scholarly journals Raman and infrared spectra, conformations and ab initio calculations of 3-methoxymethylene-2,4-pentanedione

2015 ◽  
Vol 8 (2) ◽  
pp. 203-216
Author(s):  
Anton Gatial ◽  
Viktor Milata ◽  
Nadežda Prónayová ◽  
Klaus Herzog ◽  
Reiner Salzer
Keyword(s):  
Ab Initio ◽  
Vibrational Spectra ◽  
Methoxy Group ◽  
Solid Phase ◽  
Polarizable Continuum Model ◽  
Basis Sets ◽  
Crystalline Solid ◽  
Heavy Atoms ◽  
Different Temperatures ◽  
Wide Scale

Abstract The IR (4000-400 cm-1) and Raman (4000-50 cm-1) spectra of 3-methoxymethylene-2,4-pentanedione [H3C-O-CH=C(COCH3)2] as a liquid and solutes in various solvents of different polarity have been recorded at ambient temperature. Additional IR and Raman spectra were obtained for amorphous and crystalline solid state at low temperature. The vibrational spectra revealed that the compound exists at least in two dominant conformers of different polarity and that the conformer present in the solid phase is less polar. NMR spectra in various solvents at different temperatures were also obtained. The compound can exist in several conformers due to the rotation around O-C= and both =C-C bonds with planar or nonplanar arrangements of heavy atoms. Ab initio MP2 and DFT calculations using a wide scale of basis sets were carried out. According to these calculations six conformational structures of the eight theoretically possible conformational structures with the methoxy group oriented as anti or syn and carbonyl groups oriented as Z or E towards the C=C double bond were obtained at potential energy surface. It has been shown that the conformers with the E orientations of both acetyl groups are not the stable ones. The calculated ab initio MP2 and DFT energies of all found conformers in vacuum suggest the most stable ZEa conformer where Z and E regard to the trans and cis acetyl groups, respectively and a denotes the orientation of the methoxy group. The EZa conformer was calculated as the second most stable one with the energy by at least 10 kJ mol-1 higher. Corrections of the relative energies of single conformers obtained in vacuum on the polar surroundings were done by including the solvent effect into the calculations using IEF Polarizable Continuum Model. Assignments of the vibrational spectra for the studied compound were made with the aid of normal coordinate calculations employing scaled ab initio force field. The scaled ab initio frequencies as well as calculated energies indicate that ZEa is the conformer present in the solid phase.

scholarly journals DFT calculation and assignment of vibrational spectra of aryl and alkyl chlorophosphates

2014 ◽  
Vol 12 (2) ◽  
pp. 153-163
Author(s):  
Viktor Anishchenko ◽  
Vladimir Rybachenko ◽  
Konstantin Chotiy ◽  
Andrey Redko
Keyword(s):  
Vibrational Spectra ◽  
Basis Sets ◽  
Heavy Atoms ◽  
Wide Range ◽  
Complete Assignment ◽  
Key Factor ◽  
Polarization Functions ◽  
Experimental Values ◽  
Semi Empirical ◽  
Good Agreement

AbstractDFT calculations of vibrational spectra of chlorophosphates using wide range of basis sets and hybrid functionals were performed. Good agreement between calculated and experimental vibrational spectra was reached by the combination of non-empirical functional PBE0 with both middle and large basis sets. The frequencies of the stretching vibrations of the phosphate group calculated using semi-empirical functional B3LYP for all basis sets deviate significantly from the experimental values. The number of polarization functions on heavy atoms was shown to be a key factor for the calculation of vibrational frequencies of organophosphates. The importance of consideration of all the stable rotamers for a complete assignment of fundamental modes was shown.

Borinine (Borabenzene): Its Structure and Vibrational Spectrum. A Quantumchemical Study

1987 ◽  
Vol 42 (4) ◽  
pp. 352-360 ◽  
Author(s):  
Gerhard Raabe ◽  
Wolfgang Schleker ◽  
Eberhard Heyne ◽  
Jörg Fleischhauer
Keyword(s):  
Electronic Structure ◽  
Vibrational Spectrum ◽  
Ab Initio ◽  
Vibrational Spectra ◽  
Photoelectron Spectrum ◽  
High Reactivity ◽  
Basis Sets ◽  
Rare Gas ◽  
Ab Initio Theory ◽  
Semiempirical Mndo

