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    An efficient method for the azocino[4,3-b]indole framework of strychnos alkaloids: OFT investigations on the electronic and spectroscopic properties
    (Scientific Publ-India, 2019) Uludag, Nesimi; Serdaroglu, Goncagul; Colak, Naki
    Tetracyclic 1,5-methanoazocino[4,3-b]indole (2) was achieved via a new synthetic approach for the synthesis of related strychnos alkaloids. These products embody the ABCD-ring system associated with the title alkaloids, as well as a one-pot construction of the ABCD ring system using tetrachloro-1,4-benzoquinone and tetrafluoro-1,4-benzoquinone, were involved as key steps. Also, the DFT-based quantum chemical calculations have been performed to evaluate the structural, electronic, and spectroscopic properties of the compound. PES (potential energy surface) scan revealed three stable conformers of the compound. The calculated FT-IR and NMR spectral data were compared with the corresponding observed values for the most stable conformer of the compound. Frontier Molecular Orbital analysis has revealed the chemical reactivity tendency and sites of the compound.
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    Preparation and spectroscopic studies of Fe(II), Ru(II), Pd(II) and Zn(II) complexes of Schiff base containing terephthalaldehyde and their transfer hydrogenation and Suzuki-Miyaura coupling reaction
    (Sciendo, 2019) Turan, Nevin; Buldurun, Kenan; Colak, Naki; Ozdemir, Ismail
    This study describes synthesis, spectroscopic characterization and catalytic activities of Fe(II), Ru(II), Pd(II) and Zn(II) complexes with a novel Schiff base ligand (L) derived from methyl 2-amino-5,5,7,7-tetramethyl-4,5,6,7-tetrahydrobenzo[b] thiophene-3-carboxylate and terephthalaldehyde. We used spectroscopic techniques including IR, UV-Vis, H-1-NMR, C-13-NMR, elemental analysis and also mass analysis and magnetic susceptibility measurements to identify the products. The Pd(II) complex was used as a potential catalyst for Suzuki-Miyaura coupling reaction of some aryl halides under optimized conditions. The effect of various bases such as NaOH, KOH, and KOBut was investigated in transfer hydrogenation (TH) of ketones by isopropyl alcohol as the hydrogen source. Ru(II) and Pd(II) complexes showed catalytic activity while Zn(II) and Fe(II) metal complexes failed to do that.
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    Preparation, spectral characterization, ESR measurements and DFT calculations of Schiff base copper(II) complex
    (Taylor & Francis Inc, 2021) Tokdemir Ozturk, Sibel; Aksu, Perihan; Turan, Nevin; Buldurun, Kenan; Tanis, Emine; Colak, Naki
    The title compound ([CuClL(H2O)]center dot 2H(2)O) were synthesized. The copper(II) complex in square planar geometry were identified by using elemental analysis, magnetic susceptibility, mass spectra, FT-IR, UV-Vis. and ESR techniques. DFT calculations at the UB3LYP/LANL2DZ level of theory were conducted to obtain vibrational and electronic properties of the copper(II) complex. Vibrational assignments of the observed infrared spectra of title compound were carried out based on the calculated potential energy distributions (PEDs). The sensitive measurement results indicated that the observed values were reasonable. The energy values were determined to describe electronic properties of the title molecules. Furthermore, NBO analysis was performed to analyze the hyper-conjugative stability of the molecule, molecular orbital interaction and charge delocalization.
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    Solvent effects on the electronic and optical properties of Ni(II), Zn(II), and Fe(II) complexes of a Schiff base derived from 5-bromo-2-hydroxybenzaldehyde
    (Sage Publications Ltd, 2021) Buldurun, Kenan; Tanis, Emine; Turan, Nevin; Colak, Naki; Cankaya, Nevin
    In this article, the electronic, optical, and charge transfer properties of a Schiff base ligand prepared using 5-bromo-2-hydroxybenzaldehyde and ethyl 6-acetyl-2-amino-4,5,6,7-tetrahydrothieno[2,3-c]pyridine-3-carboxylate (C19H19BrN2O4S) and its Fe(II) (C19H30BrN2O10SClFe), Ni(II) (C19H28BrN2O9SClNi), and Zn(II) (C19H28BrN2O9SClZn) complexes are described based on different solvents environments and supported by theoretical calculations. Theoretical calculations are carried out using density functional theory (DFT/UB3LYP/LANL2DZ). The optical densities, optical band gaps, and refractive indices of the ligand and its Fe(II), Ni(II), and Zn(II) complexes in different solvent environments are obtained. The reorganization energies are calculated to determine the charge transfer rate of the studied compounds using both experimental and theoretical data. These experimental and theoretical results show that the ligand and its metal complexes can be used for optoelectronic applications and charge transfer materials in organic light-emitting diode applications.
