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Öğe Analysis of the xylenol isomers by femtosecond laser time of flight mass spectrometry(CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS, 2018) Kepceoglu, A.; Koklu, N.; Gundogdu, Y.; Dereli, O.; Kilic, H. S.Xylenol is a phenolic chemical substance having two methyl groups and one hydroxyl group attached to a benzene ring and has six isomers. 2,4-xylenol is the only isomer of the xylenol molecule that is in the liquid phase while the remaining isomers are all in crystal form at room temperature. In the scope of this study, we have experimentally investigated ionization and dissociation properties of xylenol isomers. All experiments were carried out by using a time of flight mass spectrometry (TOF-MS) system coupled with a femtosecond laser system. The laser pulse power-dependent multiphoton ionization of xylenol isomers was investigated by using IR (800 nm) femtosecond laser pulses having a pulse width of similar to 90 fs in duration and laser intensities changing from 2.6 x 10(13) to 2.6 x 10(14) W/cm(2). Theoretically, molecular orbitals (LUMO+1, LUMO, HOMO, HOMO-1), vertical and adiabatic ionization energies were calculated using density functional theory (DFT) with B3LYP functional and 6-311++G(d,p) basis set by following geometry optimization and performing conformational analysis.Öğe Density functional theory - electron paramagnetic resonance study of gamma-irradiated single crystal of amphi-chloroglyoxime(TAYLOR & FRANCIS LTD, 2009) Turkkan, E.; Dereli, O.; Tasdemir, H. U.; Cavusoglu, H.The density functional theory was studied to examine the suggested type of model radicals RI, RII and RIII that have been formed upon gamma-irradiation of single crystals of amphi-chloroglyoxime (ACG). RI, RII and RIII type model radicals were obtained by abstraction of Cl and H atoms from ACG. The possible conformations of these model radicals were obtained using the semi-empirical Austin Model 1 method. Subsequently, hyperfine coupling constants and atomic spin density calculations of these conformations were performed using the Becke-3-Lee-Yang-Parr functional in combination with a split-valence Gaussian basis set. Theoretically calculated values were compared with the experimental values. Calculated isotropic and anisotropic hyperfine coupling constant values of conformations of model radical RII were in good agreement with experimental values. However, the agreement was rather poor in the case of the model radicals RI and RIII. Thus, the findings from the present study clearly suggest that the experimentally observed radical should be the model radical RII.Öğe DFT simulations, FT-IR, FT-raman, and FT-NMR spectra of 4-(4-chlorophenyl)-1H-imidazole molecules(PLEIADES PUBLISHING INC, 2012) Erdogdu, Y.; Gulluoglu, M. T.; Yurdakul, S.; Dereli, O.The FT-IR, FT-Raman and FT-NMR spectra of the compound 4-(4-Chlorophenyl)-1H-imidazole (4-ClPI) was recorded and analyzed. Density functional method has been used to compute optimized geometry, vibrational wavenumbers and NMR spectra of the 4-ClPI. Only one tautomeric form was found most stable by using B3LYP functional with the 6-311++G(d,p) as basis sets. The detailed interpretation of the vibrational spectra was carried out with the aid of total energy distribution (TED) following the scaled quantum mechanical force field methodology.Öğe DFT-based molecular modeling, NBO analysis and vibrational spectroscopic study of 3-(bromoacetyl)coumarin(PERGAMON-ELSEVIER SCIENCE LTD, 2011) Sajan, D.; Erdogdu, Y.; Reshmy, R.; Dereli, O.; Thomas, K. Kurien; Joe, I. HubertThe NIR-FT Raman and FT-IR spectra of 3-(bromoacetyl)coumarin (BAC) molecule have been recorded and analyzed. Density functional theory (DFT) calculation of two BAC conformers has been performed to find the optimized structures and computed vibrational wavenumbers of the most stable one. The obtained vibrational wavenumbers and optimized geometric parameters were seen to be in good agreement with the experimental data. Characteristic vibrational bands of the pyrone ring and methylene and carbonyl groups have been identified. The lowering of HOMO-LUMO energy gap clearly explains the charge transfer interactions taking place within the molecule. (C) 2011 Elsevier B.V. All rights reserved.