Browsing by Author "Polat T."

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DFT, FT-IR and FT-Raman investigations of 1-methyl-2- imidazolecarboxaldehyde
(2013-10-01) Polat T.; Yurdakul S.
The FT-IR and FT-Raman spectra of 1-methyl-2-imidazolecarboxaldehyde were recorded in the region 4000-400 cm-1 and 3500-50 cm-1, respectively. Optimized geometric parameters, conformational equilibria, normal mode frequencies, and corresponding vibrational assignments of title molecule were examined by means of density functional theory (DFT) method with B3LYP/6-311++G(d,p) basis set. All vibrational frequencies were assigned in detail with the help of total energy distribution (TEDs). The results showed that the DFT/B3LYP method predics vibrational frequencies and the structural parameters effectively. Furthermore, solvent effects are investigated in different solvents (chloroform, dimethylsulfoxide and water) using the self-consistent isodensity polarizable continuum model (SCI-PCM). All results indicate that the combination of SCI-PCM model and DFT/B3LYP/6-311++G(d,p) calculation could give excellent explanations of the solvent effects. Intermolecular hydrogen bonding between 1-methyl-2-imidazolecarboxaldehyde and water was investigated using quantum chemical methods. DFT calculations were used to optimize the adducts of heterocycle with the single water molecule. © 2013 Elsevier B.V. All rights reserved.
Effect of organic and inorganic fertilizers, or their combinations on yield and quality components of oil seed sunflower in a semi-arid environment
(2021-01-01) Sefaoglu F.; Ozturk H.; Ozturk E.; Sezek M.; Toktay Z.; Polat T.
Producers in semi-arid and highland regions have difficulty in increasing diversity in crop rotations due to unfavorable conditions imposed by cool temperatures, inadequate rainfall, and shorter growing periods. In such conditions, some cultural practices that increase productivity such as fertilization appear as a promising alternative. Fertilization and the form of fertilizer have a substantial influence on sunflower (Helianthus annuus L.) seed yield and quality. The objective of this study was to determine the responses of the oilseed sunflower to organic (vermicompost and leonardite) and inorganic (nitrogen and phosphorus) fertilizers, or their combinations in a semiarid conditions. To this end, the field research was carried out in 2017 and 2018 in Erzurum, Eastern Anatolia, Turkey. In this study, it was found that the organic and inorganic fertilizers alone and their combinations significantly affected all the plant parameters. The highest seed yield (4854 kg ha-1) and oil yield (2114 kg ha-1) were obtained from the combined use of nitrogen and vermicompost. Moreover, the use of vermicompost alone yielded the highest oil content (46.8%). According to the results of this study, combined applications of organic (vermicompost) and inorganic (nitrogen) fertilizers had the highest yield and agronomic characteristics in oilseed sunflower production; so, these applications can be recommended for the similar ecological conditions, that is, short growing season and high altitude.
Electronic-topological and neural network approaches to the structure-antimycobacterial activity relationships study on hydrazones derivatives
(2015-01-01) Kandemirli F.; Vurdu C.D.; Başaran M.A.; Sayiner H.S.; Shvets N.; Dimoglo A.; Kovalish V.; Polat T.
That the implementation of Electronic-Topological Method and a variant of Feed Forward Neural Network (FFNN) called as the Associative Neural Network are applied to the compounds of Hydrazones derivatives have been employed in order to construct model which can be used in the prediction of antituberculosis activity. The supervised learning has been performed using (ASNN) and categorized correctly 84.4% of them, namely, 38 out of 45. Ph1 pharmacophore and Ph2 pharmacophore consisting of 6 and 7 atoms, respectively were found. Anti-pharmacophore features socalled "break of activity" have also been revealed, which means that APh1 is found in 22 inactive molecules. Statistical analyses have been carried out by using the descriptors, such as EHOMO, ELUMO, ΔE, hardness, softness, chemical potential, electrophilicity index, exact polarizibility, total of electronic and zero point energies, dipole moment as independent variables in order to account for the dependent variable called inhibition efficiency. Observing several complexities, namely, linearity, nonlinearity and multi-co linearity at the same time leads data to be modeled using two different techniques called multiple regression and Artificial Neural Networks (ANNs) after computing correlations among descriptors in order to compute QSAR. Computations resulting in determining some compounds with relatively high values of inhibition are presented.
