MCBÜ Açıkerişim Sistemi :: Browsing by Author "Atac, A"

Browsing by Author "Atac, A"

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The spectroscopic (FT-IR, FT-Raman, dispersive Raman and NMR) study of ethyl-6-chloronicotinate molecule by combined density functional theory
Karabacak, M; Calisir, Z; Kurt, M; Kose, E; Atac, A
In this study, ethyl-6-chloronicotinate (E-6-ClN) molecule is recorded in the region 4000-400 cm(-1) and 3500-100 cm(-1) (FT-IR, FT-Raman and dispersive Raman, respectively) in the solid phase. H-1 and C-13 nuclear magnetic resonance (NMR) spectra are recorded in DMSO solution. The structural and spectroscopic data of the molecule are obtained for two possible isomers (S1 and S2) from OFT (B3LYP) with 6-311++G(d,p) basis set calculations. The geometry of the molecule is fully optimized, vibrational spectra are calculated and fundamental vibrations are assigned on the basis of the potential energy distribution (PED) of the vibrational modes. H-1 and C-13 NMR chemical shifts are calculated by using the gauge-invariant atomic orbital (GIAO) method. The electronic properties, such as excitation energies, oscillator strengths, wavelengths, HOMO and LUMO energies, are performed by time-dependent density functional theory (TD-DFT). Total and partial density of state and overlap population density of state diagrams analysis are presented for E-6-ClN molecule. Furthermore, frontier molecular orbitals (FMO), molecular electrostatic potential, and thermodynamic features are performed. In addition to these, reduced density gradient of the molecule is performed and discussed. As a conclusion, the calculated results are compared with the experimental spectra of the title compound. The results of the calculations are applied to simulate the vibrational spectra of the molecule, which show excellent agreement with the observed ones. The theoretical and tentative results will give us a detailed description of the structural and physicochemical properties of the molecule. Natural bond orbital analysis is done to have more information stability of the molecule arising from charge delocalization, and to reveal the information regarding charge transfer within the molecules. (C) 2015 Elsevier B.V. All rights reserved.
Vibrational (FT-IR and FT-Raman), electronic (UV-Vis), NMR (1H and 13C) spectra and reactivity analyses of 4,5-dimethyl-o-phenylenediamine
Atac, A; Karaca, C; Gunnaz, S; Karabacak, M
The structure of 4,5-dimethyl-o-phenylenediamine (C8H12N2, DMPDA) was investigated on the basis of spectroscopic data and theoretical calculations. The sterochemical structure was determined by FT-IR, FT-Raman, UV, H-1 and C-13 NMR spectra. An experimental study and a theoretical analysis were associated by using the B3LYP method with Gaussian09 package program. FT-IR and FT-Raman spectra were recorded in the region of 4000-400 cm(-1) and 4000-10 cm(-1), respectively. The vibrational spectra were calculated by DFT method and the fundamental vibrations were assigned on the basis of the total energy distribution (TED), calculated with scaled quantum mechanics (SQM) method with Parallel Quantum Solutions (PQS) program. The UV absorption spectrum of the compound that dissolved in ethanol solution were recorded in the range of 190-400 nm. Total density of state (TDOS) and partial density of state (PDOS) of the DMPDA in terms of HOMOs and LUMOs were calculated and analyzed. Chemical shifts were reported in ppm relative to tetramethylsilane (TMS) for H-1 and C-13 NMR spectra. The compound was dissolved in dimethyl sulfoxide (DMSO). Also, H-1 and C-13 chemical shifts calculated using the gauge independent atomic orbital (GIAO) method. Mullikan atomic charges and other thermo-dynamical parameters were investigated with the help of B3LYP (DFT) method using 6-311++G** basis set. On the basis of the thermodynamic properties of the title compound at different temperatures have been carried out, revealing the correlations between heat capacity (C), entropy (S), enthalpy changes (H) and temperatures. The optimized bond lengths, bond angles, chemical shifts and vibrational wavenumbers showed the best agreement with the experimental results. (C) 2014 Elsevier B.V. All rights reserved.
