scholarly journals Comparative Studies of Infrared Spectral Simulation of Some Benzoyl Derivatives of N-Heterocyclic Compounds Using Semi-Empirical Methods

2020 ◽  
Vol 32 (10) ◽  
pp. 2463-2468
Author(s):  
Pradeep Kumar Gupta ◽  
Kishor Arora
Keyword(s):  
Heterocyclic Compounds ◽  
Density Functional ◽  
Theoretical Chemistry ◽  
Am1 Method ◽  
Simulation Studies ◽  
Empirical Methods ◽  
Spectral Simulation ◽  
Infrared Spectral ◽  
Semi Empirical ◽  
Derivatives Of

Simulation studies based on ab initio, semi-empirical or density functional (DFT) calculations are now becoming common among the researchers who are pursuing their intereset in theoretical chemistry. These studies are based on quantum chemical softwares. These studies provide better insight for the structural and other parameters of the compounds. The present paper includes the studies on synthesis or procurement along with the simulated IR spectra of some benzoyl derivatives of N-heterocyclic compounds viz. 2-aminopyridine, 4-aminoantipyrine, 2-aminopyrimidine or 3-aminopyridine using four different AM1, PM3, MNDO and ZINDO1 semi-empirical methods. Among the methods used for the study, AM1 method is more reliable and more accurate so far as the prediction of spectral results is concerned.

scholarly journals Studies on Simulation of Spectra of Some Organic Compounds

2019 ◽  
Vol 35 (6) ◽  
pp. 1655-1668
Author(s):  
Pradeep Kumar Gupta ◽  
Kishor Arora
Keyword(s):  
Ab Initio ◽  
Organic Compounds ◽  
Quantum Chemical ◽  
Theoretical Chemistry ◽  
Simulation Studies ◽  
Empirical Methods ◽  
Present Communication ◽  
Semi Empirical ◽  
Simulation Of Spectra

Quantum chemical viz. ab initio or semi-empirical based simulation studies are now prevailing among workers / scientists pursuing their studies in theoretical chemistry. These studies provide better insight for the compounds so far as the studies of their structural orother parameters are concern. Studies involving the packages developed on the basis of ab-initio or semi-empirical methods are proven to be more effective and as a better tool because of number of their advantages. The present communication includes the studies on synthesis or procurement along with the simulation of spectra viz. I.R. of some heterocyclic organic compounds.

QSAR Analysis of Selected Antimicrobial Structures Belonging to Nitro-derivatives of Heterocyclic Compounds

2020 ◽  
Vol 17 (2) ◽  
pp. 214-225 ◽  
Author(s):  
Piotr Kawczak ◽  
Leszek Bober ◽  
Tomasz Bączek
Keyword(s):  
Antimicrobial Activity ◽  
Heterocyclic Compounds ◽  
Molecular Descriptors ◽  
Microbiological Activity ◽  
Activity Data ◽  
Qsar Analysis ◽  
Qsar Models ◽  
Nitro Derivatives ◽  
Semi Empirical ◽  
Derivatives Of

Background: Nitro-derivatives of heterocyclic compounds were used as active agents against pathogenic microorganisms. A set of 4- and 5-nitroimidazole derivatives exhibiting antimicrobial activity was analyzed with the use of Quantitative Structure-Activity Relationships (QSAR) method. The study included compounds used both in documented treatment and those described as experimental. Objective: The purpose of this study was to demonstrate the common and differentiating characteristics of the above-mentioned chemical compounds alike physicochemically as well as pharmacologically based on the quantum chemical calculations and microbiological activity data. Methods: During the study PCA and MLR analysis were performed, as the types of proposed chemometric approach. The semi-empirical and ab initio level of in silico molecular modeling was performed for calculations of molecular descriptors. Results: QSAR models were proposed based on chosen descriptors. The relationship between the nitro-derivatives structure and microbiological activity data was able to class and describe the antimicrobial activity with the use of statistically significant molecular descriptors. Conclusion: The applied chemometric approaches revealed the influential features of the tested structures responsible for the antimicrobial activity of studied nitro-derivatives.

scholarly journals STRUCTURAL AND ELECTRONIC PROPERTIES OF BRIDGED BITHIOPHENE S-OXIDES (BTO) WITH S, S=O, O, SiH2 and BH2 BRIDGE: SEMI-EMPIRICAL AND AB INITIO STUDY

2010 ◽  
Vol 18 (18) ◽  
pp. 1-10
Author(s):  
Banjo Semire ◽  
Isaiah Ajibade Adejoro ◽  
Olusegun Ayobami Odunola
Keyword(s):  
Density Functional Theory ◽  
Thermodynamic Properties ◽  
Ab Initio ◽  
Density Functional ◽  
Ab Initio Study ◽  
Empirical Methods ◽  
Functional Theory ◽  
Structural And Electronic Properties ◽  
Semi Empirical ◽  
Good Agreement

In this paper, we theoretically studied the geometries, stabilities, electronic and thermodynamic properties of bridged bithiophene S-oxide (BTO-X) derivates (with X = BH2, SiH2, S, S=O, and O) by using semi-empirical methods, ab-initio, and Density functional theory. The geometries and thermodynamic parameters calculated by PM3 were in good agreement with that of B3LYP/6-31G(d). The bandgap calculated by B3LYP/6-31G(d) ranged from 3.94eV (BTO-O)-3.16eV (BTO-BH2). The absorption λmax calculated suing B3LYP/6-31G(d) shifted to longer wavelength with X=BH2, SiH2, and S=O due to enhancement of π-conjugated system whereas, BTO-S and BTO-O shifted to shorter wavelengths as compared to dimmer thiophene S-oxide (2TO).

