Experimental and computed dipole moments in donor–bridge–acceptor systems with p-phenylene and p-carboranediyl bridges

2009 ◽  
Vol 74 (1) ◽  
pp. 131-146 ◽  
Author(s):  
Ladislav Drož ◽  
Mark A. Fox ◽  
Drahomír Hnyk ◽  
Paul J. Low ◽  
J. A. Hugh MacBride ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Dipole Moments ◽  
Electronic Effects ◽  
Electronic Interactions ◽  
Donor And Acceptor ◽  
Homo And Lumo ◽  
Pull Systems ◽  
The Difference ◽  
Experimental Values ◽  
2D And 3D

Dipole moments were measured for a series of substituted benzenes, biphenyls, terphenyls, C-monoaryl- and C,C′-diaryl-p-carboranes. For the donor–bridge–acceptor systems, Me2N–X–NO2, where X is 1,4-phenylene, biphenyl-4,4′-diyl, terphenyl and 1,4-C6H4-p-CB10H10C-1,4-C6H4, the measured interaction dipole moments are 1.36, 0.74, 0.51 and 0.00 D, respectively. The magnitude of the dipole moment reflects the ability of the bridge to transmit electronic effects between donor and acceptor groups. Thus, whilst the 1,4-phenylene bridges allow moderate electronic interactions between the remote groups, the p-carboranediyl unit is less efficient as a conduit for electronic effects. Averaged dipole moments computed at the DFT (B3LYP/6-31G*) level of theory from two distinct molecular conformers are in good agreement with the experimental values. Examination of the calculated electronic structures provides insight into the nature of the interactions between the donor and acceptor moieties through these 2D and 3D aromatic bridges. The most significant cooperative effect of the bridge on the dipole moment occurs in systems where there is some overlap between the HOMO and LUMO orbitals. This orbital overlap criterion may help to define the difference between “push-pull” systems in which electronic effects are mediated by the bridging moiety, and simpler systems in which the bridge acts as an electronically innocent spacer unit and through-space charge transfer/separation is dominant.

Charge-Transfer Dipoles at the Si-SiO2 Interface and the Metal-Semiconductor Worfunction Difference In Mos Devices.

1987 ◽  
Vol 105 ◽  
Author(s):  
Hisham Z. Massoud
Keyword(s):  
Dipole Moment ◽  
Charge Transfer ◽  
Dipole Moments ◽  
Silicon Substrates ◽  
Interface Dipole ◽  
Mos Devices ◽  
Flatband Voltage ◽  
The Difference ◽  
Definition Of ◽  
Mos Structures

AbstractThe magnitude of the dipole moment at the Si-SiO2 interface resulting from partial charge transfer that takes place upon the formation of interface bonds has been calculated. The charge transfer occurs because of the difference in electronegativity between silicon atoms and SiO2 molecules which are present across the interface. Results obtained for (100) and (111) silicon substrates indicate that the magnitude of the interface dipole moment is dependent on substrate orientation and the interface chemistry. Dipole moments at the Si-SiO2 and gate-SiO2 interfaces should be included in the definition of the flatband voltage VFB of MOS structures. CV-based measurements of the metal-semiconductor workfunction difference φms on (100) and (111) silicon oxidized in dry oxygen and metallized with Al agree with the predictions of this model. Other types of interface dipoles and their processing dependence are briefly discussed.

The Electrostatic Moments of a Charge Distribution

1997 ◽  
Author(s):  
Philip Coppens
Keyword(s):  
Dipole Moment ◽  
Charge Distribution ◽  
Dipole Moments ◽  
Practical Importance ◽  
Diffraction Method ◽  
Quadrupole Moments ◽  
Charge Densities ◽  
Moment Vector ◽  
Experimental Values ◽  
A Charge