Recently we reported the results of some semiempirical and ab initio studies in which we compared the electronic structure of the hitherto unknown borinine with those of benzene and pyridine. The results of our calculations led us to the conclusion that the elusive nature of borabenzene is caused by its high reactivity, which might at least in part be due to the pronounced σ acceptor properties of a low-lying σ* molecular orbital.We now present the results of further ab initio and semiempirical (MNDO) investigations in which we performed full geometry optimizations for the molecule using two different basis sets (STO-3G, 4-31G) and also calculated the vibrational spectra of the 10B and 11B isotopomeric borabenzene molecules at the 4-31 G level of ab initio theory and with the semiempirical MNDO method.The calculated vibrational spectrum might be helpful to the experimentalist in identifying the molecule, for example trapped in a rare gas matrix among the side products.The calculated orbital energies can be useful in identifying the molecule by means of its photoelectron spectrum.

scholarly journals ab-Initio Study of Hydrogen Bond Networks in 1,2,3-Triazole Phases

Molecules ◽  
2020 ◽  
Vol 25 (23) ◽  
pp. 5722
Author(s):  
Christopher Peschel ◽  
Christian Dreßler ◽  
Daniel Sebastiani
Keyword(s):  
Ab Initio ◽  
Solid Phase ◽  
Temperature Limit ◽  
Proton Conduction ◽  
Dynamics Simulation ◽  
Ab Initio Molecular Dynamics ◽  
Ab Initio Study ◽  
Hydrogen Bond Networks ◽  
Different Temperatures ◽  
Dynamical Properties

The research in storage and conversion of energy is an everlasting process. The use of fuel cells is very tempting but up to now there are still several conceptual challenges to overcome. Especially, the requirement of liquid water causes difficulties due to the temperature limit. Therefore, imidazoles and triazoles are increasingly investigated in a manifold of experimental and theoretical publications as they are both very promising in overcoming this problem. Recently, triazoles were found to be superior to imidazoles in proton conduction. An ab-initio molecular dynamics simulation of pure triazole phases for investigating the behavior of both tautomer species of the triazole molecule has never been done. In this work, we investigate the structural and dynamical properties of two different solid phases and the liquid phase at two different temperatures. We are able to show how the distinct tautomers contribute to the mechanism of proton conduction, to compute dynamical properties of the four systems and to suggest a mechanism of reorientation in solid phase.

Ab initio and Semiempirical Studies on H3C-B=O and H-B=O. Their Structure and Vibrational Spectra

1987 ◽  
Vol 42 (9) ◽  
pp. 1027-1036
Author(s):  
Gerhard Raabe ◽  
Wolfgang Schleker ◽  
Wolfgang Straßburger ◽  
Eberhard Heyne ◽  
Jörg Fleischhauer ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Vibrational Spectra ◽  
Basis Sets ◽  
Vertical Ionization Potential ◽  
Methyl Substitution ◽  
Isotopic Shifts ◽  
The Difference ◽  
Semiempirical Mndo

The electronic structure of H3C -BO and H - BO is elucidated employing one determinant ab initio calculations with STO-3G and 4-31G basis sets and the semiempirical MNDO theory. The vibrational spectra of both molecules including various isotopic shifts have been calculated at the 4-31G level. The influence of methyl substitution on the vibrational frequencies, BO stretching force constant, Mulliken charges, and vertical ionization potential is examined and compared with that in the pairs H-CN/H3C-CN and H-NC/H3C-NC , isoelectronic with H-BO/H3C-BO.As judged from a comparison of the force constants for stretching the XY bonds in the H3C -XY and H-XY molecules, the XY bond is “softened” upon methyl substitution. This effect is found to decrease in the order H3C-BO>H3C-CN>H3C-NC.For XY=BO the difference between the first ionization potentials of H-XY and H3C-XY is found to be somewhat smaller than for XY = CN but slightly higher than for the isonitril compounds (XY = NC).

Synthesis, Characterization and TheoreticalStudies of Nand#39;-(4-methoxybenzylidene)benzenesulfonohydrazide

2021 ◽  
Vol 43 (2) ◽  
pp. 212-212
Author(s):  
H G zin Aslan and L tfiye Aydin H G zin Aslan and L tfiye Aydin
Keyword(s):  
Potential Energy ◽  
Gas Phase ◽  
Vibrational Spectra ◽  
Potential Energy Surfaces ◽  
Solid Phase ◽  
Nbo Analysis ◽  
Basis Set ◽  
Basis Sets ◽  
Stable Conformer ◽  
Energy Surfaces

Nand#39;-(4-methoxybenzylidene)benzenesulfonohydrazide was synthesized and elemental analysis was conducted; IR, Raman, 1H, and 13C NMR spectral data were recorded. The potential energy surfaces (PES) of the Nand#39;-(4-methoxybenzylidene)benzenesulfonohydrazide molecule were obtained by selected degree of torsional freedom, which varied from 0o to 360and#186; in 4and#186; increments. The conformers were optimized by using a (DFT/B3LYP/6-31G(d,p)) basis set in the gas phase. The eleven conformers in the gas phase of the obtained molecule were determined and the most stable conformer (conformer 1) was re-optimized by three different basis sets of 6-31G(d,p), 6-311G(d,p), and LanL2Dz. HOMO-LUMO analyses were performed. NBO analysis was performed to describe the around of intramolecular charge transfer. The vibrational spectra were measured in solid phase IR and detailed analysis of the vibrational spectra of conformer 1 was done; all the bands of the spectra were interpreted by the use of the potential energy distributions (PED) and the molecular electrostatic potential (MEP) was plotted.

