FT-IR, UV spectroscopic and DFT quantum chemical study on the molecular conformation, vibrational and electronic transitions of 2-aminoterephthalic acid

Department of Physics, Afyon Kocatepe University, 03040 Afyonkarahisar, Turkey; Department of Physics, Ahi Evran University, 40100 Kırşehir, Turkey
Journal of Molecular Structure (Impact Factor: 1.4). 01/2010; 982:22-27. DOI: 10.1016/j.molstruc.2010.07.033

ABSTRACT In this work, the molecular conformation, vibrational and electronic analysis of 2-aminoterephthalic acid are presented for the ground state using FT-IR experimental technique and density functional theory (DFT) employing B3LYP exchange correlation functional with the 6-311++G(d,p) basis set. FT-IR spectrum was recorded in the region of 400–4000 cm−1. The ultraviolet absorption spectrum of studied compound that dissolved in ethanol was examined in the range of 190–450 nm. The complete assignments of fundamental vibrations were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. Optimized structure of title compound was interpreted and compared with the earlier reported experimental values of a similar compound. A study on the electronic properties, such as HOMO and LUMO energies, were performed by time-dependent DFT (TD-DFT) approach.

  • [Show abstract] [Hide abstract]
    ABSTRACT: The FT-IR, FT-Raman and FT-NMR spectra of 4-Methyl-2-phenylimidazole (4M2PI)molecule was recorded and analyzed. The tautomeric, structural and spectroscopic analysis of the title molecule was made by using density functional harmonic calculations. For the title molecule, only one tautomeric form was found most stable structure by using B3LYP level with the 6-311G++(d,p) as basis set. Selected experimental bands were assigned and characterized based on the scaled theoretical wave numbers by their total energy distribution (TED).
    Optics and Spectroscopy 12/2012; 113(6). · 0.56 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The optimized geometrical structure, vibrational and electronic transitions, chemical shifts and non-linear optical properties of ethyl trans-alfa-cyano-3-indole-acrylate (C(14)H(12)N(2)O(2)) compound were presented in this study. The ground state geometrical structure and vibrational wavenumbers were carried out by using density functional (DFT/B3LYP) method with 6-311++G(d,p) as basis set. The vibrational spectra of title compound were recorded in solid state with FT-IR and FT-Raman in the range of 4000-400cm(-1) and 4000-10cm(-1), respectively. The fundamental assignments were done on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanical (SQM) method. The (1)H, (13)C and DEPT NMR spectra were recorded in DMSO solution, and gauge-invariant atomic orbitals (GIAO) method was used to predict the isotropic chemical shifts. The UV-Vis absorption spectra of the compound were recorded in the range of 200-800nm in various solvents of different polarity (acetone, benzene, chlorobenzene, chloroform, DMSO, ethanol, methanol and toluene). Solvent effects were calculated using TD-DFT and CIS method. To investigate the non-linear optical properties, the polarizability, anisotropy of polarizability and molecular first hyperpolarizability were computed. A detailed description of spectroscopic behaviors of compound was given based on the comparison of experimental measurements and theoretical computations.
    Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 12/2012; 104C:428-436. · 1.98 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this work, the molecular structure, vibrational, UV and NMR spectra of 3-methoxyaniline (abbreviated as 3MOA, C7H9NO) were studied. The FT-IR and FT-Raman spectra were recorded. The ground-state molecular geometry and vibrational frequencies were calculated by using the Hartree–Fock (HF) and density functional theory (DFT)/B3LYP methods and 6-311++G(d, p) as a basis set. The fundamental vibrations were assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method and PQS program. Comparison of the observed fundamental vibrational frequencies of 3MOA with calculated results by HF and DFT methods indicates that B3LYP is superior to HF method for molecular vibrational problems. The difference between the observed and scaled wavenumber values is very small. The theoretically predicted FT-IR and FT-Raman spectra of the title molecule have been constructed. A study on the Mulliken atomic charges, the electronic properties were performed by time-dependent DFT (TD-DFT) approach, Frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) and thermodynamic properties were performed and compared with methoxybenzene and aniline. The electric dipole moment (μ) and the first hyperpolarizability (β) values of the investigated molecule were computed using ab initio quantum mechanical calculations. The calculated results also show that the 3MOA molecule might have microscopic nonlinear optical (NLO) behavior with non-zero values. The 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results.
    Journal of Molecular Structure 01/2014; s 1056–1057:176–188. · 1.40 Impact Factor


Available from
May 16, 2014