Browsing by Author "Çavuş M."

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An application of fractional calculus to dielectric relaxation processes
(2012-01-01) Çavuş M.; Bozdemir S.
Recently fractional calculus has been successfully applied in the description of complex dynamics and proved to be a valuable tool for the solution of non-linear differential equations. In this study, an autocorrelation function obtained from the one-dimensional stochastic Ising model is assumed to be identical to the dipole correlation function of a molecular chain, and the fractional calculus method is applied to obtain a fractional diffusion equation derived from the stochastic Ising model applicable to the dielectric relaxation processes observed in polar materials. The equation is solved by using the Adomian decomposition method. At low temperatures, the solution of the equation is found to be compatible with the Cole-Cole and KWW (Kohlrausch-William-Watts) equations, and also with the algebraic decay relaxation function. Copyright © 2002 IFAC.
Phthalocyanines including 2-mercaptobenzimidazole analogs: Synthesis, spectroscopic characteristics, quantum-chemical studies on the relationship between electronic and antioxidant properties
(2020-02-15) Yakan H.; Çavuş M.; Güzel E.; Arslan B.; Bakır T.; Muğlu H.
In this study, peripherally tetra 2-mercaptobenzimidazole group substituted cobalt and indium phthalocyanine complexes (2 and 3) were prepared from 4-(benzo[d]imidazole-2-ylthio)phthalonitrile (1) for the first time. Antioxidant behaviors and theoretical calculations of benzimidazole-substituted metallophthalocyanines are presented. The structures of these compounds were determined by the spectroscopic methods (IR, 1H NMR, UV–Vis and mass spectroscopies) and elemental analysis. Antioxidant activities of the compounds (1–3) were measured using 1,1-diphenyl-2-picrylhydrazyl (DPPH) method. Antioxidant activity was followed by 1 > 3 > 2 > Trolox. In addition, density functional theory (DFT) calculations were carried out to determine the stable electronic structure, charge density distributions, FMO energy eigenvalues, and electronegativity of the ligand (1) and complexes (2 and 3). NBO and QTAIM analysis were performed to investigate the relationship between the electronic properties and antioxidant activity of the compounds.
Structural, absorption, and molecular properties of o,o'-dihydroxyazo resorcinol dyes bearing an acryloyloxy group
(2017-12-05) Özkınalı S.; Çavuş M.; Ceylan A.; Gür M.
To the best of our knowledge, this is the first study reporting the synthesis and characterization of o,o′-dihydroxyazo dyes bearing an acryloyl group. The o,o′-dihydroxyazo dyes were synthesized through coupling of resorcinol with the diazonium salts of 2-amino-4-methylphenol, 2-aminophenol, 2-amino-4-chlorophenol, and 2-amino-4-nitrophenol. Their acryloyl derivatives were synthesized using metallic sodium and acryloyl chloride under an inert atmosphere. Characterization of the compounds was conducted using infrared (IR), ultraviolet–visible (UV–vis), proton nuclear magnetic resonance (1H NMR), and carbon nuclear magnetic resonance (13C NMR) spectroscopic methods. The tautomerism of the synthesized compounds' was also evaluated. The results were compared with theoretical results obtained by density functional theory (DFT). The DFT calculations were performed to obtain ground-state optimized geometries and calculate the relevant electronic and chemical reactivity parameters. Furthermore, possible tautomers deduced from the UV–vis spectra were investigated using theoretical calculations. Both the IR and NMR spectral data showed that azo tautomers predominate in the solid state and DMSO solvent. The effects of pH, solvent, and substituent on the predominant tautomers were further investigated through UV–vis spectroscopy. The results indicate that hydrazone tautomers were dominant at pH 12 in dimethylformamide (DMF), whereas azo tautomers were dominant at pH 2 in EtOH or CHCl3.
Synthesis of new azo schiff bases of pyrazole derivatives and their spectroscopic and theoretical investigations
(2018-12-15) Özkınalı S.; Gür M.; Şener N.; Alkın S.; Çavuş M.
