Dipole Moment Of Electron Research Articles

Synthesis and analgesic effects of new pyrrole derivatives of phencyclidine in mice

Phencyclidine (1-(1-phenylcyclohexyl)piperidine, CAS 956-90-1, PCP, I) and many of its analogues have shown some pharmacological effects. In this study, new pyrrole derivatives of I (1-(1-phenylcyclohexyl)pyrrole, II and 1-[1-(4-methylphenyl)(cyclohexyl)]pyrrole, III) and their intermediates were synthesized and the acute and chronic pains were examined on mice using tail immersion (as a model of acute thermal pain) and formalin (as a model of acute and chronic chemical pain) tests and the results were compared with the PCP and control groups. The results indicated that III generated higher analgesic effects in the tail immersion test compared to the PCP and control (dimethyl sulfoxide, DMSO) groups, demonstrating a marked and significant increase in tail immersion latency, but this effect was not observed for II in the dose of 1 mg/kg. The formalin test showed that III was effective in acute chemical pain (phase I, 0-5 min after injection), but was not effective for II at the same dosage compared to the PCP and control groups. Also chronic pain will be significantly attenuated by III but II was not effective as compared to the other groups. It is concluded that substitution of the aromatic pyrrole ring instead of piperidine in the PCP molecule will not be effective alone in tail immersion and formalin tests but the addition of a methyl group (with high electron donating and dipole moments) on the phenyl group plus substitution of the aromatic pyrrole ring can be effective in acute and chronic pain compared to the PCP and control groups.

Theoretical Study on the Chiroptical Optical Properties of Chiral Fullerene C60Derivative

Time-dependent density functional theory (TDDFT) calculations have been used to investigate UV/CD spectra and nonlinear optical (NLO) property of the C(60)-fullerene bisadduct (R,R,(f,s)A)-[CD(+)280] for the first time. The electron transition natures of the four main measured bands are analyzed, and their results are used to designate the excited states involved in an electron-transfer process of the studied compound. On a comparative scale, the predicted excitation energies and oscillator strengths are in reasonable agreement with the observed values, demonstrating the efficiency of TDDFT in predicting the localized and charge transfer transitions. The good agreement between the experimental and the simulated CD spectra shows that TDDFT calculations can be used to assign the absolute configurations (ACs) of chiral fullerene C(60) derivatives with high confidence. The observed large dissymmetry ratio g (g = Δε/ε) at about 700 nm results from the orbital characters of the local fullerene excited state, which leads to large transition magnetic dipole moment and small transition electronic dipole moment. The different functionals and solvent effects on UV/CD spectra were also considered. The studied compound has a possibility to be an excellent second-order NLO material from the standpoint of transparency and large second-order polarizability value.

Investigation of 6-fluoroquinolones activity against Mycobacterium tuberculosis using theoretical molecular descriptors: a case study

Abstract A quantitative structure-activity relationship (QSAR) study on a set of 66 structurally-similar 6-fluoroquinolones was performed using a large pool of theoretical molecular descriptors. Ab initio geometry optimizations were carried out to reproduce the geometrical and electronic structure parameters. The resulting molecular structures were confirmed to be minima via harmonic frequency calculations. Obtained atomic charges, HOMO and LUMO energies, orbital electron densities, dipole moment, energy and many other properties served as quantum-chemical descriptors. A multiple linear regression (MLR) technique was applied to generate a linear model for predicting the biological activity, Minimal Inhibitory Concentration (MIC), treated as negative decade logarithm, (pMIC). The heuristic method was used to optimize the model parameters and select the most significant descriptors. The model was tested internally using the CV LOO procedure on the training set and validated against the external validation set. The result (Q 2 ext = 0.7393), which was obtained on an external, previously excluded validation data set, shows the predictive performances of this model (R 2tr = 0.7416, Q 2 tr = 0.6613) in establishing (Q)SAR of 6-fluoroquinolones. This validated model could be proficiently used to design new 6-fluoroquinolones with possible higher activity.