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    Synthesis, Characterization and Theoretical Calculations of Schiff Base Containing Thiophene Ring System
    (Gazi Univ, 2017) Balaban Gunduzalp, Ayla; Colak, Naki; Altiner, Saliha; Sahin, Zarife Sibel
    Schiff base titled as 2-[(2-methoxybenzylidene)amino]-6-methyl-4,5,6,7-tetrahydrobenzo [b]thiophene-3-carbonitrile was obtained by condensation of amine with 2-methoxybenzaldehyde. Imine compound was characterized by using elemental analysis, FT-IR (fourier transform infrared), NMR (nuclear magnetic resonance)-APT (attached proton test) techniques and X-ray diffraction analysis. X-ray studies reveal that singly crystals were obtained in triclinic system. The optimized structure, chemical shifts (H-1 and C-13-NMR) and geometrical parameters (bond lenghts and angles) of Schiff base were obtained by DFT (densital functional theory) with B3LYP (Becke's three parameter hybrid functional combined with the Lee-Yang-Parr correlation functional) using 6-311+G(2d,p) level of theory in Gaussian 09W software. The FMOs (frontier molecular orbitals) levels were also determined by this quantum set.
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    Synthesis, characterization, powder X-ray diffraction analysis, thermal stability, antioxidant properties and enzyme inhibitions of M(II)-Schiff base ligand complexes
    (Taylor & Francis Inc, 2021) Buldurun, Kenan; Turan, Nevin; Bursal, Ercan; Aras, Abdulmelik; Mantarci, Asim; Colak, Naki; Gulcin, Ilhami
    The Schiff base ligand ((E)-6-methyl-2-(2,3,4-trimethoxybenzylideneamino)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbonitrile) and its cobalt(II) and palladium(II) complexes were successfully prepared. The structure of the compounds was elucidated by various techniques (NMR, FT-IR, powder X-ray diffraction, microanalysis, TGA, magnetic susceptibility, mass spectrometry). The Pd(II) complex showed a square planar geometry and the Co(II) complex had an octahedral geometry. ABTS (2,2-azino-bis 3-ethylbenzothiazloine-6-sulphonic acid), DPPH (1,1-diphenyl-2-picrylhydrazyl), FRAP (ferric-reducing antioxidant power) and CUPRAC (cupric reducing antioxidant capacity)in vitromethods were applied to identify the antioxidant features of the synthesized compounds. In addition, glutathione S-transferase and acetyl/butyryl cholinesterase enzymes were examined for possible inhibition capacities of the complexes. According to the enzyme activity measurements, Ru(II) complex inhibited both GST and BChE enzymes, while Fe(II) complex inhibited only AChE enzyme. Furthermore, the antioxidant activities and enzyme inhibitions of the previously synthesized Fe(II) and Ru(II) complexes of the same ligand were examined to make a comparison of the metal complexes. Communicated by Ramaswamy H. Sarma
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    Synthesis, Spectroscopic and Computational Studies of (E)-2-(2,3-dihydroxy)-benzylidene)amino)-6-methyl-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbonitrile
    (Gazi Univ, 2017) Colak, Naki; Altiner, Saliha; Sahin, Zarife Sibel; Gunduzalp, Ayla Balaban
    Heteroaromatic Schiff base was synthesized by the reaction of 2-amino-6-methyl-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbonitrile with 2,3-dihydroxybenzaldehyde. Titled compound was characterized by elemental analysis, FT-IR, H-1-NMR, C-13/APT-NMR and X-ray diffraction methods. Imine compound was crystallized in triclinic crystal system with space group P-1. Xray studies reveal that our molecule is stabilized by O-H center dot center dot center dot N and C-H center dot center dot center dot O hydrogen bonds and intermolecular pi center dot center dot center dot pi interactions. The molecular structure of Schiff base was optimized by density functional theory (DFT) method using B3LYP/6-311+G(2d, p) quantum set in Gaussian 09W software program. The chemical shifts and geometrical parameters were also computed by the same quantum level and compared with the experimental results of (E)-2-(2,3-dihydroxy)-benzylidene)amino)-6-methyl-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbonitrile.
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    Synthesis, structural studies and antioxidant activities of M(II) complexes with NOS donor schiff base ligand
    (Yildiz Technical Univ, 2021) Turan, Nevin; Bingol, Mustafa; Savci, Ahmet; Kocpinar, Enver Fehim; Colak, Naki
    Schiff base ligand, (E)-methyl 6-acetamido-2-(5-bromo-2-hydroxybenzylideneamino)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate, was successfully prepared with condensation reaction. The newly obtained Schiff base used to synthesize five new complex,[FeLCl(H2O)(2)]center dot 1.5H(2)O, [CoLCl(H2O)(2)]center dot 2H(2)O, [NiLCl(H2O)(2)]center dot H2O, [RuLCl(p-cymene)]center dot 3.5H(2)O and [PdLCl center dot H2O]center dot 3H(2)O. From the magnetic and spectral data, the geometric structures of these complexes were found to be square planar and octahedral. The characterizations of ligand and complexes were done by FT-IR, UV-Vis, H-1 and C-13-NMR, microanalyses, magnetic susceptibility, mass spectra and thermogravimetry analysis (TGA) and further were screened for antioxidant activities. Antioxidant properties of synthesized compounds were examined using different methods including total antioxidant activity, FRAP (ferric reducing antioxidant power), CUPRAC (cupric reducing antioxidant capacity) and DPPH (2,2-diphenyl-1-picrylhydrazyl). The Ru(II), Pd(II), Fe(II) and Co(II) metal complexes generally exhibited good antioxidant properties.