scholarly journals Theoretical study of structure, vibrational and electronic spectra of isomers of methyl-3-methoxy-2-propenoate

2004 ◽  
Vol 2 (3) ◽  
pp. 456-479 ◽  
Author(s):  
Ajit Virdi ◽  
V. Gupta ◽  
Archna Sharma
Keyword(s):  
Electronic Spectra ◽  
Density Functional ◽  
Substantial Reduction ◽  
Basis Sets ◽  
Potential Energy Distribution ◽  
Functional Theory ◽  
Symmetry Coordinates ◽  
Mechanical Study ◽  
Quantum Mechanical Study ◽  
Vibrational Bands

AbstractA systematic quantum mechanical study of the possible conformations, their relative stabilities, vibrational and electronic spectra and thermodynamic parameters of methyl-3-methoxy-2-propenoate has been reported for the electronic ground (S0) and first excited (S1) states using time-dependent and time-independent Density Functional Theory (DFT) and RHF methods in extended basis sets. Detailed studies have been restricted to the E-isomer, which is found to be substantially more stable than the Z-isomer. Four possible conformers c′Cc, c′Tc, t′Cc, t′Tc, of which the first two are most stable, have been identified in the S0 and S1 states. Electronic excitation to S1 state is accompanied with a reversal in the relative stability of the c′Cc and c′Tc conformers and a substantial reduction in the rotational barrier between them, as compared with the S0 state. Optimized geometries of these conformers in the S0 and S1 states are being reported. Based on suitably scaled RHF/6-31G** and DFT/6-311G** calculations, assignments have been provided to the fundamental vibrational bands of both these conformers in terms of frequency, form and intensity of vibrations and potential energy distribution across the symmetry coordinates in the S0 state. A complete interpretation of the electronic spectra of the conformers has been provided.

Conformational stability, barriers to internal rotations, and normal coordinate analysis of acetone and its2H-isotopomers

2016 ◽  
Vol 94 (10) ◽  
pp. 818-826 ◽  
Author(s):  
Mahboobeh Gholamhoseinpour ◽  
Sayyed Faramarz Tayyari ◽  
Saeedreza Emamian
Keyword(s):  
Density Functional ◽  
Conformational Stability ◽  
Normal Modes ◽  
Normal Coordinate Analysis ◽  
Basis Set ◽  
Basis Sets ◽  
Potential Energy Distribution ◽  
Normal Coordinate ◽  
Functional Theory ◽  
Vibrational Bands

Molecular structure and vibrational spectra of acetone, acetone-d3, and acetone-d6were investigated by means of ab initio and density functional theory (DFT) calculations. The harmonic and anharmonic vibrational frequencies of the acetone isotopomers were calculated at the B3LYP (using the 6–311++G(3df,3pd) basis set) and B2PLYP (using the 6–31+(2d,p) and 6–311G(2df,p) basis sets) levels. The calculated frequencies and the Raman and infrared (IR) intensities were compared with the experimental results. Excellent agreement between calculated and observed vibrational wavenumbers was obtained. Additionally, a normal coordinate analysis (NCA) was also done by using the normal mode eigenvectors obtained at the B3LYP/6–311++G(3df,3pd) level. All fundamental vibrational bands were assigned to the normal modes with the aid of the potential energy distribution (PED) values obtained from normal coordinate calculations. To study the internal rotation of CH3groups, single CH3rotation and synchronous rotations of both CH3groups (clockwise–clockwise and clockwise–counterclockwise) were analyzed using the MP2/6–311++G(3df,2pd) and B3LYP/6–311++G(3df,2pd) levels.

A Quantum Mechanical Study of the Thermal Conduction Across a ZrB2-SiC Interface as a Function of Temperature and Strain

2011 ◽  
Author(s):  
Vikas Samvedi ◽  
Vikas Tomar
Keyword(s):  
Density Functional Theory ◽  
Thermal Properties ◽  
First Principles ◽  
Thermal Conduction ◽  
Density Functional ◽  
Basis Sets ◽  
Quantum Mechanical ◽  
Functional Theory ◽  
Mechanical Study ◽  
Quantum Mechanical Study

Atomistic analyses of thermal conduction across ZrB2/SiC based nanocomposite interface are performed using first principles density functional theory (DFT) with plane-wave basis sets. The changes in the thermal properties of nanocomposites have been analyzed under the effect of straining and temperature and compared for their phononic and electronic dependence.