Öğe EPR study of a gamma-irradiated (2-hydroxyethyl)triphenylphosphonium chloride single crystal(TAYLOR & FRANCIS LTD, 2011) Karakas, E.; Turkkan, E.; Dereli, O.; Sayin, U.; Tapramaz, R.In this study, gamma-irradiated single crystals of (2-hydroxyethyl)triphenylphosphonium chloride [CH(2)CH(2)OHP(C(6)H(5))(3)Cl] were investigated with electron paramagnetic resonance (EPR) spectroscopy at room temperature for different orientations in the magnetic field. The single crystals were irradiated with a (60)Co-gamma-ray source at 0.818 kGy/h for about 36 h. Taking the chemical structure and the experimental spectra of the irradiated single crystal of the title compound into consideration, a paramagnetic species was produced with the unpaired electron delocalized around (31)P and several (1)H nuclei. The anisotropic hyperfine values due to the (31)P nucleus, slightly anisotropic hyperfine values due to the (1)H nuclei and the g-tensor of the radical were measured from the spectra. Depending on the molecular structure and measured parameters, three possible radicals were modeled using the B3LYP/6-31+G(d) level of density-functional theory, and EPR parameters were calculated for modeled radicals using the B3LYP/TZVP method/basis set combination. The calculated hyperfine coupling constants were found to be in good agreement with the observed EPR parameters. The experimental and theoretically simulated spectra for each of the three crystallographic axes were well matched with one of the modeled radicals (discussed in the text). We thus identified the radical (C) over dotH(2)CH(2)P(C(6)H(5))(3)Cl as a paramagnetic species produced in a single crystal of the title compound in two magnetically distinct sites. The experimental g-factor and hyperfine coupling constants of the radical were found to be anisotropic, with the isotropic values g(iso)(=)2.0032, A(rad)(P2) = 118.6G, A(CH2)(H23) = 28.4G, A(CH2)(H24) = 4.2 G and A(CH2)(H40-41) = 18.5 G for site 1 and g(iso) = 2.0031, A(rad)(P2) = 118.9G, A(CH2)(H23) = 28.5 G A(CH2)(H24) = 4.3G and A(CH2)(H40-41) = 17.3 G for site 2.Öğe EPR study of gamma irradiated 2,5-di-tert-butyl-hydroquinone single crystals(PERGAMON-ELSEVIER SCIENCE LTD, 2011) Sayin, U.; Dereli, O.; Turkkan, E.; Yuksel, H.; Birey, M.gamma-irradiated single crystals of 2,5-di-tert-butyl-hydroquinone (DTBHQ) were investigated using the electron paramagnetic resonance (EPR) technique. The spectra of the crystals at different orientations in the magnetic field between temperatures of 120 and 450 K, were found to be temperature dependent. Taking into consideration the chemical structure and the experimental spectra of the irradiated single crystals of DTBHQ we assumed that one or more paramagnetic species were produced, each having an unpaired electron delocalized in the phenyl ring. Pursuant to this assumption, four possible radicals were modeled using the B3LYP/6-31+G(d) level of density-functional theory. EPR parameters were calculated for these modeled radicals using the B3LYP method and TZVP basis set. The calculated hyperfine-coupling constants were used as starting points for simulations. The experimental and simulated spectra for each of the three crystallographic axes were well matched for the modeled radical R4; we thus identified the hydroquinone anion radical as a paramagnetic species produced in DTBHQ. The experimental g-factor of the hydroquinone anion radical were found to be anisotropic with the average value g(iso)=2.0096. The hyperfine coupling constants of the H-alpha proton was found anisotropic with the average value (a(H7)(alpha))(iso) = 6.3 G and H-beta proton was found isotropic with the average value (a(H8)(beta))= 3.5 G. (C) 2010 Elsevier Ltd. All rights reserved.Öğe EPR study of gamma-irradiated amphi-phenylglyoxime single crystals(PERGAMON-ELSEVIER SCIENCE LTD, 2011) Dereli, O.; Turkkan, E.; Ozmen, A.; Yuksel, H.Gamma-irradiated single crystals of Amphi-phenylglyoxime (APGO) were investigated using electron paramagnetic resonance (EPR) at different orientations in a magnetic field at room temperature (298 K). Considering the chemical structure and the experimental spectra of the irradiated single-crystals of APGO, we assumed that two different paramagnetic species, labeled as R* and R**, are either two iminoxy radicals formed by the abstraction of a H atom from different oxime branches or are different conformations of an iminoxy radical. Pursuant to this assumption, RA- and RB-type iminoxy radicals were modeled by the abstraction of H atoms from different oxime branches, and conformational analysis of these modeled radicals was performed using the semi-empirical AM1 and B3LYP/6-31 +G(d,p) methods. EPR parameters were calculated for the modeled radicals using the B3LYP method and EPR-III basis set. Theoretically calculated values of the most stable conformers (RA-1 and RB-1) of the modeled radicals are in good agreement with the experimental EPR parameters determined from the spectra (differences in isotropic hyperfine coupling constant values <5%, and differences in isotropic g values fall into 1 ppt). Thus, from the findings of the present study, we strongly suggest that the experimentally observed R* and R** radicals in the single crystal of amphi-phenylglyoxime are the most stable conformers of RA- and RB-type modeled iminoxy radicals, respectively. The experimental g factors and hyperfine coupling constants were found to be anisotropic, with average values of g=2.0052, A(N-14)=29.50 G, A(H-1)=25.30 G for R*, and g=2.0057, A(N-14)=34.50 G for R**. (C) 2011 Elsevier Ltd. All rights reserved.