Results of theoretical treatment of the proton transfer dynamics depend strongly on the potential... more Results of theoretical treatment of the proton transfer dynamics depend strongly on the potential energy surface (PES) used for the hydrogen bonded system description. The quantum chemical calculations1–15 of PES are however still very approximate especially when a condensed phase is considered. The environmental effect on the PES shape can be very strong whereas the quantum chemical calculation deals usually with isolated systems. Practically some simple analytical function of nuclear coordinates, having a double well, is preferred for proton transfer treatment.
The structures, relative stability, infrared (IR) and Raman spectra of the most-stable forms of [... more The structures, relative stability, infrared (IR) and Raman spectra of the most-stable forms of [H9O4]+ and [H13O6]+ ions in acetonitrile are computed using the B3LYP functional combined with the Polarizable Continuum Model approximation. These forms are hydrated [H3O]+ and [H5O2]+ cores. Of interest are two main environmental effects on the spectroscopic features of protonated water hydrates: (i) polarization of the solvent by the hydrate dipole moment; (ii) formation of H-bonds with bulky counterions (ClO4- and BF4-). The effect of the polarization on the structure of the [H3O]+ core strongly depends on the symmetry of the hydration shell. A distortion of a hydrated [H3O]+ easily changes its structure to the [H7O3]+ one that causes a change in the nature of the most IR-intensive bands. Thus, the specificity of this core can be easily lost that prevents identification of the corresponding species. By contrast, the [H5O2]+ core is more stable against distortion. It is characterized by the short O…O distance (< 2.45 Å), IR-intensive band near 1720 cm-1 and Raman-intensive line around 500 cm-1. The [H5O2]+ core remains identifiable even when protonated hydrate is involved in specific interactions with a bulky counterion. Geometrical criteria for identification of the [H3O]+, [H5O2]+ and [H7O3]+ cores are discussed.
Hydrogenation of 10H-indeno[1,2-b]quinoline in benzene in the presence of R2S 7 (250 ~ PH2 = 140 ... more Hydrogenation of 10H-indeno[1,2-b]quinoline in benzene in the presence of R2S 7 (250 ~ PH2 = 140 atm, 4 h) gave 5,5a, 10a,11-tetrahydro-10H-indeno[1,2-b]quinoline, the structure of which was established by mass-, IR, UV, 13C, and lH NMR spectra. The cis filsion of the indan and tetrahydroquinoline fragments, the axial orientation of the proton at C(5a), and the equatorial orientation of the proton at C(10a) were confirmed by molecular mechanics calculations using the PC MODEL program.
In this chapter we will consider molecular crystals with normal hydrogen bonds in which the donor... more In this chapter we will consider molecular crystals with normal hydrogen bonds in which the donor A:H interacts with an acceptor :B. The so-called “bifurcated” and “trifurcated” H-bonds [1] as well as the new multiform unconventional Hbonds [2] are beyond the scope of the present chapter. We will focus on the proton dynamics in molecular crystals with strong and moderate H-bonds [3] in the ground electronic state. Attention will be focused on the interpretation of the structural and spectroscopic manifestations of the dynamics of the bridging proton as established in X-ray, neutron diffraction, infrared, and inelastic neutron scattering (INS) studies of H-bonded crystals. Various theoretical approaches have been developed for the description of the structure, spectral properties, and proton tunneling in H-bonded systems [4–7]. Computations for particular H-bonded species in the gas phase have been performed [8]. Due to strong environmental effects the applicability of gas-phase calculations to the proton dynamics in H-bonded crystals is questionable. Many theoretical approaches are based on oversimplified models (harmonic potentials and one-dimensional treatment of proton tunneling) and they usually contain parameters obtained from the experiment to be interpreted. This is why a consistent view on hydrogen bonding phenomenon in molecular crystals is still far from being achieved. The aims of this article are: 1. To show that a uniform and noncontradictory description of the specific properties of molecular crystals with quasi-linear H-bonds can be obtained in terms of a two-dimensional (2D) treatment assuming strong coupling between the protontransfer coordinate and a low-frequency vibration. 2. To interpret experimental structural and spectroscopic regularities of crystals with a quasi-symmetric A A H fragment using a model 2D potential energy surface (PES).