Study of absorption spectra of organic light emitting materials (triphenyl derivatives of amine): A quantum mechanical study

2017 ◽  
Vol 3 (01) ◽  
Author(s):  
Jitendra Kumar P. Deshmukh ◽  
Ankur Trivedi ◽  
Deep Kumar ◽  
Devesh Kumar
Keyword(s):  
Absorption Spectra ◽  
Density Functional ◽  
Quantum Mechanical ◽  
Functional Theory ◽  
Light Emitting ◽  
Organic Light ◽  
Mechanical Study ◽  
Td Dft ◽  
Quantum Mechanical Study ◽  
Derivatives Of

Density Functional theory (DFT) is used to study the effect of substituents on the electronic and optical property of organic light emitting material 1,3,5-tris(4’-(1’’- phenyl-benzimidazol-2’’- yl)phenyl) amine (TPBB) and its derivatives (MeO-TPBB, Br-TPBB and Bu-TPBB ). TD – DFT has been used to study the absorption spectra of these molecules. This study suggests that each derivative of TPBB shows a UV – VIS spectra at slightly different frequency.

scholarly journals Coordination Behavior of Ni2+, Cu2+, and Zn2+ in Tetrahedral 1-Methylimidazole Complexes: A DFT/CSD Study

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Samuel Tetteh
Keyword(s):  
Density Functional ◽  
Population Analysis ◽  
Substantial Reduction ◽  
Nbo Analysis ◽  
Basis Sets ◽  
Dft Methods ◽  
Functional Theory ◽  
Formal Charge ◽  
Coordination Behavior ◽  
The Stability

The interaction between nickel (Ni2+), copper (Cu2+), and zinc (Zn2+) ions and 1-methylimidazole has been studied by exploring the geometries of eleven crystal structures in the Cambridge Structural Database (CSD). The coordination behavior of the respective ions was further investigated by means of density functional theory (DFT) methods. The gas-phase complexes were fully optimized using B3LYP/GENECP functionals with 6-31G∗ and LANL2DZ basis sets. The Ni2+ and Cu2+ complexes show distorted tetrahedral geometries around the central ions, with Zn2+ being a perfect tetrahedron. Natural bond orbital (NBO) analysis and natural population analysis (NPA) show substantial reduction in the formal charge on the respective ions. The interaction between metal d-orbitals (donor) and ligand orbitals (acceptor) was also explored using second-order perturbation of the Fock matrix. These interactions followed the order Ni2+ > Cu2+ > Zn2+ with Zn2+ having the least interaction with the ligand orbitals. Examination of the frontier orbitals shows the stability of the complexes in the order Ni2+ > Cu2+ < Zn2+ which is consistent with the Irving–Williams series.

Quantum Mechanical Study of γ-Fe2O3 Nanoparticle as a Nanocarrier for Anticancer Drug Delivery

2018 ◽  
Vol 0 (0) ◽  
Author(s):  
Hadi Lari ◽  
Ali Morsali ◽  
Mohammad Momen Heravi
Keyword(s):  
Anticancer Drug ◽  
Density Functional ◽  
Noncovalent Interactions ◽  
Free Energies ◽  
Functional Theory ◽  
Quantum Molecular Descriptors ◽  
Anticancer Drug Delivery ◽  
Mechanical Study ◽  
Quantum Mechanical Study ◽  
Fe2o3 Nanoparticle

Abstract Using density functional theory (DFT), noncovalent interactions and four mechanisms of covalent functionalization of melphalan anticancer drug onto γ-Fe2O3 nanoparticles have been studied. Quantum molecular descriptors of noncovalent configurations were investigated. It was specified that binding of melphalan onto γ-Fe2O3 nanoparticles is thermodynamically suitable. Hardness and the gap of energy between LUMO and HOMO of melphalan are higher than the noncovalent configurations, showing the reactivity of drug increases in the presence of γ-Fe2O3 nanoparticles. Melphalan can bond to γ-Fe2O3 nanoparticles through NH2 (k1 mechanism), OH (k2 mechanism), C=O (k3 mechanism) and Cl (k4 mechanism) groups. The activation energies, the activation enthalpies and the activation Gibbs free energies of these reactions were calculated. Thermodynamic data indicate that k3 mechanism is exothermic and spontaneous and can take place at room temperature. These results could be generalized to other similar drugs.

A quantum mechanical study of water adsorption on the (110) surfaces of rutile SnO2 and TiO2: investigating the effects of intermolecular interactions using hybrid-exchange density functional theory

2014 ◽  
Vol 16 (39) ◽  
pp. 21002-21015 ◽  
Author(s):  
M. Patel ◽  
F. F. Sanches ◽  
G. Mallia ◽  
N. M. Harrison
Keyword(s):  
Density Functional Theory ◽  
Intermolecular Interactions ◽  
Density Functional ◽  
Water Adsorption ◽  
Quantum Mechanical ◽  
Structure And Properties ◽  
Functional Theory ◽  
Mechanical Study ◽  
Quantum Mechanical Study

Periodic hybrid-exchange DFT is used to explore the structure and properties of SnO2(110) and TiO2(110) surfaces in contact with water.