Öğe EPR study of gamma-irradiated diaminoglyoxime single crystals(ELSEVIER SCIENCE BV, 2011) Ates, L.; Dereli, O.; Turkkan, E.; Sayin, U.; Sevgi, F.; Tapramaz, R.; Birey, M.Gamma irradiated single crystals of diaminoglyoxime (DAG), were investigated with electron paramagnetic resonance (EPR) spectroscopy at room temperature and at different orientations in the magnetic field. Taking the chemical structure and the experimental spectra of the irradiated DAG single-crystal into consideration we assumed that iminoxy type paramagnetic species were produced where the unpaired electron is delocalized on N atoms. Depending on this assumption, an iminoxy radical was modeled and EPR parameters were calculated using the MP2/6-311++G(d,p)-level of theory and then the calculated hyperfine-coupling constants were used as initial guess for simulations. The experimental and simulated spectra for each of the three crystallographic axes well matched with the modeled radical. We thus identified an iminoxy radical as a paramagnetic species produced in DAG. The experimental g-factor and theoretically calculated hyperfine coupling constants of this radical were found to be anisotropic, with the average values g(iso) = 2.0150, a(N(4)) = -2.71 mT, a(N(3)) = 1.46 mT, a(N(9)) = 0.29 mT, a(N(12)) = 0.51 mT, a(H(10)) = -0.53 mT, a(H(11)) = -0.55 mT, a(H(13)) = -0.36 mT and a(H(14)) = -0.42 mT, respectively. (C) 2011 Elsevier B.V. All rights reserved.Öğe Experimental, theoretical calculations of the vibrational spectra and conformational analysis of 2,4-di-tert-butylphenol(PERGAMON-ELSEVIER SCIENCE LTD, 2012) Kalaichelvan, S.; Sundaraganesan, N.; Dereli, O.; Sayin, U.In the present work, we reported a combined experimental and theoretical study on conformational stability, molecular structure and vibrational spectra of 2,4-di-tert-butylphenol (2,4-DTBP). The FT-IR (400-4000 cm(-1)) and FT-Raman spectra (50-3500 cm(-1)) of 2,4-DTBP were recorded. The molecular geometry, harmonic vibrational frequencies and bonding features of 2,4-DTBP in the ground-state have been calculated by using the density functional BLYP/B3LYP methods. The energy calculated by time-dependent density functional theory (TD-DFT) result complements with the experimental findings. The calculated highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies show that charge transfer occurs within the molecule. Finally the calculation results were compared with measured infrared and Raman spectra of the title compound which showed good agreement with observed spectra. (C) 2011 Elsevier B.V. All rights reserved.Öğe FT-IR, FT-Raman spectra, density functional computations of the vibrational spectra and molecular conformational analysis of 2,5-di-tert-butyl-hydroquinone(PERGAMON-ELSEVIER SCIENCE LTD, 2011) Subramanian, N.; Sundaraganesan, N.; Dereli, O.; Turkkan, E.The purpose of finding conformer among six different possible conformers of 25-di-tert-butyl-hydroquinone (DTBHQ), its equilibrium geometry and harmonic wavenumbers were calculated by the B3LYP/6-31G(d,p) method. The infrared and Raman spectra of DTBHQ were recorded in the region 400-4000 cm(-1) and 50-3500 cm(-1), respectively. In addition, the IR spectra in CCl(4) at various concentrations of DTBHQ are also recorded. The computed vibrational wavenumbers were compared with the IR and Raman experimental data. Computational calculations at B3LYP level with two different basis sets 6-31G(d,p) and 6-311++G(d,p) are also employed in the study of the possible conformer of DTBHQ. The complete assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes, calculated using VEDA 4 program. The general agreement between the observed and calculated frequencies was established. (C) 2011 Elsevier B.V. All rights reserved.