Theoretical Study of Solvent Effect on π-EDA Complexation I. SCF and DFT Calculations Within Polarized Continuum Model on TCNE-Benzene Complex

2003 ◽  
Vol 68 (12) ◽  
pp. 2355-2376 ◽  
Author(s):  
Ondrej Kyseľ ◽  
György Juhász ◽  
Pavel Mach
Keyword(s):  
Complex Formation ◽  
Gibbs Energy ◽  
Solvent Effect ◽  
Gas Phase ◽  
Continuum Model ◽  
Solvent Polarity ◽  
Polar Solvents ◽  
Complexation Constant ◽  
Polarized Continuum Model ◽  
Eda Complex

SCF, MP2, DFT(B3LYP) and the polarizable continuum model (PCM) were used to study geometry, charge distribution and energetics of the π-EDA complex formation between tetracyanoethene (TCNE) and benzene both in gas phase and in various polar solvents (cyclohexane, dichloromethane and water). MP2/6-31G*, MP2/6-31+G*, MP2/6-31G*(0.25) calculations have shown that geometry of the complex is planparallel with interplane distance of 3.05 × 10-10 m on the MP2/6-31G* level and the complexation energy is equal to -6.8 to -8.95 kcal/mol, while dominant contributions to the complexation energy come from intermolecular correlation and energy. The PCM continuum model of polar solvents describes well both the Gibbs energy of solvation of individual solutes and the difference between the complex and its constituents and also agrees with the experimental finding that the polar solvent effect decreases the complexation constant of the π-EDA complex formation by a factor of 2-4 when chloroform is replaced by more polar dichloromethane, and by a factor of 9, when tetrachlormethane is replaced by dichloromethane. It seems that the solvation Gibbs energy of the π-EDA complex formation always prefers stability of solvated constituents to that of the solvated complex. The electrostatic polarization Gibbs energy of solvation is responsible for the tendency of complexation constants to decrease with increasing solvent polarity; however, non-electrostatic terms contribute as well. While the enthalpy of complexation between benzene and TCNE in gas phase is about -10.0 kcal/mol due to the negative complexation entropy ∆(∆S) = -22.56 cal/mol K, the ∆G of complexation is -3.8 kcal/mol. The solvation part of the complexation Gibbs energy in dichloromethane is +5.14 kcal/mol (PCM-SCF/6-31G* calculation) so that complexation constant K = 0.1 dm3/mol in this solvent was found.

scholarly journals PROTON TRANSFER IN PHOSPHORUS-CONTAINING ACID–N,N-DIMETHYLFORMAMIDE SYSTEM WITH GLANCE OF ENVIRONMENT

2018 ◽  
Vol 59 (6) ◽  
pp. 37
Author(s):  
Lyubov P. Safonova ◽  
Irina V. Fedorova ◽  
Michael A. Krestyaninov
Keyword(s):  
Proton Transfer ◽  
Solvent Effect ◽  
Gas Phase ◽  
Energy Barrier ◽  
Continuum Model ◽  
Energy Surface ◽  
Molecular Complexes ◽  
Transfer Processes ◽  
Polarized Continuum Model ◽  
Phosphorus Containing

Proton transfer processes in the molecular and ion-molecular complexes of phosphorus acids (phosphoric H3PO4, phosphorous H3PO3, methylphosphonic СН3Н2РО3) with N,N-dimethylformamide (DMF) was studied. The potential energy surface (PES) for proton transfer was studied using the B3LYP/6-31++G(d,p) level of theory, and the solvent effect (here DMF) on the PES was included using the conductor polarized continuum model (CPCM). For all cases, the energy profile for proton transfer represents a double well curve, if intermolecular O…Odistance for the hydrogen bond considered has a fixed length equal to 2.7 Å. The solvent effect favors a proton transfer in the molecular complexes, but no shift of the equilibrium towards ionic pairs is observed. As a result, the energy values associated with proton transfer are significantly reduced in comparison with those found for the gas phase. The proton transfer in the complexes of H3PO4 with DMF is more favored than this process for the cases with H3PO3 and СН3Н2РО3. The probability of proton transfer in the Н3РО4–DMF and (Н3РО4)2–DMF is nearly identical. On the contrary, the barrier height for transfer in Н3РО4–(DMF)n for n=1÷3 increases with increasing number of DMF molecules. The energy barrier for proton transfer in the DMFH+–DMF and H3PO4–H2PO4– is lower than the ones for the molecular complexes.