Intermolecular interactions and molecular docking investigations on 4-methoxybenzaldehyde
Ghalla, H; Issaoui, N; Bardak, F; Atac, A
In this work, a structural and electronic properties of 4-methoxybenzaldehyde (4MBA) have been presented. The density functional theory (DFT) along with B3LYP hybrid functional is employed. The optimized structure was found to be in well consistent with the X-ray diffraction geometry. The 4MBA crystal is stabilized by C-H center dot center dot center dot O intermolecular interactions along with pi center dot center dot center dot pi interactions. Various intermolecular interactions involved in 4MBA crystal have been analyzed deeply through topological atom-in-molecules (AIM) analysis and noncovalent interactions (NCI) method. Besides, Hirshfeld surface (HS) analysis and fingerprint plots are performed to determine the contribution of intermolecular contacts in 4MBA crystal packing. The electronic properties of the title compound have been investigated. Nonlinear optic (NLO) properties of 4MBA have been interpreted through the calculated first hyperpolarizability value. 4-substituted benzaldehydes, including 4MBA, are known with their competitive inhibitory activity on Tyrosinase, which also known as polyphenol oxidase (PPO). This enzyme is a rate limiting enzyme that controls the production of melamine and brown coloring of foods. Thus, molecular docking behaviors of 4MBA are presented in comparison with that of benzaldehyde (BA), 4-ethylBA, 4-tertbutylBA, 4-isoprophylBA, 4-propoxyBA, 4-butoxyBA, and Hexylresorcinol on four selected PPOs from sweet potato, grape, and mushroom.
Synthesis, analysis of spectroscopic and nonlinear optical properties of the novel compound: (S)-N-benzyl-1-phenyl-5-(thiophen-3-yl)-4-pentyn-2-amine
Karabacak, M; Karaca, C; Atac, A; Eskici, M; Karanfil, A; Kose, E
In this study, a novel compound (S)-N-benzyl-1-phenyl-5-(thiophen-3-yl)-4-pentyn-2-amine (abbreviated as BPTPA) was synthesized and structurally characterized by FT-IR, NMR and UV spectroscopy. The molecular geometry and vibrational frequencies of BPTPA in the ground state have been calculated by using the density functional method (B3LYP) invoking 6-311++G(d,p) basis set. The geometry of the molecule was fully optimized, vibrational spectra were calculated. 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. Total and partial density of state (TDOS and PDOS) and also overlap population density of state (OPDOS) diagrams analysis were given. The energy and oscillator strength of each excitation were calculated by time-dependent density functional theory (TD-DFT) results complements with the experimental findings. The NMR chemical shifts (H-1 and C-13) were recorded and calculated using the gauge invariant atomic orbital (CIAO) method. The dipole moment, linear polarizability and first hyperpolarizability values were also computed. The linear polarizability and first hyper polarizability of the studied molecule indicate that the compound is a good candidate of nonlinear optical materials. Finally, vibrational wavenumbers, absorption wavelengths and chemical shifts were compared with calculated values, and found to be in good agreement with experimental results. (C) 2012 Elsevier B.V. All rights reserved.
Molecular structure (monomeric and dimeric structure) and HOMO-LUMO analysis of 2-aminonicotinic acid: A comparison of calculated spectroscopic properties with FT-IR and UV-vis
Karabacak, M; Kose, E; Atac, A
The experimental (UV-vis and FT-IR) and theoretical study of 2-aminonicotinic acid (C6H6N2O2) was presented in this work. The ultraviolet absorption spectrum of title molecule that dissolved in ethanol and water were examined in the range of 200-400 nm. The FT-IR spectrum of the title molecule in the solid state were recorded in the region of 400-4000 cm(-1). The geometrical parameters and energies of 2-aminonicotinic acid have been obtained for all four conformers/isomers (Cl, C2, C3, C4) from DFT (B3LYP) with 6-311++G(d,p) basis set calculations. C1 form has been identified the most stable conformer clue to computational results. Therefore, spectroscopic properties have been searched for the most stable form of the molecule. The vibrational frequencies were calculated and scaled values were compared with experimental FT-IR spectrum. The complete assignments were performed based on the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. Also the molecular structures, vibrational frequencies, infrared intensities were calculated for a pair of molecules linked by the intermolecular O-H center dot center dot center dot O hydrogen bond. Moreover, the thermodynamic properties of the studied compound at different temperatures were calculated. Besides, charge transfer occurring in the molecule between HOMO and LUMO energies, frontier energy gap, molecular electrostatic potential (MEP) were calculated and presented. The spectroscopic and theoretical results are compared to the corresponding properties for monomer and dimer of Cl conformer. The optimized bond lengths, bond angles, calculated frequencies and electronic transitions showed the agreement with the experimental results. (C) 2012 Elsevier B.V. All rights reserved.