Benchmark of Simplified Time-Dependent Density Functional Theory for UV-Vis Spectral Properties of Porphyrinoids

2019 ◽  
Author(s):  
Kamal Batra ◽  
Stefan Zahn ◽  
Thomas Heine
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Large Scale ◽  
Absolute Error ◽  
Time Dependent ◽  
Basis Set ◽  
Basis Sets ◽  
Functional Theory ◽  
Framework Materials ◽  
Dependent Density

<p>We thoroughly benchmark time-dependent density- functional theory for the predictive calculation of UV/Vis spectra of porphyrin derivatives. With the aim to provide an approach that is computationally feasible for large-scale applications such as biological systems or molecular framework materials, albeit performing with high accuracy for the Q-bands, we compare the results given by various computational protocols, including basis sets, density-functionals (including gradient corrected local functionals, hybrids, double hybrids and range-separated functionals), and various variants of time-dependent density-functional theory, including the simplified Tamm-Dancoff approximation. An excellent choice for these calculations is the range-separated functional CAM-B3LYP in combination with the simplified Tamm-Dancoff approximation and a basis set of double-ζ quality def2-SVP (mean absolute error [MAE] of ~0.05 eV). This is not surpassed by more expensive approaches, not even by double hybrid functionals, and solely systematic excitation energy scaling slightly improves the results (MAE ~0.04 eV). </p>

scholarly journals 1,3,5-Triaza-7-Phosphaadamantane (PTA) as a 31P NMR Probe for Organometallic Transition Metal Complexes in Solution

Molecules ◽  
2021 ◽  
Vol 26 (5) ◽  
pp. 1390 ◽  
Author(s):  
Ilya G. Shenderovich
Keyword(s):  
Chemical Shift ◽  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Density Functional ◽  
Molecular Structures ◽  
Basis Sets ◽  
Functional Theory ◽  
Non Covalent Interactions ◽  
Covalent Interactions

Due to the rigid structure of 1,3,5-triaza-7-phosphaadamantane (PTA), its 31P chemical shift solely depends on non-covalent interactions in which the molecule is involved. The maximum range of change caused by the most common of these, hydrogen bonding, is only 6 ppm, because the active site is one of the PTA nitrogen atoms. In contrast, when the PTA phosphorus atom is coordinated to a metal, the range of change exceeds 100 ppm. This feature can be used to support or reject specific structural models of organometallic transition metal complexes in solution by comparing the experimental and Density Functional Theory (DFT) calculated values of this 31P chemical shift. This approach has been tested on a variety of the metals of groups 8–12 and molecular structures. General recommendations for appropriate basis sets are reported.

Theoretical study on the formation of carbon disulfide and ammonia from thermal decomposition products of thiourea

2014 ◽  
Vol 13 (04) ◽  
pp. 1450022 ◽  
Author(s):  
Zerong Daniel Wang ◽  
Meagan Hysmith ◽  
Perla Cristina Quintana
Keyword(s):  
Thermal Decomposition ◽  
Carbon Disulfide ◽  
Density Functional ◽  
Basis Sets ◽  
Structural Isomer ◽  
Consecutive Reaction ◽  
Functional Theory ◽  
Decomposition Products ◽  
Thermal Decomposition Products ◽  
Hybrid Module

The formation of carbon disulfide ( CS 2) and ammonia ( NH 3) from the thermal decomposition products of thiourea has been studied with MP2, and hybrid module-based density functional theory methods (B3LYP, MPW1PW91 and PBE1PBE), each in conjunction with five different basis sets (6-31+G(2d,2p), 6-311++G(2d,2p), DGDZVP, DGDZVP2 and DGTZVP). The free energy changes and activation energies for all the five primitive reactions involved in the formation of CS 2 and NH 3 have been compared and discussed. The results indicate that CS 2 is most likely formed in a consecutive reaction path that consists of the addition of hydrogen sulfide ( H 2 S ) to isothiocyanic acid (HNCS) to generate carbamodithioic acid and subsequent decomposition of carbamodithioic acid. By contrast, thiocyanic acid (HSCN) as the structural isomer of isothiocyanic acid is not likely the source of CS 2.

scholarly journals Structures and Electronic Spectra of CdSe−Cys Complexes: Density Functional Theory Study of a Simple Peptide-Coated Nanocluster

2009 ◽  
Vol 113 (1) ◽  
pp. 292-301 ◽  
Author(s):  
Sang-Yoon Chung ◽  
Sungyul Lee ◽  
Christopher Liu ◽  
Daniel Neuhauser
Keyword(s):  
Density Functional Theory ◽  
Electronic Spectra ◽  
Density Functional ◽  
Density Functional Theory Study ◽  
Functional Theory
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