Solvent and temperature effects on the tautomerization of a carbonitrile molecule: A conductor-like polarizable continuum model (CPCM) study

2021 ◽  
Vol 20 (1) ◽  
pp. 59-68
Author(s):  
Zohreh Khanjari ◽  
Bita Mohtat ◽  
Reza Ghiasi ◽  
Hoorieh Djahaniani ◽  
Farahnaz Kargar Behbahani
Keyword(s):  
Gas Phase ◽  
Solvent Effects ◽  
Continuum Model ◽  
Solvent Polarity ◽  
Polarizable Continuum Model ◽  
Dielectric Constants ◽  
Frontier Orbitals ◽  
Reaction Field ◽  
Polarizable Continuum ◽  
Homo Lumo

This research examined the effects of solvent polarity and temperature on the tautomerization of a carbonitrile molecule at CAM-B3LYP/6-311G (d,p) level of theory. The selected solvents were n-hexane, diethyl ether, pyridine, ethanol, methanol, and water. The solvent effects were examined by the self-consistent reaction field theory (SCRF) based on conductor-like polarizable continuum model (CPCM). The solvent effects were explored on the energy barrier, frontier orbitals energies, and HOMO-LUMO gap. Dependencies of thermodynamic parameters (ΔG and ΔH) on the dielectric constants of solvents were also tested. Specifically, the temperature dependencies of the thermodynamics parameters were studied within 100–1000 K range. The rate constant of the tautomerism reaction was computed from 300 to 1200 K, in the gas phase.

scholarly journals Improving Solvation Energy Predictions Using The SMD Solvation Method and Semiempirical Electronic Structure Methods

2018 ◽  
Author(s):  
Jimmy C. Kromann ◽  
Casper Steinmann ◽  
Jan Halborg Jensen
Keyword(s):  
Continuum Model ◽  
Solvation Energy ◽  
Solvation Model ◽  
Polar Solvents ◽  
Data Set ◽  
Solvation Energies ◽  
Polarized Continuum Model ◽  
Electronic Structure Methods ◽  
Aqueous Solvation ◽  
Model C

The PM6 implementation in the GAMESS program is extended to elements requiring d-integrals and interfaced with the conducter-like polarized continuum model (C-PCM) of solvation, in- cluding gradients. The accuracy of aqueous solvation energies computed using AM1, PM3, PM6, and DFTB and the SMD continuum solvation model is tested using the MNSOL data set. The errors in SMD solvation energies predicted using NDDO-based methods is considerably larger than when using DFT and HF, with RMSE values of 3.4-5.9 (neutrals) and 6-15 kcal/mol (ions) compared to 2.4 and ca 5 kcal/mol for HF/6-31G(d). For the NDDO-based methods the errors are especially large for cations and considerably higher than the corresponding COSMO results, which suggests that the NDDO/SMD results can be improved by re-parameterizing the SMD parameters focusing on ions. We found the best results are obtained by changing only the radii for hydrogen, carbon, oxygen, nitrogen, and sulfur and this leads to RMSE values for PM3 (neutrals: 2.8/ions: ca 5 kcal/mol), PM6 (4.7/ca 5 kcal/mol), and DFTB (3.9/ca 5 kcal/mol) that are more comparable to HF/6-31G(d) (2.4/ca 5 kcal/mol). Though the radii are optimized to reproduce aqueous solvation energies, they also lead more accurate predictions for other polar solvents such as DMSO, acetonitrile, and methanol, while the improvements for non-polar solvents are negligible.

scholarly journals Effects of Solvent Polarity on Solvation Free Energy, Dipole Moment, Polarizability, Hyperpolarizability and Molecular Properties of Metronidazole

2016 ◽  
Vol 19 (1) ◽  
pp. 9-14 ◽  
Author(s):  
Mohammad Firoz Khan ◽  
Ridwan Bin Rashid ◽  
Md Yeunus Mian ◽  
Mohammad S Rahman ◽  
Mohammad A Rashid
Keyword(s):  
Free Energy ◽  
Dipole Moment ◽  
Gas Phase ◽  
Chemical Potential ◽  
Solvent Polarity ◽  
Solvation Free Energy ◽  
Molecular Properties ◽  
Chemical Hardness ◽  
Electrophilicity Index ◽  
Polar Solvents

