may be of great utility for spatial and temporal precision chemistry.

Nonlinear optical properties and spectroscopic characterization of Y-shaped polymer using quantum chemical approach.

The present study reports nonlinear optical properties such as the first and second hyper polarizabilities (β and γ) of Y-shaped polymer (P1) and substituted polymers. The basic Y-shaped polymer (R = R1 = H) was named as P1. Upon substitution of one OCH3 group in ortho position of oxygen, it becomes polymer P2 (R1 = H, R = OCH3) and other OCH3 group on another ortho becomes P3 (R1 = R = OCH3). We have also reported structural parameters, vibrational and electronic absorption spectra of polymer, and its substituted polymers. The geometrical parameters such as dipole moment, bond length, and angles are reported at B3LYP/6-311++g** level of theory. In addition, the vibrational, electronic absorption spectra and nonlinear optical (NLO) properties are also reported at the same level of theory. There is a significant change in dipole moment and in energy observed whereas symmetry, bond length, and angles are resembling Y-shaped and substituted polymer. The vibrational spectra of Y-shaped polymer (P1) having the intense peak are C-H stretching mode observed at 1258cm-1. These theoretical vibrational modes are well matching with available experimental determinations. The method dependent hyperpolarizabilities calculated by applying the field along the X, Y, and Z direction. This study confirms the polymer P1 and P2 showing first and second hyperpolarizability response whereas P3 do not show. The electronic absorption spectra for polymer and substituted polymers are also reported at the same level of theory using (TDDFT) approach. The wavelength of electronic transition, oscillator strength, and HOMO-LUMO gap was also reported.

Ag/AgCl sensitized n-type ZnO and p-type PANI composite as an active layer for hybrid solar cell application

Acceptor annealed Zinc oxide (ZnO) based donor polyaniline (PANI) composite was synthesized via in-situ polymerization and sensitized with silver/silver chloride (Ag/AgCl) particles for enhancing the optoelectronic response. The sensitized composite is characterized, and the electron transfer mechanism is explained in detail. The absorbance wavelength enhanced for the sensitized composite is the result of a synergistic combination of annealing and sensitization. Elemental composition revealed the formation of sensitized composite inferred via energy dispersive spectroscopy (EDAX) using high-resolution transmission electron microscopy (HRTEM) and filed-emission scanning electron microscopy (FESEM). Selected area diffraction (SAED) pattern unveiled the coexistence of the amorphous and crystalline phase. The change in dipole moment and polarizability of molecules was evaluated using Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy, respectively. Current-voltage (I–V) characteristics proved annealing of ZnO and sensitization of polyaniline composite with annealed ZnO beneficial for current enhancement, which was further validated via cyclic voltammetry in the form of redox reaction current response.

Adsorption behaviour of metronidazole drug molecule on the surface of hydrogenated graphene, boron nitride and boron carbide nanosheets in gaseous and aqueous medium: A comparative DFT and QTAIM insight

In this present study, we have theoretically scrutinized the interaction mechanism of Metronidazole drug on the surface of graphene, boron carbide and boron nitride nanosheets in gas and aqueous phase applying density functional theory with B3LYP/6-31G method to sort a path for minimizing the adverse effects of this drug on the human and animal body. The maximum adsorption energy (A.E) value is −44.50 kj/mol which indicates the adsorption of all complexes is physisorption type and our complexes benefit from the short recovery time. Weak electrostatic nature of the interaction is also revealed by the QTAIM study. The reduction of E g for the adsorption of ML on BN sheet is the highest (up to 55%) indicating the highest sensitivity while the sensitivity trend is σ (BN) > σ (GNS) > σ (BC3). The UV–Vis spectra investigation also validates this sensitivity trend. The dipole moment and A.E data in case of the solvent effect upon the complexes claim the favourable adsorption process in aqueous medium. Consequently, this comparative study reveals the ability of BN nanosheet to sense ML drug is higher than that of GNS and BC3, which will help to protect human and wildlife from the side effect of this drug. Adsorption and desorption process of metronidazole drug with nanosheets. • The sensitivity of BN nanosheet towards metronidazole (ML) drug is highest due to the reduction of HOMO-LUMO gap up to 55%. • The energetic parameters show the spontaneous, exothermic physisorption of ML on the surface of GNS, BC3 and BN nanosheets. • The changes of adsorption energy and dipole moment in water media specify the good adsorption of ML in the human body. • The adsorbent (nanosheets) and adsorbate (ML) acts as donor and acceptor respectively. • The reactivity of the nanosheets increases due to the adsorption of ML drug molecule.

