Experimental (FT-IR, Laser-Raman and NMR) and theoretical spectroscopic analysis of 3-[(N-methylanilino)methyl]-5-(thiophen-2-yl)-1,3,4-oxadiazole-2(3H)-thione

2017 ◽  
Vol 16 (03) ◽  
pp. 1750024 ◽  
Author(s):  
Yusuf Sert ◽  
Nuri Öztürk ◽  
Fatmah A. M. Al-Omary ◽  
Can Alaşalvar ◽  
Mona M. Al-Shehri ◽  
...  
Keyword(s):  
Molecular Orbital ◽  
Chemical Shifts ◽  
Molecular Structures ◽  
Basis Set ◽  
Spectroscopic Techniques ◽  
Nmr Chemical Shifts ◽  
Laser Raman ◽  
Ft Ir ◽  
Experimental Values ◽  
Vibrational Wavenumbers

The structure of a potential bioactive agent namely, 3-[([Formula: see text]-methylanilino)methyl]-5-(thiophen-2-yl)-1,3,4-oxadiazole-2(3[Formula: see text]-thione was characterized by proton and carbon-13 nuclear magnetic resonance (NMR) chemical shifts, Fourier transform infrared (FT-IR) and Laser-Raman spectroscopic techniques. The quantum chemical computations of molecular structures (disorder I and disorder II forms), vibrational wavenumbers, carbon-13 and proton chemical shifts and UV-Vis spectroscopic parameters have been performed with DFT/B3LYP method at 6-311[Formula: see text]G(d,p) basis set. The highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), nonlinear optical (NLO) properties and natural bond orbital (NBO) analyses have been theoretically examined with the mentioned calculation level. The calculated values have been compared with the recorded experimental data. The computed molecular geometric parameters, vibrational wavenumbers, NMR chemical shifts, and UV-Vis wavelengths have been found to be in a good harmony with the experimental values and spectral results of similar structures in the literature. We believe that the work will be of considerable interest to anyone working in the area of theoretical chemistry, whether in industry or academics.

Experimental (FT-IR, Laser-Raman and NMR) and theoretical comparative study on 2-benzylsulfanyl-4-pentyl-6-(phenylsulfanyl)pyrimidine-5-carbonitrile, a potential bioactive agent

2018 ◽  
Vol 17 (05) ◽  
pp. 1850035 ◽  
Author(s):  
Lamya H. Al-Wahaibi ◽  
Nuri Öztürk ◽  
Hanan M. Hassan ◽  
Yusuf Sert ◽  
Ali A. El-Emam ◽  
...  
Keyword(s):  
Molecular Orbital ◽  
Chemical Shifts ◽  
Pyrimidine Derivative ◽  
Basis Set ◽  
Potential Energy Distribution ◽  
Laser Raman ◽  
Highest Occupied Molecular Orbital ◽  
Laser Raman Spectra ◽  
Lowest Unoccupied Molecular Orbital ◽  
Ft Ir

In this paper, the experimental and theoretical vibrational frequencies of a potential bioactive pyrimidine derivative molecule named 2-benzylsulfanyl-4-pentyl-6-(phenylsulfanyl)pyrimidine-5-carbonitrile has been investigated. The experimental FT-IR and Laser-Raman spectra of the studied molecule are in the region (4000–400[Formula: see text]cm[Formula: see text] and (4000–100[Formula: see text]cm[Formula: see text], respectively, in gas phase. The vibrational modes and optimized ideal structure parameters(bond lengths, bond angles and selected dihedral angles) were calculated by using DFT/B3LYP, DFT/BHandHLYP and DFT/PBE1PBE methods with 6-311[Formula: see text]G(d,p) basis set. The theoretical mode assignments have been obtained by using potential energy distribution (PED) with the VEDA4 software program. Additionally, infrared and Raman intensities, the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) energies and their clouds, and other related molecular properties were calculated and evaluated. The proton (1H) and carbon-13 ([Formula: see text]C) nuclear magnetic resonance (NMR) chemical shifts have been investigated for the title molecule, both experimentally (in DMSO-d[Formula: see text] and theoretically (in vacuum and DMSO). The thermodynamic properties of the tile compound have been investigated using the mentioned theoretical computational methods. The results revealed that there isgood agreement between experimental and theoretical results and these results have supported the related literature.

