Browsing by Author "Cipiloglu, MA"

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    Molecular structure investigation and spectros copic studies on 2,3-difluorophenylboronic acid: A combined experimental and theoretical analysis
    Karabacak, M; Kose, E; Atac, A; Cipiloglu, MA; Kurt, M
    This work presents the characterization of 2,3-difluorophenylboronic acid (abbreviated as 2,3-DFPBA. C6H3B(OH)(2)F-2) by quantum chemical calculations and spectral techniques. The spectroscopic properties were investigated by FT-IR, FT-Raman UV-Vis, H-1 and C-13 nuclear magnetic resonance (NMR) techniques. The FT-IR spectrum (4000-400 cm(-1)) and the FT-Raman spectrum (3500-10 cm(-1)) in the solid phase were recorded for 2.3-DFPBA. The H-1 and C-13 NMR spectra were recorded in DMSO solution. The UV-Vis absorption spectra of the 2,3-DFPBA that dissolved in water and ethanol were recorded in the range of 200-400 nm. There are four possible conformers for this molecule. The computational results diagnose the most stable conformer of the 2,3-DFPBA as the trans-cis form. The structural and spectroscopic data of the molecule were obtained for all four conformers from DFT (B3LYP) with 6-311++G (d,p) basis set calculations. The theoretical wavenumbers were scaled and compared with experimental FT-IR and FT-Raman spectra. The complete assignments were performed on the basis of the experimental results and total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method, interpreted in terms of fundamental modes. We obtained good consistency between experimental and theoretical spectra. C-13 and H-1 NMR chemical shifts of the molecule were calculated by using the gauge-invariant atomic orbital (CIAO) method. The electronic properties, such as excitation energies, absorption wavelengths, HOMO and LUMO energies, were performed by time-dependent DFT (TD-DFT) approach. Finally the calculation results were analyzed to simulate infrared, Raman, NMR and UV spectra of the 2,3-DFPBA which show good agreement with observed spectra. (C) 2012 Elsevier B.V. All rights reserved.
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    Determination of structural and vibrational spectroscopic features of neutral and anion forms of dinicotinic acid by using NMR, infrared and Raman experimental methods combined with DFT and HF
    Kose, E; Bardak, F; Atac, A; Karabacak, M; Cipiloglu, MA
    In this study; the experimental (NMR, infrared and Raman) and theoretical (HF and DFT) analysis of dinicotinic acid were presented. H-1 and C-13 NMR spectra were recorded in DMSO solution and chemical shifts were calculated by using the gauge-invariant atomic orbital (MO) method. The vibrational spectra of dinicotinic acid were recorded by FT-Raman and FT-IR spectra in the range of 4000-10 cm(-1) and 4000-400 cm(-1), respectively. To determine the most stable neutral conformer of molecule, the selected torsion angle was changed every 10 degrees and molecular energy profile was calculated from 0 degrees to 360 degrees. The geometrical parameters and energies were obtained for all conformers form from density functional theory (DFT/B3LYP) and HF with 6-311++G(d,p) basis set calculations. However, the results of the most stable neutral and two anion forms (anion(-1) and anion(-2) forms) of dinicotinic acid are reported here. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational wavenumbers, calculated with scaled quantum mechanics (SQM) method and PQS program. (C) 2013 Elsevier B.V. All rights reserved.