Investigation of solvent polarity effect on molecular structure and vibrational spectrum of xanthine with the aid of quantum chemical computations
(2014-04-05) Polat T.; Yildirim G.
The main scope of this study is to determine the effects of 8 solvents on the geometric structure and vibrational spectra of the title compound, xanthine, by means of the DFT/B3LYP level of theory in the combination with the polarizable conductor continuum model (CPCM) for the first time. After determination of the most-steady state (favored structure) of the xanthine molecule, the role of the solvent polarity on the SCF energy (for the molecule stability), atomic charges (for charge distribution) and dipole moments (for molecular charge transfer) belonging to tautomer is discussed in detail. The results obtained indicate not only the presence of the hydrogen bonding and strong intra-molecular charge transfer (ICT) in the compound but the increment of the molecule stability with the solvent polarity, as well. Moreover, it is noted that the optimized geometric parameters and the theoretical vibrational frequencies are in good agreement with the available experimental results found in the literature. In fact, the correlations between the experimental and theoretical findings for the molecular structures improve with the enhancement of the solvent polarity. At the same time, the dimer forms of the xanthine compound are simulated to describe the effect of intermolecular hydrogen bonding on the molecular geometry and vibrational frequencies. It is found that the CO and NH stretching vibrations shift regularly to lower frequency value with higher IR intensity as the dielectric medium enhances systematically due to the intermolecular NH-O hydrogen bonds. Theoretical vibrational spectra are also assigned based on the potential energy distribution (PED) using the VEDA 4 program. © 2013 Elsevier B.V. All rights reserved.
Quantum chemical and spectroscopic (FT-IR and FT-Raman) investigations of 3-methyl-3h-imidazole-4-carbaldehyde
(2014-12-10) Polat T.; Yurdakul S.
FT-IR and FT-Raman spectra of 3-methyl-3h-imidazole-4-carbaldehyde (3M3HI4C) were recorded in the region 4000-400 cm-1 and 3500-50 cm-1, respectively. Optimized geometric parameters, conformational equilibria, normal mode frequencies, and corresponding vibrational assignments of 3M3HI4C were theoretically examined by quantum chemical methods for the first time. All vibrational frequencies were assigned in detail with the help of total energy distribution (TEDs). The experimental wavenumbers were compared with the scaled vibrational frequencies determined by DFT/B3LYP method. The results showed that the B3LYP/6-311++G(d,p) method predicts vibrational frequencies and the structural parameters effectively. The most stable conformer of the title compound was determined. The total electron density and molecular electrostatic potential surfaces of the molecule were constructed by using B3LYP/6-311++G(d,p) method to display electrostatic potential (electron + nuclei) distribution. The electronic properties HOMO and LUMO energies were measured. The lower energy band was assigned to the HOMO → LUMO transition. Natural bond orbital analysis of title molecule has been performed to indicate the presence of intramolecular charge transfer. Energies, relative stabilities, and dipole moments of title molecule were also compared and analyzed in the gas phase and in solvents. Furthermore, solvent effects on the geometry and vibrational frequency of 3M3HI4C were studied theoretically at the DFT/B3LYP level in combination with the conductor polarizable continuum model (C-PCM). © 2014 Elsevier B.V. All rights reserved.
Theoretical study of the solvent effects on the molecular structure and vibrational spectra of 2-hydroxy-4-methyl-3-nitropyridine
(2014-06-05) Polat T.