Diclofenac (active ingredient of Voltaren) has a significant, multifaceted role in medicine, phar... more Diclofenac (active ingredient of Voltaren) has a significant, multifaceted role in medicine, pharmacy, and biochemistry. Its physical properties and impact on biomolecular structures still attract essential scientific interest. However, its interaction with water has not been described yet at the molecular level. In the present study, we shed light on the interaction between the steric hindrance (the intramolecular N−H•••O bond, etc.) carboxylate group (−CO 2 −) with water. Aqueous solution of sodium declofenac is investigated using attenuated total reflection-infrared (ATR-IR) and computational approaches, i.e., classical molecular dynamics (MD) simulations and density functional theory (DFT). Our coupled classical MD simulations, DFT calculations, and ATR-IR spectroscopy results indicated that the −CO 2 − group of the diclofenac anion undergoes strong specific interactions with the water molecules. The combined experimental and theoretical techniques provide significant insights into the spectroscopic manifestation of these interactions and the structure of the hydration shell of the −CO 2 − group. Moreover, the developed methodology for the theoretical analysis of the ATR-IR spectrum could serve as a template for the future IR/Raman studies of the strong interaction between the steric hindrance −CO 2 − group of bioactive molecules with the water molecules in dilute aqueous solutions.
The effect of the local structure on the 31 P NMR chemical shift tensor (CST) has been studied ex... more The effect of the local structure on the 31 P NMR chemical shift tensor (CST) has been studied experimentally and simulated theoretically using the density functional theory gauge-independent-atomic-orbital approach. It has been shown that the dominating impact comes from a small number of noncovalent interactions between the phosphorus-containing group under question and the atoms of adjacent molecules. These interactions can be unambiguously identified using the Bader analysis of the electronic density. A robust and computationally effective approach designed to attribute a given experimental 31 P CST to a certain local morphology has been elaborated. This approach can be useful in studies of surfaces, complex molecular systems, and amorphous materials.
Computational and Theoretical Chemistry, Sep 1, 2016
Intrinsic solubility of the isoniazid-carboxylic acid cocrystals is explored using thermodynamic ... more Intrinsic solubility of the isoniazid-carboxylic acid cocrystals is explored using thermodynamic cycle of transferring from crystal to gas and then to solution. The enthalpy/Gibbs free energy of phase transitions is computed by solid-state DFT (crystal) and DFT methods with/without accounting for polar solvent (aqueous solution/gas). The dissolution process of the isoniazid-dicarboxylic acid 2:1 cocrystals is found to be enthalpy-determined. The linear correlation between the theoretical sublimation enthalpies and experimental Gibbs energy of solution is established. According to it, the increase of stability causes the decrease of the considered cocrystals solubility. We conclude that a soluble and relatively stable cocrystal of isoniazid should be characterized by the sublimation enthalpy varying from 185 to 200 kJÁmol À1. Bader analysis of theoretical periodic electron density enables us to quantify the noncovalent interactions and clarify their role in formation of the isoniazid cocrystals. The sublimation enthalpy of the cocrystals is defined by the structure of the coformer molecule. Its value is less 150 kJÁmol À1 in the case of aromatic acids and larger than 180 kJÁmol À1 for the aliphatic dicarboxylic acids. The sublimation enthalpy increases with the increase of the dicarboxylic acid hydrocarbon chain.
Temperature dependence of the proton spin-lattice relaxation time (T1) in powdered benzoic acid d... more Temperature dependence of the proton spin-lattice relaxation time (T1) in powdered benzoic acid dimer and in its deuterated analog is calculated. The model assumes that two protons (deuterons) synchronously move in the double-minimum potential of the dimer. The two-dimensional potential energy surface was constructed previously, which adequately describes the static properties of the hydrogen-bonded complex. The important characteristics of this potential are a very strong mode coupling and a very high proton potential barrier (≳25 kcal/mol), whereas the experimental activation energy for the proton transfer is known to be on the order of 1 kcal/mol only. This apparent discrepancy is removed by our suggestion that the proton transfer is driven by the transitions between OHO fragment vibrational levels under the action of random forces of the surrounding. The excitation of the low-frequency intermolecular vibrations assists such transfer mechanism strongly. Using four fitting parameters to allow for the medium repolarization, the calculated T1 temperature dependence is found to be in good agreement with the experiments in the natural and deuterated benzoic acid dimer. The agreement is best at high temperature where the apparent activation energy for proton transfer was found to be 2.3 kcal/mol.