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.

Spectroscopic investigation of 2-(4-benzoyl-1,5-diphenyl-1H-pyrazol-3-yl)-4H-naphto[2,3-d][1,3]oxazin-4-one molecule

2017 ◽  
Vol 16 (05) ◽  
pp. 1750039
Author(s):  
Yusuf Sert ◽  
Mehmet Gümüş ◽  
Volkan Kamaci ◽  
Halil Gökce ◽  
İbrahim Kani ◽  
...  
Keyword(s):  
Molecular Orbital ◽  
Title Compound ◽  
Chemical Shifts ◽  
Basis Set ◽  
Potential Energy Distribution ◽  
Distribution Analysis ◽  
Laser Raman ◽  
Laser Raman Spectra ◽  
Software Program ◽  
Lowest Unoccupied Molecular Orbital

In this present study, the experimental and theoretical vibrational frequencies of an important pharmacological molecule 2-(4-benzoyl-1,5-diphenyl-1[Formula: see text]-pyrazol-3-yl)-4[Formula: see text]-naphto[2,3-[Formula: see text]][1,3]oxazin-4-one have been researched. The experimental FT-IR and laser-Raman spectra of the title compound have been taken in the region (4000–400[Formula: see text]cm[Formula: see text]) and (4000–100[Formula: see text]cm[Formula: see text]), respectively. The vibrational modes and optimized structure parameters have been computed by using DFT/B3LYP methods with 6-311[Formula: see text]G(d,p) basis set. In our calculations, Gaussian 09W software program has been used. Assignments of theoretical vibrations have been obtained by potential energy distribution analysis using VEDA 4 software program. This program is important because it performs assignments with 10% precision. We have obtained a fairly good agreement between experimental and theoretically obtained results, and these results have supported the literature. Additionally, we have examined the highest occupied molecular orbital and the lowest unoccupied molecular orbital energies, the other related molecular energy values, nuclear magnetic resonance ([Formula: see text]C and 1H-proton) chemical shifts, and UV–Vis wavelengths (electronic absorption wavelengths of the title compound) by using the mentioned calculation level. The nonlinear optical properties of the title compound have also been determined by using DFT/B3LYP/6-311[Formula: see text]G(d,p) level.

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 Quantum chemical studies on structural, spectroscopic, nonlinear optical, and thermodynamic properties of the 1,2,4-triazole compound

2021 ◽  
Vol 27 (1) ◽  
pp. 112-132
Author(s):  
Hilal Medetalibeyoğlu ◽  
Haydar Yüksek
Keyword(s):  
Density Functional Theory ◽  
Molecular Orbital ◽  
Density Functional ◽  
Chemical Shifts ◽  
Atomic Orbital ◽  
Fluorescence Emission ◽  
Strong Relationship ◽  
Basis Set ◽  
Functional Theory ◽  
Nmr Chemical Shifts

Abstract In this study, the structure of 4-[4-(diethylamino)-benzylideneamino]-5-benzyl-2H-1,2,4-triazol-3(4H)-one (DBT) was examined through spectroscopic and theoretical analyses. In this respect, the geometrical, vibrational frequency, 1H and 13C-nuclear magnetic resonance (NMR) chemical shifts, thermodynamic, hyperpolarizability, and electronic properties including the highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) energies of DBT as a potential non-linear optical (NLO) material were investigated using density functional theory at the B3LYP level with the 6-311G basis set. 1H and 13C-NMR chemical shifts of DBT with the gauge-invariant atomic orbital and continuous set of gauge transformation methods (in the solvents) were estimated, and the computed chemical shift values displayed excellent alignment with observed ones. Time-dependent density-functional theory (TD-DFT) calculations with the integral equation formalism polarizable continuum model within various solvents and gas phases in the ground state were used to evaluate UV-vis absorption and fluorescence emission wavelengths. Thermodynamic parameters including enthalpy, heat capacity, and entropy for DBT were also calculated at various temperatures. Moreover, calculations of the NLO were carried out to obtain the title compound’s electric dipole moment and polarizability properties. To illustrate the effect of the theoretical method on the spectroscopic and structural properties of DBT, experimental data of structural and spectroscopic parameters were used. The correlational analysis results were observed to indicate a strong relationship between the experimental and theoretical results.

