scholarly journals A Theoretical Study of 5-methyl-2-isopropylphenol (Thymol) by DFT

2021 ◽  
pp. 812-830
Author(s):  
Raksha Gupta
Keyword(s):  
Population Analysis ◽  
Dft Method ◽  
Geometric Optimization ◽  
Oscillator Strengths ◽  
Basis Set ◽  
Excitation Energies ◽  
Mulliken Population ◽  
Visible Absorption ◽  
Vertical Excitation ◽  
Td Dft

Gaussian 09, RevisionA.01, software package was used for the theoretical quantum chemical calculations of 5-methyl-2-isopropylphenol. DFT/B3LYP/6-311G (d, p) basis was used to perform geometric optimization and vibrational frequency determination of the molecule. The statistical thermochemical calculations of the molecule were done at DFT/B3LYP/6-311G (d, p) basis set to calculate the standard thermodynamic functions: heat capacity (CV), entropy (S) and Enthalpy (E). Various NLO properties like total dipole moment (µ), mean linear polarizability (α), anisotropic polarizability (Δα), first order polarizability (β), and second order hyperpolarizability (γ) in terms of x, y, z components were calculated at DFT/B3LYP/6-311G (d, p) basis set for 5-methyl-2-isopropylphenol. Mulliken population analysis was also done using the same basis set. Time Dependent DFT (TD-DFT) method using the same basis set was used to compute UV-Visible absorption spectra, ECD spectra, electronic transitions, vertical excitation energies and oscillator strengths of 5-methyl-2-isopropylphenol.FMO analysis, ESP study were also done using the same basis set.

scholarly journals Physico-Chemical Properties and Quantum Chemical Calculation of 2-methoxy-4-(prop-2-en-1-yl) phenol (EUGENOL)

2021 ◽  
pp. 01-22
Author(s):  
Dr. Raksha Gupta
Keyword(s):  
Quantum Chemical ◽  
Population Analysis ◽  
Chemical Properties ◽  
Geometric Optimization ◽  
Oscillator Strengths ◽  
Basis Set ◽  
Chemical Calculation ◽  
Excitation Energies ◽  
Mulliken Population ◽  
Physico Chemical

Physico-chemical properties plays an important role in determining toxicity of a material hence were calculated using acdlab/chemsketch and the data predicted is generated using ACD/Labs Percepta Platform - PhysChem Module. Gaussian 09, RevisionA.01, software package was used for the theoretical quantum chemical calculations of 2-methoxy-4-(prop-2-en-1-yl) phenol commonly called Eugenol. DFT/B3LYP/6-311G (d, p) basis was used to perform geometric optimization and vibrational frequency determination of the molecule. The statistical thermochemical calculations of the molecule were done at DFT/B3LYP/6-311G (d, p) basis set to calculate the standard thermodynamic functions: heat capacity (CV), entropy (S) and Enthalpy (E). DFT/B3LYP/6-311G (d, p) basis set was used to calculate the various NLO properties like dipole moment (µ), mean linear polarizability (α), anisotropic polarizability (Δα), first order hyperpolarizability (β), second order hyperpolarizability (γ) in terms of x, y, z components for Eugenol (2-methoxy-4-(prop-2-en-1-yl) phenol. Same basis set was used to carry out Mulliken population analysis. UV-Visible absorption spectra, ECD spectra, electronic transitions, vertical excitation energies and oscillator strengths of Eugenol (2-methoxy-4-(prop-2-en-1-yl) phenol) were computed by Time Dependent DFT (TD-DFT) method using the same basis set. FMO analysis, Molecular electrostatic potential study was also done using the same basis set.

The ground state and low-lying excited states of CCCN radical and its ions: a CASSCF/CASPT2 study

2016 ◽  
Vol 94 (9) ◽  
pp. 803-807
Author(s):  
Angyang Yu
Keyword(s):  
Excited States ◽  
Ground State ◽  
Linear Structure ◽  
Electronic Configuration ◽  
Geometric Optimization ◽  
Oscillator Strengths ◽  
Basis Set ◽  
Excitation Energies ◽  
Complete Active Space ◽  
Vertical Excitation

