scholarly journals A computational study of the fluctional behaviour of group 14 substituted ortho-semiquinone radicals

2011 ◽  
Vol 89 (2) ◽  
pp. 235-240 ◽  
Author(s):  
K. U. Ingold ◽  
Gino A. DiLabio
Keyword(s):  
Experimental Data ◽  
Density Functional Theory ◽  
Rate Constant ◽  
Density Functional ◽  
Computational Study ◽  
Group 14 ◽  
Functional Theory ◽  
Semiquinone Radicals ◽  
Experimental Values ◽  
Good Agreement

The dynamics of the 1,4-migration of some O-substituted 3,5-di-tert-butyl-ortho-semiquinone radicals have been calculated by density-functional theory (DFT). There is very good agreement in the rate constant and Arrhenius parameters between these calculations and experimental values for migration of H, D, and the Me3Si group. For the Me3Sn group, the calculations indicate an incredibly fast migration (k293K = 2.0 × 1012 s–1), a result that is consistent with experimental data (k293K > 109 s–1). Other O-substituents examined by DFT and compared with experimental data were H3C and Me2ClSn.

Density functional theory (DFT) and Hartree–Fock (HF) calculations of potential p–vinylbenzyl chloride-based macroinitiator for atom transfer radical polymerization

2016 ◽  
Vol 94 (3) ◽  
pp. 290-304 ◽  
Author(s):  
Feride Akman
Keyword(s):  
Experimental Data ◽  
Density Functional Theory ◽  
Potential Energy ◽  
Density Functional ◽  
Energy Surface ◽  
Functional Theory ◽  
Hartree Fock ◽  
Experimental Values ◽  
Good Agreement ◽  
Hf Calculations

The spectroscopic properties of poly (styrene–co–p–vinylbenzyl chloride) (poly (St-co-VBC)) were investigated by Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopic techniques. The molecular geometry and vibrational frequencies of macroinitiator, poly (St-co-VBC), were calculated by using density functional theory (DFT) and Hartree–Fock (HF) methods with 6–31 G+ (d, p) as a basis set. Calculated theoretical values are shown to be in good agreement with that of experimental values. An excellent harmony between the two data sets was verified. Besides, the experimental data of macroinitiator were compared with experimental data of its corresponding monomers such as St and VBC. The dimer and trimer forms of macroinitiator are used as significant contributions for getting an accurate interpretation of the experimental frequencies of poly (St-co-VBC). The results revealed that the change from St and VBC to poly (St-co-VBC) should be characterized by the disappearance of the CH2=CH bonds of the vinyl group and the appearance of the aliphatic C–H and CH2 bonds. The geometrical parameters, Mulliken atomic charges and frontier molecular orbitals energies were also calculated using the same theoretical methods. The chemical shifts were calculated by using the gauge–including atomic orbital method and all the theoretically predicted values were shown to be in good agreement with experimental values. Molecular orbital properties, molecular electrostatic potential, and the potential energy surface for the atom transfer radical polymerization (ATRP) of the macroinitiator were studied with DFT and HF calculations. The potential energy surface of the ATRP initiator is decided by their electronic effect and steric hindrance effect simultaneously.

scholarly journals Hetarylazopyrazolone Dyes Based on Benzothiazole and Benzimidazole Ring Systems: Synthesis, Spectroscopic Investigation, and Computational Study

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Ebru Aktan ◽  
Tahsin Uyar
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Computational Study ◽  
Benzimidazole Ring ◽  
Acid Base ◽  
Functional Theory ◽  
Ring Systems ◽  
Td Dft ◽  
Elemental Analyses ◽  
Experimental Values

In this study, the synthesized coupling component 1-(2-benzothiazolyl)-3-methylpyrazol-5-one reacted with diazotised heterocyclic amines to afford six novel hetarylazopyrazolone dyes. These azo dyes based on benzothiazole and benzimidazole ring systems were characterized by spectral methods and elemental analyses. The solvatochromic behaviors of these dyes in various solvents were evaluated. The ground state geometries of the dyes were optimized using density functional theory (DFT). Solvent, acid-base, and substituent influences on the wavelength of the maximum absorption were examined in detail. Time-dependent density functional theory (TD-DFT) calculations were performed to obtain the absorption spectra of the dyes in various solvents and the results compared with experimental values. Besides, frontier molecular orbitals (FMO) analysis for the dyes is also described from the computational process.

