Theoretical investigations on the structure and vibrational spectra of N-(2-hydroxy-1-naphthylidene)threonine (original) (raw)
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Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2006
An extensive computational study of thiophene-2-aldehyde conformers syn and anti has been carried out using density functional (DFT). From these calculations, B3LYP/6-31G(d) has been chosen as it produces results remarkably close in comparison with experimental ones, with less demanding computational time. Data obtained from DFT computation were used to perform a normal coordinate analysis to complement and give insight in the experimental vibrational assignment. Calculated dipole moments and relative stabilities of isomers coherently support experimental statements given in the literature.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2011
The FT-IR and FT-Raman vibrational spectra of 2,3-naphthalenediol (C 10 H 8 O 2 ) have been recorded using Bruker IFS 66V spectrometer in the range of 4000-100 cm −1 in solid phase. A detailed vibrational spectral analysis has been carried out and the assignments of the observed fundamental bands have been proposed on the basis of peak positions and relative intensities. The optimized molecular geometry and vibrational frequencies in the ground state are calculated by using the ab initio Hartree-Fock (HF) and DFT (LSDA and B3LYP) methods with 6-31+G(d,p) and 6-311+G(d,p) basis sets. There are three conformers, C1, C2 and C3 for this molecule. The computational results diagnose the most stable conformer of title molecule as the C1 form. The isotropic computational analysis showed good agreement with the experimental observations. Comparison of the fundamental vibrational frequencies with calculated results by HF and DFT methods. Comparison of the simulated spectra provides important information about the capability of computational method to describe the vibrational modes. A study on the electronic properties, such as absorption wavelengths, excitation energy, dipole moment and Frontier molecular orbital energies, are performed by time dependent DFT approach. The electronic structure and the assignment of the absorption bands in the electronic spectra of steady compounds are discussed. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. On the basis of the thermodynamic properties of the title compound at different temperatures have been calculated. The statistical thermodynamic properties (standard heat capacities, standard entropies, and standard enthalpy changes) and their correlations with temperature have been obtained from the theoretical vibrations.
Bulletin of the Chemical Society of Japan, 2013
The effect of substitution (F, Cl, SH, NO 2 , CH 2 F, CH 2 Cl, CH 2 COOH, CH 2 OCH 3 , and SCOCH 3) on the hydrogenbond strengths, vibrational frequencies, and physical properties such as dipole moment, chemical potential, and chemical hardness of substituted (Z)-N-(thionitrosomethylene)thiohydroxylamine compound has been systematically explored. All the studied derivatives have been optimized at the B3LYP/6-311++G** level of theory in gas phase, water and carbon tetrachloride solutions. The aromaticity of the formed ring is measured through the structurally based harmonic oscillator model of aromaticity (HOMA), and the magnetic based nucleus independent chemical shift (NICS) measurements. The topological properties of the electron density distributions for SH£S intramolecular bridges have been analyzed in terms of the Bader theory of atoms in molecules (AIM). Natural population analysis data, the electron density and Laplacian properties, as well as¯(SH) have been used to evaluate the hydrogen-bonding interactions. Furthermore, calculated 1 H NMR chemical shifts (¤ H) correlate well with the hydrogen-bond distance and¯(SH) as well as electron density at the bond critical points in the molecular electron density topography.
Density Functional Study of 2-[(R-Phenyl)amine]-1,4-naphthalenediones
Journal of Chemical Theory and Computation, 2007
The molecular and electronic structures of a series of 2-[(R-phenyl)amine]-1,4naphthalenediones (R) m-Me, p-Me, mEt , p-CF 3 , p-Hex, pEt , m-F, m-Cl, p-OMe, p-COMe, p-Bu, m-COOH, p-Cl, p-COOH, p-Br, m-NO 2 , m-CN, and p-NO 2) and their anions are investigated in the framework of density functional theory. The calculations are of all-electron type using a double zeta valence polarization basis set optimized for density functional theory methods. The theoretical study shows that all compounds are nonplanar. The nonplanarity can be rationalized in terms of occupied π orbitals. A linear correlation between the measured half-wave potentials and the calculated gas-phase electron affinities is found. It holds for local as well as generalized gradient corrected functionals. Structural parameters, harmonic vibrational frequencies, and adiabatic and vertical electron affinities as well as orbital and spin density plots of the studied compounds are presented.