The ground state and low-lying excited states of the CCCN radical and its ions have been investigated systematically using the complete active space self-consistent field (CASSCF) and multi-configuration second-order perturbation theory (CASPT2) methods in conjunction with the ANO-RCC-TZP basis set. The calculated results show that the state 12Σ+ has the lowest CASPT2 energy among the electronic states. By means of the geometric optimization of this radical, it could be found that the molecule exhibits linear structure, with the bond lengths R1 = 1.214 Å, R2 = 1.363 Å, R3 = 1.162 Å, which are very close to the experimental values. The calculated vertical excitation energies and the corresponding oscillator strengths show that there are three relatively strong peaks at energies 0.63, 4.04, and 5.49 eV, which correspond to the transitions 12Σ+ → 12Π, 12Σ+ → 22Π, and 12Σ+ → 22Σ+, respectively. Additionally, the electronic configuration and the harmonic vibration frequencies of each state are also investigated.

X-ray and DFT Investigation of (E)-4-bromo-5-methoxy-2-((o-tolylimino)methyl)phenol Compound

2018 ◽  
pp. 454-461
Keyword(s):  
Density Functional ◽  
Theoretical Calculations ◽  
Population Analysis ◽  
Diffraction Method ◽  
Dft Method ◽  
Basis Set ◽  
X Ray Diffraction ◽  
Mulliken Population ◽  
Charge Delocalization ◽  
X Ray

(E)-4-bromo-5-methoxy-2-((o-tolylimino)methyl)phenol was investigated by experimental and theoretical methodologies. The solid state molecular structure was determined by X-ray diffraction method. All theoretical calculations were performed by density functional theory (DFT) method by using B3LYP/6-31G(d,p) basis set. The titled compound showed the preference of enol form, as supported by X-ray diffraction method. The geometric and molecular properties were compaired for both enol-imine and keto-amine forms for title compound. Stability of the molecule arises from hyperconjugative interactions, charge delocalization and intramolecular hydrogen bond has been analyzed using natural bond orbital (NBO) analysis. Mulliken population method and natural population analysis (NPA) have been studied. Also, condensed Fukui function and relative nucleophilicity indices calculated from charges obtained with orbital charge calculation methods (NPA). Molecular electrostatic potential (MEP) and non linear optical (NLO) properties are also examined.

scholarly journals Molecular, Electronic, Nonlinear Optical and Spectroscopic Analysis of Heterocyclic 3-Substituted-4-(3-methyl-2-thienylmethyleneamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones: Experiment and DFT Calculations

2021 ◽  
Vol 27 (1) ◽  
pp. 1-16
Author(s):  
Murat Beytur ◽  
Ihsan Avinca
Keyword(s):  
Nonlinear Optical ◽  
Chemical Potential ◽  
Energy Gap ◽  
Basis Set ◽  
Molecular Vibration ◽  
Excitation Energies ◽  
Visible Absorption ◽  
Td Dft ◽  
Uv Visible ◽  
Experimental Values

Abstract In the present study, 3-p-methoxybenzyl/m-chlorobenzyl/phenyl-4-(3-methyl-2-thienylmethyleneamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones were obtained from the reaction between 3-methylthiophene-2-carbaldehyde and three different 4-amino-(3-p-methoxybenzyl/m-chlorobenzyl/phenyl)-4,5-dihydro-1H-1,2,4-triazole-5-ones. In order to compare experimental and theoretical values, the geometric parameter, electronic, nonlinear optical properties, molecular electrostatic potentials and spectroscopic properties of 3-substituted-4-(3-methyl-2-thienylmethyleneamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones have been simulated. The electronic properties of the newly synthesized compounds were calculated using DFT/B3LYP and DFT/B3PW91 methods revealing parameters such as ionization potential, electron affinity, energy gap, electronegativity, molecular hardness, molecular softness, electrophilic index, nucleophilic index and chemical potential, all obtained from HOMO and LUMO energies, dipole moments and total energies. UV-visible absorption spectra and the stimulation contributions in UV-visible transitions were obtained by using TD-DFT/B3LYP/6-311G(d,p) and TD-DFT/B3PW91/6-311G(d,p) methods in ethanol. The calculated absorption wavelengths, oscillator power and excitation energies were compared with experimental values. In line with DFT, the numbers of molecular vibration were analyzed through the basis set of 6-311G(d,p). The recording of FT-IR frequencies was done for the pertinent compound. The recorded frequencies through DFT/B3LYP and DFT/B3PW91 methods were compared to experimental values, with a result gained closest to the values of B3LYP. Finally, the Gaussian09W program package in DMSO phase, starting from the optimized structure, has been instrumental in calculating the 13C-NMR and 1H-NMR chemical shift values of the GIAO method.