Öğe FT-IR, FT-Raman spectra, density functional computations of the vibrational spectra and molecular geometry of butylated hydroxy toluene(PERGAMON-ELSEVIER SCIENCE LTD, 2011) Babu, P. Chinna; Sundaraganesan, N.; Dereli, O.; Turkkan, E.The FT-IR spectrum of 2,6-di-tert-butyl-4-methylphenol [butylated hydroxy toluene] was recorded in the region 4000-400 cm(-1). The FT-Raman spectrum of butylated hydroxy toluene was also recorded in the region 3500-50 cm(-1). The molecular structure and vibrational frequencies of butylated hydroxy toluene (BHT) have been investigated with combined experimental and theoretical study. Two stable conformers of the title compound were obtained from the result of geometry optimizations of these possible conformers. The conformer 1 is (approximately 2.6 kcal/mol) more stable than conformer 2. Geometry optimizations and vibrational frequency calculations were performed by BLYP and B3LYP methods using 6-31G(d), 6-31G(d,p) and 6-31+G(d,p) as basis sets. The scaled frequencies were compared with experimental spectrum and on the basis of this comparison; assignments of fundamental vibrational modes were examined. Comparison of the experimental spectra with harmonic vibrational wavenumbers indicates that B3LYP/6-31G(d) results are more accurate. Predicted electronic absorption spectra of BHT from TD-DFT calculation have been analyzed and compared with the experimental UV-vis spectrum. The calculated HOMO and LUMO energies show that the charge transfer occurs within the molecule. (C) 2011 Elsevier B.V. All rights reserved.Öğe Molecular Structure and the EPR Calculation of the Gas Phase Succinonitrile Molecule(AMER INST PHYSICS, 2017) Kepceoglu, A.; Kilic, H. S.; Dereli, O.Succinonitrile (Le. butanedinitrile) is a colorless nitrile compound that can be used in the gel polymer batteries as a solid-state solvent electrolytes and has a plastic crystal structure. Prior to the molecular structure calculation of the succinonitrile molecule, the conformer analysis were calculated by using semi empirical method PM3 core type Hamiltonian and eight different contbrmer structures were determined. Molecular structure with energy related properties of these confomiers having the lowest energy was calculated by using DFT (B3LYP) methods with 6-311++G(4) basis set. Possible radicals, can be formed experimentally. were modeled in this study. EPR parameters of these model radicals were calculated and then compared with that obtained experimentally.Öğe Molecular structure and vibrational spectra of 4-phenylsemicarbazide by density functional method(ELSEVIER, 2011) Dereli, O.; Sudha, S.; Sundaraganesan, N.In this paper, combined experimental and theoretical study on molecular and vibrational structure of 4-phenylsemicarbazide (4PSC) were reported. The Fourier transform infrared (FT-IR) spectrum of 4PSC was recorded in the region 4000-400 cm(-1). Fourier transform Raman (FT-Raman) spectrum of 4PSC was also recorded in the region 3500-50 cm(-1). Semi-empirical PM3 method was used for conformational distribution of possible conformers. The molecular geometry and vibrational frequencies of the most stable conformer of 4PSC in the ground state have been calculated by using the density functional BLYP and B3LYP methods with 6-31G(d) and 6-31G(d,p) as basis sets. The optimized geometrical parameters obtained from theoretical calculations show good agreement with the XRD experimental values. The ground state energies, dipole moments and thermodynamic parameters have also been computed. The calculated and scaled frequencies were compared with experimental values and on the basis of this comparison and PED data assignments of fundamental vibrational modes were examined. The differences between the observed and BLYP/6-31G(d) scaled wavenumber values of most of the fundamentals are very small. (C) 2011 Elsevier B.V. All rights reserved.Öğe Molecular structure and vibrational spectra of 7-Ethoxycoumarin by density functional method(ELSEVIER, 2013) Sarikaya, E. Karakas; Dereli, O.; Erdogdu, Y.; Gulluoglu, M. T.In the present study, as a result of detailed conformational search of the 7-Ethoxycoumarin, four different conformers of (7EC) have been obtained. The FT-IR and Raman spectra of 7EC were recorded in the region 4000-400 cm(-1) and 3500-50 cm(-1), respectively. Vibrational frequences of the title compound were calculated by B3LYP method using 6-311++G(d,p) basis sets. The calculated vibrational frequences were analyzed and compared with experimental results. Characteristic vibrational bands of the pyrone ring, methylene and CO groups have been identified. (c) 2013 Elsevier B.V. All rights reserved.Öğe Molecular structure and vibrational spectra of 7-Methoxy-4-mehylcoumarin by density functional method(ELSEVIER, 2013) Sarikaya, E. Karakas; Dereli, O.In the present study, as a result of detailed structural and conformational analysis of the 7-Methoxy-4-methylcoumarin, two different conformers have been obtained. The FT-IR and Raman spectra were recorded in the region 4000-400 cm(-1) and 3500-50 cm(-1), respectively. Vibrational frequences of the title compound were calculated by Becke3-Lee-Yang-Parr (B3LYP) functional using 6-311++G(d,p) basis sets. The ground state energies and dipole moments have also been computed. The calculated and scaled frequencies were compared with experimental values and on the basis of this comparison and total-energy distribution data assignments of fundamental vibrational modes were examined. The differences between the observed and scaled wavenumber values of most of the fundamentals are very small. (C) 2013 Elsevier B.V. All rights reserved.