NMR, UV, FT-IR, FT-Raman spectra and molecular structure (monomeric and dimeric structures) investigation of nicotinic acid N-oxide: A combined experimental and theoretical study
Atac, A; Karabacak, M; Karaca, C; Kose, E
In this work, the experimental and theoretical UV, NMR, and vibrational features of nicotinic acid N-oxide (abbreviated as NANO. C6H5NO3) were studied. The ultraviolet (UV) absorption spectrum of studied compound that dissolved in water was examined in the range of 200-800 nm. FT-IR and FT-Raman spectra in solid state were observed in the region 4000-400 cm(-1) and 3500-50 cm(-1), respectively. The H-1 and C-13 NMR spectra in DMSO were recorded. The geometrical parameters, energies and the spectroscopic properties of NANO were obtained for all four conformers from density functional theory (DFT) B3LYP/6-311++G(d,p) basis set calculations. There are four conformers, C-n, n = 1-4 for this molecule. The computational results identified the most stable conformer of title molecule as the Cl form. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. C-13 and H-1 nuclear magnetic resonance (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 CIS approach. Finally the calculation results were applied to simulate infrared, Raman, and UV spectra of the title compound which show good agreement with observed spectra. (C) 2011 Elsevier B.V. All rights reserved.
Spectral investigation and theoretical study of zwitterionic and neutral forms of quinolinic acid
Karabacak, M; Sinha, L; Prasad, O; Bilgili, S; Sachan, AK; Asiri, AM; Atac, A
In this study, molecular structure and vibrational analysis of quinolinic acid (2,3-pyridinedicarboxylic acid), in zwitterionic and neutral forms, were presented using FT-IR, FT-Raman, NMR, UV experimental techniques and quantum chemical calculations FT-IR and FT-Raman spectra of 2,3-pyridinedicarboxylic acid (2,3-PDCA) in the solid phase were recorded in the region 4000-400 cm(-1) and 3500-0 cm(-1), respectively. The geometrical parameters and energies were obtained for zwitter and neutral forms by using density functional theory (DFT) at B3LYP/6-311++G(d,p) level of theory. 3D potential energy scan was performed by varying the selected dihedral angles using M06-2X and B3LYP functionals at 6-31G(d) level of theory and thus the most stable conformer of the title compound was determined. The most stable conformer was further optimized at higher level and vibrational wavenumbers were calculated. Theoretical vibrational assignment of 2,3-PDCA, using percentage potential energy distribution (PED) was done with MOLVIB program. C-13 and H-1 NMR spectra were recorded in DMSO. Chemical shifts were calculated at the same level of theory. The UV absorption spectra of the studied compound in ethanol and water were recorded in the range of 200-400 nm. The optimized geometric parameters were compared with experimental data. (C) 2015 Elsevier B.V. All rights reserved.
Spectroscopic studies on 9H-carbazole-9-(4-phenyl) boronic acid pinacol ester by DFT method
Sas, EB; Kurt, M; Can, M; Horzum, N; Atac, A
9H-Carbazole-9-(4-phenyl) boronic acid pinacol ester (9-CPBAPE) molecule was investigated by FT-IR, Raman, UV vis, H-1 and C-13 NMR spectra. FT-IR, FT-Raman and dispersive Raman spectra were recorded in the solid phase. H-1, C-13 NMR and UV-vis spectra were recorded in dimethyl sulfoxide (DMSO) solution. The results of theoretical calculations for the spectra of the title molecule were compared with the experimental spectra. The highest occupied molecular orbital (HOMO) the lowest unoccupied molecular orbital (LUMO) and molecular electrostatic potential (MEP) analyses were performed. The theoretical calculations for the molecular structure and spectroscopic studies were performed with DFT (B3LYP) and 6-311G (d,p) basis set calculations using the Gaussian 09 program. The total (TDOS), partial (PDOS) density of state and overlap population density of state (OPDOS) diagrams analyses were performed using GaussSum 2.2 program. (C) 2016 Elsevier B.V. All rights reserved.
