Browsing by Author "Bilgili S."
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Item Molecular structure, spectroscopic characterization (FT-IR, FT-Raman, UV and NMR), HOMO and LUMO analysis of 3-ethynylthiophene with DFT quantum chemical calculations(Elsevier B.V., 2013) Karabacak M.; Bilgili S.; Mavis T.; Eskici M.; Atac A.In this work, FT-IR, FT-Raman, UV and NMR spectra of 3-ethynylthiophene (3-ETP, C6H4S) were carried out by using density functional theory DFT/B3LYP method with the 6-311++G(d,p), 6-311+G(d,p), 6-311G(d,p), 6-31++G(d,p), 6-31+G(d,p), 6-31G(d,p) basis sets. FT-IR and FT-Raman spectra were recorded in the regions of 3500-400 cm1 and 3500-50 cm 1, respectively. The geometrical parameters, energies and wavenumbers were obtained and 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 and PQS program. The 1H, 13C and HMQC (1H- 13C correlation) NMR spectra in chloroform (CDCl3) were recorded and calculated. The UV spectrum of investigated compound were recorded in the region of 200-400 nm in ethanol solution. The electronic properties, such as excitation energies, absorption wavelengths, HOMO and LUMO energies were performed by DFT/B3LYP approach and the results were compared with experimental observations. The thermodynamic properties such zero-point vibrational energy, thermal energy, specific heat capacity, rotational constants, entropy, and dipole moment of the studied compound were calculated. As a result, the calculated results were compared with the observed data and found to be in good agreement. © 2013 Elsevier B.V. All rights reserved.Item Spectral investigation and theoretical study of zwitterionic and neutral forms of quinolinic acid(Elsevier, 2015) Karabacak M.; Sinha L.; Prasad O.; Bilgili S.; Sachan A.K.; Asiri A.M.; 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. 13C and 1H 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. © 2015 Elsevier B.V. All rights reserved.Item Molecular structure, spectroscopic characterization, HOMO and LUMO analysis of 3,3′-diaminobenzidine with DFT quantum chemical calculations(Elsevier, 2015) Karabacak M.; Bilgili S.; Atac A.In this work, infrared, Raman and UV spectra of 3,3′-diaminobenzidine (3,3-DAB) were carried out by using density functional theory (DFT)/B3LYP method with 6-311G(d,p) basis set. FT-IR and FT-Raman spectra were recorded in the region 4000-400 and 4000-50 cm-1, respectively. The geometrical parameters, energies and wavenumbers were obtained and fundamental vibrations were assigned on the basis of the potential energy distribution (PED) of the vibrational modes. The UV spectrum of the investigated compound was recorded in the range of 200-400 nm in ethanol and water solutions. The electronic properties, such as excitation energies, absorption wavelengths, HOMO and LUMO energies were performed by DFT/B3LYP approach and the results were compared with experimental observations. Thermodynamic properties, Mulliken atomic charges and molecular electrostatic potential (MEP) were calculated for the title molecule. Also the nonlinear optical properties of 3,3-DAB molecule were explored theoretically. As a result, the calculated results were compared with the observed values and generally found to be in good agreement. © 2015 Elsevier B.V. All rights reserved.Item Molecular structure investigation of neutral, dimer and anion forms of 3,4-pyridinedicarboxylic acid: A combined experimental and theoretical study(Elsevier, 2015) Karabacak M.; Bilgili S.; Atac A.In this study, the structural and vibrational analysis of 3,4-pyridinedicarboxylic acid (3,4-PDCA) are presented using experimental techniques as FT-IR, FT-Raman, NMR, UV and quantum chemical calculations. FT-IR and FT-Raman spectra of 3,4-pyridinedicarboxylic acid in the solid phase are recorded in the region 4000-400 cm-1 and 4000-50 cm-1, respectively. The geometrical parameters and energies of all different and possible monomer, dimer, anion-1 and anion-2 conformers of 3,4-PDCA are obtained from Density Functional Theory (DFT) with B3LYP/6-311++G(d,p) basis set. There are sixteen conformers (C1C16) for this molecule (neutral form). The most stable conformer of 3,4-PDCA is the C1 conformer. The complete assignments are performed on the basis of the total energy distribution (TED) of the vibrational modes calculated with scaled quantum mechanics (SQM) method. 1H and 13C NMR spectra are recorded and the chemical shifts are calculated by using DFT/B3LYP methods with 6-311++G(d,p) basis set. The UV absorption spectrum of the studied compound is recorded in the range of 200-400 nm by dissolved in ethanol. The optimized geometric parameters were compared with experimental data via the X-ray results derived from complexes of this molecule. In addition these, molecular electrostatic potential (MEP), thermodynamic and electronic properties, HOMO-LUMO energies and Mulliken atomic charges, are performed. © 2014 Elsevier B.V. All rights reserved.Item Theoretical study on molecular structure and vibrational analysis included FT-IR, FT-Raman and UV techniques of 2,4,5-trimethylbenzoic acid (monomer and dimer structures)(Elsevier, 2015) Karabacak M.; Bilgili S.; Atac A.Theoretical study on the structural and vibrational analysis of monomer and dimer structures of 2,4,5-trimethylbenzoic acid (2,4,5-TMBA, C 10H12O2) were presented. The geometry of the molecule was fully optimized. The Fourier transform infrared (FT-IR) and the Fourier transform Raman (FT-Raman) spectra of the title molecule in solid phase were recorded in the region 4000-400 cm-1 and 4000-50 cm -1, respectively. The geometrical parameters and energies were investigated with the help of Density Functional Theory (DFT) employing B3LYP method and 6-311++G(d,p) basis set. The spectroscopic data of the molecule in the ground state were calculated by using DFT/B3LYP method with the 6-311++G(d,p) basis set. The vibrational spectra were calculated and fundamental vibrations were assigned on the basis of the potential energy distribution (PED) of the vibrational modes. The geometric parameters were compared with experimental data of the title molecule. The UV absorption spectrum of the studied compound was computed and recorded in the range of 190-400 nm dissolved in water and ethanol. Besides, charge transfer occurring in the molecule between HOMO and LUMO energies, frontier energy gap, molecular electrostatic potential (MEP) were calculated and presented. In addition these, thermodynamic properties and Mulliken atomic charges were performed. © 2014 Elsevier B.V. All rights reserved.Item Conformational, electronic, and spectroscopic characterization of isophthalic acid (monomer and dimer structures) experimentally and by DFT(Elsevier B.V., 2016) Bardak F.; Karaca C.; Bilgili S.; Atac A.; Mavis T.; Asiri A.M.; 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, 1H and 13C 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 (1H and 13C) 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 13C and 1H 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. © 2016 Elsevier B.V. All rights reserved.Item 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(Elsevier B.V., 2020) 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 (DFT) 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 DFT 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 1H and 13C 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. © 2020 Elsevier B.V.Item Anionic dependency of electronic and nonlinear optical properties of ionic liquids(Elsevier B.V., 2022) Bardak F.; Bardak C.; Karaca C.; Kose E.; Bilgili S.; Atac A.Nonlinear optical phenomena play significant roles in the bulk properties and responsive characteristics of ionic liquids, especially when used under strong electric fields. The variability of the anion-cation pair in ionic liquids makes them designer solvents; thus, the anion or cation dependency of the physicochemical properties should be understood in depth. Accordingly, the electric field-induced characteristics of eight ionic liquids with [Br]−, [BF4]−, [PF6]−, [Ac]−, [TFAc]−, [MS]−, [NTf2]−, and [Tos]− anions paired with the 1-butyl-3-methyl imidazolium cation were investigated using density functional theory modeling at four theoretical levels: B3LYP-6-31G(d), M06-2X 6-31G(d), M06-2X 6-311++G(d,p), and M06-2X aug-cc-PVTZ. The frontier molecular orbitals, electrostatic potential surface, and electron density difference maps were obtained to visualize the electrostatic characteristics. The permanent electric dipole moment, linear electric polarizability, and first-order and second-order hyperpolarizabilities were also determined. While the static dipole moment and dipole polarizabilities could be obtained using low-level quantum chemistry at a satisfactory level, the functionalization of more intensive methods was required to accurately obtain the nonlinear optical properties. © 2021 Elsevier B.V.Item 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(Elsevier B.V., 2022) 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-3-methylimidazolium 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. © 2022 Elsevier B.V.Item Effect of anion and methylation on the interionic interactions and reactivity of 1-butyl-2,3-dimethyl imidazolium-based ionic liquids(Elsevier B.V., 2023) Bilgili S.; Bardak F.; Atac A.The study presents the investigation of anion and methylation effects on the interionic interactions, thus explaining the variations in the reactivity, electronic, and spectroscopic features in 1-butyl-2,3-dimethyl imidazolium-based ionic liquids with chloride, tetrafluoroborate, and hexafluorophosphate anions. Ground state electronic structures, IR and Raman spectra, electronic transition characteristics, and chemical shifts of the ionic liquids were obtained using DFT calculations at the B3LYP/6–311++G(d,p) level of theory. The calculated electron densities were analyzed to determine intra- and interionic interactions at critical points using Reduced Density Gradient and topological analysis through the atoms-in-molecules approach. Experimental spectroscopic characterizations were performed using the FT-IR, FT-Raman, NMR, and UV–vis techniques. These techniques and DFT calculations provide essential contributions to interpreting spectral features concerning the structure and dynamics of ionic liquids. Furthermore, molecular docking studies were performed to determine the binding status of studied ionic liquids with human serum albumin to explore their activity, thus reporting their potential due to their demand in pharmacology. © 2023 Elsevier B.V.