Theoretical Studies on the Structure and Spectroscopic Properties of 2,4-D (2,4-Diclorofenoxiacetic Acid)

The 2,4-dichlorophenoxyacetic acid (2,4-D) is applied to and recovered from the leaf surfaces of garden bean and corn plants. This paper examines the theoretical study of the 2,4-D IR and UV spectra as well as the determination of its optimized molecular structure. Theoretical calculations are performed at the density functional theory (DFT) levels. The different structural and electronic effects determining the molecular stability of the conformers are discussed in a comparative fashion. The optimized geometry was calculated via the B3LYP method with 6-311G(d,p) and 6-311++G(d,p) basis sets and the FT-IR spectra was calculated by the density functional B3LYP method with the 6-311++G(d,p) basis set. The scaled theoretical wavenumbers show good agreement with the experimental values. A detailed interpretation of the infrared spectra of 2,4-D is reported.

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Synthesis and Characterization of 4-Phenylethynylphthalic Anhydride

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.750-752.1769 ◽

2013 ◽

Vol 750-752 ◽

pp. 1769-1772

Author(s):

Xing Li Meng ◽

Zhan Yu Zhao ◽

Xiao Bin Chen

Keyword(s):

Single Crystal ◽

Density Functional ◽

Coupling Reaction ◽

Basis Sets ◽

Diffusion Method ◽

H Nmr ◽

B3lyp Method ◽

The Density Functional Theory ◽

Sonogashira Coupling Reaction ◽

Experimental Values

4-phenylethynylphthalic anhydride (4-PEPA) was synthesized by the palladium/copper catalyzed Sonogashira coupling reaction between phenylacetylene and 4-bromophthalic anhydride. The yield achieved 85.48%. The single crystal of 4-PEPA was grown and crystallized by solvent diffusion method. The structure of the compound was characterized by single crystal X-ray diffract-tion method, UV-vis, 1H NMR, 13C NMR and FTIR. All characterizations above demonstrated the structure of 4-PEPA. HPLC gave the purity achieving 96.62%. TGDSC was used to investigate the thermal stability of the compound. Vibrational frequencies of 4-PEPA calculated using the density functional theory (DFT/B3LYP) method with the 6-31G(d) basis sets were in good agreement with experimental values.

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AlN Nanotubes: A DFT Study of Al-27 and N-14 Electric Field Gradient Tensors

Zeitschrift für Naturforschung A ◽

10.1515/zna-2007-1206 ◽

2007 ◽

Vol 62 (12) ◽

pp. 711-715 ◽

Cited By ~ 2

Author(s):

Ahmad Seif ◽

Mahmoud Mirzaei ◽

Mehran Aghaie ◽

Asadollah Boshra

Keyword(s):

Electric Field ◽

Electric Field Gradient ◽

Field Gradient ◽

Density Functional ◽

Quadrupole Coupling Constant ◽

Basis Set ◽

Basis Sets ◽

B3lyp Method ◽

Package Program ◽

Nqr Parameters

Density functional theory (DFT) calculations were performed to calculate the electric field gradient (EFG) tensors at the sites of aliminium (27Al) and nitrogen (14N) nuclei in an 1 nm of length (6,0) single-walled aliminium nitride nanotube (AlNNT) in three forms of the tubes, i. e. hydrogencapped, aliminium-terminated and nitrogen-terminated as representatives of zigzag AlNNTs. At first, each form was optimized at the level of the Becke3,Lee-Yang-Parr (B3LYP) method, 6-311G∗∗ basis set. After, the EFG tensors were calculated at the level of the B3LYP method, 6-311++G∗∗ and individual gauge for localized orbitals (IGLO-II and IGLO-III) types of basis sets in each of the three optimized forms and were converted to experimentally measurable nuclear quadrupole resonance (NQR) parameters, i. e. quadrupole coupling constant (qcc) and asymmetry parameter (ηQ). The evaluated NQR parameters revealed that the considered model of AlNNT can be divided into four equivalent layers with similar electrostatic properties.With the exception of Al-1, all of the three other Al layers have almost the same properties, however, N layers show significant differences in the magnitudes of the NQR parameters in the length of the nanotube. Furthermore, the evaluated NQR parameters of Al-1 in the Al-terminated form and N-1 in the N-terminated form revealed the different roles of Al (base agent) and of N (acid agent) in AlNNT. All the calculations were carried out using the GAUSSIAN 98 package program.