Ab Initio Study of Clean and Hydrogen-Saturated Unreconstructed SiC{0001} Surfaces

2007 ◽  
Vol 556-557 ◽  
pp. 493-496 ◽  
Author(s):  
Alexander Mattausch ◽  
T. Dannecker ◽  
Oleg Pankratov
Keyword(s):  
Experimental Data ◽  
Density Functional Theory ◽  
Density Functional ◽  
Surface States ◽  
Correlation Effects ◽  
Ab Initio Study ◽  
Functional Theory ◽  
Hubbard U ◽  
The Impact ◽  
Good Agreement

Using density functional theory, we investigate the 6H-SiC{0001} surfaces in the unreconstructed 1 × 1 and the H-passivated configuration. The strong correlation effects of the dangling bonds at the surface are treated by spin-polarised calculations including the Hubbard-U parameter. We find that the clean surfaces are semiconducting with surface states in good agreement with experimental data. The impact of the Hubbard-U is stronger on the C-terminated face. For the H-passivated surfaces we find resonances in the valence band. The antibonding C−H state is located in the upper part of the bandgap around the ¯􀀀-point.

Electronic structure and spectroscopy of homoleptic compounds of dimolybdenum using TDDFT

2016 ◽  
Vol 94 (1) ◽  
pp. 20-27
Author(s):  
Pere Vilarrubias
Keyword(s):  
Experimental Data ◽  
Density Functional Theory ◽  
Electronic Structure ◽  
Density Functional ◽  
Molecular Orbitals ◽  
Time Dependent ◽  
Electronic Transitions ◽  
Functional Theory ◽  
Dependent Density ◽  
Good Agreement

Ten compounds of dimolybdenum are studied using density functional theory and time-dependent density functional theory. The energy of the strongest symmetry-allowed bands is calculated. The results are then compared with experimental data, when available. The PW91 functional gives results for geometry and for the energy of the δ→δ* band that show good agreement with experimental data. However, the B3LYP functional gives more realistic values for the whole spectrum when the results are compared with experimental data. Finally, the different values of energy of these bands are explained analyzing the molecular orbitals involved in these transitions. Some ligands can act as an unsaturated system in conjugation with the delta bond, modifying the energies of the electronic transitions.

scholarly journals Mechanism, kinetics and selectivity of selenocyclization of 5-alkenylhydantoins: an experimental and computational study

2015 ◽  
Vol 11 ◽  
pp. 1865-1875 ◽  
Author(s):  
Biljana M Šmit ◽  
Radoslav Z Pavlović ◽  
Dejan A Milenković ◽  
Zoran S Marković
Keyword(s):  
Density Functional Theory ◽  
Double Bond ◽  
Density Functional ◽  
Computational Study ◽  
Theoretical Calculations ◽  
Reaction Products ◽  
Dft Methods ◽  
Functional Theory ◽  
H Nmr ◽  
Good Agreement

The mechanism and selectivity of a bicyclic hydantoin formation by selenium-induced cyclization are investigated. The proposed mechanism involves the intermediates formed by an electrophilic addition of the selenium reagent on a double bond of the starting 5-alkenylhydantoin prior the cyclization. These intermediates are readily converted into the more stable cyclic seleniranium cations. A key step of the mechanism is an intramolecular cyclization which is realized through an anti-attack of the internal nucleophile, the amidic nitrogen, to the seleniranium cation yielding the intermediate imidazolinium cations. Their deprotonation is followed by the formation of the fused bicyclic reaction products. Important intermediates and key transition states are studied by using density functional theory (DFT) methods. The pathways of the reaction are investigated in detail. There are two regioselective pathways related to 5-exo and 6-endo products. Theoretical calculations and the monitoring of the cyclization reaction using 1H NMR spectroscopy are in a good agreement with the proposed mechanism and are consistent with our experimental results. The preferred pathway for formation of 5-exo products is confirmed.

scholarly journals Computational Study of 3,4-Diphenyl-1,2,5-Thiadiazole 1-Oxide for Organic Photovoltaics

2009 ◽  
Vol 2009 ◽  
pp. 1-8 ◽  
Author(s):  
Daniel Glossman-Mitnik
Keyword(s):  
Molecular Structure ◽  
Experimental Data ◽  
Density Functional Theory ◽  
Free Energy ◽  
Density Functional ◽  
Computational Study ◽  
Chemical Reactivity ◽  
Functional Theory ◽  
Free Energy Of Solvation ◽  
Proposed Model