The moments of a charge distribution provide a concise summary of the nature of that distribution. They are suitable for quantitative comparison of experimental charge densities with theoretical results. As many of the moments can be obtained by spectroscopic and dielectric methods, the comparison between techniques can serve as a calibration of experimental and theoretical charge densities. Conversely, since the full charge density is not accessible by the other experimental methods, the comparison provides an interpretation of the results of the complementary physical techniques. The electrostatic moments are of practical importance, as they occur in the expressions for intermolecular interactions and the lattice energies of crystals. The first electrostatic moment from X-rays was obtained by Stewart (1970), who calculated the dipole moment of uracil from the least-squares valence-shell populations of each of the constituent atoms of the molecule. Stewart’s value of 4.0 ± 1.3 D had a large experimental uncertainty, but is nevertheless close to the later result of 4.16 ± 0.4 D (Kulakowska et al. 1974), obtained from capacitance measurements of a solution in dioxane. The diffraction method has the advantage that it gives not only the magnitude but also the direction of the dipole moment. Gas-phase microwave measurements are also capable of providing all three components of the dipole moment, but only the magnitude is obtained from dielectric solution measurements. We will use an example as illustration. The dipole moment vector for formamide has been determined both by diffraction and microwave spectroscopy. As the diffraction experiment measures a continuous charge distribution, the moments derived are defined in terms of the method used for space partitioning, and are not necessarily equal. Nevertheless, the results from different techniques agree quite well. A comprehensive review on molecular electric moments from X-ray diffraction data has been published by Spackman (1992). Spackman points out that despite a large number of determinations of molecular dipole moments and a few determinations of molecular quadrupole moments, it is not yet widely accepted that diffraction methods lead to valid experimental values of the electrostatic moments.

Electric dipole moment of X2Π OH and OD in several vibrational states

1984 ◽  
Vol 62 (12) ◽  
pp. 1502-1507 ◽  
Author(s):  
K. I. Peterson ◽  
G. T. Fraser ◽  
W. Klemperer
Keyword(s):  
Dipole Moment ◽  
Electric Dipole ◽  
Vibrational State ◽  
Molecular Beam ◽  
Dipole Moments ◽  
Vibrational States ◽  
Electric Resonance ◽  
Resonance Technique ◽  
The Difference ◽  
Theoretical Results

Dipole moments are measured for OH (2Π) in the ν = 0, 1, and 2 vibrational states and for OD in the ν = 0 and 1 states using the molecular beam electric resonance technique. These are listed in the table below.[Formula: see text]A very accurate value of 0.00735(7) D is obtained for the difference in dipole moments between the ν = 0 and 1 vibrational states of OH. This is within 20% of the best theoretical results. The dependence on vibrational state is very nonlinear, which is also in agreement with theoretical results. Finally, the difference between the ν = 0 dipole moments of OH and OD is close to the expected value.

Dielectric properties of hexafluoroacetone and hexachloroacetone

1969 ◽  
Vol 47 (12) ◽  
pp. 2253-2256 ◽  
Author(s):  
R. K. Chan
Keyword(s):  
Dipole Moment ◽  
Dielectric Properties ◽  
Liquid State ◽  
Dipole Moments ◽  
Dielectric Constants ◽  
Pure Liquid ◽  
Gaseous State ◽  
Vector Addition ◽  
Inductive Effects ◽  
Experimental Values

The dielectric constants of hexafluoro- and hexachloro-acetone are measured in the solid and liquid state. They show negligible association in the liquid state. The dipole moments are 0.648 D measured in the gaseous state and 0.63 D in pure liquid for hexafluoroacetone, and 1.24 D in carbon tetrachloride solution and 1.34 D in pure liquid for hexachloroacetone. If the differences between inductive effects due to CX3 and C=O groups can be ignored, the vector addition of bond moments gives values of dipole moment which are compatible with the experimental values.

scholarly journals Solvent effect on the absorption and emission spectra of carbon dots: evaluation of ground and excited state dipole moment

BMC Chemistry ◽  
2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Parisa Mohammad-Jafarieh ◽  
Abolfazl Akbarzadeh ◽  
Rahman Salamat-Ahangari ◽  
Mohammad Pourhassan-Moghaddam ◽  
Kazem Jamshidi-Ghaleh
Keyword(s):  
Dipole Moment ◽  
Excited State ◽  
Ground State ◽  
Carbon Dots ◽  
Dipole Moments ◽  
Emission Spectra ◽  
Aprotic Solvents ◽  
One Step ◽  
The Difference ◽  
Excited State Dipole Moment