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REEXAMINATION OF LOW ENERGY STRUCTURES OF ${\rm Au}_{4}^{-}$ AND Au4

Journal of Theoretical and Computational Chemistry ◽

10.1142/s0219633610005499 ◽

2010 ◽

Vol 09 (supp01) ◽

pp. 1-7 ◽

Cited By ~ 8

Author(s):

YI GAO ◽

YU ZHAO ◽

X. C. ZENG

Keyword(s):

Free Energy ◽

Density Functional ◽

Photoelectron Spectrum ◽

Global Minimum ◽

Low Energy ◽

Basis Sets ◽

Cluster Method ◽

Energy Calculation ◽

Couple Cluster ◽

B3lyp Method

Low energy isomers of [Formula: see text] and Au4 were reexamined using the hybrid density functional B3LYP method and the couple-cluster method with the aug-cc-pVDZ-PP and aug-cc-pVTZ-PP basis sets. For [Formula: see text], the B3LYP method favors the zigzag isomer and the second order Moller–Plesset perturbation (MP2) total energy calculation favors the D2h rhombus isomer, whereas the couple-cluster singles and doubles with perturbative triples [CCSD(T)] level of theory favors the Y-shaped C2v isomer. The pyramid isomer is much higher in energy and could be easily excluded. The Gibbs free energy correction based on harmonic approximation suggests that the zigzag isomer is lower in free energy than the D2h rhombus isomer at 298.15 K. These results confirm that the Y-shaped C2v isomer is the global minimum at both 0 K and room temperature and is thus the major isomer to account for the experimental photoelectron spectrum. The zigzag isomer is suggested, as a minor isomer, to account for the weak second peak at 3.40 eV in the experimental photoelectron spectrum. For neutral Au4 , the zigzag isomer is more stable than D2h rhombus isomer at the B3LYP level and the D2h rhombus isomer is the global minimum on basis of all post Hartree–Fock levels of theory.

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Experimental and Density Functional Theory Characteristics of Ibrutinib, a Bruton’s Kinase Inhibitor Approved for Leukemia Treatment

Journal of Spectroscopy ◽

10.1155/2021/9968797 ◽

2021 ◽

Vol 2021 ◽

pp. 1-8

Author(s):

Ali I. Ismail

Keyword(s):

Density Functional Theory ◽

Density Functional ◽

Kinase Inhibitor ◽

Theoretical Calculations ◽

Dft Method ◽

Vibrational Frequencies ◽

Basis Sets ◽

Electronic Transitions ◽

Functional Theory ◽

Leukemia Treatment

Ibrutinib, a Bruton’s tyrosine kinase that plays an essential role in the B-cell development and cancer cells, has been recently approved to treat chronic, lymphocytic, and other types of leukemia. This study focused on investigating ibrutinib by its electronic transitions, vibrational frequencies, and electrospray mass spectra. The experimental peaks for electronic spectrum were found at 248.0 and 281.0 nm, whereas the νC = 0 stretching frequency was found at 1652.4 and 1639.19 cm−1. These experimental properties were compared with the corresponding theoretical calculations in which density functional theory was applied. The optimized structure was obtained with the calculations using a hybrid function (B3LYP) and high-level basis sets [6-311G++(d,p)]. Most of the calculated vibrational frequencies showed a relatively good agreement with the experimental ones. The electronic transitions of ibrutinib calculated using time-dependent DFT method were performed at two different solvation methods: PCM and SMD. The mass spectrum of ibrutinib, its fragments, and its isotopic pattern agreed well with the expected spectra.

