Synthesis, spectroscopic characterization and quantum chemical computational studies of (S)-N-benzyl-1-phenyl-5-(pyridin-2-yl)-pent-4-yn-2-amine (original) (raw)
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Computational and Theoretical Chemistry, 2013
The structural and vibrational properties of a potential anticancer agent, the 5-difluoromethyl-1,3,4 thiadiazole-2-amino derivative and its tautomeric forms were studied by using the available experimental infrared and 1 H, 13 C and 19 F NMR spectra and theoretical calculations based the density functional theory (DFT). The bonds order, atomic charges, charge-transfers and topological properties were studied by means of the Natural Bond Orbital (NBO) and the Atoms in Molecules theory (AIM) calculations. The harmonic vibrational wavenumbers for the optimized geometries were calculated at B3LYP/6-31G ⁄ and B3LYP/6-311++G ⁄⁄ levels. For a complete assignment of the compound infrared spectrum, the DFT calculations were combined with Pulay's scaled quantum mechanical force field (SQMFF) methodology in order to fit the theoretical wavenumbers values to the experimental ones. The results were then used to predict the Raman spectra, for which there are no experimental data. An agreement between theoretical and available experimental results was found and a complete assignment of all the observed bands in the vibrational spectra was performed. The theoretical vibrational calculations allowed us to obtain a set of scaled force constants fitting the observed wavenumbers. Additionally, the frontier molecular HOMO and LUMO orbitals for the compound were analyzed and compared with those calculated for the 2amino-1,3,4 thiadiazole molecule. The calculated 1 H, 13 C and 19 F chemicals shifts are in good agreement with the corresponding experimental NMR spectra of the compound in solution.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2007
The molecular structures, vibrational frequencies and corresponding vibrational assignments of xanthine and its methyl derivatives (caffeine and theobromine) have been calculated using ab initio Hartree-Fock (HF) and density functional theory (B3LYP) methods with 6-31G(d, p) basis set level. The calculations were utilized to the C S symmetries of the molecules. The obtained vibrational frequencies and optimised geometric parameters (bond lengths and bond angles) were seen to be well agreement with the experimental data. The used scale factors which have been obtained the ratio of the frequency values of the strongest peaks in the calculated and experimental spectra seem to cause the gained vibrations well corresponding to the experimental ones. Theoretical infrared intensities and Raman activities are also reported. analogues of xanthine prototropic tautomers is rather good approach to experimental study of the prototroic tautomeric equilibrium in nucleotide basis if relative energies of high-energy tautomers are not less than a few kcal/mol [10]. Some authors have described that in the preparation of xanthine and its methyl derivatives some care should be taken since sample handling may affect the water content of these samples which causes pseudopolymorphic transformations affecting their biavailability and stability .
Journal of The Serbian Chemical Society, 2009
The solid phase FT-IR and FT-Raman spectra of 6-amino-3-methyl- -1-phenyl-1H-pyrazolo(3,4-b)pyridine-5-carboxylic acid (PYRPCA) and 6,7-di- hydro-3-methyl-6-oxo-1-phenyl-1H-pyrazolo(3,4-b)pyridine-5-carbonitrile (PYR- PCN) were recorded in the region 4000-400 cm -1 . The spectra were interpreted with the aid of normal coordinate analysis following full structure optimization and force field calculations based on the density functional theory (DFT) using standard B3LYP, BLYP and ab initio RHF methods with 6-31G basis set and were scaled using a recommended set of scaling factors yielding fairly good agreement between the observed and calculated frequencies. Based on the pre- sent good quality, the scaled quantum mechanical (SQM) force field, a reliable description of the fundamentals of PYRPCA and PYRPCN, was provided. The calculations predicated a predominance of different tautomers in PYRPCA and keto-enol tautomers in PYRPCN. For PYRPCA, the most stable conformer is stabilized by...
Journal of Molecular Structure, 2011
The molecular geometry, vibrational frequencies, gauge including atomic orbital (GIAO) 1H and 13C chemical shift values and several thermodynamic parameters of 6-(2-hydroxyethyl)-2,3,4-triphenyl-2,6-dihydro-7H-pyrazolo[3,4-d]pyridazin-7-one in the ground state have been calculated by using the Hartree–Fock (HF) and density functional methods (B3LYP) with 6–31G(d) basis set. The results of the optimised molecular structure are presented and compared with the experimental X-ray diffraction. The calculated results show that the optimised geometries can well reproduce the crystal structural parameters and the theoretical vibrational frequencies, and 1H and 13C NMR chemical shift values show good agreement with experimental data. The computed vibrational frequencies are used to determine the types of molecular motions associated with each of the experimental bands observed. To determine conformational flexibility, molecular energy profile of the title compound was obtained by semi-empirical (AM1) with respect to selected degree of torsional freedom, which were varied from −180° to +180° in steps of 10°. Besides, molecular electrostatic potential (MEP), frontier molecular orbitals (FMO), and thermodynamic properties were performed at HF and DFT levels of theory.
American Academic Scientific Research Journal for Engineering, Technology, and Sciences, 2019
The title compound, pyrazole carbaldehyde have been optimized using Gaussian 9 software program, via density functional theory framework (DFT/B3LYP) by 6-311G (d, p) basis set, the output file was visualize using Gaussian view program, geometric properties, thermochemical and reactivity descriptors such as ionization potential (IP), electron affinity (EA), electronegativity (χ), chemical potential (μ), hardness (η), softness (σ), electrophilicity index (ω) and nucleophilicity index (N) were calculated. Mapping of electrostatic surface potential (MESP) allow us to establish trends that enable making predictions about the reactive sites of the studied compound. Besides, the optimized structure is subjected to frequency analysis at the same level of theory to obtain thermodynamic correction values. Vibrational assignments and nuclear magnetic resonance (1 H-& 13 C-NMR) chemical shifts of the molecule were calculated by gauge independent atomic orbital (GIAO) method using the CPCM model, and mapping of current density shielding of proton and carbon nucleus of the aldehyde group shied light on the molecular properties and reactivity of 5-oxo-1-phenyl-4-(2-phenylhydrazono)-4,5-dihydro-1H-pyrazole-3-carbaldehyde .
DFT and quantum chemical investigation of molecular properties of substituted pyrrolidinones
Arabian Journal of Chemistry, 2012
The DFT, quantum-chemical calculations and thermodynamics parameters of 1-{2-[(2hydroxyethyl)thio]ethyl}pyrrolidin-2-one (HTEP); [2-(2-oxo-pyrrolidin-1-yl)-ethyl]-phosphonic acid diethyl ester (EOEP); {[2-(2-oxopyrrolidin-1-yl)ethyl]thio}acetic acid (OETA); (2-pyridin-4yl-ethyl]thio}acetic acid (PTA) and pyridine (PY) have been calculated with Gaussian 94 and Hybrid B3LYP functional density with 6-31G* basis set. Moreover, the electronic properties such as highest occupied molecular orbital (HOMO), lowest unoccupied orbital (LUMO) energy and molecular densities have been investigated.