New pyrazole Schiff bases containing azo groups, 4-((E)-phenyldiazenyl)-3-(4-nitrobenzylidene)-1-phenyl-pyrazole-5-amine and its series, were synthesized using the condensation reaction between p-nitrobenzaldehyde and (E)-1-phenyl-4-(phenyldiazenyl)-1H-pyrazole-3,5-diamine in the molar ratio of 1:1. The compounds were characterized using IR, UV–Vis, 1H-NMR and 13C-NMR spectroscopies. The UV–Vis spectral data were obtained in ethanol, chloroform, N,N-dimethylformamide (DMF), DMF (pH = 2) and DMF (pH = 12), which have different polarity and pH values. Meanwhile, the experimental spectral analyses were supported by the theoretical calculations based on the density functional theory (DFT) using the B3LYP/cc-pvtz level. Structural analyses, vibrational frequencies, UV, and NMR calculations were performed at the same level of the theory. In addition, via using HOMO-LUMO energies, the electrochemical quantities such as chemical hardness and electronegativity were calculated and analyzed.
Synthesis, characterisation and DFT calculations of azo-imine dyes
(2018-01-01) Özkınalı S.; Çavuş M.; Sakin B.
In this study, azo dyes containing an imine group were synthesised by coupling p-hydroxybenzylidene aniline with the diazonium salts of p-toluidine, 4-aminophenol, aniline, p-chloroaniline, p-fluoroaniline and p-nitroaniline. The compounds were characterised by melting point, elemental, UV-Vis and IR analyses as well as1H-NMR and13 C-NMR spectroscopies. Moreover, the experimental data were supplemented with density functional theory (DFT) calculations. The experimental data on FT-IR and UV–Vis spectra of the compounds were compared with theoretical results. The DFT calculations were performed to obtain the ground state geometries of the compounds using the B3LYP hybrid functional level with 6-311++g(2d,2p) basis set. Frontier molecular orbital energies, band gap energies and some chemical reactivity parameters, such as chemical hardness and electronegativity, were calculated and compared with experimental values. A significant correlation was observed between the dipole moment and polarities of the solvents and the absorption wavelength of the compounds.
Synthesis, characterization, quantum chemical calculations and antioxidant activity of new bis-isatin carbohydrazone and thiocarbohydrazone derivatives
(2019-11-15) Muğlu H.; Çavuş M.; Bakır T.; Yakan H.
1,5-Bis(5-chloro-2-oxoindolin-3-ylidene)thiocarbohydrazone (3), 1,5-Bis(5-metoxy-2-oxoindolin-3-ylidene)thiocarbohydrazone (4), 1,5-Bis(5-metoxy-2-oxoindolin-3-ylidene)carbohydrazone (5) were obtained from isatins and thio/carbohydrazides under reflux in absolute ethanol. The structures of these synthesized compounds were determined using FT-IR, 1H NMR, 13C NMR spectroscopy, and elemental analysis. Quantum chemical calculations were also performed at B3LYP/6-311++G(2d,2p) level in order to obtain information about the molecular geometries and electronic data, such as HOMO-LUMO energy eigenvalues and density of states (DOSs). In addition, structural and antioxidant properties of the compounds were studied theoretically. QTAIM analysis was performed to investigate the relationship between intramolecular interactions, electronic data and antioxidant activity. The in vitro antioxidant activity of all the compounds was determined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging method. Antioxidant activity was followed by Ascorbic acid > 3 > 4 > 5.
Synthesis, electronic and spectral properties of new 1,3,4-thiadiazole compounds and the spectral analysis of their conformers using density functional theory
(2019-01-01) Çavuş M.; Çelik T.
In this study, new 1,3,4-thiadiazole compounds were synthesised and characterised by FT-IR, 1H-NMR, UV–vis spectroscopy and elemental analysis, Furthermore, the relationship between the electronic and spectral data of the 16 conformers of each compound was investigated by theoretical calculations; the theoretical data were compared with the experimental results. The B3LYP hybrid functional level with a 6-311++g(2d,2p) basis set was used to obtain the ground state geometries, frontier molecular orbital energies, band gap energies and chemical reactivity parameters and to perform a spectral analysis of the compounds. Significant correlations were calculated between the minimum molecular energy and the N–H and C=O vibrational frequencies and the NH proton chemical shifts of the conformers. The charge density on the nitrogen atom and the delocalisation index of the highly polar N–H covalent bond were investigated by quantum theory of atoms in molecules. The effect of conformer structure on the theoretical results and its role in interpreting the experimental data were presented, and it was theoretically shown that the activity degree of the non-aromatic electronegative atoms or groups of atoms in the intramolecular interaction was a very important factor in determining the electronic and spectral properties of each compound.