A combined experimental and theoretical DFT (B3LYP, CAM-B3LYP and M06-2X) study on electronic structure, hydrogen bonding, solvent effects and spectral features of methyl 1H-indol-5-carboxylate (original) (raw)
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Open Chemistry, 2017
(5-Methoxy-1H-indol-1-yl)(5-methoxy-1H-indol-2-yl)methanone (MIMIM) is a bis-indolic derivative that can be used as a precursor to a variety of melatonin receptor ligands. In this work, the energetic and spectroscopic profiles of MIMIM were studied by a combined DFT and experimental approach. The IR, Raman, UV-Vis, 1 H NMR and 13 C NMR spectra were calculated by PBEPBE and B3LYP methods, and compared with experimental ones. Results showed good agreement between theoretical and experimental values. Mulliken population and natural bond orbital analysis were also performed by time-dependent DFT approach to evaluate the electronic properties of the title molecule.
The Journal of Physical Chemistry A, 2003
In this study, a range of computational methods including time-dependent density functional theory, configuration interaction, and Zerner's spectroscopic intermediate neglect of differential overlap are used to classify spectroscopic properties of indoline and indoline-2-carboxylic acid. By examining transition densities, the 1 L a and 1 L b states of indoline and indoline-2-carboxylic acid are assigned. Aniline is used as a reference system. Excitation energies, oscillator strengths, dipole moments, and transition dipoles have been calculated and are found to be in close agreement with experiment. We find that the electronic transitions of indoline are similar to those for aniline. The lowest excited singlet state in indoline, as in aniline, is the 1 L b state with a low oscillator strength. The 1 L a state is higher in energy and possesses a larger oscillator strength as well as a larger dipole moment. For indoline-2-carboxylic acid, 1 L b -and 1 L a -like states can be identified, but an evaluation of their properties reveals mixed 1 L a and 1 L b character. Ground-state energies for conformations of indoline-2-carboxylic acid differing in the orientation of the carboxylic group indicate the presence of two ground-state conformations of similar energy.
Research Journal of Pharmaceutical, Biological and Chemical Sciences
Molecular geometry, vibrational frequencies, energy gaps, net charges, dipole moments and heats of indole formation at the ground state have been calculated by using the Molecular Mechanics, PM3, ab initio/HF and DFT/B3LYP methods. The optimized geometrical parameters are in good agreement with experimental values. Comparison of the obtained fundamental vibrational frequencies of Indole result by DFT/B3LYP (6-311G++(d,p)) method, are in a close agreement with the experimental data. Ab initio/HF with 6-31G basis set was used to investigate the effects of a variety of substituents (methyl, cyanide and dimethylamino) on the electronic properties of Indole derivatives.
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, 2015
In this article, a brief conformational and spectroscopic characterization of 5-methoxyindole-2-carboxylic acid (5-MeOICA) via experimental techniques and applications of quantum chemical methods is presented. The conformational analysis of the studied molecule was determined theoretically using density functional computations for ground state, and compared with previously reported experimental findings. The vibrational transitions were examined by measured FT-IR and FT-Raman spectroscopic data, and also results obtained from B3LYP and CAM-B3LYP functionals in combination with 6-311++G(d,p) basis set. The recorded proton and carbon NMR spectra in DMSO solution were analyzed to obtain the exact conformation. Due to intermolecular hydrogen bondings, NMR calculations were performed for the dimeric form of 5-MeOICA and so chemical shifts of those protons were predicted more accurately. Finally, electronic properties of steady compound were identified by a comparative study of UV absorpt...