Journal of materials chemistry. A, Materials for energy and sustainability, 2018
IR spectra were recorded on a BrukerALPHA instrument in KBr pellets. 1 Н, 13 C, and 14 N spectra ... more IR spectra were recorded on a BrukerALPHA instrument in KBr pellets. 1 Н, 13 C, and 14 N spectra were acquired on a Bruker AМ-300 instrument (300.13, 75.47 and 21.69 MHz, respectively) in DMSO-d 6 at 299 K. The chemical shifts of 1 H and 13 C nuclei were reported relative to TMS, for 14 Nrelative to MeNO 2 , high-filed chemical shifts are given with a minus sign. High-resolution mass spectra with electrospray ionization were recorded on a Bruker MicroOTOF II instrument. Elemental analysis was performed on a PerkinElmer 2400 Series II instrument. The reaction progress and purity of the obtained compounds were controlled by TLC on Merck Silicagel 60 F 254 plates. Visualization of spots on TLC plate was accomplished with UV light (254 nm). Density was determined by helium gas pycnometer AccuPyc II 1340 at 298 K. Enthalpy of formation values were determined with high-precision combustion bomb calorimeter developed in Semenov Institute of Chemical physics. [1,2] Impact and friction sensitivities were measured with BAM-type apparatus in a series of experiments according to STANAG procedures. [3,4] Detonation parameters were calculated with Smirnov [5] and Kamlet-Jacobs equations. [6] Thermal stability of the compounds was monitored using DSC 204 HP (Netzsch) apparatus. Samples 0.5-2 mg mass were placed in closed Al pans with laser-cut pinholes and heated at constant rate of 5 K min-1 rates under nitrogen flow (100 ml min-1). Environmental pressure was increased to 2 MPa for selected materials to reveal the decomposition rather than evaporation. [7] Materials Most of the reagents and starting materials were purchased from commercial sources and used without additional purification. The starting 3,5-dinitroaniline (1c), [8] 1-(4nitrophenyl)-1H-1,2,3,4-tetrazole (4a) [9] , 1-(3-nitrophenyl)-1H-1,2,3,4-tetrazole (4b), [10] 4nitroazidobenzene 5a [11] and 3-nitroazidobenzene 5b [12] were obtained published procedures. Caution! Although we have encountered no difficulties during preparation and handling of these compounds, they are potentially explosive energetic materials. Manipulations must be carried out by using appropriate standard safety precautions (earthed equipment, Kevlar® gloves, Kevlar® sleeves, face shield, leather coat, and ear plugs). General procedure for synthesis of hydrazones 2а-d. [13] A suspension of appropriate amine 1а-d (0.02 mol) in hydrochloric acid (19%, 30 ml) was stirred at 0-5 o C and treated by dropwise addition of a solution NaNO 2 (1.86 g, 0.027 mol) in H 2 O (6 ml). The mixture was stirred for 40 min, gave a solution of the diazonium salt.
The vibrational spectrum of the formic acid dimer in the OH stretch region is calculated by solvi... more The vibrational spectrum of the formic acid dimer in the OH stretch region is calculated by solving a 3D vibrational Schr odinger equation and employing an electronic potential and dipole moment calculated at the MP2 level of theory. Two Raman-active bands of the symmetric OH stretch fundamental are located around 2600 cm À1 ; the gap between them ($300 cm À1) is caused by concerted proton tunneling. IR-active bands around 3100 cm À1 are assigned to the antisymmetric OH stretch fundamental, its ®rst overtone and two complex transitions. The calculated H =D isotope eect on the intensity of the antisymmetric OH fundamental is 1.92.