scholarly journals Predicting Heats of Explosion of Nitroaromatic Compounds through NBO Charges and 15N NMR Chemical Shifts of Nitro Groups

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Ricardo Infante-Castillo ◽  
Samuel P. Hernández-Rivera
Keyword(s):  
Cross Validation ◽  
Chemical Shifts ◽  
Quantitative Model ◽  
Nitroaromatic Compounds ◽  
Basis Set ◽  
15N Nmr ◽  
Prediction Ability ◽  
Heat Of Explosion ◽  
Nmr Chemical Shifts ◽  
Nbo Charges

This work presents a new quantitative model to predict the heat of explosion of nitroaromatic compounds using the natural bond orbital (NBO) charge and 15N NMR chemical shifts of the nitro groups (15NNitro) as structural parameters. The values of the heat of explosion predicted for 21 nitroaromatic compounds using the model described here were compared with experimental data. The prediction ability of the model was assessed by the leave-one-out cross-validation method. The cross-validation results show that the model is significant and stable and that the predicted accuracy is within 0.146 MJ kg−1, with an overall root mean squared error of prediction (RMSEP) below 0.183 MJ kg−1. Strong correlations were observed between the heat of explosion and the charges (R2 = 0.9533) and 15N NMR chemical shifts (R2 = 0.9531) of the studied compounds. In addition, the dependence of the heat of explosion on the presence of activating or deactivating groups of nitroaromatic explosives was analyzed. All calculations, including optimizations, NBO charges, and 15NNitro NMR chemical shifts analyses, were performed using density functional theory (DFT) and a 6-311+G(2d,p) basis set. Based on these results, this practical quantitative model can be used as a tool in the design and development of highly energetic materials (HEM) based on nitroaromatic compounds.

Liquid Crystalline Properties of 4,4and#39;-methylenebis(N-(4-Alkanoxybenzylidene)aniline): Synthesis, Characterization, and Theoretical study

2019 ◽  
Vol 41 (6) ◽  
pp. 1107-1107
Author(s):  
Mohammed Taha Yaseen and Abdullah Hussein Kshash Mohammed Taha Yaseen and Abdullah Hussein Kshash
Keyword(s):  
Liquid Crystalline ◽  
Theoretical Study ◽  
Basis Set ◽  
Spectroscopic Techniques ◽  
Benzene Nucleus ◽  
Crystal Properties ◽  
Ft Ir ◽  
Alkoxy Groups ◽  
Gaussian Program ◽  
Mesomorphic Properties

The paper presents six homologues series of Schiff bases ether compounds distinguished by the length of terminal alkoxy groups which substituted on a side benzene nucleus. The above structures were demonstrated through the use of spectroscopic techniques, like FT- IR and 1H-NMR. Polarized hot stage optical microscopy was used to study both mesomorphic properties and phase transitions. The results showed that out of the six compounds only three (B2, B3 and B4) were pure (marble) nematic mesophase, while no liquid crystal properties for (B5, B6 and B7) compounds. The theoretical study for the electronic structures was intended to study the effects of alkyl chain length on the electronic structure by using Gaussian program, DFT and 6-31G as basis set. The theoretical results indicate that there is no effect to the terminal substituted alkoxy groups on the HOMO energies but there is an effect on LUMO energies through decreasing energy for the prepared compounds.

THE RELATION OF 15N NMR, 1H NMR CHEMICAL SHIFTS WITH THE ATOMIC NET CHARGE AND MOLECULAR STRUCTURES

1987 ◽  
Vol 3 (06) ◽  
pp. 632-637
Author(s):  
Chen Yuehua ◽  
◽  
Guo Guolin ◽  
Shen Qifeng ◽  
Zhao Yufen ◽  
...  
Keyword(s):  
Chemical Shifts ◽  
Molecular Structures ◽  
Net Charge ◽  
Nmr Chemical Shifts ◽  
H Nmr
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