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Öğe An Experimental and Computational Evaluation of the Interaction Between Intelligent Ampholyte Acrylamide/Acrylic Acid/2-(Acryloyloxy)ethyl Trimethylammonium Chloride Hydrogel and Dyes(Springer, 2024) Isikver, Yasemin; Saraydin, Dursun; Karakus, NihatNovel intelligent ampholyte hydrogel (IAH) was prepared by a free radical solution redox polymerization of acrylamide, acrylic acid, 2-(acryloyloxy)ethyl trimethylammonium chloride as monomers, and ethylene glycol dimethacrylate as crosslinker. Spectroscopic, thermal, and surface properties of IAH were performed using ATR/FTIR, molecular electrostatic potential maps, TGA and DSC. Swelling studies were performed at increasing pH and temperature. IAH has been identified as intelligent and ampholyte. Cavity sizes of IAH were calculated from SEM photographs by digital image analysis method. Due to the large cavities of IAH, this hydrogel was used for dye sorption. The binding of carminic acid to IAH was L-type according to the Giles classification system, while crystal violet and methyl violet were S-type. Binding parameters of dyes such as binding constant, monolayer coverage, and maximum fractional occupancy were calculated from the Langmuir model or Saraydin model. It was observed that the binding between the dyes used and the IAH was realized by electrostatic interaction, and the hydrogen bonds in the carminic acid increased this bonding. This study could be a pioneering model for the preparation of potential and effective intelligent ampholyte hydrogels for the removal of both anionic and cationic dyes from aquatic environments by electrostatic interaction/H-bonding.Öğe Computational study of the intramolecular proton transfer reactions of 3-hydroxytropolone (2,7-dihydroxycyclohepta-2,4,6-trien-1-one) and its dimers(SPRINGER, 2010) Isin, Dilara Ozbakir; Karakus, NihatThe proton transfer reaction and dimerization processes of 3-hydroxytropolone (3-OHTRN) have been investigated using density functional theory (DFT) at the B3LYP/6-31+G** level. The influence of the solvent on the proton transfer reaction of 3-OHTRN was examined using the self-consistent isodensity polarized continuum model (SCI-PCM) with different dielectric constants (epsilon = 4.9, CHCI(3); epsilon = 32.63, CH(3)OH; epsilon = 78.39, H(2)O). The intramolecular proton transfer reaction occurs more readily in the gas phase than in solution. Results also show that the stability of 3-OHTRN dimers in the gas phase is directly affected by the hydrogen bond length in the dimer structure.Öğe Effect of electron-donating and -withdrawing substitutions in naphthoquinone sensitizers: The structure engineering of dyes for DSSCs in Quantum Chemical Study(Elsevier, 2024) Sari, Secil; Karakus, NihatDye-sensitized solar cells (DSSCs) are cost-effective photovoltaic devices that convert solar energy into electricity using a dye sensitizer, TiO2 photoanode, electrolyte, and counter electrode. This study investigates the impact of substituents on the performance of naphthoquinone-based dye sensitizers in DSSCs. We analyzed various naphthoquinone derivatives' electronic structures and light absorption properties using DFT and TD-DFT. Our results demonstrate that electron-donating groups enhance DSSC performance by improving light absorption and electron injection. Specifically, naphthoquinone derivatives with methoxy (Dye-2) and methyl (Dye-3) groups showed superior properties. TD-DFT analysis revealed high molar extinction coefficients over a broad spectrum, making these dyes efficient at capturing sunlight. Additionally, these dyes effectively interact with TiO2, which is crucial for photostability and photovoltaic performance. In conclusion, naphthoquinone derivatives with electron-donating groups significantly improve DSSC performance, with Dye-2 and Dye-3 being strong candidates for high-performance applications.