Поступила в редакцию 30.05.2016 г. Aqueous solutions of glycine, phenylalanine and proline were s... more Поступила в редакцию 30.05.2016 г. Aqueous solutions of glycine, phenylalanine and proline were studied using the classical MD simulations. The amino acids were described by Amber and OPLS-AA force fields. The SPC/E and TIP3P models were used for water. Pair correlation functions of the amino acids evaluated using the Amber-TIP3P scheme agree well with the experimental data. This scheme was used in the subsequent simulations. The IR spectrum was obtained from Fourier transform of the autocorrelation function of classical dipole moment of the amino acids. The theoretical frequencies of the IR-intensive bands of glycine in water, associated with N−H and C−H stretching, and N−H bending vibrations, agree with the experimental data. The appearance of band near 2300 cm-1 is a characteristic feature of the theoretical IR spectra of aqueous glycine and phenylalanine. This band is associated with the stretching vibrations of the NH 3 + group forming strong +N−H…O w bonds with the adjacent water molecules. This band appears in the experimental IR spectrum of aqueous solution of glycine, and was treated as a combination band (Spectrochim. Acta A 61 (2005) 2741). In the theoretical IR spectrum of proline no band around 2300 cm-1 was obtained. This difference could be explained by inability of the proline NH 2 + group to form strong +N−H…O w bonds with water molecules.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The adiabatic separation of the vibrational variables of a hydrogen-bonded AHA fragment with a sy... more The adiabatic separation of the vibrational variables of a hydrogen-bonded AHA fragment with a symmetric double-well potential is considered using two approaches. In the first approach the A... A stretch vibration is slow in comparison to the proton vibration. It is applicable to the energy level calculations of an AHA fragment with a potential barrier of arbitrary height. In the alternative approach the proton is considered to be a "slow" subsystem. This approach appears to be of limited applicability. For an AHA fragment with a symmetric double-well potential the Born-Oppenheimer criterion is shown to contain the frequency corresponding to the proton 0 ~ 2 transition in both approaches.
ChemInform Abstract Die Racemisierung der Antipo-den (I) F' (II) wird durch verschiedene Russsort... more ChemInform Abstract Die Racemisierung der Antipo-den (I) F' (II) wird durch verschiedene Russsorten katalysiert und die Art der Modifizierung des Katalysators in seiner kinetischen Wirksamkeit diskutiert. Die Herstellung dieser Verbindungen aus optisch aktivem 1,1 '-Binaphthyl durch z.B. Bromierung, Nitrierung etc. wird angegeben. (IR-, NMR-, MS-Daten).
Rapid progress in organic electronics demands new highly efficient organic semiconducting materia... more Rapid progress in organic electronics demands new highly efficient organic semiconducting materials. Nevertheless, only few materials have been created so far that show reliable band-like transport with high charge mobilities, which reflects the two main obstacles in the field: the poor understanding of charge transport in organic semiconductors (OSs) and the difficulty of its quantification in devices. Here, we present a spectroscopic method for assessment of the charge transport in organic semiconductors. We show that the intensities of the lowfrequency Raman spectrum allow calculation of the dynamic disorder that limits the charge carrier mobility. The spectroscopically evaluated mobility clearly correlates with the device charge mobility reported for various OSs. The proposed spectroscopic method can serve as a powerful tool for a focused search of new materials and highlights the disorder bottleneck in the intrinsic charge transport in high-mobility organic semiconductors.
Anharmonic frequencies of the O PPP H PPP O fragment of H O q were evaluated using the adiabatic ... more Anharmonic frequencies of the O PPP H PPP O fragment of H O q were evaluated using the adiabatic separation of 5 2 Ž. vibrational variables. The relaxed 3D potential energy surface was calculated by the MP2 method using the T O DZP basis y1 w set. The symmetric and asymmetric stretching frequencies obtained, 588 and 1226 cm , agree with previous 2D results L. Ž. x Ojamae et al., Int. J. Quantum Chem. Symp. 29 1995 657 and show a modest shift from the harmonic values only. Thë O PPP H PPP O bending frequency is ca. 1025 cm y1 , significantly lower than the harmonic result of 1524 cm y1. Comparison is made with results of MD simulations using ab initio forces.
International Reviews in Physical Chemistry, Jul 1, 2009
Ability to form a strong quasisymmetric H-bond is a fundamental property of the proton. This H-bo... more Ability to form a strong quasisymmetric H-bond is a fundamental property of the proton. This H-bond determines the stability of the proton hydrates and acid–base complexes, which defines the specific features (catalytic, electrochemical, etc.) of acidic solutions. The protonated water dimer can be treated as a simplest stable proton hydrate in aqueous acid solutions. Its lifetime is larger than characteristic
Results of theoretical treatment of the proton transfer dynamics depend strongly on the potential... more Results of theoretical treatment of the proton transfer dynamics depend strongly on the potential energy surface (PES) used for the hydrogen bonded system description. The quantum chemical calculations1–15 of PES are however still very approximate especially when a condensed phase is considered. The environmental effect on the PES shape can be very strong whereas the quantum chemical calculation deals usually with isolated systems. Practically some simple analytical function of nuclear coordinates, having a double well, is preferred for proton transfer treatment.
