scholarly journals Quantum chemical insight into molecular structure, spectroscopic and nonlinear optical studies on methylene bis(dithiobenzoate)-=SUP=-*-=/SUP=-

2021 ◽  
Vol 129 (9) ◽  
pp. 1136
Author(s):  
Davut Avci ◽  
Semiha Bahceli
Keyword(s):  
Title Compound ◽  
Quantum Chemical ◽  
Density Functional ◽  
Nonlinear Optical ◽  
Chemical Shifts ◽  
Basis Set ◽  
Spectral Studies ◽  
Nmr Chemical Shifts ◽  
Vis Spectroscopy ◽  
C Nmr

In this study, the methylene bis(dithiobenzoate) molecule, (C15H12S4), as a bioactive molecule has been subjected to quantum chemical computations using density functional theory (DFT) in order to investigate the molecular geometry, IR, UV-visible and NMR spectral studies. The title molecule has been optimized at the B3LYP, B3PW91 and PBE11PBE levels of DFT and 6-311G(d,p) basis set. Furthermore, the vibrational frequencies, the HOMO-LUMO energy levels, the 1H and 13C NMR chemical shifts (ppm), nonlinear optical properties calculations of the title compound were obtained by B3LYP, B3PW91 and PBE1PBE levels. The maximum electronic transition wavelengths, oscillator strengths, excited state and transition dipole moments for the title compound were also investigated by B3LYP, B3PW91 and PBE1PBE levels of time-dependent (TD)-DFT. Keywords: methylene bis(dithiobenzonoate), IR and UV-vis spectroscopy, 1H and 13C NMR chemical shifts, NLO DFT method.

Synthetic, Infrared, 1H and 13C NMR Spectral Studies on N-(2/3/4-Substituted Phenyl)-2,4-Disubstituted Benzenesulphonamides, 2,4-(CH3)2/2-CH3-4-Cl/2,4-Cl2C6H3SO2NH(i-XC6H4) (i-X = H, 2-CH3, 3-CH3, 4-CH3, 2-Cl, 3-Cl, 4-Cl, 4-F, 4-Br)

2006 ◽  
Vol 61 (10-11) ◽  
pp. 600-606
Author(s):  
Savitha M. Basappa ◽  
Basavalinganadoddy Thimme Gowda
Keyword(s):  
Solid State ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Spectral Studies ◽  
1H And 13C Nmr ◽  
Nmr Chemical Shifts ◽  
Benzene Rings ◽  
Stretching Vibrations ◽  
Absorption Frequencies ◽  
C Nmr

Twenty six N-(2/3/4-substituted phenyl)-2,4-disubstituted benzenesulphonamides of the general formulae 2,4-(CH3)2C6H3SO2NH(i-XC6H4), 2-CH3-4-ClC6H3SO2NH(i-XC6H4) and 2,4- Cl2C6H3SO2NH(i-XC6H4), where i-X = H, 2-CH3, 3-CH3, 4-CH3, 2-Cl, 3-Cl, 4-Cl, 4-F or 4-Br, have been prepared, characterized and their infrared spectra in the solid state and 1H and 13C NMR spectra in solution studied. The infrared N-H stretching vibrational frequencies vary in the range 3298 - 3233 cm−1. Asymmetric and symmetric SO stretching vibrations appear in the ranges 1373 - 1311 cm−1 and 1177 - 1140 cm−1, respectively, while C-S, S-N and C-N stretching absorptions vary in the ranges 840 - 812 cm−1, 972 - 908 cm−1 and 1295 - 1209 cm−1, respectively. The various 1H and 13C NMR chemical shifts are assigned to the protons and carbon atoms of the two benzene rings in line with those for similar compounds. The incremental shifts due to the groups in the parent compounds have been computed by comparing the chemical shifts of the protons or carbon atoms in these compounds with those of benzene or aniline, respectively. The computed incremental shifts and other data were used to calculate the 1H and 13C NMR chemical shifts of the substituted compounds in three different ways. The calculated chemical shifts by the three methods compared well with each other and with the observed chemical shifts. It is observed that there are no particular trends in the variation of either the infrared absorption frequencies or the chemical shifts with the nature or site of substitution.

First theoretical probe for alkynyl bridged thiophene modified coumarin nonlinear optical materials with D-π-A and A-π-D-π-A structures

2022 ◽  
Author(s):  
Shanggeng Li ◽  
Fanghua Zhu ◽  
Yawen Zhou ◽  
Jiaming Hu ◽  
Jing Li ◽  
...  
Keyword(s):  
Density Functional ◽  
Nonlinear Optical ◽  
Molecular Design ◽  
Energy Levels ◽  
Basis Set ◽  
Hybrid Functional ◽  
Functional Theory ◽  
Text Structures ◽  
Polar Moment ◽  
Vis Spectroscopy