Öğe Molecular Structure and Vibrational Spectra of Alpha-Benzoinoxime by Density Functional Method(MAIK NAUKA/INTERPERIODICA/SPRINGER, 2014) Dereli, O.; Erdogdu, Y.; Gulluoglu, M. T.; Sundaraganesan, N.; Turkkan, E.; Sayin, U.; Ozmen, A.In the present study, an exhaustive conformational search of the Alpha-benzoinoxime has been performed. The FT-IR spectrum of this compound was recorded in the region 4000-400 cm(-1). The FT-Raman spectrum was also recorded in the region 3500-50 cm(-1). Vibrational frequences of the title compound were calculated by B3LYP method using 6-311++G(d, p) basis set. The calculated vibrational frequences were analysed and compared with experimental results.Öğe Radiation Damage Centers in Cholesteryl Heptanoate(POLISH ACAD SCIENCES INST PHYSICS, 2013) Sayin, U.; Can, C.; Turkkan, E.; Dereli, O.; Ozmen, A.; Yuksel, H.Cholesterol takes part significantly in many biological mechanisms and as important component for manufacture of bile acids, steroid hormones, and several fat-soluble vitamins. To determine magnetic properties of cholesteryl heptanoate (C34H58O2) which is an important cholesteryl ester in human life and new technology, the single crystals of cholesteryl heptanoate were grown by slow evaporation of concentrated ethyl acetate solution and the grown single crystals were irradiated at room temperature with Co-60 gamma ray. The radical produced by gamma irradiation has been investigated in the range of temperatures 123-330 K for different orientations of the crystal in a magnetic field by EPR. Radiation damage center was attributed to radical (C) over dotH(alpha)CH(2 beta). The g factor and hyperfine coupling constants have slight dependence on temperature and evident dependence on the orientation of the magnetic field. Determined g factor and hyperfine coupling constants for the radical (C) over dotH(alpha)CH(2 beta) were found to be anisotropic with the average values g(av) = 2.0036, (a(CH alpha))(av) = 14.52 G, (a(CH2 beta))(av) = 25.78 G.Öğe Study on molecular structure and vibrational spectra of 5,7-dimethoxycoumarin using DFT: A combined experimental and quantum chemical approach(MAIK NAUKA/INTERPERIODICA/SPRINGER, 2014) Sarikaya, E. Karakas; Dereli, O.Conformational analysis of 5,7-Dimethoxycoumarin was performed and two stable conformers were obtained. The difference between the total energies of these conformers was 1.4698 kcal/mol and the difference between the zero point corrected energies was nearly zero. Vibrational frequencies of these conformers were calculated by B3LYP method using 6-311++G(d, p) basis sets and compared with experimentally recorded FT-IR and Raman spectra. Vibrational assignments were made by calculated total energy distributions. Time dependent density functional theory calculations were done by the same level of theory in order to investigate low-lying excited state and obtained results were compared with the maximum absorbtion peak value of experimental UV-visible spectrum.Öğe A theoretical study about factors affecting conformational stabiltiy order of glyoxime(SILA SCIENCE, 2011) Dereli, O.; Cavusoglu, H.; Turkkan, E.; Ozmen, A.; Ilik, A.In this study, stable conformers and the effects determining conformational stability of the glyoxime (GO) molecule are inspected. Semiemprical PM3 method is used for conformer distribution. Geometry optimizations are performed by MP2/6-311++G(d,p) level of theory. We obtained twenty stable conformers for the title compound; however conformer 1 is (approximately 17 kcal/mol) more stable than conformer 20. Calculated geometry parameters for the most stable conformer are consistent with experimental results. Long range electrostatic, conjugation, and hydrogen bonding effects are found responsible for stability order of GO. Four conformers which can be determined experimentally are isolated theoretically. Thermodynamic and geometrical parameters of these isomers are given first time in this study. Calculated relative energies of these conformers are very close to each other. For this reason, isolation of these conformers is very difficult for experimentalists. The chemical reactivities of GO conformers were investigated by HOMO-LUMO energy gaps.