The structures, relative stability, infrared (IR) and Raman spectra of the most-stable forms of [... more The structures, relative stability, infrared (IR) and Raman spectra of the most-stable forms of [H9O4]+ and [H13O6]+ ions in acetonitrile are computed using the B3LYP functional combined with the Polarizable Continuum Model approximation. These forms are hydrated [H3O]+ and [H5O2]+ cores. Of interest are two main environmental effects on the spectroscopic features of protonated water hydrates: (i) polarization of the solvent by the hydrate dipole moment; (ii) formation of H-bonds with bulky counterions (ClO4- and BF4-). The effect of the polarization on the structure of the [H3O]+ core strongly depends on the symmetry of the hydration shell. A distortion of a hydrated [H3O]+ easily changes its structure to the [H7O3]+ one that causes a change in the nature of the most IR-intensive bands. Thus, the specificity of this core can be easily lost that prevents identification of the corresponding species. By contrast, the [H5O2]+ core is more stable against distortion. It is characterized by the short O…O distance (< 2.45 Å), IR-intensive band near 1720 cm-1 and Raman-intensive line around 500 cm-1. The [H5O2]+ core remains identifiable even when protonated hydrate is involved in specific interactions with a bulky counterion. Geometrical criteria for identification of the [H3O]+, [H5O2]+ and [H7O3]+ cores are discussed.
Hydrogenation of 10H-indeno[1,2-b]quinoline in benzene in the presence of R2S 7 (250 ~ PH2 = 140 ... more Hydrogenation of 10H-indeno[1,2-b]quinoline in benzene in the presence of R2S 7 (250 ~ PH2 = 140 atm, 4 h) gave 5,5a, 10a,11-tetrahydro-10H-indeno[1,2-b]quinoline, the structure of which was established by mass-, IR, UV, 13C, and lH NMR spectra. The cis filsion of the indan and tetrahydroquinoline fragments, the axial orientation of the proton at C(5a), and the equatorial orientation of the proton at C(10a) were confirmed by molecular mechanics calculations using the PC MODEL program.
In this chapter we will consider molecular crystals with normal hydrogen bonds in which the donor... more In this chapter we will consider molecular crystals with normal hydrogen bonds in which the donor A:H interacts with an acceptor :B. The so-called “bifurcated” and “trifurcated” H-bonds [1] as well as the new multiform unconventional Hbonds [2] are beyond the scope of the present chapter. We will focus on the proton dynamics in molecular crystals with strong and moderate H-bonds [3] in the ground electronic state. Attention will be focused on the interpretation of the structural and spectroscopic manifestations of the dynamics of the bridging proton as established in X-ray, neutron diffraction, infrared, and inelastic neutron scattering (INS) studies of H-bonded crystals. Various theoretical approaches have been developed for the description of the structure, spectral properties, and proton tunneling in H-bonded systems [4–7]. Computations for particular H-bonded species in the gas phase have been performed [8]. Due to strong environmental effects the applicability of gas-phase calculations to the proton dynamics in H-bonded crystals is questionable. Many theoretical approaches are based on oversimplified models (harmonic potentials and one-dimensional treatment of proton tunneling) and they usually contain parameters obtained from the experiment to be interpreted. This is why a consistent view on hydrogen bonding phenomenon in molecular crystals is still far from being achieved. The aims of this article are: 1. To show that a uniform and noncontradictory description of the specific properties of molecular crystals with quasi-linear H-bonds can be obtained in terms of a two-dimensional (2D) treatment assuming strong coupling between the protontransfer coordinate and a low-frequency vibration. 2. To interpret experimental structural and spectroscopic regularities of crystals with a quasi-symmetric A A H fragment using a model 2D potential energy surface (PES).