A computational study of medium effect on solvation free energy, dipole moment, polarizability, hyperpolarizability and different molecular properties like chemical hardness & softness, chemical potential, electronegativity and electrophilicity index of metronidazole have been reported in this paper. Becke, 3-parameter, Lee-Yang-Parr (B3LYP) level of theory with 6-31G (d,p) basis set was applied for gas phase and solution. The effect of solvent polarity on solvation free energy, dipole moment, polarizability, hyperpolarizability and molecular properties were calculated by employing Solvation Model on Density (SMD). The solvation free energies and dipole moment of metronidazole were found to be increased in nonpolar to polar solvents. The dipole moment of metronidazole was higher in different solvent than that of the gas phase. Moreover, from non-polar to polar solvents the chemical potential, electronegativity and electrophilicity index were increased. On the other hand, opposite relation was found in the case of chemical hardness and softness. The results obtained in this study may lead to understand the stability and reactivity of metronidazole and the results will be of assistance to use the title molecule as reaction intermediates and pharmaceuticals.Bangladesh Pharmaceutical Journal 19(1): 9-14, 2016

scholarly journals Improving Solvation Energy Predictions Using The SMD Solvation Method and Semiempirical Electronic Structure Methods

2018 ◽  
Author(s):  
Jimmy C. Kromann ◽  
Casper Steinmann ◽  
Jan Halborg Jensen
Keyword(s):  
Continuum Model ◽  
Solvation Energy ◽  
Solvation Model ◽  
Polar Solvents ◽  
Data Set ◽  
Solvation Energies ◽  
Polarized Continuum Model ◽  
Electronic Structure Methods ◽  
Aqueous Solvation ◽  
Model C

The PM6 implementation in the GAMESS program is extended to elements requiring d-integrals and interfaced with the conducter-like polarized continuum model (C-PCM) of solvation, in- cluding gradients. The accuracy of aqueous solvation energies computed using AM1, PM3, PM6, and DFTB and the SMD continuum solvation model is tested using the MNSOL data set. The errors in SMD solvation energies predicted using NDDO-based methods is considerably larger than when using DFT and HF, with RMSE values of 3.4-5.9 (neutrals) and 6-15 kcal/mol (ions) compared to 2.4 and ca 5 kcal/mol for HF/6-31G(d). For the NDDO-based methods the errors are especially large for cations and considerably higher than the corresponding COSMO results, which suggests that the NDDO/SMD results can be improved by re-parameterizing the SMD parameters focusing on ions. We found the best results are obtained by changing only the radii for hydrogen, carbon, oxygen, nitrogen, and sulfur and this leads to RMSE values for PM3 (neutrals: 2.8/ions: ca 5 kcal/mol), PM6 (4.7/ca 5 kcal/mol), and DFTB (3.9/ca 5 kcal/mol) that are more comparable to HF/6-31G(d) (2.4/ca 5 kcal/mol). Though the radii are optimized to reproduce aqueous solvation energies, they also lead more accurate predictions for other polar solvents such as DMSO, acetonitrile, and methanol, while the improvements for non-polar solvents are negligible.

scholarly journals Solvation enthalpies of the proton in polar and non-polar solvents: Theoretical study

2013 ◽  
Vol 6 (1) ◽  
pp. 60-63 ◽  
Author(s):  
Lenka Rottmannová ◽  
Peter Škorňa ◽  
Ján Rimarčík ◽  
Vladimír Lukeš ◽  
Erik Klein
Keyword(s):  
Integral Equation ◽  
Proton Transfer ◽  
Continuum Model ◽  
Theoretical Study ◽  
Solvent Molecule ◽  
Solution Phase ◽  
Basis Sets ◽  
Polar Solvents ◽  
Polarized Continuum Model ◽  
Acceptor Atom

Abstract In spite of the importance of proton transfer in solution-phase processes, there is still no systematic theoretical study of proton solvation enthalpies. We have investigated the solvation enthalpies of the proton in seven solvents of various polarities (benzene, chloroform, acetone, methanol, ethanol, DMSO, water) using the Integral Equation Formalism Polarized Continuum Model (IEF-PCM). All computations were performed at the B3LYP and BHLYP levels of theory with aug-cc-pVDZ, aug-cc-pVTZ and aug-cc-pVQZ basis sets. Our calculations have shown that the B3LYP and BHLYP functionals provide similar solvation enthalpies. Finally, differences in the solvation enthalpy of the proton values stemming from the various basis sets do not exceed 6 kJ mol-1, with exception of DMSO and chloroform. Distance between H+ and the acceptor atom of the solvent molecule is the shortest in the case of water. It has been also found that the B3LYP distances are slightly longer.