scholarly journals ABSORPTION OF SOME SMALL SILVER CLUSTERS: DFT AND CASPT2 CALCULATIONS

2018 ◽  
Vol 55 (6A) ◽  
pp. 72
Author(s):  
Ngo Tuan Cuong
Keyword(s):  
Absorption Spectra ◽  
Density Functional ◽  
Noble Gas ◽  
Silver Cluster ◽  
Dft Method ◽  
Basis Sets ◽  
Silver Clusters ◽  
Excitation Energies ◽  
Complete Active Space ◽  
Td Dft

Two quantum chemical methods which are the time-dependent density functional theory (TD-DFT) and the complete active space CASPT2/CASSCF have been used in modeling absorption spectra of silver clusters Agn (n = 2, 3, 4, 6, 8). There is an overall good agreement between TD-DFT and CASPT2 results for transition energies. The absorption spectra of the Agn clusters examined can reasonably be simulated using the excitation energies obtained by either TD-DFT or CASPT2 method.  The main result emerged from this calculation is that the TD-DFT method is suitable for treatment of excited states of Ag clusters. The choice of specific functionals and basis sets to be used in some cases induces important effects on the calculated spectra. It is also noteworthy to mention that for some clusters, the neutral Ag6 for instance, the effect of noble gas environment is significant, while for some others such as the neutral Ag8, it is not. Therefore, carrying out TD-DFT calculations to reproduce and to assign a given structure to an experimental absorption spectrum of a silver cluster, it is not only to select suitable functionals but also to take enough effects of environments into account. 

MR-CISD and MR-AQCC Calculation of Excited States of Malonaldehyde: Geometry Optimizations Using Analytical Energy Gradient Methods and a Systematic Investigation of Reference Configuration Sets

2003 ◽  
Vol 68 (3) ◽  
pp. 447-462 ◽  
Author(s):  
Silmar A. do Monte ◽  
Michal Dallos ◽  
Thomas Müller ◽  
Hans Lischka
Keyword(s):  
Excited States ◽  
Ground State ◽  
Transition Energy ◽  
Gradient Methods ◽  
Systematic Investigation ◽  
Oscillator Strengths ◽  
Excitation Energies ◽  
Band Maximum ◽  
Vertical Excitation ◽  
Energy Gradient

Extended MR-CISD and MR-AQCC calculations have been performed on the ground state and the first two excited states of malonaldehyde. Full geometry optimizations have been carried for Cs and C2v structures both at MR-CISD and MR-AQCC levels. Vertical and minimum-to-minimum excitation energies and oscillator strengths have been computed. Systematic studies have been undertaken concerning several types of reference spaces. Agreement with the experimental 0-0 transition energy to the S1 state (expt. 3.50 eV, calc. 3.56 eV) and for the vertical excitation to S2 (expt. band maximum 4.71 eV, best estimate 4.86 eV) is very good. In agreement with the CASSCF/CASPT2 results by Sobolewski and Domcke (J. Phys. Chem. A 1999, 103, 4494), we find that the hydrogen bond in malonaldehyde is weakened by excitation to the S1 state. The barrier for proton transfer in the S1 state is increased in comparison with the ground state.

Theoretical study of the geometrical and electronic properties of Be2Mg+ n (n = 1–11) clusters

2019 ◽  
Vol 9 (7) ◽  
pp. 778-785 ◽  
Author(s):  
Ben-Chao Zhu ◽  
Zhang Yu ◽  
Wang Ping ◽  
Lu Zeng ◽  
Shuai Zhang
Keyword(s):  
Electronic Properties ◽  
Ground State ◽  
Density Functional ◽  
Population Analysis ◽  
Dft Method ◽  
Mulliken Population ◽  
Functional Theory ◽  
Fragmentation Energy ◽  
Average Binding Energy ◽  
Ground State Structures