Base Promoted Synthesis of 2-((5-methoxynaphthalen-1-yl)methyl)-3-methyl-5-sec-amino-[1,1′-biphenyl]-4-carbonitrilederivatives: Photophysical, Solvatochromic and DFT studies

Newer, simple and efficient synthesis of 2-((5-methoxynaphthalen-1-yl)methyl)-3-methyl-5-sec-amino-[1,1′-biphenyl]-4-carbonitrile derivatives using ring transformation strategy. The synthesized products were characterized by spectral analysis, fluorescence emission and absorption measurements were studied in various solvents having varying polarity and dielectric constants to find out a change in dipole moment in ground state and excited state of derivatives. Lippert–Mataga plots were utilized to know the effect of solvent polarity on spectral behavior of molecules. The position of the Stokes shifts was found to be depends on specific solute–solvent interactions, playing a vital role in electronic excitation of molecules. A rational relationship is examined between fluorescence quantum efficiencies and calculated HOMO and LUMO energies by DFT calculations. The electrochemical investigation of derivatives was performed by cyclic voltammetry.

Solvent polarity indicators based on bithiophene carboxamidine hydrochloride salt derivatives

The photophysical properties of water soluble 5′-(4-methoxyphenyl)-2,2′-bithiophene-5-carboxamidine hydrochloride salt (MBTCH) and 5′-(3,5-dimethoxyphenyl)-2,2′-bithiophene-5-carboxamidine hydrochloride salt (DMBTCH) were studied in different solvents. The absorption spectra of MBTCH and DMBTCH show very weak solvent dependence, while the fluorescence emission spectra show bathochromic shift of about 35 nm and 48 nm on changing the solvent from cyclohexane to DMSO for DMBTCH and MBTCH, respectively. In protic solvents further bathochromic shift is observed in case of DMBTCH. The excited state time resolved decay of MBTCH and DMBTCH were measured over the entire fluorescence spectra and fitted very well with bi-exponential function in all solvents. Correlation of MBTCH and DMBTCH photophysical properties with ETN (Reichardt’s normalized polarity parameter) was successful when the solvents are classified according to their hydrogen bonding properties, namely, protic and aprotic solvent categories. Reichardt-Ravi equation was used to determine dipole moment changes, Δμ, in both categories of solvents. Several multiple linear regression solvation energy relationships were used to assess the dependence of the photophysical properties on specific and non-specific properties of the solvents, such as Kamlet-Taft, Catalán and Laurence et al. relationships. These relationships have shown that hydrogen bonding interactions (specific interactions) and dipolar interaction (non-specific) competes strongly in their contribution to the photophysical properties of the studied compounds with slight domination of the latter.

ESIPT-Related Origin of Dual Fluorescence in the Selected Model 1,3,4-Thiadiazole Derivatives.

In our previous work, we discussed the emergence of the dual fluorescence phenomenon in selected compounds from the group of 1,3,4-thiadiazoles. The results obtained in a number of experimental studies, supported by [TD]DFT calculations, clearly indicated that the phenomenon of dual fluorescence stemmed from an overlap of several factors, including the correct conformation of the analyzed molecule and, very significantly in this context, aggregation effects. Where those two conditions were met, we could observe the phenomenon of intermolecular charge transfer (CT) and the emergence of electronic states responsible for long wave emissions. However, in light of the new studies presented in this paper, we were able, for the first time, to provide a specific theory for the effect of dual fluorescence observed in the analyzed group of 1,3,4-thiadiazoles. We present the results of spectroscopic measurements conducted for two selected analogues from the 1,3,4-thiadiazole group, both in polar and non-polar solvents, which clearly evidence (as we have already suspected in the past, albeit have not shown in publications to date) the possibility of processes related to emission from the tautomer formed in the process of excited state intramolecular proton transfer, which is responsible for the long-wavelength emissions observed in the selected analogues. The presented results obtained with the use of UV-Vis, fluorescence (stationary and time-resolved), FTIR, and Raman spectroscopy, as well as from calculations of dipole moment changes between the ground and excited state with the use of two derivatives with different structures of the resorcylic system, corroborated our standing hypothesis. At the same time, they excluded the presence of ground state keto forms of the analyzed analogues unless necessitated by the structure of the molecule itself. In this case, aggregation factors enhance the observed effects related to the dual fluorescence of the analyzed compounds (by way of AIE—aggregated induced emissions).