Öğe Feasibility of tetracycline, a common antibiotic, as chelating agent for spectrophotometric determination of UO22+ after cloud point extraction(SPRINGER, 2014) Bagda, Esra; Yabas, Ebru; Karakus, NihatA cloud point extraction (CPE) procedure was presented for the preconcentration of UO22+ ion in different water samples. Tetracycline (TC) is the second most widely used antibiotics in the world and is used as chelating agent. To the best of our knowledge, this is the first work that an antibiotic is used as a chelating agent for CPE of UO22+. Besides, the use of TC as complexing agent provides excellent chelating features. TC molecule has large numbers of functional groups (adjacent hydroxyl oxygen atoms and cyclohexanone oxygen atoms, amide groups) which can form stable complex with UO22+. After complexation with TC, UO22+ ions were quantitatively recovered in Triton X-100 after cooling in the ice bath. 3.0 mL of acetate buffer was added to the surfactant-rich phase prior to its analysis by UV-Vis spectrophotometer. The influence of analytical parameters including pH, buffer volume, TC, Triton X-100 concentrations, bath temperature, incubation time were optimized. The effect of the matrix ions on the recovery of UO22+ ions was investigated. The limit of detection was 0.0746 mu g mL(-1) along with enrichment factor of 14.3 with a R. S. D. of 3.6 %. The proposed procedure was applied to the analysis of various environmental water samples. On the other hand, the electronic distribution of TC molecule is investigated with their frontier molecular orbital density distributions.Öğe The investigation of corrosion inhibition efficiency on some benzaldehyde thiosemicarbazones and their thiole tautomers: Computational study(ELSEVIER SCIENCE BV, 2015) Karakus, Nihat; Sayin, KorayQuantum chemical calculations using three methods, Hartree-Fock (HF), Moller-Plesset (MP) and density functional theory (DFT/B3LYP) method with SOD, 6-31G(d,p) and 6-31++G(d,p) basis sets are performed some benzaldehyde thiosemicarbazones and their thiole tautomers. The results of the quantum chemical calculations and experimental IE% which are belong to thione tautomers are subjected to correlation analysis and indicate that their inhibition effect are closely related to some quantum chemical parameters. The active sites are determined by using MEP diagrams, proton affinities and Fukui functions. The theoretically obtained results are found to be consistent with the experimental data which are reported for thione tautomers. (C) 2014 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.Öğe Kaya's composite descriptor and Maximum Composite Hardness Rule for chemical reactions(Elsevier, 2022) Kaya, Savas; Isin, Dilara Ozbakir; Karakus, NihatWithin the framework of Maximum Hardness and Minimum Polarizability Principles and as compatible with Jenkins Volume Based Thermodynamics approach, Kaya and coworkers calculated the lattice energies of inorganic ionic crystals using their eta(M)/V-m(1/3) ratio (here eta(M) and V-m represent the chemical hardness and molar volume of any molecule, respectively). This ratio is called as Kaya's composite descriptor. It is apparent that Kaya's composite descriptor can be considered in the analysis of the chemical stability of compounds and the directions of chemical reactions. In a recent paper, Szentpaly, Kaya and Karakus proposed Maximum Composite Hardness Rule for solid state double exchange reactions. To see the validity in other reaction types also of Kaya's composite descriptor and Maximum Composite Hardness Rule, twenty-eight chemical reactions including especially organic molecules were investigated. Reactivity descriptors such as chemical hardness, molar volume, polarizability regarding reactants and products putting in an appearance were calculated at B3LYP/6-31thornthorng (d, p) calculation level with the help of computational chemistry tools. The result showed that instead of using separately the chemical hardness, polarizability and molar volume concepts, the use of Kaya chemical reactivity approach will be more useful to predict whether the reactions are exothermic or endothermic. It can be concluded from here that new composite descriptors should be derived and used for the accurate prediction of the reactivities of the chemical systems.