SUSY CP problem in gauge mediation model

SUSY CP problem in the gauge mediation supersymmetry breaking model is reconsidered. We pay particular attention to two sources of CP violating phases whose effects were not seriously studied before; one is the effect of the breaking of the GUT relation among the gaugino masses due to the field responsible for the GUT symmetry breaking, and the other is the supergravity effect on the supersymmetry breaking parameters, in particular, on the bi-linear supersymmetry breaking Higgs mass term. We show that both of them can induce too large electric dipole moments of electron, neutron, and so on, to be consistent with the experimental bounds.

First-principle calculations on optical properties of C–N-doped and C–N-codoped anatase TiO 2

The electronic structures, dipole moment and optical properties of C–N-doped and C–N-codoped anatase titanium dioxide (TiO 2) are studied using the plane-wave ultrasoft pseudopotential method of density functional theory (DFT). The results revealed that the absorption coefficients of pure TiO 2 and N-doped TiO 2 are consistent with experimental values in the visible-light region. The bands originating from C/N-2p states lie in the band gap of doped TiO 2. A visible-light absorption edge red-shift can be observed. The atomic charges have changed, resulting in devation of the center of gravity of the negative electric charge from the positive electric charge in the super-cell, and their dipole moment would not be zero. The dipole moment has large influence on the optical responses in the visible region of TiO 2. Because of the small distance (0.531 nm) between C and N atoms, the covalent bond component was easily enhanced between C atom and adjacent O atom, the covalent bonds making it more difficult for the carrier transfer. Moreover, its optical absorption coefficient is going to reduce in the visible-light region. Under the condition of the larger distance (0.691 nm) between C and N atoms, their interaction can be reduced, which is beneficial to electrons transition; as a result, a significant improvement of the photocatalytic activity of TiO 2 has been found under the visible-light irradiation.

PPP Hamiltonian for polar polycyclic aromatic hydrocarbons

Total energies of charged states and configurations of different spin multiplicity of two polar non-alternant polycyclic aromatic hdrocarbons (PAH), namely, pentaheptafulvalene and azulene, calculated by means of a Multi-Configurational (MCSCF) method which includes correlation only amongst π orbitals, have been fitted by exact solutions of the Pariser-Parr-Pople (PPP) and the Hubbard Hamiltonians for π electrons. As both molecules are planar, such an approach is in principle feasible. As found in our previous analysis of PAH, PPP fittings are significantly better than those attained with the Hubbard Hamiltonian. In addition, parameters for the Hubbard Hamiltonian are around twice those derived for the PPP model, indicating that parameters are not model independent. Fitted PPP parameters are close to those derived from a similar study of the PAH 2, 5, 8-trihydrogenated phenalene and those originally proposed by Pariser et al. providing further support to a wide applicability of the fitted parameters. Fittings obtained for a MCSCF method that MM298001also includes σσ and σπ correlations (MCSCF/MP2) are slightly less accurate giving an on-site repulsion 10–15% smaller. The accuracy of the fittings further diminishes when parameters are derived from energies obtained by means of a DFT method (B3LYP) with an additional decrease in U of 5–25%. In the latter two cases, parameters have to be considered as effective, accounting for effects of σ orbitals not explicitly included in the model Hamiltonians. Electron affinities, ionization energies and dipole moments, calculated by means of the model Hamiltonians, are compared to those derived from DFT and ab initio methods and, whenever available, to experimental data.

Crystalline Behavior and Structure of a Liquid Crystal Compound, 5-{[4′-(((Pentyl)oxy)-4-biphenylyl)carbonyl]oxy}-1-pentyne