Diclofenac (active ingredient of Voltaren) has a significant, multifaceted role in medicine, phar... more Diclofenac (active ingredient of Voltaren) has a significant, multifaceted role in medicine, pharmacy, and biochemistry. Its physical properties and impact on biomolecular structures still attract essential scientific interest. However, its interaction with water has not been described yet at the molecular level. In the present study, we shed light on the interaction between the steric hindrance (the intramolecular N−H•••O bond, etc.) carboxylate group (−CO 2 −) with water. Aqueous solution of sodium declofenac is investigated using attenuated total reflection-infrared (ATR-IR) and computational approaches, i.e., classical molecular dynamics (MD) simulations and density functional theory (DFT). Our coupled classical MD simulations, DFT calculations, and ATR-IR spectroscopy results indicated that the −CO 2 − group of the diclofenac anion undergoes strong specific interactions with the water molecules. The combined experimental and theoretical techniques provide significant insights into the spectroscopic manifestation of these interactions and the structure of the hydration shell of the −CO 2 − group. Moreover, the developed methodology for the theoretical analysis of the ATR-IR spectrum could serve as a template for the future IR/Raman studies of the strong interaction between the steric hindrance −CO 2 − group of bioactive molecules with the water molecules in dilute aqueous solutions.
The effect of the local structure on the 31 P NMR chemical shift tensor (CST) has been studied ex... more The effect of the local structure on the 31 P NMR chemical shift tensor (CST) has been studied experimentally and simulated theoretically using the density functional theory gauge-independent-atomic-orbital approach. It has been shown that the dominating impact comes from a small number of noncovalent interactions between the phosphorus-containing group under question and the atoms of adjacent molecules. These interactions can be unambiguously identified using the Bader analysis of the electronic density. A robust and computationally effective approach designed to attribute a given experimental 31 P CST to a certain local morphology has been elaborated. This approach can be useful in studies of surfaces, complex molecular systems, and amorphous materials.
Computational and Theoretical Chemistry, Sep 1, 2016
Intrinsic solubility of the isoniazid-carboxylic acid cocrystals is explored using thermodynamic ... more Intrinsic solubility of the isoniazid-carboxylic acid cocrystals is explored using thermodynamic cycle of transferring from crystal to gas and then to solution. The enthalpy/Gibbs free energy of phase transitions is computed by solid-state DFT (crystal) and DFT methods with/without accounting for polar solvent (aqueous solution/gas). The dissolution process of the isoniazid-dicarboxylic acid 2:1 cocrystals is found to be enthalpy-determined. The linear correlation between the theoretical sublimation enthalpies and experimental Gibbs energy of solution is established. According to it, the increase of stability causes the decrease of the considered cocrystals solubility. We conclude that a soluble and relatively stable cocrystal of isoniazid should be characterized by the sublimation enthalpy varying from 185 to 200 kJÁmol À1. Bader analysis of theoretical periodic electron density enables us to quantify the noncovalent interactions and clarify their role in formation of the isoniazid cocrystals. The sublimation enthalpy of the cocrystals is defined by the structure of the coformer molecule. Its value is less 150 kJÁmol À1 in the case of aromatic acids and larger than 180 kJÁmol À1 for the aliphatic dicarboxylic acids. The sublimation enthalpy increases with the increase of the dicarboxylic acid hydrocarbon chain.
Temperature dependence of the proton spin-lattice relaxation time (T1) in powdered benzoic acid d... more Temperature dependence of the proton spin-lattice relaxation time (T1) in powdered benzoic acid dimer and in its deuterated analog is calculated. The model assumes that two protons (deuterons) synchronously move in the double-minimum potential of the dimer. The two-dimensional potential energy surface was constructed previously, which adequately describes the static properties of the hydrogen-bonded complex. The important characteristics of this potential are a very strong mode coupling and a very high proton potential barrier (≳25 kcal/mol), whereas the experimental activation energy for the proton transfer is known to be on the order of 1 kcal/mol only. This apparent discrepancy is removed by our suggestion that the proton transfer is driven by the transitions between OHO fragment vibrational levels under the action of random forces of the surrounding. The excitation of the low-frequency intermolecular vibrations assists such transfer mechanism strongly. Using four fitting parameters to allow for the medium repolarization, the calculated T1 temperature dependence is found to be in good agreement with the experiments in the natural and deuterated benzoic acid dimer. The agreement is best at high temperature where the apparent activation energy for proton transfer was found to be 2.3 kcal/mol.