Electronic structure and conformational properties of 1H-indole-3-acetic acid
Journal of Molecular Modeling, 2011
The conformational space of 1H-Indole-3-Acetic Acid (IAA) was scanned using molecular dynamics at semiempirical level, and complemented with functional density calculations at B3LYP/6-31G** level, 14 conformers of lowest energy were obtained. Electronic distributions were analyzed at a higher calculation level, thus improving the basis set (B3LYP/6-311++G**). A topological study based on Bader's theory (AIM: atoms in molecules) and natural bond orbital (NBO) framework performed with the aim to analyze the stability and reactivity of the conformers allowed the understanding of electronic aspects relevant in the study of the antioxidant properties of IAA. Intramolecular hydrogen bonds were found and were characterized as blue-shifting hydrogen bonding interactions. Furthermore, molecular electrostatic potential maps (MEPs) were obtained and analyzed in the light of AIM and NBO results, thus showing subtle but essential features related not only to reactivity but also with intramolecular weak interactions, charge delocalization and structure stabilization. Keywords Atoms in molecules (AIM theory). Density functional theory. 1H-indole-3-acetic acid (IAA). Maps of electrostatic potential. Natural bond orbital analysis. Topological properties Electronic supplementary material The online version of this article
Structural Chemistry, 2014
Quantum chemical calculations of geometric structure, the intramolecular hydrogen bond, harmonic vibrational frequencies, NMR spin-spin coupling constants, and physical properties such as chemical potential and chemical hardness of the 2-(E)-imino methyl benzenethiol and its nineteen derivatives were carried out using density functional theory (DFT/B3LYP/6-311??G**) method in the gas phase and the water solution. Furthermore, the topological properties of the electron density distributions for S-HÁÁÁN intramolecular hydrogen bond have been analyzed in terms of the Bader's theory of atoms in molecules (AIM). Natural bond orbital (NBO) analysis also performed for better understanding the nature of intramolecular interactions, the results of analysis by quantum theory of AIM and NBO method fairly supported the DFT results. Besides, MEP was performed by the DFT method. On the other hand, the aromaticity of the formed ring has been measured using several well-established indices of aromaticity such as nucleus-independent chemical shift, harmonic oscillator models of the aromaticity, para-delocalization index, average two-center indices, and aromatic fluctuation index. Also, the excited-state properties of intramolecular hydrogen bonding in these systems have been investigated theoretically using the timedependent DFT method. Keywords Electronic structure Á DFT calculations Á 2-[(E)-imino methyl] benzenethiol Á Intramolecular hydrogen bond Á Resonance parameters Á Spin-spin coupling constants Electronic supplementary material The online version of this article (
Journal of Molecular Structure, 1991
The asymmetric transfer hydrogenation (ATH) of imines catalyzed by the Noyori-Ikariya [RuCl(η 6-arene)(N-arylsulfonyl-DPEN)] (DPEN = 1,2-diphenylethylene-1,2-diamine) half-sandwich complexes is a research topic that is still being intensively developed. This article focuses on selected aspects of this catalytic system. First, a great deal of attention is devoted to the N-arylsulfonyl moiety of the catalysts in terms of its interaction with protonated imines (substrates) and amines (components of the hydrogen-donor mixture). The second part is oriented toward the role of the η 6-coordinated arene. The final part concerns the imine substrate structural modifications and their importance in connection with ATH. Throughout the text, the summary of known findings is complemented with newly-presented ones, which have been approached both experimentally and computationally.
Journal of Molecular Structure, 2018
This study examines the synthesis of azocino[4,3-b]indole structure, which constitutes the tetracyclic framework of uleine, dasycarpidoneand tubifolidineas well as ABDE substructure of the strychnosalkaloid family. It has been synthesized by Fischer indolization of 2 and through the cylization of 4 by 2,3-dichlor-5-6dicyanobenzoquinone (DDQ). 1 H and 1 C NMR chemical shifts have been predicted with GIAO approach and the calculated chemical shifts show very good agreement with observed shifts. FT-IR spectroscopy is important for the analysis of functional groups of synthesized compounds and we also supported FT-IR vibrational analysis with computational IR analysis. The vibrational spectral analysis was performed at B3LYP level of the theory in both the gas and the water phases and it was compared with the observed IR values for the important functional groups. The DFT calculations have been conducted to determine the most stable structure of the 1,2,3,4,5,6,7-Hexahydro-1,5-methanoazocino[4,3-b] indole (5). The Frontier Molecular Orbital Analysis, quantum chemical parameters, physicochemical properties have been predicted by using the same theory of level in both gas phase and the water phase, at 631+g** and 6311++g** basis sets. TD-DFT calculations have been performed to predict the UV-Vis spectral analysis for this synthesized molecule. The Natural Bond Orbital (NBO) analysis have been performed at B3LYP level of theory to elucidate the intra-molecular interactions such as electron delocalization and conjugative interactions. NLO calculations were conducted to obtain the electric dipole moment and polarizability of the title compound.