Single crystals of two liquid crystal compounds, 5-{[4′-(((pentyl)oxy)-4-biphenylyl)carbonyl]oxy}-1-pentyne (A3EO5) and 5-{[(4′-nonyloxy-4-biphenylyl)carbonyl]oxy}-1-pentyne (A3EO9), have been prepared by solution growth technique. The morphologies and structures of A3EO5 and A3EO9 crystals were investigated by wide angle X-ray diffraction (WXRD), atom force microscope (AFM) and transmission electron microscope (TEM). In contrast to the same series of compounds which have a longer alkyl tail, 5-{[(4′-heptoxy-4-biphenylyl)carbonyl]oxy}-1-pentyne (A3EO7), 5-{[(4′-heptoxy-4-biphenylyl)oxy]carbonyl}-1-pentyne (A3E′O7) and A3EO9, A3EO5 shows strikingly different crystalline behavior. The former three compounds have only one crystal form, whereas A3EO5 exhibits polymorphism. Specifically, A3EO5 crystals grown from toluene solution show two crystal forms. The first one is crystal I which adopts a monoclinic P112/m space group with unit cell parameters of a5.79 Å, b8.34 Å, c43.92 Å, γ96°, and the other one is crystal II which adopts a monoclinic P112 space group with unit cell parameters of a5.55 Å, b7.38 Å, c31.75 Å, γ94°. When using dioxane as the solvent to grow A3EO5 crystal, we can selectively obtain crystal I. A3EO5 melt-grown crystals also have two crystal forms which derive from crystal I and crystal II, respectively. The different crystalline behavior of the compounds should correlate with their different electron dipole moment resulting from the different length of alkyl tail.

Protolytic dissociation of cyanophenols in ground and excited states in alcohol and water solutions

The effect of cyano substituents on acidity in ground and excited states of mono- and dicyanophenols was investigated. The equilibrium dissociation constants of 3,4-dicyanophenol in ground and lowest excited states in water solution and the change of these constants in the excited state during the transfer to the ground state for o-, m-, p-cyanophenol and 3,4-dicyanophenol in alcohol and water solutions were determined. It was shown that the cyano substitution increases the acidity of ortho-, meta- and dicyano-derivative in ground state in comparison to the phenol, which makes the anions of these derivatives appear in solutions from methanol to 1-butanol. In the excited state the acidity of investigated compounds changes significantly in comparison to the ground state. 3,4-Dicyanophenol is the strongest acid in the lowest excited singlet state, while p-cyanophenol is the weakest one in both alcohol and water solutions. The distribution of the electronic charge and dipole moments of all investigated cyanophenols in ground and excited states were determined on the basis of ab initio calculations using the GAMESS program.

Attosecond pumping of nonstationary electronic states of LiH: Charge shake-up and electron density distortion

Electronic reorganization during and after excitation by an intense ultrashort pulse is computed for LiH in a many-electron multireference time-dependent approach at a fixed nuclear geometry. The electronic dipole moment is used to probe the temporal response of the charge density. Above a field-strength threshold, there is an extensive Stark shifting and Rabi broadening of levels with corresponding distortion of the charge distribution whose response at strong fields is neither adiabatic nor diabatic. A nonresonant IR pulse is more effective in inducing charge shake-up during the pulse.

Quantitative model for the change of optical resonance in neural activity detection systems based on surface plasmon resonance

The mechanism of neural activity detection using the surface plasmon resonance (SPR) phenomenon was theoretically explored in this paper. Investigating the mechanism of SPR neural recordings has been difficult due to the complex relationship between different physiological and physical processes such as excitation of a nerve fiber and coherent charge fluctuations on the metal surface. This paper examines how these different processes may be connected by introducing a set of compartmental theoretical models that deal with the molecular scale phenomena; Poisson–Boltzmann (PB) equation, which was used to describe the ion concentration change under the time varying electrostatic potential, Drude–Lorentz electron model, which was used to describe electron dynamics under the time varying external forces, and a Fresnel's three-layered model, which expresses the reflectivity of the SPR system in terms of the dielectric constants. Each physical theoretical model was numerically analyzed using the finite element method (FEM) formulated for the PB equation and the Green's method formulated for the Drude–Lorentz electron equation. The model predicts that the ionic thermal force originating from the opening of the K + ion channel is fundamental for modifying the dipole moment of the gold's free electron; thus, the reflectivity is changed in the SPR system. The discussion was done also on important attributes of the SPR signal such as biphasic fluctuation and the electrical noise-free characteristics.

Forbidden Singlet Exciton Transitions Induced by Localization in Polymer Light-Emitting Diodes in a Strong Electric Field

Through combining the electron transition process and dipole moment evolution as well as electron-phonon coupling, molecular dynamics calculations show that the radiative decay of singlet excitons in a conjugated polymer, such as a polymer light-emitting diode (PLED), is largely determined by the evolution of the dipole moment. Without an electric field, the decay life of a singlet exciton is about 1 ns. Once an electric field is applied and exceeds a critical value, with electron-phonon coupling, the original lattice structure evolves into two new localized lattice distortions, consistent with the experimental results. Owing to the new lattice structure and self-trapping, the dipole moment rapidly decreases to zero within 5 fs, eliminating the radiative decay of the singlet exciton.