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Synthesis, characterization and theoretical calculations of Cu(I) complex of trithiocyanuric acid [Cu(ttc)3]

Universitas Scientiarum ◽

10.11144/javeriana.sc23-2.scat ◽

2018 ◽

Vol 23 (2) ◽

pp. 241-266 ◽

Cited By ~ 1

Author(s):

Ximena Verónica Jaramillo-Fierro ◽

César Zambrano ◽

Francisco Fernández ◽

Regino Saenz-Puche ◽

César Costa ◽

...

Keyword(s):

Computational Study ◽

Theoretical Calculations ◽

Photophysical Properties ◽

Vibrational Frequencies ◽

Basis Sets ◽

Vertical Excitation ◽

Experimental Values ◽

Homo Lumo ◽

Perchlorate Hexahydrate ◽

Good Agreement

A new Cu(I) complex constructed by reaction of trithiocyanuric acid (ttc) and copper (II) perchlorate hexahydrate has been successfully synthesized by a slow sedimentation method in a DMF solvent at room temperature. The molecular structure of the compound was elucidated by MALDI-TOFMS, UV Vis and FTIR spectroscopy, DSC-TGA analysis and magnetic susceptibility measurement. The proposed structure was corroborated by a computational study carried out with the Gaussian09 and AIMAII programs using the RB3LYP hybrid DFT functional with both 6-31G and Alhrich-TZV basis sets. The calculated vibrational frequencies values were compared with experimental FTIR values. Photophysical properties of the synthesized complex were evaluated by UV-Visible spectroscopy and compared with computed vertical excitation obtained from TDDFT. The theoretical vibrational frequencies and the UV Vis spectra are in good agreement with the experimental values. Additionally, the Frontier Molecular Orbitals (HOMO-LUMO) and the Molecular Electrostatic Potential of the complex was calculated using same theoretical approximation. The results showed the interaction between three coordinatedl igand atoms and the Cu(I) ion.

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Structural, Electronic, and Vibrational Properties of Isoniazid and Its Derivative N-Cyclopentylidenepyridine-4-carbohydrazide: A Quantum Chemical Study

Journal of Theoretical Chemistry ◽

10.1155/2014/894175 ◽

2014 ◽

Vol 2014 ◽

pp. 1-15 ◽

Cited By ~ 4

Author(s):

Anoop kumar Pandey ◽

Abhishek Bajpai ◽

Vikas Baboo ◽

Apoorva Dwivedi

Keyword(s):

Density Functional ◽

Quantum Chemical Study ◽

Chemical Study ◽

Basis Sets ◽

Ground State Structure ◽

Vibrational Modes ◽

Functional Theory ◽

Complete Assignment ◽

Experimental Values ◽

Homo Lumo

Isoniazid (Laniazid, Nydrazid), also known as isonicotinylhydrazine (INH), is an organic compound that is the first-line medication in prevention and treatment of tuberculosis. The optimized geometry of the isoniazid and its derivative N-cyclopentylidenepyridine-4-carbohydrazide molecule has been determined by the method of density functional theory (DFT). For both geometry and total energy, it has been combined with B3LYP functionals having LANL2DZ and 6-311 G (d, p) as the basis sets. Using this optimized structure, we have calculated the infrared wavenumbers and compared them with the experimental data. The calculated wavenumbers by LANL2DZ are in an excellent agreement with the experimental values. On the basis of fully optimized ground-state structure, TDDFT//B3LYP/LANL2DZ calculations have been used to determine the low-lying excited states of isoniazid and its derivative. Based on these results, we have discussed the correlation between the vibrational modes and the crystalline structure of isoniazid and its derivative. A complete assignment is provided for the observed FTIR spectra. The molecular HOMO, LUMO composition, their respective energy gaps, and MESP contours/surfaces have also been drawn to explain the activity of isoniazid and its derivative.