Solvent effects on 2-hydroxy-4-methyl-3-nitropyridine molecule in different solvents (benzene, toluene, chloroform, acetone and water) were studied theoretically at the DFT/B3LYP level in combination with the conductor polarizable continuum model (CPCM) for the first time. Based on these results vibrational spectra were simulated. The role of the solvent polarity on the molecule stability, the optimized geometry, atomic charges (for charge distribution), dipole moments (for molecular charge transfer) and vibrational spectra belonging to title molecule was discussed in detail. It was found that the OH and NO2 stretching vibrations shift regularly to lower frequency value with higher IR intensity and the CH stretching vibrations shift to higher frequency value. The results obtained indicate not only the presence of the hydrogen bonding and strong intra-molecular charge transfer in the compound but the molecule stability with the solvent polarity, as well. Additionally, the complexes of title molecule-water were simulated to describe the effect of intermolecular hydrogen bonding on the molecular geometry and vibrational frequencies. It was found that the OH stretching vibrations shift regularly to lower frequency value with higher IR intensity due to the intermolecular H⋯O hydrogen bonds. © 2014 Elsevier B.V. All rights reserved.
Theoretical study of the solvent effects on the molecular structure and vibrational spectra of 2-hydroxy-4-methyl-3-nitropyridine
(2014-06-05) Polat T.; Polat, T
Solvent effects on 2-hydroxy-4-methyl-3-nitropyridine molecule in different solvents (benzene, toluene, chloroform, acetone and water) were studied theoretically at the DFT/B3LYP level in combination with the conductor polarizable continuum model (CPCM) for the first time. Based on these results vibrational spectra were simulated. The role of the solvent polarity on the molecule stability, the optimized geometry, atomic charges (for charge distribution), dipole moments (for molecular charge transfer) and vibrational spectra belonging to title molecule was discussed in detail. It was found that the OH and NO2 stretching vibrations shift regularly to lower frequency value with higher IR intensity and the CH stretching vibrations shift to higher frequency value. The results obtained indicate not only the presence of the hydrogen bonding and strong intra-molecular charge transfer in the compound but the molecule stability with the solvent polarity, as well. Additionally, the complexes of title molecule-water were simulated to describe the effect of intermolecular hydrogen bonding on the molecular geometry and vibrational frequencies. It was found that the OH stretching vibrations shift regularly to lower frequency value with higher IR intensity due to the intermolecular H⋯O hydrogen bonds. © 2014 Elsevier B.V. All rights reserved.
Vibrational assignments, spectroscopic investigation (FT-IR and FT-Raman), NBO, MEP, HOMO-LUMO analysis and intermolecular hydrogen bonding interactions of 7-fluoroisatin, 7-bromoisatin and 1-methylisatin - A comparative study
(2015-12-05) Polat T.; Bulut F.; Arican I.; Kandemirli F.; Yildirim G.
In this comprehensive study, theoretical and experimental studies were carried out on 7-fluoroisatin, 7-bromoisatin and 1-methylisatin using FT-Raman and FT-IR spectra. The optimized geometrical parameters and theoretical vibrational frequencies were calculated by means of density functional theory (DFT/B3LYP) with 6-311++G(d,p) basis set based on scaled quantum mechanical (SQM) method for the first time. The relative abundances of the possible tautomers or conformers found were calculated with respect to the Boltzmann distribution. Moreover, the harmonic vibrational frequencies including IR and Raman intensities, thermodynamic and electronic parameters were computed in detail. The effects of substituents -F, -Br and -CH3 on the crucial characteristics pertaining to the title compound of isatin were investigated, and the obtained data were compared with each other. Natural bond orbital (NBO) analysis was applied to study the stability arising from charge delocalization along with the compound. The chemical reactivity parameters (chemical hardness and softness, electronegativity, chemical potential and electrophilicity index) were discussed clearly. The HOMO and LUMO energies determined showed that the serious charge transfer occurs in the title molecules studied. Furthermore, the size, shape, charge density distributions and chemical reactivity sites belonging to the molecules were obtained by mapping electron density isosurface with electrostatic potential surfaces (ESP). Additionally, the hydrogen-bonded complexes were simulated to describe the roles of intermolecular hydrogen bonding on the molecular structures and vibrational frequencies.