Öğe Quantum chemical study on the inhibition efficiencies of some sym-triazines as inhibitors for mild steel in acidic medium(ELSEVIER SCIENCE BV, 2015) Isin, Dilara Ozbakir; Karakus, NihatQuantum chemical calculations using density functional theory (DFT) at the B3LYP/6-31++G(d,p) basis set level were performed on five sym-triazines used as corrosion inhibitors for mild steel in acidic medium to determine the relationship between molecular structure and their percentage inhibition efficiencies. The results of the calculations and experimental IE% were subjected to correlation analysis and indicate that their inhibition effect are closely related to EHOMO, ELUMO, energy gap, hardness, softness, electronegativity and the fraction of electrons transferred were calculated. The theoretically obtained results were found to be consistent with the experimental data reported. (C) 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.Öğe Removal of food dyes from aqueous solution by chitosan-vermiculite beads(Elsevier, 2020) Senol, Zeynep Mine; Gursoy, Nevcihan; Simsek, Selcuk; Ozer, Ali; Karakus, NihatIn this study, Chitosan (Ch)-Vermiculite (V) composite beads material which is a low-cost and naturally effective adsorbent were used for efficient removal of Sunset Yellow FCF (Sy) and Brilliant Blue FCF (Bb) food dyes from aqueous solution. Ch-V composite beads were characterized by using FTIR, SEM, XRD and PZC analysis. The adsorbent properties of Ch-V composite beads for Sy and Bb dyes were evaluated in terms of pH, concentration, kinetic (time) and thermodynamic (temperature) of adsorption. The experimental data presented were obtained from Langmuir, Freundlich and Dubinin-Radushkevich (DR) isotherm models. The maximum adsorption capacity for the Langmuir equation was found to be 0387 mol kg(-1) for Sy and 0229 mol kg(-1) for Bb, respectively. The results showed that the experimental data were better fit the Langmiur model for Sy and the Freundlich model for Bb. Adsorption energies obtained from DR model for Sy and Bb showed that adsorption processes were chemically. The pseudo-second order and intra-particle diffusion models of adsorption kinetics are in accordance with Sy and Bb. As a result of thermodynamic evaluation of Sy and Bb adsorption, it was found that adsorption processes were endothermic, entropy increased and reaction was spontaneous. (C) 2020 Elsevier B.V. All rights reserved.Öğe Revealing the antioxidant properties of alkyl gallates: a novel approach through quantum chemical calculations and molecular docking(Springer, 2024) Karakus, NihatContextThis study investigates the antioxidant potential of alkyl gallates (C1-C10), focusing on the impact of alkyl chain length and solvent polarity on their antioxidant properties. Known for their biomedical relevance in mitigating oxidative stress, alkyl gallates' structure-activity relationships, particularly regarding chain length and environmental factors, still need to be explored. Key thermochemical parameters, including bond dissociation enthalpy (BDE), ionization potential (IP), proton affinity (PA), and electron transfer enthalpy (ETE), reveal that shorter alkyl chains (C1-C4) exhibit superior antioxidant activity. In contrast, longer chains (C5-C10) show reduced effectiveness due to steric hindrance and lower solubility in polar solvents. Molecular docking studies also demonstrated favorable binding interactions with vital biological targets, further reinforcing their antioxidant potential.MethodsQuantum chemical calculations were performed using Gaussian 16 with the B3LYP/6-311G(dp) basis set for geometry optimizations. Solvent effects were modeled using the integral equation formalism-polarized continuum model (IEF-PCM). Molecular docking studies were conducted using AutoDockTools 4.2, targeting Tyrosine Kinase Hck, Heme Oxygenase, and Human Serum Albumin to evaluate fundamental binding interactions. These computational methods provided insights into alkyl gallates' chemical reactivity and antioxidant efficiency, allowing for the rational design of more potent antioxidant compounds.