Journal of materials chemistry. A, Materials for energy and sustainability, 2018
IR spectra were recorded on a BrukerALPHA instrument in KBr pellets. 1 Н, 13 C, and 14 N spectra ... more IR spectra were recorded on a BrukerALPHA instrument in KBr pellets. 1 Н, 13 C, and 14 N spectra were acquired on a Bruker AМ-300 instrument (300.13, 75.47 and 21.69 MHz, respectively) in DMSO-d 6 at 299 K. The chemical shifts of 1 H and 13 C nuclei were reported relative to TMS, for 14 Nrelative to MeNO 2 , high-filed chemical shifts are given with a minus sign. High-resolution mass spectra with electrospray ionization were recorded on a Bruker MicroOTOF II instrument. Elemental analysis was performed on a PerkinElmer 2400 Series II instrument. The reaction progress and purity of the obtained compounds were controlled by TLC on Merck Silicagel 60 F 254 plates. Visualization of spots on TLC plate was accomplished with UV light (254 nm). Density was determined by helium gas pycnometer AccuPyc II 1340 at 298 K. Enthalpy of formation values were determined with high-precision combustion bomb calorimeter developed in Semenov Institute of Chemical physics. [1,2] Impact and friction sensitivities were measured with BAM-type apparatus in a series of experiments according to STANAG procedures. [3,4] Detonation parameters were calculated with Smirnov [5] and Kamlet-Jacobs equations. [6] Thermal stability of the compounds was monitored using DSC 204 HP (Netzsch) apparatus. Samples 0.5-2 mg mass were placed in closed Al pans with laser-cut pinholes and heated at constant rate of 5 K min-1 rates under nitrogen flow (100 ml min-1). Environmental pressure was increased to 2 MPa for selected materials to reveal the decomposition rather than evaporation. [7] Materials Most of the reagents and starting materials were purchased from commercial sources and used without additional purification. The starting 3,5-dinitroaniline (1c), [8] 1-(4nitrophenyl)-1H-1,2,3,4-tetrazole (4a) [9] , 1-(3-nitrophenyl)-1H-1,2,3,4-tetrazole (4b), [10] 4nitroazidobenzene 5a [11] and 3-nitroazidobenzene 5b [12] were obtained published procedures. Caution! Although we have encountered no difficulties during preparation and handling of these compounds, they are potentially explosive energetic materials. Manipulations must be carried out by using appropriate standard safety precautions (earthed equipment, Kevlar® gloves, Kevlar® sleeves, face shield, leather coat, and ear plugs). General procedure for synthesis of hydrazones 2а-d. [13] A suspension of appropriate amine 1а-d (0.02 mol) in hydrochloric acid (19%, 30 ml) was stirred at 0-5 o C and treated by dropwise addition of a solution NaNO 2 (1.86 g, 0.027 mol) in H 2 O (6 ml). The mixture was stirred for 40 min, gave a solution of the diazonium salt.
The vibrational spectrum of the formic acid dimer in the OH stretch region is calculated by solvi... more The vibrational spectrum of the formic acid dimer in the OH stretch region is calculated by solving a 3D vibrational Schr odinger equation and employing an electronic potential and dipole moment calculated at the MP2 level of theory. Two Raman-active bands of the symmetric OH stretch fundamental are located around 2600 cm À1 ; the gap between them ($300 cm À1) is caused by concerted proton tunneling. IR-active bands around 3100 cm À1 are assigned to the antisymmetric OH stretch fundamental, its ®rst overtone and two complex transitions. The calculated H =D isotope eect on the intensity of the antisymmetric OH fundamental is 1.92.