Depolarization of Luminescence from Dye Molecules in Solutions or Embedded in Zeolite Pores

Depolarization of luminescence from pyronine B dye molecules was studied using polarized photoluminescence spectroscopy. When the molecules were dissolved in a solvent, the viscosity and the electronic dipole moment of the solvent affected the depolarization ratio and the photoluminescence peak position, respectively. In addition, the concentration of the dye molecules also influenced the depolarization ratio and the photoluminescence. For pyronine B molecules embedded in zeolite-L crystals, the photoluminescence peak position was independent of the concentration, and the depolarization ratio showed a dependence on the concentration that was opposite to the case of dye molecules in a solvent. The energy transfer between the molecules or the re-absorption process is suggested to explain the experimental results.

The electronic structure and dipole moment of charybdotoxin, a scorpion venom peptide with K + channel blocking activity

The electronic structure of charybdotoxin (ChTX), a scorpion venom peptide that is known to act as a potassium channel blocker, is investigated with the aid of semiempirical molecular orbital (MO) calculations. The dipole moment vector ( μ = 145 D at pH = 3.5 and μ = 116 D at pH = 7.5) of ChTX can be steered by the KcsA potassium channel’s macrodipole thereby assuming the proper orientation before the peptide binds the ion channel on the cell surface. The localization of the frontier orbitals of ChTX has been revealed for the first time. HOMO is localized on Trp14 while the three lowest-unoccupied MOs (LUMO, LUMO + 1, and LUMO + 2) are localized on the three disulfide bonds that characterize this peptide. An effective approach to engineer the HOMO–LUMO (H–L) gap of ChTX is replacing its Trp14 residue with Ala14 whereas deletion of the LUMO-associated disulfide bond Cys13-Cys33 through the insertion of a pair of l-α-aminobutyric acid residues does not affect the H–L energy gap. Molecular electrostatic potential surfaces for three ChTX models, two of them charged and one neutral, are in good agreement with the direction of the corresponding electric dipole moments.

Anharmonic Electron−Phonon Coupling in Condensed Media: 2. Application to Electronic Dephasing, Hole-Burning, and Photon Echo

While different expressions of homogeneous linear electronic dipole moment time correlation functions and their respective absorption lineshapes of anharmonic systems were derived and discussed at length in part I [Toutounji, M. J. Phys. Chem. B 2010, in press] of this study, the electronic dephasing (zero-phonon line width), caused by pseudolocal phonons, and vibrational relaxation time scales were treated equally, hence, unphysical. In this study electronic dephasing and vibrational structure are correctly accounted for in harmonic and anharmonic multimode systems. Model calculations are presented. Anharmonic hole-burned spectra are calculated using linear anharmonic absorption lineshapes. An analytical expression of hole-burned absorption line shape in terms of the linear dipole moment time correlation function, leading to a hole-burned absorption line shape expressed in time-domain, is reported. An elementary method is utilized to treat nonlinear spectra in anharmonic molecules. The link between a hole-burned spectrum and a 2-pulse photon echo profile is established by combining the theoretical framework of Mukamel and that of Hays-Small, thereby calculating photon echo signals of anharmonic systems. Model photon echo calculations of a solvable harmonic model and an anharmonic system are reported. Applications to Al-phthaolcyanine tetrasulphonate (APT) in hyperquenched glassy ethanol and special pair bacterial reaction center are presented and discussed in detail.

Carcinogenic potential of endosulfan and its metabolites based on a quantum chemical model

The aim of the present study was to investigate the carcinogenic potential of endosulfan and its metabolites through electronic parameters that characterize the action of carcinogens, i.e. descriptors such as electron affinity, Δ (HOMO–LUMO), dipole moments, electrostatic attraction, formation heat (H f) and permeability of the cell membrane (c Log P). The results reveal that both endosulfan and its metabolites are electrophilic and have carcinogenic potential. Although there are few data on its carcinogenicity in the literature, the findings of the present study indicate that the use of this pesticide represents a risk to the health of the general population, especially rural workers.