FT-IR and FT-Raman, NMR and UV spectroscopic investigation and hybrid computational (HF and DFT) analysis on the molecular structure of mesitylene
Kose, E; Atac, A; Karabacak, M; Nagabalasubramanian, PB; Asiri, AM; Periandy, S
The spectroscopic properties of mesitylene were investigated by FT-IR, FT-Raman, UV, H-1 and C-13 NMR techniques. The geometrical parameters and energies have been obtained from density functional theory (DFT) B3LYP method and Hartree-Fock (HF) method with 6-311++G(d,p) and 6-311G(d,p) basis sets calculations. The geometry of the molecule was fully optimized, vibrational spectra were calculated and 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. Total and partial density of state (TDOS and PDOS) and also overlap population density of state (OPDOS) diagrams analysis were presented. C-13 and H-1 NMR chemical shifts were calculated by using the gauge-invariant atomic orbital (GIAO) method. The electronic properties, such as excitation energies, oscillator strength, wavelengths, HOMO and LUMO energies, were performed by time-dependent density functional theory (TD-DFT) results complements with the experimental findings. The results of the calculations were applied to simulate spectra of the title compound, which show excellent agreement with observed spectra. Besides, frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) and thermodynamic properties were performed. Reduced density gradient (RDG) of the mesitylene was also given to investigate interactions of the molecule. (C) 2013 Elsevier B.V. All rights reserved.
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.
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.
FT-Raman, FT-IR, UV spectra and DFT and ab initio calculations on monomeric and dimeric structures of 3,5-pyridinedicarboxylic acid
Nataraj, A; Balachandran, V; Karthick, T; Karabacak, M; Atac, A
The FT-IR and FT-Raman spectra of 3,5-pyridinedicarboxylic acid (dinicotinic acid, C7H5NO4) in the solid phase were recorded. The fundamental vibrational wavenumbers, intensities of vibrational bands and the optimized geometrical parameters of the compound are evaluated using HF and DFT (B3LYP) methods with 6-311G(d) basis set. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. The computed dimer parameters also show agreement with experimental data. The complete assignments were performed on the basis of the total energy distribution (TED). Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. UV-visible spectrum of the compound was recorded in the region 200-400 nm and the electronic properties HOMO and LUMO energies were measured by time-dependent TD-DFT approach. Thermodynamic properties (heat capacity, entropy and enthalpy) of the title compound at different temperatures were calculated. (c) 2012 Elsevier B.V. All rights reserved.
Conformational, electronic, and spectroscopic characterization of isophthalic acid (monomer and dimer structures) experimentally and by DFT
Bardak, F; Karaca, C; Bilgili, S; Atac, A; Mavis, T; Asiri, AM; Karabacak, M; Kose, E
Isophthalic acid (C6H4(CO2H)(2)) is a noteworthy organic compound widely used in coating and synthesis of resins and the production of commercially important polymers such as drink plastic bottles. The effects of isophthalic acid (IPA) on human health, toxicology, and biodegradability are the main focus of many researchers. Because structural and spectroscopic investigation of molecules provides a deep understanding of interactional behaviors of compounds, this study stands for exploring those features. Therefore, the spectroscopic, structural, electronic, and thermodynamical properties of IPA were thoroughly studied in this work experimentally using UV-Vis, H-1 and C-13 NMR, FT-IR, FT-Raman and theoretically via DFT and TD-DFT calculations. The UV-Vis absorption spectrum in water was taken in the region 200-400 nm. The NMR chemical shifts CH and C-13) were recorded in DMSO solution. The infrared and Raman spectra of the solid IPA were recorded in the range of 4000-400 cm(-1) and 3500-50 cm(-1), respectively. DFT and TD-DFT calculations were performed at the level of B3LYP/6-311 ++G(d,p) in determination of geometrical structure, electronic structure analysis and normal mode. The C-13 and H-1 nuclear magnetic resonance (NMR) spectra were estimated by using the gauge-invariant atomic orbital (GIAO) method. The scaled quantum mechanics (SQM) method was used to determine the total energy distribution (TED) to assign the vibrational modes accurately. Weak interactions such as hydrogen bonding and Van der Walls were analyzed via reduced density gradient (RDG) analysis in monomeric and dimeric forms. Furthermore, the excitation energies, density of state (DOS) diagram, thermodynamical properties, molecular electro-static potential (MEP), and nonlinear optical (NLO) properties were obtained. (C) 2016 Elsevier B.V. All rights reserved.