Öğe Spectroscopic investigation, FMOs and NLO analyses of Zn(II) and Ni(II) phenanthroline complexes: A DFT approach(PERGAMON-ELSEVIER SCIENCE LTD, 2015) Sayin, Koray; Karaka, Duran; Karakus, Nihat; Sayin, Tuba Alagoz; Zaim, Zinet; Kariper, Sultan ErkanComputational studies were carried out on three Zn(II) and three Ni(II) complexes, namely [NiL1(phen)(2)], [ZnL1(phen)(2)], [NiL2(phen)(2)], [ZnL2(phen)(2)], [NiL3(phen)(2)] and [ZnL3(phen)(2)]. These complexes were synthesized in 2014 by Raman and Mahalalcshmi. Optimized structures of the studied complexes were calculated. IR and UV Vis spectra were calculated and examined in detail. Additionally, non-linear optical (NLO) properties and natural electron configurations of the metal atoms were investigated 'using some quantum chemical parameters and natural bond orbital (NBO) analysis. (C) 2015 Elsevier Ltd. All rights reserved.Öğe Synthesis, characterization and antiproliferative activities of novel modified poly (maleic anhydride-co-vinyl acetate)/cytosine beta-D-arabinofuranoside hydrochloride conjugate(MARMARA UNIV, FAC PHARMACY, 2015) Karakus, Gulderen; Yaglioglu, Ayse Sahin; Zengin, Haci Bayram; Karakus, NihatPoly (maleic anhydride-co-vinyl acetate) (MAVA) copolymer was synthesized by free-radical-polymerization reaction in methyl ethyl ketone (MEK) at 80 degrees C using benzoyl-peroxide (BPO) as the radical-initiator. MAVA was then modified with anti-leukemic chemotherapy-agent cytosine beta-D-arabinofuranoside hydrochloride (CF). Modification was performed at 70 degrees C in dimethylformamide (DMF) containing triethylamine (Et3N) as the catalyst. Structural characterization of the copolymer and copolymer/drug couple (MAVA/CF) was carried out by Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (H-1-NMR). FTIR and H-1-NMR spectra confirmed the modification reaction. UV-Spectrophotometric measurements indicated that MAVA/CF kept its molecular integrity in physiological-body-fluid, PBS, for first four days. Antiproliferative activities of MAVA/CF were also determined by BrdU-cell-proliferation-ELISA assays using C6 and HeLa cell lines (cisplatin and 5-fluorouracil used as positive control). MAVA/CF appeared to have little antiproliferative activity against C6 cell line while samples didn't have antiproliferative activity against HeLa cell line at low concentrations (<100 mu g/ml). Reaction mechanism was also recommended for modification product MAVA/CF.Öğe Theoretical insights about inhibition efficiencies of some 8-Hydroxyqionoline derivatives against the corrosion of mild steel(Taylor & Francis Ltd, 2020) Ozbakir Isin, Dilara; Karakus, Nihat; Lgaz, Hassane; Kaya, Savas; Chung, Iii-MinIn the present study, we theoretically analysed the corrosion inhibition performances of some novel 8-Hydroxyqionoline derivatives, namely 5-(((2-hydroxyethyl) thio) methyl) quinolin-8-ol (Q-OH) and 5-(((2-aminoethyl) thio) methyl) quinolin-8-ol (Q-NH2) against the corrosion of mild steel. In the section about DFT and HF calculations of the study, quantum chemical descriptors like frontier orbital energies, HOMO-LUMO energy gap, chemical hardness, electronegativity, softness, chemical potential, electrophilicity, nucleophilicity, proton affinity, electrons transferred from inhibitor to metal surface, electron-donating power, electron-accepting power, dipole moment, polarisability regarding protonated and neutral forms of the mentioned molecules were calculated and commented. In the section including the use of Molecular Dynamics Simulation approach of the analysis, adsorption behaviours of studied organic molecules on Fe (110) surface were investigated. To detect the power of the interactions between novel 8-Hydroxyqionoline derivatives and the mentioned metal surface, adsorption energy and binding energy values were calculated. It is important to note that these resuls determined are in good agreement with experimentally observed results. In addition to these analyses made, the validities of chemical reactivity principles such as Maximum Hardness, Minimum Polarisability and Minimum Electrophilicity Principles in corrosion inhibition studies were also reported.