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Theoreticalversusexperimental geometries in S-bridged manganese carbonyl complexes

Journal of Applied Crystallography ◽

10.1107/s0021889803010276 ◽

2003 ◽

Vol 36 (4) ◽

pp. 1050-1055 ◽

Cited By ~ 2

Author(s):

Juan F. Van der Maelen Uría ◽

Javier Ruiz ◽

Santiago García-Granda

Keyword(s):

Density Functional ◽

Theoretical Calculations ◽

Basis Sets ◽

Medium Size ◽

Carbonyl Complexes ◽

X Ray Diffraction ◽

Bond Lengths ◽

Hartree Fock ◽

Experimental Geometry ◽

Manganese Carbonyl

The experimental geometry obtained from single-crystal X-ray diffraction for a number of binuclear S-bridged manganese complexes is compared with the results of theoretical calculations made at theab initiolevel by using Hartree–Fock and density functional theory methods with medium-size and large basis sets. The optimized geometries obtained were somewhat relaxed when compared with the experimental ones, with very similar bond and torsion angles but longer bond lengths. The mean square deviation for bond lengths (angles) was found to be between 0.046 Å (1.1°) and 0.004 Å (0.7°) depending on the theoretical model used.

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Density functional theory study on the molecular structure of loganin

Spectroscopy An International Journal ◽

10.1155/2011/361849 ◽

2011 ◽

Vol 25 (6) ◽

pp. 287-302 ◽

Cited By ~ 2

Author(s):

Anoop Kumar Pandey ◽

Shamoon Ahmad Siddiqui ◽

Apoorva Dwivedi ◽

Kanwal Raj ◽

Neeraj Misra

Keyword(s):

Molecular Structure ◽

Density Functional ◽

Solid Phase ◽

Density Functional Method ◽

Functional Method ◽

Basis Set ◽

Equilibrium Geometry ◽

B3lyp Method ◽

Ft Ir ◽

Detailed Interpretation

The computational Quantum Chemistry (QC) has been used for different types of problems, for example: structural biology, surface phenomena and liquid phase. In this paper we have employed the density functional method for the study of molecular structure of loganin. The equilibrium geometry, harmonic vibrational frequencies and infrared intensities were calculated by B3LYP/6-311G (d, p) method and basis set combinations. It was found that the optimized parameters obtained by the DFT/B3LYP method are very near to the experimental ones. A detailed conformational analysis was carried out. A detailed interpretation of the infrared spectra of loganin is also reported in the present work. The FT-IR spectra of loganin were recorded in solid phase. The thermodynamic calculations related to the title compound were also performed at B3LYP/6-311G (d, p) level of theory.

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FIRST-PRINCIPLES STUDY OF THE ELECTRONIC, LINEAR, AND NONLINEAR OPTICAL PROPERTIES OF Li(Nb, Ta)O3

International Journal of Modern Physics B ◽

10.1142/s0217979210054415 ◽

2010 ◽

Vol 24 (32) ◽

pp. 6277-6290 ◽

Cited By ~ 3

Author(s):

SULEYMAN CABUK

Keyword(s):

First Principles ◽

Density Functional ◽

Nonlinear Optical ◽

Energy Gap ◽

Local Density ◽

Theoretical Calculations ◽

Total Density ◽

Functional Theory ◽

Experimental Values ◽

Electron Energy Loss

We investigate the energy band structure, total density of states, the linear, nonlinear optical (NLO) response, and the electron energy-loss spectrum for Li(Nb, Ta)O 3 using first principles calculations based on density functional theory in its local density approximation. Our calculation shows that these compounds have similar structures. The indirect band gaps of 3.39 eV (LiNbO3) and 3.84 eV (LiTaO3) at the Γ–Z direction in the Brillouin zone are found. A simple scissor approximation is applied to adjust the band energy gap from the calculations to match the experimental values. The optical spectra are analyzed and the origins of some of the peaks in the spectra are discussed in terms of calculated electronic structure. Calculations are reported for the frequency-dependent complex second-order NLO susceptibilities [Formula: see text] up to 10 eV and for zero-frequency limit [Formula: see text]. The results are compared with the theoretical calculations and the available experimental data.

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