First-principles exploration is very important to molecular design. In this study, geometric structure, intramolecular charge transfer (ICT), energy levels, polar moment, and ultraviolet–visible (UV–Vis) spectroscopy of eight novel and different alkynyl bridged thiophene modified coumarin nonlinear optical molecules with [Formula: see text]-[Formula: see text]-[Formula: see text] and [Formula: see text]-[Formula: see text]-[Formula: see text]-[Formula: see text]-[Formula: see text] structures had been studied by density-functional theory (DFT) calculations within B3LYP hybrid functional using 6-31 [Formula: see text], [Formula: see text] Gaussian type molecular-orbital basis set. This has guiding significance for the design of nonlinear optical molecules and the development of coumarin-based photoelectric molecules.

scholarly journals A theoretical study on 2-chloro-5-(2-hydroxyethyl)-4-methoxy-6-methylpyrimidine by DFT/ab initio calculations

2015 ◽  
Vol 33 (2) ◽  
pp. 369-380
Author(s):  
Hacer Pir Gümüs ◽  
Davut Avci ◽  
Yusuf Atalay ◽  
Ömer Tamer
Keyword(s):  
Energy Level ◽  
Chemical Shifts ◽  
Molecular Geometry ◽  
Energy Difference ◽  
Basis Set ◽  
Nmr Chemical Shifts ◽  
Title Molecule ◽  
Experimental Values ◽  
C Nmr ◽  
Molecular Energy Level

AbstractQuantum chemical calculations have been performed to study the molecular geometry, 1H and 13C NMR chemical shifts, conformational, natural bond orbital (NBO) and nonlinear optical (NLO) properties of the 2-chloro-5-(2-hydroxyethyl)-4- methoxy-6-methylpyrimidine molecule in the ground state using DFT and HF methods with 6-311++G(d,p) basis set. The optimized geometric parameters and 1H and 13C NMR chemical shifts have been compared with the experimental values of the title molecule. The results of the calculations show excellent agreement between the experimental and calculated frequencies at B3LYP/6-311++G(d,p) level. In order to provide a full understanding of the properties of the title molecule in the context of molecular orbital picture, the highest occupied molecular energy level (EHOMO), the lowest unoccupied molecular energy level (ELUMO), the energy difference (DE) between EHOMO and ELUMO, electronegativity (χ), hardness (η) and softness (S) have been calculated using B3LYP/6-311++G(d,p) and HF/6-311++G(d,p) levels. The calculated HOMO and LUMO energies show that the charge transfer occurs within the title molecule.

scholarly journals Molecular modelling, spectroscopic characterization and nonlinear optical analysis on N-Acetyl-DL-methionine

2020 ◽  
Vol 66 (6 Nov-Dec) ◽  
pp. 749
Author(s):  
N. Günay ◽  
Ö. Tamer ◽  
D. Avcı ◽  
E. Tarcan ◽  
Y. Atalay
Keyword(s):  
Electronic Properties ◽  
Title Compound ◽  
Density Functional ◽  
Nonlinear Optical ◽  
Energy Gap ◽  
Spectroscopic Characterization ◽  
Oscillator Strengths ◽  
Basis Set ◽  
Molecular Electrostatic Potential Surface ◽  
Experimental Values

In this present methodical study, on the basis of the density functional theory (DFT), the first-principles calculations have been employed successfully to study the structural and electronic properties of N-acetyl-DL-methionine (C7H13NO3S) which is a derivative of DL-methionine which is also known DL-2-amino-4-methyl-thiobutanoic acid. Optimized molecular structure, vibrational frequencies and also 13C and 1H NMR chemical shift values of the title compound are provided in a detailed manner by using B3LYP and HSEH1PBE functionals by applying 6-311++G(d,p) basis set for calculations using Gaussian 09W program. The comparison of the calculated values with the experimental values provides important information about the title compound. In addition, the electronic properties (UV-Vis calculations) of the title compound, such as HOMO-LUMO energy values and energy gap, absorption wavelengths, oscillator strengths were performed basing on the optimized structure in gas phase. Moreover, the molecular electrostatic potential surface, dipole moment, nonlinear optical properties, linear polarizabilities and first hyperpolarizabilities and chemical parameters have also been studied.

scholarly journals Quantum-chemical study of C— H bond dissociation enthalpies of various small non-aromatic organic molecules

2013 ◽  
Vol 6 (1) ◽  
pp. 64-72 ◽  
Author(s):  
Peter Poliak ◽  
Adam Vagánek
Keyword(s):  
13C Nmr ◽  
Linear Correlation ◽  
Density Functional ◽  
Chemical Shifts ◽  
Basis Set ◽  
Basis Sets ◽  
Nmr Chemical Shifts ◽  
Bond Dissociation ◽  
13C Nmr Chemical Shifts ◽  
Experimental Values