Journal of The American Chemical Society, 1985
Restricted Hartree-Fock calculations have been carried out for 1,3,&cycloheptatriene, norcaradiene, lH-azepine, benzenimine (azanorcardiene), oxepine and benzene oxide (oxanorcaradiene) employing the STO-3G, 4-31G and 6-31G* basis sets. Theoretical geometries, conformations and barriers to ring inversion have been obtained and compared with the available experimental structural data. It has been found that the cyclotrienes possess a boat conformation with a constant admixture of 22% chair character leading to a flattening of the triene part and n-electron delocalization typical for a planar polyene. The structural data obtained in this work suggest that cyclic delocalization of either 6~ (homoaromaticity) or 8~ electrons (antiaromaticity) is not present in the three cyclotrienes. The former possibility, however, cannot be excluded in the case of the three norcaradienes.
Conformational studies of dithiastannolanes by dynamic nuclear magnetic resonance spectroscopy
Journal of the Chemical Society, Dalton Transactions, 1982
The barriers to conformational interconversion of the five-membered rings of the title compounds of general type SnRR'(SCH,CHR"S) (R, R' = M e or Ph; R" = H or Me) have been measured for the first time by low-temperature n.m.r. studies. Room-temperature measurements indicate that the chelate rings exist as half-chair conformations with the -CH2CH R"moiety in a fully staggered configuration, as in the solid state. These findings are at variance with a previous n.m.r. study of this type of system. The AGI values for the interconversion of the two half-chair conformations lie in the range 30-32 kJ mol-' and are essentially indep.endent of the substituents on the SnlV atom and on the five-membered ring.
Journal of Molecular Structure, 2002
The infrared (3400-50 cm 21 ) and/or Raman (3400 -10 cm 21 ) spectra of gaseous, xenon solution, liquid and solid 5chloropent-2-yne, CH 2 ClCH 2 CCCH 3 , have been recorded. These data indicate that the molecule exists in the anti (the C -Cl bond is trans to the CxC bond) and the gauche conformations in the vapor and liquid but only the anti conformer remains in the solid state. From a variable temperature infrared study of the xenon solution, the anti conformation has been determined to be more stable than the gauche form by 233^23 cm 21 (2.79^0.28 kJ/mol) and it is estimated that 39% of the sample is in the gauche form at ambient temperature. The optimized geometries, conformation stabilities, harmonic force fields, Raman activities, depolarization ratios, and infrared intensities have been obtained from ab initio MP2/6-31G(d) calculations with full electron correlation. These predicted quantities are compared to the corresponding experimental quantities when appropriate. Equilibrium geometries and energies for both conformers have been obtained from ab initio MP2/6-311G(d,p), MP2/6-311G(2d,2p) and MP2/6-311G(2df,2pd) calculations. Vibrational assignments for the 24 normal modes for the anti conformer are proposed and several of the fundamentals for the gauche conformer are assigned. The sub-band structure on the pseudodegenerate vibrations of the methyl group indicates that it is almost free internal rotation. From this fine structure, the Coriolis coupling constants, j, have been determined. These experimental and theoretical results are compared to the corresponding quantities of some similar molecules. q
ACTA PHYSICA POLONICA A, 2017
Vibrational frequencies of 2-Amino-4,5,6,7- Tetrahydrobenzo[b]Thiophene-3-Carbonitrile were calculated using density functional (DFT/B3YLP) method with 6-311++G(d,p) basis set by Gaussian 09. The assignments of the vibrational frequencies have been done by potential energy distribution analysis, using VEDA 4 software. The density functional theory and time dependent density functional theory methods have been used to study the electronic properties of 2-Amino-4,5,6,7-Tetrahydrobenzo[b]Thiophene-3-Carbonitrile. Isotropic chemical shifts were calculated using the gauge-invariant atomic orbital method. All computed spectroscopic properties were compared with experimental ones. The simulated spectra of the molecule show excellent agreement with the experimental spectra.