Abstract Background Carbon dots (C-dots) are photoluminescent nanoparticles with less than 10 nm in size. Today, many studies are performed to exploit the photoluminescence (PL) property of carbon dots, and our focus in this study is to estimate the dipole moment of carbon dots. For reaching our aims, C-dots were synthesized and dissolved in the different solvents. Results Carbon dots with intense photoluminescence properties have been synthesized by a one-step hydrothermal method from a carbon bio-source. In this research, we report on the effect of aprotic solvents on absorption and fluorescence spectra and dipole moments of C-dots dispersed in a range of many aprotic solvents with various polarity and dielectric constant at room temperature. The change in the value of dipole moment was estimated by using the Stokes shifts. The difference between the dipole moment of the excited state and the ground state was shown using an extended form of Lippert equations by Kawski and co-workers. Conclusions The values found for μg = 1.077 D, and μe = 3.157 D, as well as the change in the dipole moments. The results showed that the dipole moment of the excited state is more than the ground state, indicating a high density and redistribution of electrons in the excited state. Finally, the quantum yield of C-dots in the eclectic aprotic solvents was communicated and discussed.

Experimentelle und Quantenchemische Untersuchungen der Dipolmomente von Substituierten Stilbenen im Ersten Angercgten Singulettzustand / Experimental and Quantum Chemical Investigations of Dipole Moments of Substituted Stilbens in the First Excited Singlet State

1977 ◽  
Vol 32 (5) ◽  
pp. 420-425 ◽  
Author(s):  
A. Kawski ◽  
I. Gryczyński
Keyword(s):  
Dipole Moment ◽  
Excited States ◽  
Ground State ◽  
Quantum Chemical ◽  
Singlet State ◽  
Dipole Moments ◽  
Excited Singlet State ◽  
Excited Singlet ◽  
Fluorescent State ◽  
Experimental Values

Abstract The values a/a3 (α = polarizability), the Onsager cavity radii a and the dipole moments μe of six substituted stilbens in the fluorescent state have been determined. It is shown that if the dipole moment of the lowest excited singlet state μe is parallel to the dipole moment in the ground state μg, the values of μe and a can be determined from the solvent effects. Moreover, quantum chemical investigations of the dipole moments in the ground and excited states were carried out with the Pariser-Parr-Pople method and compared with the experimental values.

π-Elektronen-Dipolmoment eines Pyridinium-N-phenol-betains

1966 ◽  
Vol 21 (9) ◽  
pp. 1373-1376 ◽  
Author(s):  
A. Schweig ◽  
C. Reichardt
Keyword(s):  
Dielectric Constant ◽  
Dipole Moment ◽  
Ground State ◽  
Dipole Moments ◽  
Saturated Hydrocarbon ◽  
Dilute Solution ◽  
Uniform Medium ◽  
Order Of Magnitude ◽  
Dimensional Electron Gas ◽  
Experimental Values

The ground state dipole moment of the π-electrons of 2.4.6-triphenyl-N- [3.5-di-tert-butyl-4-hydroxy-phenyl] -pyridinium-betain I, a highly solvatochromic substance, was determined by measuring the dielectric constant of a dilute solution and calculating first the dipole moment of the whole system (σ- and π-electrons) using the method of HALVERSTADT and KUMLER. The dipole moment of the π-electrons was then calculated, asuming the π-electron dipole to be imbedded in a spherical medium of dielectric constant 2. The value calculated by this method was compared with the π-electron dipole moment directly obtained from the dielectric constant of the dilute solution using a method of H. KUHN. This method is based on the assumption that a π-electron of a dissolved molecule sees the σ-electrons of the molecule and of the surrounding solvent, a saturated hydrocarbon, as a continuous uniform medium of dielectric constant 2. Thus the π-electron dipole of the solute molecule is regarded as being imbedded in a continuous medium of dielectric constant 2. It was found that the values of the π-electron dipole moments determined by the two methods agree well. Furthermore these experimental values agree with a theoretical value obtained in the case of N- [4-hydroxy-phenyl] -pyridinium-betain II using the one dimensional electron gas method including electron repulsion. The order of magnitude of the π-electron dipole moment of I clearly shows that the ground state of this molecule is highly polar.