Abstract In this work, C-H bond dissociation enthalpies (BDE) and vertical ionization potentials (IP) for various hydrocarbons and ketones were calculated using four density functional approaches. Calculated BDEs and IPs were correlated with experimental data. The linearity of the corresponding dependences can be considered very good. Comparing two used functionals, B3LYP C-H BDE values are closer to experimental results than PBE0 values for both used basis sets. The 6-31G* basis set employed with both functionals, gives the C-H BDEs closer to the experimental values than the 6-311++G** basis set. Using the obtained linear dependences BDEexp = f (BDEcalc), the experimental values of C-H BDEs for some structurally related compounds can be estimated solely from calculations. As a descriptor of the C-H BDE, the IPs and 13C NMR chemical shifts have been investigated using data obtained from the B3LYP/6-31G* calculations. There is a slight indication of linear correlation between IPs and C-H BDEs in the sets of simple alkanes and alkenes/ cycloalkenes. However, for cycloalkanes and aliphatic carbonyl compounds, no linear correlation was found. In the case of the 13C NMR chemical shifts, the correlation with C-H BDEs can be found for the sets of alkanes and cycloalkanes, but for the other studied molecules, no trends were detected.

scholarly journals Effect of Substituents on Phenazine Derivatives by Spectral Studies

2015 ◽  
Vol 48 ◽  
pp. 114-122
Author(s):  
G. Thirunarayanan ◽  
I. Muthuvel ◽  
V. Sathiyendiran
Keyword(s):  
Regression Analysis ◽  
Statistical Analysis ◽  
Spectral Data ◽  
Chemical Shifts ◽  
Spectral Studies ◽  
Nmr Chemical Shifts ◽  
Effect Of Substituents ◽  
Substituent Constants ◽  
Infrared Frequencies ◽  
C Nmr

A series of eleven substituted dipyrido[3,2-a; 2′,3′-c]phenazine derivatives have been synthesized and examined their purities by literature method. The infrared and 13C NMR spectral data of prepared phenazines were correlated with Hammett substituent constants, F and R parameters using single and multi-regression analysis. From the results of statistical analysis, the effect of substituents on the infrared frequencies (ν, cm-1) and 13C nmr chemical shifts(δ, ppm) has been studied.

DFT QUANTUM CHEMICAL STUDIES ON 1-[N-(2-PYRİDYL) AMİNOMETHYLİDENE]-2(1H)-NAPHTALENONE

2012 ◽  
Vol 11 (04) ◽  
pp. 745-762 ◽  
Author(s):  
MEHMET TOY ◽  
HASAN TANAK
Keyword(s):  
Title Compound ◽  
Quantum Chemical ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Formation Enthalpy ◽  
Polarizable Continuum Model ◽  
Second Order ◽  
Basis Set ◽  
Frontier Molecular Orbital ◽  
Statistical Thermodynamic

Quantum chemical calculations of the structure, molecular electrostatic potential and thermodynamic functions have been performed using the density functional (DFT/B3LYP) method with the 6-311++G(d,p) basis set for the title compound 1-[N-(2-pyridyl)aminomethylidene}-2(1H)-Naphtalenone. The energetic behavior of the title compound in solvent media has been examined by applying the Onsager and the polarizable continuum model. To investigate second order nonlinear optical properties of the title compound, the electric dipole μ, the polarizability α and the first hyperpolarizability β were computed using the density functional B3LYP and CAM-B3LYP methods with the 6-311++G(d,p) basis set. According to our calculations, the title compound exhibits nonzero β value revealing second order NLO behavior. The changes of thermodynamic properties for the formation of the title compound with the temperature ranging from 200 K to 500 K have been obtained using the statistical thermodynamic method. The relationship between formation enthalpy and entropy changes has been investigated with the entropy–enthalpy compensation. Besides, natural bond orbital and frontier molecular orbital analysis of the title compound were investigated by theoretical calculations.

scholarly journals Evaluation of 13C NMR spectra of cyclopropenyl and cyclopropyl acetylenes by theoretical calculations

2004 ◽  
Vol 2 (1) ◽  
pp. 196-213 ◽  
Author(s):  
Valentine Ananikov
Keyword(s):  
13C Nmr ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Chemical Shifts ◽  
Cyclopropane Ring ◽  
Density Functional Method ◽  
Basis Set ◽  
Nmr Chemical Shifts ◽  
13C Nmr Chemical Shifts ◽  
Giao Calculations

AbstractA convenient methodology was developed for a very accurate calculation of 13C NMR chemical shifts of the title compounds. GIAO calculations with density functional methods (B3LYP, B3PW91, PBE1PBE) and 6-311+G(2d,p) basis set predict experimental chemical shifts of 3-ethynylcyclopropene (1), 1-ethynylcyclopropane (2) and 1,1-diethynylcyclopropane (3) with high accuracy of 1–2 ppm. The present article describes in detail the effect of geometry choice, density functional method, basis set and effect of solvent on the accuracy of GIAO calculations of 13C NMR chemical shifts. In addition, the particular dependencies of 13C chemical shifts on the geometry of cyclopropane ring were investigated.

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