scholarly journals Density functional tight binding: values of semi-empirical methods in an ab initio era

2014 ◽  
Vol 16 (28) ◽  
pp. 14368-14377 ◽  
Author(s):  
Qiang Cui ◽  
Marcus Elstner
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Density Functional ◽  
Tight Binding ◽  
Empirical Methods ◽  
Functional Theory ◽  
Hartree Fock ◽  
Semi Empirical

Semi-empirical (SE) methods are derived from Hartree–Fock (HF) or Density Functional Theory (DFT) by neglect and approximation of electronic integrals.

scholarly journals THEORETICAL METHODS OF NANOSTRUCTURES INVESTIGATION

2017 ◽  
Vol 18 (9) ◽  
pp. 106-117
Author(s):  
I.N. Saliy ◽  
A.S. Kolesnikova ◽  
O.E. Glukhova ◽  
I.V. Kirillova ◽  
E.L. Kossovich ◽  
...  
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Ab Initio Methods ◽  
Empirical Methods ◽  
Theoretical Methods ◽  
Basic Concepts ◽  
Semi Empirical

In this work, a review is presented concerning the most modern theoretical methods aimed at investigation of various nanostructures properties. The basic concepts of ab initio methods, density functional, semi-empirical and empirical methods are considered. The applicability boundaries of calculation schemes utilized in the aforementioned methods are denoted.

scholarly journals Comparing Study of The Stability and spectral properties vibrations for some Tellurium (IV) compounds containing cycloctadienyl group by Quantum Mechanical Calculations

2013 ◽  
Vol 10 (3) ◽  
pp. 1041-1049
Author(s):  
Baghdad Science Journal
Keyword(s):  
Density Functional ◽  
Heat Of Formation ◽  
Basis Set ◽  
Orbital Energy ◽  
Empirical Methods ◽  
Geometrical Structures ◽  
Functional Theory ◽  
Exchange Correlation ◽  
The Stability ◽  
Semi Empirical

Density Functional Theory (DFT) with B3LYP hybrid exchange-correlation functional and 3-21G basis set and semi-empirical methods (PM3) were used to calculate the energies (total energy, binding energy (Eb), molecular orbital energy (EHOMO-ELUMO), heat of formation (?Hf)) and vibrational spectra for some Tellurium (IV) compounds containing cycloctadienyl group which can use as ligands with some transition metals or essential metals of periodic table at optimized geometrical structures.

scholarly journals Do Better Quality Embedding Potentials Accelerate the Convergence of QM/MM Models? The Case of Solvated Acid Clusters

Molecules ◽  
2018 ◽  
Vol 23 (10) ◽  
pp. 2466 ◽  
Author(s):  
Junming Ho ◽  
Yihan Shao ◽  
Jin Kato
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Water Model ◽  
Reaction Centre ◽  
Empirical Methods ◽  
Functional Theory ◽  
Highly Sensitive ◽  
Solvent Molecules ◽  
Dynamics Simulations ◽  
Semi Empirical

This study examines whether the use of more accurate embedding potentials improves the convergence of quantum mechanics/molecular mechanics (QM/MM) models with respect to the size of the QM region. In conjunction with density functional theory calculations using the ωB97X-D functional, various embedding potentials including the TIP3P water model, the effective fragment potential (EFP), and semi-empirical methods (PM6, PM7, and DFTB) were used to simulate the deprotonation energies of solvated acid clusters. The calculations were performed on solvated neutral (HA) and cationic (HB+) acids clusters containing 160 and 480 water molecules using configurations sampled from molecular dynamics simulations. Consistently, the ωB97X-D/EFP model performed the best when using a minimal QM region size. The performance for the other potentials appears to be highly sensitive to the charge character of the acid/base pair. Neutral acids display the expected trend that semi-empirical methods generally perform better than TIP3P; however, an opposite trend was observed for the cationic acids. Additionally, electronic embedding provided an improvement over mechanical embedding for the cationic systems, but not the neutral acids. For the best performing ωB97X-D/EFP model, a QM region containing about 6% of the total number of solvent molecules is needed to approach within 10 kJ mol−1 of the pure QM result if the QM region was chosen based on the distance from the reaction centre.

Theoretical study of the electronic spectra of s-triazine vapour

2009 ◽  
Vol 87 (8) ◽  
pp. 1148-1153 ◽  
Author(s):  
Delano P. Chong
Keyword(s):  
Experimental Data ◽  
Gas Phase ◽  
Electronic Spectra ◽  
Density Functional ◽  
Theoretical Study ◽  
Empirical Methods ◽  
Excitation Energies ◽  
Excitation Spectra ◽  
Core Electrons ◽  
Semi Empirical

The ionization and excitation spectra of valence and core electrons of s-triazine in the gas phase are studied with ab initio, density functional, and semi-empirical methods. The results are compared with available experimental data and previous calculations. New estimates are proposed for the ionization energies of both valence and core electrons. The calculated excitation energies are consistent with experiment.

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