Поступила в редакцию 30.05.2016 г. Aqueous solutions of glycine, phenylalanine and proline were s... more Поступила в редакцию 30.05.2016 г. Aqueous solutions of glycine, phenylalanine and proline were studied using the classical MD simulations. The amino acids were described by Amber and OPLS-AA force fields. The SPC/E and TIP3P models were used for water. Pair correlation functions of the amino acids evaluated using the Amber-TIP3P scheme agree well with the experimental data. This scheme was used in the subsequent simulations. The IR spectrum was obtained from Fourier transform of the autocorrelation function of classical dipole moment of the amino acids. The theoretical frequencies of the IR-intensive bands of glycine in water, associated with N−H and C−H stretching, and N−H bending vibrations, agree with the experimental data. The appearance of band near 2300 cm-1 is a characteristic feature of the theoretical IR spectra of aqueous glycine and phenylalanine. This band is associated with the stretching vibrations of the NH 3 + group forming strong +N−H…O w bonds with the adjacent water molecules. This band appears in the experimental IR spectrum of aqueous solution of glycine, and was treated as a combination band (Spectrochim. Acta A 61 (2005) 2741). In the theoretical IR spectrum of proline no band around 2300 cm-1 was obtained. This difference could be explained by inability of the proline NH 2 + group to form strong +N−H…O w bonds with water molecules.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The adiabatic separation of the vibrational variables of a hydrogen-bonded AHA fragment with a sy... more The adiabatic separation of the vibrational variables of a hydrogen-bonded AHA fragment with a symmetric double-well potential is considered using two approaches. In the first approach the A... A stretch vibration is slow in comparison to the proton vibration. It is applicable to the energy level calculations of an AHA fragment with a potential barrier of arbitrary height. In the alternative approach the proton is considered to be a "slow" subsystem. This approach appears to be of limited applicability. For an AHA fragment with a symmetric double-well potential the Born-Oppenheimer criterion is shown to contain the frequency corresponding to the proton 0 ~ 2 transition in both approaches.
ChemInform Abstract Die Racemisierung der Antipo-den (I) F' (II) wird durch verschiedene Russsort... more ChemInform Abstract Die Racemisierung der Antipo-den (I) F' (II) wird durch verschiedene Russsorten katalysiert und die Art der Modifizierung des Katalysators in seiner kinetischen Wirksamkeit diskutiert. Die Herstellung dieser Verbindungen aus optisch aktivem 1,1 '-Binaphthyl durch z.B. Bromierung, Nitrierung etc. wird angegeben. (IR-, NMR-, MS-Daten).
Rapid progress in organic electronics demands new highly efficient organic semiconducting materia... more Rapid progress in organic electronics demands new highly efficient organic semiconducting materials. Nevertheless, only few materials have been created so far that show reliable band-like transport with high charge mobilities, which reflects the two main obstacles in the field: the poor understanding of charge transport in organic semiconductors (OSs) and the difficulty of its quantification in devices. Here, we present a spectroscopic method for assessment of the charge transport in organic semiconductors. We show that the intensities of the lowfrequency Raman spectrum allow calculation of the dynamic disorder that limits the charge carrier mobility. The spectroscopically evaluated mobility clearly correlates with the device charge mobility reported for various OSs. The proposed spectroscopic method can serve as a powerful tool for a focused search of new materials and highlights the disorder bottleneck in the intrinsic charge transport in high-mobility organic semiconductors.
Anharmonic frequencies of the O PPP H PPP O fragment of H O q were evaluated using the adiabatic ... more Anharmonic frequencies of the O PPP H PPP O fragment of H O q were evaluated using the adiabatic separation of 5 2 Ž. vibrational variables. The relaxed 3D potential energy surface was calculated by the MP2 method using the T O DZP basis y1 w set. The symmetric and asymmetric stretching frequencies obtained, 588 and 1226 cm , agree with previous 2D results L. Ž. x Ojamae et al., Int. J. Quantum Chem. Symp. 29 1995 657 and show a modest shift from the harmonic values only. Thë O PPP H PPP O bending frequency is ca. 1025 cm y1 , significantly lower than the harmonic result of 1524 cm y1. Comparison is made with results of MD simulations using ab initio forces.
International Reviews in Physical Chemistry, Jul 1, 2009
Ability to form a strong quasisymmetric H-bond is a fundamental property of the proton. This H-bo... more Ability to form a strong quasisymmetric H-bond is a fundamental property of the proton. This H-bond determines the stability of the proton hydrates and acid–base complexes, which defines the specific features (catalytic, electrochemical, etc.) of acidic solutions. The protonated water dimer can be treated as a simplest stable proton hydrate in aqueous acid solutions. Its lifetime is larger than characteristic
Uploads
Papers by Mikhail Vener