Examining the spectroscopic features and quantum chemical computations of a Quinoline derivative: Experimental and theoretical insights into the photophysical characteristics

The solvatochromic studies in a Quinoline derivative molecule namely Quinolin-8-ol (QO) have been carried out at ambient temperature using absorption and fluorescence spectroscopy. The QO molecule shows the bathochromic shift with increase in solvent polarity demonstrating π → π* transition. The solvatochromic data coupled with quantum mechanical calculations has been used to estimate change in dipole moment of the molecule after excitation. It has been found that excited state dipole moment is greater than the corresponding ground state dipole moment. Further, it is observed that excited and ground state dipole moments are parallel. The chemical reactivity and kinetic stability of QO molecule are investigated using Frontier molecular orbital (FMO) analysis. Natural bond orbital (NBO) analysis shows proton transfer within the selected donor-acceptor depicting large energy of stabilization for QO molecule. The calculated Fukui functions infer the local softness and local eletrophilicity index of QO molecule. The theoretically simulated UV-Vis absorption spectrum of QO molecule matches well with the experimental spectrum.

Semiempirical Molecular Modeling Analyses for Graphene/Nickel Oxide Nanocomposite

Graphene metal oxide composite show applications in many areas according to their excellent electronic properties. Accordingly, graphene was subjected to interaction with NiO as adsorbing and a complex state. Semiempirical quantum mechanical calculations at PM6 was used to study the total energy, the final heat of formation, ionization energy, total dipole moment as well the charge distribution of the surface of graphene metal oxide composite. Calculated data indicated that graphene symmetry is changed into the C1 point group, forming stable composites with NiO that the complex composites were more stable compared with adsorb state composites. The change in the partial charge of graphene is responsible for the change in total dipole moment and hence affecting the increase in the reactivity of graphene/nickel oxide composite.

Unlabeled lysophosphatidic acid receptor binding in free solution as determined by a compensated interferometric reader

Native interactions between lysophospholipids (LPs) and their cognate LP receptors are difficult to measure because of lipophilicity and/or the adhesive properties of lipids, which contribute to high levels of nonspecific binding in cell membrane preparations. Here, we report development of a free-solution assay (FSA) where label-free LPs bind to their cognate G protein-coupled receptors (GPCRs), combined with a recently reported compensated interferometric reader (CIR) to quantify native binding interactions between receptors and ligands. As a test case, the binding parameters between lysophosphatidic acid (LPA) receptor 1 (LPA1; one of six cognate LPA GPCRs) and LPA were determined. FSA-CIR detected specific binding through the simultaneous real-time comparison of bound versus unbound species by measuring the change in the solution dipole moment produced by binding-induced conformational and/or hydration changes. FSA-CIR identified KD values for chemically distinct LPA species binding to human LPA1 and required only a few nanograms of protein: 1-oleoyl (18:1; KD = 2.08 ± 1.32 nM), 1-linoleoyl (18:2; KD = 2.83 ± 1.64 nM), 1-arachidonoyl (20:4; KD = 2.59 ± 0.481 nM), and 1-palmitoyl (16:0; KD = 1.69 ± 0.1 nM) LPA. These KD values compared favorably to those obtained using the previous generation back-scattering interferometry system, a chip-based technique with low-throughput and temperature sensitivity. In conclusion, FSA-CIR offers a new increased-throughput approach to assess quantitatively label-free lipid ligand-receptor binding, including nonactivating antagonist binding, under near-native conditions.

Phase transformation of poly (vinylidene fluoride)/TiO2 nanocomposite film prepared by microwave-assisted solvent evaporation: An experimental and molecular dynamics study

Poly (vinylidene fluoride) (PVDF), which is a representative piezoelectric polymer, has received immense attention from various industries owing to its high flexibility, durability, and low cost. In this study, the phase transformation mechanism of TiO2 nanoparticle-reinforced PVDF composite films during microwave-assisted solvent evaporation was investigated by experimental and numerical analysis. The crystalline behaviors of the prepared PVDF/TiO2 nanocomposite films were investigated using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The degree of crystallinity of the films was calculated from the XRD results using a curve deconvolution method. In order to understand the mechanism behind the experimental results, numerical simulations based on molecular dynamics (MD) were performed. The effect of microwave irradiation on the PVDF crystalline behavior was discussed by observing the change in the dihedral angle conformation of the amorphous PVDF simulation model. In addition, molecular-level insights on the interaction of PVDF with TiO2 nanoparticle were provided using the concepts of dipole moment change and dihedral angle conformation change in order to analyze the effect of TiO2 on the crystal conformation of the PVDF. Furthermore, the change in the dihedral angle conformation of PVDF chains reinforced with TiO2 nanoparticles under microwave irradiation was observed.