Öğe The trans-cis and the azide-tetrazole ring-chain isomerization of 2-azido-1,3-azoles: Quantum chemical study(ELSEVIER SCIENCE BV, 2015) Karakus, Nihat; Demirel, MerdanQuantum chemical calculations using Density Functional Theory (DFT) at the B3LYP/6-31++G(d,p) basis set level were performed to investigate the azide group rotation from the trans to the cis isomer and the azido-tetrazole ring-chain isomerism equilibrium of 2-azido-1,3-azoles in the gas phase, carbon tetrachloride (CCl4), acetonitrile (CH3CN) and water (H2O). The solvent effect on the relative stabilities of each species was analyzed within the self-consistent field theory using the Polarized Continuum Model (PCM). The transition states (TSs) of each step was identified and confirmed. The azido-tetrazole ring-chain isomerism equilibrium was investigated in detail. In addition, the electronic characteristics of each species were analyzed by means of Molecular Electrostatic Potential (MEP) and Natural Bond Orbital (NBO) analyses. The relative energies were increased with the increasing electronegativity of X atom in the 1,3-azole ring. The study confirmed that the relative stability of the tetrazole isomers could be maximized to a great extent by increasing the polarity of solvent, and vice versa for the azido isomers. The low rotational barrier of the azido group in the trans reversible arrow cis isomerization and the significant increase of the dipole moment of the tetrazole isomers were determined factors in ring-chain isomerization. The results obtained in advance for 2-azido-1,3-thiazoles were found to be consistent with the experimental and theoretically data reported. (C) 2015 Elsevier B.V. All rights reserved.Öğe Why and When Is Electrophilicity Minimized? New Theorems and Guiding Rules(Amer Chemical Soc, 2020) von Szentpaly, Laszlo; Kaya, Savas; Karakus, NihatWe investigate the physical basis, validity, and limitations of the minimum electrophilicity principle, MEP, which postulates that the sum of the electrophilicity indices, Sigma omega, of the reaction products will be smaller than that of the reactants, Delta omega < 0. We present a much-improved understanding of the conditions for minimizing electrophilicity indices. Two indices, omega(1) = (I + A)(2)/ 8 (I - A) and omega(2) = I.A/ (I - A), are discussed, using ionization energies, I, and electron affinities, A, obtained from either ground-state (GS) or valence-state (VS) energies. The performances of omega(1 )and omega(2) are compared for a wide range of chemical species from diatomic molecules, through large clusters to liquid water and solid crystals. New analytical arguments in support of MEP are found. Two new theorems are proved, and three new rules rationalize the changes Delta omega(1) and Delta omega(2) in association reactions, X + Y -> XY. They explain why MEP is much more successful as a guiding rule than the maximum hardness postulate in such reactions. On the other hand, they also identify the increased electron affinity of the product as the reason for the rare but highly significant failures of MEP, e.g., in B-2, C-2, Si-2, and CN. As a rule, electrophilicity is minimized in association reactions. However, both omega(1 )and omega(2) are increased if the bond dissociation energy D(XY-) is larger than D(XY), which is equivalent to an increased product electron affinity. The large positive changes Delta omega(1) and Delta omega(2) in 2C -> C-2 exhibit a strong contrast to MEP. The changes in electrophilicity indices may help gain insights into the versatility of the chemistries of carbon and other elements. Solid-state double-exchange reactions are correctly assessed by Kaya's composite descriptor, somewhat less by omega(2), but not at all by omega(1). A wide class of failures of MEP is found as sizedriven electrophilicity maximization, Delta omega > 0, e.g., in fullerenes, large metal clusters, and liquid water. Many electrophiles, especially superelectrophiles, show significantly larger electrophilicity indices than the largest index of their isolated atoms. The changes Delta omega(1) and Delta omega(2) provide important information on the reactivities of chemical systems; however, it appears that the minimum electrophilicity postulate cannot serve as a basis for a theory.