The investigation of fluorine substitution in difluoroanilines with focus on 2,6-difluoroaniline by spectroscopic methods, density functional theory approach, and molecular docking
Kose, E; Bardak, F; Atac, A
In this study, the spectroscopic features and reactive nature of difluoroanilines, with special attention on 2,6-difluoroaniline (2,6-DFA), are explored thoroughly to gain insight into the effect of fluorine substitution in aniline derivatives. The quantum chemically obtained spectral properties including Fourier transform infrared, Raman, ultraviolet, and H-1 and C-13 nuclear magnetic resonance spectra were obtained by using Density Functional Theory (DFT) calculations at B3LYP/6-311++G(d,p) level of theory, and given along with the ones measured experimentally. The reactivity characteristics such as Fukui descriptor, electrostatic potential, and electronegativity were defined based on electron density generated theoretically. The position of fluorine substitution does not significantly alter the amide group reactivity making all difluoroanilines compatible to each other in terms of the reactivity. The time-dependent DFT was used to calculate the electronic properties such as excitation energies, maximum wavelengths, oscillator strengths, and molecular orbitals energies, and given along with the density of state diagrams. The intramolecular interactions were mapped by reduced density gradient method to reveal possible fluorine influence on the amide group and its reactivity, and the strongest van der Waals interactions in 2,6-DFA were observed. Besides, the thermodynamic and nonlinear optical properties of the title molecule were also investigated. The 2,6-DFA molecule seems to be appealing for multidisciplinary studies about the relevant nonlinear optical properties. To explore the binding capability of 2,6-DFA and see the influence of fluorine substitution in difluoroanilines, molecular docking was performed on a model enzyme structure of T4 lysozyme. Ligand-enzyme binding energies of 2,6-DFA is nearly the same with that of 2,5 DFA and 3,5 DFA at the same binding site which differs from the remaining derivatives. (C) 2019 Elsevier B.V. All rights reserved.
Theoretical and experimental investigation of the spectroscopic features of and interionic interactions in 1-hexyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium tetrafluoroborate and 1-hexyl-3-methylimidazolium hexafluorophosphate ionic liquids
Bilgili, S; Atac, A; Bardak, F
In this work, the spectroscopic and electronic properties of three imidazolium-based ionic liquids (ILs) with 1-Hexyl-3-methylimidazolium cation and chloride, tetrafluoroborate, and hexafluorophosphate anions have been investigated theoretically and experimentally. The ground state electronic structure features such as molecular electrostatic potential, IR and Raman spectra, have been achieved through density functional theory (OFT) calculations at the B3LYP/6-311++G(d,p) level of theory in Gaussian 16. The resulting electron density has been analyzed to reveal intra- and interionic non-covalent interactions via atoms in molecules (AIM) approach and interpreted in terms of both the anion dependency and interaction type. The electronic transition characteristics have been carried out by time-dependent OFT calculations at the same level. The nuclear magnetic resonance shielding constants and chemical shifts have been computed by applying the DFT/gauge-including atomic orbitals (GIAO) method. The experimental measurements associated with the performed calculations include FT-IR and FT-Raman, UV-Vis, and H-1 and C-13 NMR spectra. The experimental spectroscopic signatures have been interpreted under the light of theoretical calculations. The effect of anion on the electronic structure and spectroscopic features are interpreted in accordance with the that of the density, viscosity, surface tension, refractive index, and the electrical conductivity results from previous works on the physicochemical properties of [Hmim][Cl], [Hmim][BF4] and [Hmim][PF6] ionic liquids. (C) 2020 Elsevier B.V. All rights reserved.