By using Density Functional Theory (DFT) method at the B3LYP/6-311G level, the structures, stabilities, and electronic properties of cationic Be2Mg+ n (n = 1–11) clusters have been systematically studied. The optimized geometry show that the ground state structures of cationic Be2Mg+ n (n = 1–11) clusters favor 3D structures except n = 1, 2. Furthermore, the average binding energy E b, the second-order energy differences Δ2E, the fragmentation energy Ef and the HOMO-LUMO energy Egap of the ground state of cationic Be2Mg– n (n = 1–11) clusters are calculated, the final results indicate that Be2Mg+6 and Be2Mg+9 clusters have a higher stability than other clusters. Additionally, the NCP, NEC and Mulliken population analysis reveal that the charges in cationic Be2Mg+ n (n = 1–11) clusters transfer from Mg atom to Be atoms, and strong sp hybridizations are presented in Be atoms of Be2Mg+ n clusters. Finally, the polarizability analysis indicates that the nuclei and electronic clouds of clusters are affected by external field with the increase of cluster size.

Predicting Carbonyl Excitation Energies Efficiently Using EOM-CC Trends

2020 ◽  
Author(s):  
Keiran Rowell ◽  
Scott Kable ◽  
Meredith J. T. Jordan
Keyword(s):  
Single Point ◽  
Zero Point ◽  
Tropospheric Chemistry ◽  
Excitation Energies ◽  
Relaxation Energy ◽  
Point Energy ◽  
Vertical Excitation ◽  
Td Dft ◽  
Vertical Excitation Energy ◽  
Carbonyl Species

We approach the problem of predicting excitation energies of diverse, larger (5–6 carbons) carbonyl species central to earth’s tropospheric chemistry. Triples contributions are needed for the vertical excitation energy (E<sup>vert</sup>), while EOM-CCSD//TD-DFT calculations provide acceptable estimates for the S<sub>1</sub> relaxation energy (E<sup>relax</sup>), and (TD-)DFT suffices for the S<sub>0</sub> → S<sub>1</sub> zero-point vibration energy correction (∆E<sup>ZPVE</sup>). <div><br></div><div>Perturbative triples corrections deliver E<sup>vert</sup> values close in accuracy to full iterative triples EOM-CC calculations. The error between EOM-CCSD and triples-corrected E vert values appears to be systematic and can be accounted for with scaling factors. However, saturated and α,β-unsaturated carbonyls must be treated separately. Double-hybrid S<sub>0</sub> minima can be used to calculate E<sup>vert</sup> with negligible loss in accuracy, relegating the O(N<sup>5</sup>) expense of CCSD to only single-point energy and excitation calculations. </div><div><br></div><div>This affordable protocol can be applied to all volatile carbonyl species. E<sup>0−0</sup> predictions do overestimate measured values by ∼8 kJ/mol due to a lack of triples contribution in E relax, but this overestimation is systematic and the mean unsigned error is within 4 kJ/mol once this is accounted for.</div>

Geometry Optimization, UV/Vis, NBO, HOMO and LUMO, Excited State and Antioxidant Evaluation of Pyrimidine Derivatives

2020 ◽  
Vol 17 ◽  
Author(s):  
Siyamak Shahab ◽  
Masoome Sheikhi ◽  
Evgeni Kvasyuk ◽  
Aliaksei G. Sysa ◽  
Radwan Alnajjar ◽  
...  
Keyword(s):  
Density Functional ◽  
Antioxidant Properties ◽  
Geometry Optimization ◽  
Dft Method ◽  
Oscillator Strengths ◽  
Equilibrium Geometry ◽  
Pyrimidine Derivatives ◽  
Excitation Energies ◽  
Solvent Water ◽  
Homo And Lumo

: In this research, the four pyrimidine derivatives have been studied by using density functional theory (DFT/B3LYP/6-31G*) in solvent water for the first time. After quantum-chemical calculations, the title compounds have been synthesized. The electronic spectra of the new derivatives in a solvent water were performed by time-dependent DFT (TD-DFT) method. The equilibrium geometry, the HOMO and LUMO orbitals, MEP, excitation energies, natural charges, oscillator strengths for the molecules have also been calculated. NBO analysis has been calculated in order to elucidate the intramolecular, rehybridization and delocalization of electron density. These molecules have high antioxidant potential due to the planarity and formation of intramolecular hydrogen bonds. Antioxidant properties of the title compounds have been investigated and discussed.

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