Dipole moment of the intramolecular hydrogen bond. 2-Nitrophenol and its derivatives

1983 ◽  
Vol 48 (3) ◽  
pp. 735-747 ◽  
Author(s):  
Otto Exner ◽  
Juraj Koudelka ◽  
Soňa Vašíčková
Keyword(s):  
Hydrogen Bond ◽  
Electron Transfer ◽  
Dipole Moment ◽  
Intramolecular Hydrogen Bond ◽  
Dipole Moments ◽  
Charge Redistribution ◽  
Experimental Dipole Moment ◽  
Mndo Calculations ◽  
The Difference ◽  
Intramolecular Hydrogen

Dipole moments of substituted 2-nitrophenols VIa-VIf and substituted 2-nitroanisoles VIIa to VIIf were measured in benzene and dioxan solutions. Infrared spectroscopy confirmed that nitrophenols VI exist either solvent and at different concentrations as non-associated molecules with an intramolecular hydrogen bond. Therefore, the difference between the experimental dipole moment and that calculated from group moments can be attributed to charge redistribution raised by the hydrogen bond. Only a minute part of it may be due to electron transfer through the ring (conjugation of the functional groups) as follows particularly from he comparison with nitroanisoles VII. Nevertheless, the charge transfer, expressed as the vector μH, amounts only 1.7 . 10-30 Cm (at an angle of 138° to the H-O bond), i.e. several times less than observed previously in compounds with more powerful hydrogen acceptors. CNDO/2 and MNDO calculations agree fairly with the gross dipole moments of the compounds investigated but are unable to predict μH, not even as far as its direction is concerned.

Memory Effects in the Collision-Induced Spectra of Noble Gases in Liquid Argon

1971 ◽  
Vol 49 (22) ◽  
pp. 2870-2873 ◽  
Author(s):  
U. Buontempo ◽  
S. Cunsolo ◽  
G. Jacucci
Keyword(s):  
Dipole Moment ◽  
Dipole Moments ◽  
Low Frequency ◽  
Far Infrared ◽  
Liquid Argon ◽  
Low Frequencies ◽  
Line Shapes ◽  
Induced Dipole ◽  
Rapid Fall ◽  
The Difference

We have measured the far infrared absorption spectra of dilute solutions of helium and neon in liquid argon arising from collision-induced electric dipole moments. The two spectra consist of broad bands similar in shape peaked at 70 cm−1 (Ne–A) and 120 cm−1 (He–A). They are characterized by a long high-frequency tail and a rapid fall at low frequency. The reduced line shapes are compared taking into account the difference in the duration of the collision-induced dipole moment. At high frequencies the two curves are similar to those observed in the gas phase. Their departure from the gaseous spectra at low frequencies is attributed to a negative correlation of the dipole moment induced in successive repulsive interactions.

Vibrational Dynamics of the H2O . HF Complex. Potential Energy and Electric Dipole Moment Surfaces

1993 ◽  
Vol 58 (12) ◽  
pp. 2813-2830 ◽  
Author(s):  
Andrzej J. Sadlej ◽  
Ota Bludský ◽  
Vladimír Špirko
Keyword(s):  
Dipole Moment ◽  
Potential Energy ◽  
Electric Dipole Moment ◽  
Electric Dipole ◽  
Vibrational Energy ◽  
Dipole Moments ◽  
Energy Levels ◽  
Equilibrium Geometry ◽  
Two Dimensional ◽  
Experimental Values

A total of 330 points on the potential energy and electric dipole moment surfaces of the ground electronic state of the H2O . HF complex have been calculated ab initio using the SCF method and many-body perturbation theory (MBPT). To keep the calculations manageable, the geometry parameters of H2O were fixed at their experimental values and only certain two dimensional sections of the total surfaces have been evaluated. for each of the two-dimensional surface section, analytic potential energy and electric dipole moment functions have been fitted through the points and corresponding vibrational energy levels and effective electric dipole moments have been calculated using approximate vibrational Hamiltonians. The calculated values of resulting vibrational energies and effective electric dipoles from differently wide intervals for different vibrational modes. The intervals corresponding to the most interesting low frequency modes (out-of-plane and H2O vs HF stretching) are very narrow and coincide satisfactory with the corresponding experimental values. A very reasonable agreement has also been obtained for the equilibrium geometry, electric dipole moment and dissociation energy De of the complex. These findings lead us to believe that the calculated potential energy and electric dipole moment surfaces are sufficiently accurate for predicting purposes and rationalization of the so far unassigned spectral data of H2O . HF.

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