Experimental and Theoretical (ab initio and DFT) Analysis of UV-Vis Spectra, Thermodynamic Functions and Non-linear Optical Properties of 2-Chloro-3,4-Dimethoxybenzaldehyde

2015 ◽  
Vol 8 (2) ◽  
pp. 2122-2134
Author(s):  
Sarvendra Kumar ◽  
Rajesh Kumar ◽  
Jayant Teotia ◽  
M. K. Yadav
Keyword(s):  
Thermodynamic Functions ◽  
Title Compound ◽  
Density Functional ◽  
Structural Characteristics ◽  
Basis Sets ◽  
Ultraviolet Absorption Spectrum ◽  
Non Linear ◽  
Different Temperatures ◽  
Linear Optical Properties ◽  
Linear Optical

In the present work, UV- Visible spectra of 2-Chloro-3,4-Dimethoxybenzaldehyde (2,3,4-CDMB) compound  have been carried out experimentally and theoretically. The ultraviolet absorption spectrum of title compound in three solvents (Acetone, Diethyl Ether, CCl4) of different polarity were examined in the range of 200–500 nm. The structure of the molecule was optimized and the structural characteristics were determined by HF and DFT (B3LYP) methods with 6-31+G(d,p) and 6-311++G(d,p) as basis sets. The excitation energy, wavelength corresponds to absorption maxima () and oscillator strength (f) are calculated by Time-Dependent Density Functional Theory (TD-DFT) using B3LYP/6-31+G(d,p) and B3LYP/6-311++G(d,p) as basis sets. The electric dipole moment (μ), polarizability (α) and the first hyperpolarizability (β ) have been computed to evaluate the non-linear optical (NLO) response of the investigated compound by HF and DFT (B3LYP) with already mentioned basis sets. Thermodynamic functions of the title compound at different temperatures were also calculated.

A Systematic DFT Study of Two Elementary Steps Involving Hydrogen Peroxide and the Hydroxyl Radical in the Fenton Reaction

2018 ◽  
Author(s):  
Danilo Carmona ◽  
David Contreras ◽  
Oscar A. Douglas-Gallardo ◽  
Stefan Vogt-Geisse ◽  
Pablo Jaque ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Hydroxyl Radical ◽  
Ab Initio ◽  
Fenton Reaction ◽  
Basis Set ◽  
Basis Sets ◽  
Dft Methods ◽  
Elementary Steps ◽  
Oxygen Oxygen ◽  
Complete Basis Set

The Fenton reaction plays a central role in many chemical and biological processes and has various applications as e.g. water remediation. The reaction consists of the iron-catalyzed homolytic cleavage of the oxygen-oxygen bond in the hydrogen peroxide molecule and the reduction of the hydroxyl radical. Here, we study these two elementary steps with high-level ab-initio calculations at the complete basis set limit and address the performance of different DFT methods following a specific classification based on the Jacob´s ladder in combination with various Pople's basis sets. Ab-initio calculations at the complete basis set limit are in agreement to experimental reference data and identified a significant contribution of the electron correlation energy to the bond dissociation energy (BDE) of the oxygen-oxygen bond in hydrogen peroxide and the electron affinity (EA) of the hydroxyl radical. The studied DFT methods were able to reproduce the ab-initio reference values, although no functional was particularly better for both reactions. The inclusion of HF exchange in the DFT functionals lead in most cases to larger deviations, which might be related to the poor description of the two reactions by the HF method. Considering the computational cost, DFT methods provide better BDE and EA values than HF and post--HF methods with an almost MP2 or CCSD level of accuracy. However, no systematic general prediction of the error based on the employed functional could be established and no systematic improvement with increasing the size in the Pople's basis set was found, although for BDE values certain systematic basis set dependence was observed. Moreover, the quality of the hydrogen peroxide, hydroxyl radical and hydroxyl anion structures obtained from these functionals was compared to experimental reference data. In general, bond lengths were well reproduced and the error in the angles were between one and two degrees with some systematic trend with the basis sets. From our results we conclude that DFT methods present a computationally less expensive alternative to describe the two elementary steps of the Fenton reaction. However, choice of approximated functionals and basis sets must be carefully done and the provided benchmark allows a systematic validation of the electronic structure method to be employed

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