Investigation of the interionic interactions and spectroscopic features of 1-Octyl-3-methylimidazolium chloride, tetrafluoroborate, and hexafluorophosphate ionic liquids: An experimental survey and DFT modeling
Bilgili, S; Bardak, F; Kose, E; Atac, A
This study presents the spectroscopic and electronic properties of some imidazole-based ionic liquids (ILs) consisting of 1-Octyl-3-methylimidazolium cation and chloride, tetrafluoroborate, and hexafluorophosphate anions from experimental and theoretical perspectives. The ground state structural and vibrational characteristics of the ionic liquids have been achieved through Density Functional Theory (DFT) calculations at the Becke's and the Lee-Yang-Parr (B3LYP) and 6-311 ++G(d,p) level of theory in Gaussian 16. The electronic and magnetic features of the ILs have been examined by using electronic absorption spectra and Nuclear Magnetic Resonance spectroscopy (NMR) techniques along with the calculations from Time-Dependent Density Functional Theory (TD-DFT) and using Gauge-Including Atomic Orbital (GIAO) method. The intra-and interionic noncovalent interactions in the ionic liquids have been revealed via the electron density analysis based on the Atoms in Molecules (AIM) approach, and decomposed as hydrogen bonding, van der Waals interactions, and steric effects via Reduced Density Gradient (RDG) analysis. To gain insight into the possible effects of anion-cation interaction on the physicochemical properties of ionic liquids, interionic interactions, reactivity properties, topological critical points, and electrostatic potential surfaces were obtained. These interactional characteristics were interpreted in terms of both the anion dependency and interaction type. Notably, the results of this study were evaluated together with the results obtained from our previous study on ILs consisting of the same anions with the 1-Hexyl-3methylimidazolium cation to achieve the effects of the extension in the chain length of the cation in the presence of the same anion on the spectroscopic and electronic properties of ionic liquids. (c) 2022 Elsevier B.V. All rights reserved.
Spectroscopic (NMR, UV, FT-IR and FT-Raman) analysis and theoretical investigation of nicotinamide N-oxide with density functional theory
Atac, A; Karabacak, M; Kose, E; Karaca, C
The spectroscopic properties of the nicotinamide N-oxide (abbreviated as NANO, C6H6N2O2) were examined by FT-IR, FT-Raman, NMR and UV techniques. FT-IR and FT-Raman spectra in solid state were observed in the region 4000-400 cm(-1) and 3500-50 cm(-1), respectively. The H-1 and C-13 NMR spectra were recorded in DMSO. The UV absorption spectrum of the compound that dissolved in water was recorded in the range of 200-800 nm. The structural and spectroscopic data of the molecule in the ground state were calculated by using Density Functional Theory (DFT) employing B3LYP methods with the 6-311++G(d,p) basis set. The geometry of the molecule was fully optimized, vibrational spectra were calculated and 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. The optimized structure of compound was interpreted and compared with the reported experimental values. The observed vibrational wavenumbers, absorption wavelengths and chemical shifts were compared with calculated values. As a result, the optimized geometry and calculated spectroscopic data show a good agreement with the experimental results. (C) 2011 Elsevier B.V. All rights reserved.
Synthesis, spectroscopic characterization and quantum chemical computational studies of (S)-N-benzyl-1-phenyl-5-(pyridin-2-yl)-pent-4-yn-2-amine
Kose, E; Atac, A; Karabacak, M; Karaca, C; Eskici, M; Karanfil, A
The synthesis and characterization of a novel compound (S)-N-benzyl-1-phenyl-5-(pyridin-2-yl)-pent-4-yn-2-amine (abbreviated as BPPPYA) was presented in this study. The spectroscopic properties of the compound were investigated by FT-IR. NMR and UV spectroscopy experimentally and theoretically. The molecular geometry and vibrational frequencies of the BPPPYA in the ground state were calculated by using density functional theory (OFT) B3LYP method invoking 6-311++G(d,p) basis set. The geometry of the BPPPYA was fully optimized, vibrational spectra were calculated and 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. The results of the energy and oscillator strength calculated by time-dependent density functional theory (TD-OFT) and CIS approach complement with the experimental findings. Total and partial density of state (TDOS and PDOS) and also overlap population density of state (COOP or OPDOS) diagrams analysis were presented. The theoretical NMR chemical shifts (H-1 and C-13) complement with experimentally measured ones. The dipole moment, linear polarizability and first hyperpolarizability values were also computed. The linear polarizabilities and first hyper polarizabilities of the studied molecule indicate that the compound is a good candidate of nonlinear optical materials. The calculated vibrational wavenumbers, absorption wavelengths and chemical shifts showed the best agreement with the experimental results. (C) 2012 Elsevier B.V. All rights reserved.