Symmetry-adapted cluster and symmetry-adapted cluster-configuration interaction method in the polarizable continuum model: Theory of the solvent effect on the electronic excitation of molecules in solution

In this paper we present the theory and implementation of the symmetry-adapted cluster (SAC) and symmetry-adapted cluster-configuration interaction (SAC-CI) method, including the solvent effect, using the polarizable continuum model (PCM). The PCM and SAC/SAC-CI were consistently combined in terms of the energy functional formalism. The excitation energies were calculated by means of the state-specific approach, the advantage of which over the linear-response approach has been shown. The single-point energy calculation and its analytical energy derivatives are presented and implemented, where the free-energy and its derivatives are evaluated because of the presence of solute-solvent interactions. We have applied this method to s-trans-acrolein and metylenecyclopropene of their electronic excitation in solution. The molecular geometries in the ground and excited states were optimized in vacuum and in solution, and both the vertical and adiabatic excitations were studied. The PCM-SAC/SAC-CI reproduced the known trend of the solvent effect on the vertical excitation energies but the shift values were underestimated. The excited state geometry in planar and nonplanar conformations was investigated. The importance of using state-specific methods was shown for the solvent effect on the optimized geometry in the excited state. The mechanism of the solvent effect is discussed in terms of the Mulliken charges and electronic dipole moment.

Adsorption of cysteine molecule on intrinsic and Pt-doped graphene: A first-principle study

The adsorption of cysteine molecule on intrinsic and Pt-doped graphene sheets was studied by density functional theory calculations. Compared with the intrinsic graphene, Pt-doped graphene strongly adsorbs cysteine molecules with higher binding energy value and shorter distance between the cysteine molecules and the graphene surface. The calculation of electron transfers and dipole moment supports that the electronic properties of Pt-doped graphene change more significantly than that of intrinsic graphene after the cysteine molecular adsorbed. Furthermore, the density of states results shows a larger orbital hybridization between cysteine and Pt-doped graphene sheet. Therefore, Pt-doped graphene is a promising candidate for sensor detecting a variety of S-containing proteins and metalloenzymes.

Theoretical Investigation on the Origin of the CD Signal Reversal for the Closed-ring Isomer of Diarylethene with Peripherical π-Conjugated Substituents

Abstract Theoretical investigation was performed on the CD signal of the closed-ring isomer of diarylethene with an extended π-conjugated substituent. The result showed that the different contribution of the substituent to the transition electronic and magnetic dipole moments induces CD signal reversal. The obtained finding can be applied to general dyes with a chiral core and extended π-conjugated substituents.

Quantum chemical and experimental studies on the structure and vibrational spectra of efavirenz

Efavirenz, (S)-6-chloro-4(cyclopropylethynyl)-1, 4-dihydro-4-(trifluoromethyl)-2H-3,1-benzoxazin-2-one, is a anti HIV agent belonging to the class of the non-nucleoside inhibitors of the HIV-1 virus reverse transcriptase. Structural and spectral characteristics of efavirenz have been studied by methods of Raman spectroscopy and quantum chemistry. The optimized geometries, electronic charge distribution, dipole moments and electrostatic potential surface were calculated by Hartree–Fock and Density functional B3LYP method with the 6-311++G(d,p) basis sets. Electrostatic potential surfaces have been mapped over the electron density isosurfaces to obtain information about the size, shape, charge density distribution and chemical reactivity of the molecules.

Supersymmetric baryogenesis from exotic quark decays

In a simple extension of the minimal supersymmetric standard model, out-of-equilibrium decays of TeV scale exotic vector-like squarks may generate the baryon asymmetry of the universe. Baryon number and CP violation are present in the superpotential, so this mechanism does not rely on CP violation in supersymmetry breaking parameters. We discuss phenomenological constraints on the model as well as potential signals for the Large Hadron Collider and electronic dipole moment experiments. A variation on the TeV scale model allows the exotic squarks to be the messengers of gauge mediated supersymmetry breaking.