We make use of a model chemistry within Density Functional Theory (DFT) recently presented, which is called CHIH-DFT, to calculate the molecular structure of 3,4-diphenyl-1,2,5-thiadiazole 1-oxide (TSO), as well to predict its infrared (IR), ultraviolet (UV-Vis) and fluorescence (Fluo) spectra, the dipole moment and polarizability, the free energy of solvation in different solvents as an indication of solubility, and the chemical reactivity parameters that arise from Conceptual DFT. The calculated values are compared with the available experimental data for this molecule as a means of validation of our proposed model chemistry.

scholarly journals Theoretical study of the adsorption of benzene on coinage metals

2014 ◽  
Vol 10 ◽  
pp. 1775-1784 ◽  
Author(s):  
Werner Reckien ◽  
Melanie Eggers ◽  
Thomas Bredow
Keyword(s):  
Experimental Data ◽  
Density Functional Theory ◽  
Density Functional ◽  
Theoretical Study ◽  
Dispersion Correction ◽  
Functional Theory ◽  
Coinage Metals ◽  
Adsorption Energies ◽  
Theoretical Results ◽  
Good Agreement

The adsorption of benzene on the M(111), M(100) and M(110) surfaces of the coinage metals copper (M = Cu), silver (M = Ag) and gold (M = Au) is studied on the basis of density functional theory (DFT) calculations with an empirical dispersion correction (D3). Variants of the Perdew–Burke–Ernzerhof functionals (PBE, RPBE and RevPBE) in combination with different versions of the dispersion correction (D3 and D3(BJ)) are compared. PBE-D3, PBE-D3(BJ) and RPBE-D3 give similar results which exhibit a good agreement with experimental data. RevPBE-D3 and RevPBE-D3(BJ) tend to overestimate adsorption energies. The inclusion of three-center terms (PBE-D3(ABC)) leads to a slightly better agreement with the experiment in most cases. Vertical adsorbate–substrate distances are calculated and compared to previous theoretical results. The observed trends for the surfaces and metals are consistent with the calculated adsorption energies.

scholarly journals Relationship between crystal structure and thermo-mechanical properties of kaolinite clay: beyond standard density functional theory

2015 ◽  
Vol 44 (28) ◽  
pp. 12550-12560 ◽  
Author(s):  
Philippe F. Weck ◽  
Eunja Kim ◽  
Carlos F. Jové-Colón
Keyword(s):  
Crystal Structure ◽  
Mechanical Properties ◽  
Density Functional Theory ◽  
Density Functional ◽  
Dispersion Interactions ◽  
Kaolinite Clay ◽  
Functional Theory ◽  
Experimental Values ◽  
Good Agreement ◽  
Standard Density

The structural, mechanical and thermodynamic properties of 1 : 1 layered dioctahedral kaolinite clay, Al2Si2O5(OH)4, were investigated using density functional theory corrected for dispersion interactions. Good agreement is obtained with the recent experimental values reported for well-crystallized samples.

scholarly journals Terahertz Time Domain, Raman and Fourier Transform Infrared Spectroscopy of Acrylamide, and the Application of Density Functional Theory

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Ramzan Ullah ◽  
Salah Ud-Din Khan ◽  
Muhammad Aamir ◽  
Rasheed Ullah
Keyword(s):  
Density Functional Theory ◽  
Refractive Index ◽  
Time Domain ◽  
Density Functional ◽  
Frequency Range ◽  
Functional Theory ◽  
Average Value ◽  
Experimental Values ◽  
Good Agreement ◽  
Constant Refractive Index

We present terahertz time domain spectra of acrylamide in the frequency range from 0.2 to 2 THz with nearly constant refractive index having an average value of 1.33 and an absorption coefficient. Raman (95–3000 cm−1) and FTIR (450–4000 cm−1) spectra also show good agreement with density functional theory (DFT) B3LYP 6-311G++ (3df 3pd) calculations except C-H and N-H stretching frequencies even after scaling with scale factor of 0.9679. We use MOLVIB to rescale such frequencies to match experimental values.

scholarly journals Computational Study of the Electron Spectra of Vapor-Phase Indole and Four Azaindoles

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 1947
Author(s):  
Delano P. Chong
Keyword(s):  
Density Functional Theory ◽  
Vapor Phase ◽  
Density Functional ◽  
Computational Study ◽  
Geometry Optimization ◽  
The Other ◽  
Functional Theory ◽  
Electron Spectra

After geometry optimization, the electron spectra of indole and four azaindoles are calculated by density functional theory. Available experimental photoemission and excitation data for indole and 7-azaindole are used to compare with the theoretical values. The results for the other azaindoles are presented as predictions to help the interpretation of experimental spectra when they become available.

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