A comprehensive study on the effect of substitution position and solvent effect on absorption and emission characteristics of n-methylindoles via linear response and State-Specific formalisms
Karaca, C; Bardak, F; Kose, E; Atac, A
The light absorption emission characteristics of n-methylindoles (n = 1-7) have been explored thoroughly by taking solvatochromic, substitution position, and solvation model effects into account. Experimental UV-Vis and Fluorescence spectra were recorded between 200 and 400 nm, and 250-800 nm, respectively, in cyclohexane, dichloromethane, and acetonitrile. Molecular geometry optimizations and excited state calculations were conducted using DFT and TD-DFT methods with a long-range corrected hybrid exchange-correlation functional CAM-B3LYP. Absorption emission characteristics were determined based on the polarizable continuum model accompanied with Linear-Response and State-Specific formalisms. Absorption spectra were resolved using Franck-Condon analysis for a more accurate representation of experimental data and underlying vibronic transitions were determined. Overall, although the Linear-Response and State-Specific approaches provide a quantitative explanation of experimental spectra, the approach used for the calculations can affect the solvent polarity-dependent shifts by nearly an order of magnitude. Besides, the State-Specific model provides slightly better results in the determination of Stokes shifts. The shouldered fluorescence peak observed in weakly polar solvents diminishes at higher polarities indicating the elimination of solute-solute interactions and domination of solute-solvent interactions with increasing solvent polarity.
Spectral investigations of 2,5-difluoroaniline by using mass, electronic absorption, NMR, and vibrational spectra
Kose, E; Karabacak, M; Bardak, F; Atac, A
One of the most significant aromatic amines is aniline, a primary aromatic amine replacing one hydrogen atom of a benzene molecule with an amino group (NH2). This study reports experimental and theoretical investigation of 2,5-difluoroaniline molecule (2,5-DFA) by using mass, ultraviolet-visible (UV-vis), H-1 and C-13 nuclear magnetic resonance (NMR), Fourier transform infrared and Raman (FT-IR and FT-Raman) spectra, and supported with theoretical calculations. Mass spectrum (MS) of 2,5-DFA is presented with their stabilities. The UV-vis spectra of the molecule are recorded in the range of 190-400 nm in water and ethanol solvents. The H-1 and C-13 NMR chemical shifts are recorded in CDCl3 solution. The vibrational spectra are recorded in the region 4000-400 cm(-1) (FT-IR) and 4000-10 cm(-1) (FT-Raman), respectively. Theoretical studies are underpinned the experimental results as described below; 2,5-DFA molecule is optimized by using B3LYP/6-311++G(d,p) basis set. The mass spectrum is evaluated and possible fragmentations are proposed based on the stable structure. The electronic properties, such as excitation energies, oscillator strengths, wavelengths, frontier molecular orbitals (FMO), HOMO and LUMO energies, are determined by time-dependent density functional theory (TD-DFT). The electrostatic potential surface (ESPs), density of state (DOS) diagrams are also prepared and evaluated. In addition to these, reduced density gradient (RDG) analysis is performed, and thermodynamic features are carried out theoretically. The NMR spectra (H-1 and C-13) are calculated by using the gauge-invariant atomic orbital (GIAO) method. The vibrational spectra of 2,5-DFA molecule are obtained by using DFT/B3LYP method with 6-311++G(d,p) basis set. Fundamental vibrations are assigned based on the potential energy distribution (PED) of the vibrational modes. The nonlinear optical properties (NLO) are also investigated. The theoretical and experimental results give a detailed description of the structural and physicochemical properties of the title molecule and contribute to understanding of the nature of di-substituted aniline derivatives. (C) 2016 Elsevier B.V. All rights reserved.

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