On N-acetylcysteine. Part I. Experimental and theoretical approaches of the N-acetylcysteine/H2O2complexation

1994 ◽  
Vol 72 (10) ◽  
pp. 2094-2101 ◽  
Author(s):  
Jlil Arroub ◽  
Jacqueline Bergès ◽  
Zohreh Abedinzadeh ◽  
Jacqueline Langlet ◽  
Monique Gardès-Albert
Keyword(s):  
Hydrogen Peroxide ◽  
Complex Formation ◽  
Solvent Effect ◽  
Equilibrium Constant ◽  
Thermodynamic Equilibrium ◽  
Continuum Model ◽  
Theoretical Calculations ◽  
Thermodynamic Equilibrium Constant ◽  
Theoretical Approaches ◽  
Biphasic Process

The complexation of N-acetylcysteine (RSH) with hydrogen peroxide has been studied experimentally and theoretically. Experimentally we have measured the evolution of RSH, H2O2, and RSSR (N-acetylcystine) as a function of time. Surprisingly, H2O2 decays by a biphasic process, which is not the case for RSH and RSSR. In the first stage of the kinetics, H2O2 disappears without oxidizing the thiol function of RSH. By analogy with glutathione (GSH), the formation of a complex between RSH and H2O2 has been proposed. The thermodynamic equilibrium constant of complex formation has been determined. Theoretical calculations were performed within the SIBFA method to pinpoint the sites of complexation in isolated and hydrated states. A mixed "discrete–continuum" model was used to evaluate the solvent effect. The two stable complexes found in isolated state have different behaviour under the influence of the solvent. Comparison with complexed GSH is discussed.

scholarly journals Solvation enthalpies of the electron in polar and non-polar solvents: Theoretical study

2014 ◽  
Vol 7 (1) ◽  
pp. 31-33 ◽  
Author(s):  
Peter Škorňa ◽  
Ján Rimarčík ◽  
Erik Klein
Keyword(s):  
Integral Equation ◽  
Electron Transfer ◽  
Continuum Model ◽  
Theoretical Study ◽  
Solution Phase ◽  
Basis Sets ◽  
Polar Solvents ◽  
Electron Solvation ◽  
Polarized Continuum Model ◽  
Benzene Toluene

Abstract Although the electron transfer is a part of many important processes in biosystems that occur in the solution-phase, there is still no systematic theoretical study of the electron solvation enthalpies. The solvation enthalpies of the electron in different solvents of various polarities: benzene, toluene, acetone, methanol, ethanol, DMSO and water, are investigated. All calculations were performed by B3LYP, BHLYP and PBE approaches with aug-cc-pVDZ, aug-cc-pVTZ and aug-cc-pVQZ basis sets, using the Integral Equation Formalism Polarized Continuum Model (IEF-PCM). The calculations show that the B3LYP and PBE functionals provide similar results. With the exception of benzene, toluene and DMSO, the differences in values for all solvents are lower than 6 kJ mol-1. The BHLYP solvation enthalpies are higher by 20-25 kJ mol-1 than the B3LYP ones.

Comparison of Anion‐Anion Halogen Bonds with Neutral‐Anion Halogen Bonds in the Gas Phase and Polar Solvents

ChemPlusChem ◽  
2021 ◽  
Vol 86 (2) ◽  
pp. 232-240
Author(s):  
Ying Li ◽  
Lingpeng Meng ◽  
Yanli Zeng
Keyword(s):  
Gas Phase ◽  
Halogen Bonds ◽  
Polar Solvents

THEORETICAL CALCULATION OF pKb VALUES FOR ANILINES AND SULFONAMIDE DRUGS IN AQUEOUS SOLUTION

2012 ◽  
Vol 11 (02) ◽  
pp. 283-295 ◽  
Author(s):  
BAHRAM GHALAMI-CHOOBAR ◽  
ALI GHIAMI-SHOMAMI ◽  
PARIA NIKPARSA
Keyword(s):  
Gas Phase ◽  
Continuum Model ◽  
Correlation Equation ◽  
Polarizable Continuum Model ◽  
Free Energies ◽  
Pcm Model ◽  
Solvation Models ◽  
Polarizable Continuum ◽  
Better Than ◽  
Good Agreement

In this work, calculations of p K b values have been performed for aniline and its substituted derivatives and sulfonamide drugs by using Gaussian 98 software package. Gas-phase energies were calculated with HF /6-31 G ** and B3LYP /6-31 G ** levels of theory. Free energies of solvation have been computed using the polarizable continuum model (PCM), conductor-like polarizable continuum model (CPCM) and the integral equation formalism-polarizable continuum model (IEFPCM) at the same levels which have been used for geometry determination in the gas-phase. The results show that the calculated p K b values using the B3LYP /6-31 G ** are better than those using the corresponding HF /6-31 G **. At first, the correlation equation was found to determine the p K b values of the investigated anilines. Then, this correlation equation was used to calculate the p K b values of the sulfonamide drugs. The results obtained indicate that the PCM model is a suitable solvation model for calculating p K b values in comparison to the other solvation models. For the investigated compounds a good agreement between the experimental and the calculated p K b values was also observed.

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