Spectral manifestations of coal metamorphism: Insights from coal microstructural framework

The present study investigates the microstructural framework of coals from the Raniganj and the Jharia Basins as well as from the Himalayan fold-thrust belts of Sikkim, India, by vitrinite reflectance, Raman spectroscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The mean random vitrinite reflectance data may imply that the coal samples from the Raniganj and the Jharia Basins range from the bituminous D to B, and would have experienced the burial heating corresponding to ~92 °C to 143 °C unlike the anthracite A samples that might have undergone the hydrothermal metamorphism at ~333 °C to 367 °C. The Raman spectra exhibit preferential removal of sp3 hybridized moieties from the anthracite samples at anchizonal metamorphic stage due to thermo-stress degradation effect induced by the Himalayan orogeny. Further, this study records the reduction of net dipole moment change due to the expulsion of functional groups from the aromatic rings making them infrared inactive. Additionally, the C1s spectra reveal the thinning of CC peaks and the lowering of the CO peak intensity with an increase in coal rank. This study, hence, documents the microstructural transformations in coal that can be used for structural maneuvering to control the liquefaction, gasification, pyrolysis, combustion as well as synthetic graphitization behavior.

Solvatochromic triazaborolopyridinium probes toward ultra-sensitive trace water detection in organic solvents

A series of triazaborolopyridiniums (TBP) has been synthesized by varying electron-tunning substituents. The TBP derivatives with electron-withdrawing groups, including cyano, and nitro moieties, exhibited solvatochromic properties due to the internal charge transfer (ICT) effect. The density functional theory (DFT) calculations suggested that the nitro-substituted TBP derivative (8) possessed the highest change in dipole moment upon excitation (Δμ) yielding the most distinctly large stokes shift and low fluorescence quantum yields as the solvent polarity increased. In addition, compound 8 displayed an apparent fluorescence quenching in the presence of hydrogen bond-donating molecules (e.g. methanol, ethanol, water); therefore, it was chosen to be utilized as a trace water detector in four common solvents, including, tetrahydrofuran (THF), acetonitrile (MeCN), acetone, and dimethylformamide (DMF). The satisfying linear relationship between the ratios of the blank fluorescence intensity to the decreased fluorescence intensity (I0/I) and the trace water content was used to determine the limits of detection (LOD) of water. The low LODs (0.028% for THF, 0.013% for MeCN, 0.021% for acetone, and 0.045% for DMF) confirmed the capability of compound 8 as a super-sensitive water sensor in organic solvents.

Paleomagnetism, paleointensity and geochronology of a Proterozoic dolerite dyke from southern West Greenland

Archean to Paleoproterozoic rocks potentially record the evolution of the geodynamo and the tectonic mode of the early Earth. The paleomagnetic intensity and direction data provide important information on the Earth’s core–mantle revolution. Herein, we report the results of paleomagnetic and geochronological studies of a Proterozoic dolerite dyke from southern West Greenland. Clinopyroxene grains from the dyke yielded Ar–Ar plateau ages from 1808 to 1887 Ma (1816.0 ± 14.6 Ma; 2σ). The paleomagnetic direction of the dyke (D = 243.6°, I = 66.3°, α95 = 3.9°) yielded a virtual geomagnetic pole (VGP) of 33.5 °N and 96.4 °W. This 1.8 Ga pole falls in a limited area where Paleoproterozoic poles between 2.5 Ga and 1.7 Ga for southern West Greenland are distributed. Comparison of the Paleoproterozoic poles of southern West Greenland with those of North America suggests that the North Atlantic Craton of southern Greenland could have been an independent stagnant tectonic block, different from the drifting Superior and Slave Cratons in the Early Proterozoic. Thellier experiments on 13 specimens yielded a mean paleointensity value of 14.8 ± 2.3 μT, indicating a virtual dipole moment of 2.88 ± 0.46 × 1022 Am2. This value is approximately one-third of the present-day Earth's field intensity, and is consistent with the value for the period between 1400 Ma and 2400 Ma. This small paleointensity value of the Proterozoic rocks is due to a gradual dipole moment change over a long period (∼1 Gyrs) since 4000 Ma.

Estimation of Photophysical and Electrochemical Parameters of Bioactive Thiadiazole Derivative.

The absorption and fluorescence spectra of synthesized 4-[5-(2,5-Dimethyl-pyrrol-1-yl)-[1, 3, 4] thiadiazol-2-ylsulfanylmethyl]-6-methoxy-chromen-2-one (DTYMC) compound were recorded in various solvents like acetone, acetonitrile, chloroform, dimethyl formamide (DMF),1,4-dioxane, ethanol, ethyl acetate, methanol, tetrahydrofuran (THF) and dimethylsulphoxide (DMSO) at room temperature in order to estimate the ground and excited state dipole moment. The ground state dipole moment (μg) and excited state dipole moment (μe) were calculated using solvatochromic shift method which involve equations proposed by Lippert, Bakshiev and Kawski-Chamma-Viallete. The results were signified that the excited state dipole moment is greater than the ground state dipole moment, which indicates the excited state is more polar than the ground state of the molecule. The bond angle between the ground state and excited state dipole moments were found to be 00, The change in dipole moment (∆μ) was calculated using microscopic solvent polarity parameter ([Formula: see text]). Further multiple linear regression analysis of Kamlet-Taft parameter, HOMO-LUMO energy were determined by cyclic voltammetry using phosphate buffer solution.

Capacity of C4H8Ti4 cluster for adsorption of CO2 and CO: a computational study.

The adsorption of carbon dioxide and carbon monoxide molecules on the magnetic cluster C4H8Ti4 was studied within the framework of Density Functional Theory. We have showed the adsorption of eight molecules, each of CO2 and CO on a single cluster-C4H8Ti4. We have discussed binding energy, charge transfer mechanism, change in dipole moment, and HOMO-LUMO analysis.

Photophysical and TDDFT investigation for (E, E)-2, 5-bis [2-(4-(dimethylamino)phenyl) ethenyl]pyrazine (BDPEP) laser dye in restricted matrices

The Photophysical parameters such as fluorescence quantum yield (Φf), oscillator strength (f), radiative decay rate constant (kr), change of dipole moment from ground to excited state (μ12), gain coefficient and lasing efficiency of the probe molecule in both silica and copolymer hosts are determined. The optical parameters of the probe dye in sol-gel matrix are compared to copolymer host. The time dependent density function theory (TDDFT) calculations were carried out at M06-2X/6-31G++ (d, p) level. The theoretical absorption and emission spectra of the BDPEP compound in sol-gel matrix are calculated using TDDFT and compared to experimental results. Also, the effect of cadmium sulfide (CdS) quantum dots (QDs) on fluorescence intensities of the BDPEP in sol-gel host is investigated. The effect of sol-gel matrix on HOMO-LUMO energy gap (Eg) and dipole moment (μ) of the (E, E)-2, 5-bis [2-(4-(dimethylamino)phenyl) ethenyl]pyrazine (BDPEP) molecule are also investigated using M06-2X density function.

Solvent Mediated Excited State Proton Transfer in Indigo Carmine.

Excited state proton transfer (ESPT) is thought to be responsible for the photostability of biological molecules, including DNA and proteins, and natural dyes such as indigo. However, the mechanistic role of the solvent interaction in driving ESPT is not well understood. Here, the electronic excited state deactivation dynamics of indigo carmine (InC) is mapped by visible pump-infrared probe and two-dimensional electronic-vibrational (2DEV) spectroscopy and complemented by electronic structure calculations. The observed dynamics reveal notable differences between InC in a protic solvent, D2O, and an aprotic solvent, deuterated dimethyl sulfoxide (dDMSO). Notably, an acceleration in the excited state decay is observed in D2O (<10 ps) compared to dDMSO (130 ps). Our data reveals clear evidence for ESPT in D2O accompanied by a significant change in dipole moment, which is found not to occur in dDMSO. We conclude that the ability of protic solvents to form intermolecular H-bonds with InC enables ESPT, which facilitates a rapid nonradiative S1 → S0 transition via the monoenol intermediate.

Determination of structural properties in the adsorption of drugs on chitosan-hydrogels for type 2 diabetes by means of the PM6 method

Computational chemistry performs the modeling and calculation of physicochemical properties that allow understanding of the different molecular interactions at the nanometric scale in medical applications such as the design of controlled release systems. The PM6 model was used to analyze metformin and glibenclamide. First, the energy properties as the Gibbs free energy and enthalpies were obtained. The results showed the affinity of both drugs with water (glibenclamide: -7.96 and metformin: -11.49) due to the formation of hydrogen bonds, which were verified by the electronegativities corresponding to the dipole moment and to the partition coefficient (Log P).Subsequently, the main properties for the design of a release system using the metformin/glibenclamide complex in the chitosan hydrogel were determined. In this process it was appreciated that the Gibbs free energy (-2157.60 kcal/mol) determined the thermodynamic stability of the adsorption. In addition, the Log P (-25.82) indicated an instantaneous solubility through the formation of hydrogen bonds and were verified by the electronic distribution and the change in dipole moment.