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Öğe An attempt to understand the observed plateau of the magnetization in tetranuclear iron(II) complexes of thiacalixarene macrocycles(Indian Acad Sciences, 2010) Bayri, Ali; Bakir, H. Gokhan; Sulu, Mustafa; Karakaplan, MustafaThe next-nearest-neighbour (NNN) effect in tetranuclear iron(II) complexes of thiacalixarene macrocycles using the isotropic Heisenberg model has been investigated in order to understand its effects on the observed plateau of magnetization. Although NNN effect is generally very weak in these kinds of systems, it was calculated that its response is quite significant to the external perturbations in certain temperature regions. Using the isotropic Heisenberg exchange Hamiltonian, zero-field energy spectra have been calculated for this particular tetranuclear system. The average magnetic moments with and without next-nearest-neighbour interactions were also calculated. In order to verify the calculations, the results were compared with experimental data taken from the literature, whence, it is suggested that observed magnetic behaviour can be improved by taking into account the NNN effect.Öğe Cationic versus anionic Pt complex: The performance analysis of a hybrid-capacitor, DFT calculation and electrochemical properties(Pergamon-Elsevier Science Ltd, 2019) Akkoc, Mitat; Demirel, Serkan; Oz, Erdinc; Altin, Serdar; Bayri, Ali; Dorcet, Vincent; Roisnel, ThierryThe synthesis and characterization of cationic versus anionic platinum(II) complex of the type [PtCl3(DMSO)](-)[NHC](+) (NHC: N-heterocyclic carbene) is reported for the first time. The complex 3 was synthesized from silver(I)-NHC2, and K-2[PtCl4] in DMSO at 80 degrees C under exclusion of light. The ionic platinum(II) complex was obtained in high yield and fully characterized by H-1, C-13, Pt-195 NMR and HRMS spectroscopy, X-ray diffraction and elemental analysis. The structural properties of the complex were investigated by using Gaussian suit and the obtained parameters were crosschecked with the X-ray data. The HOMO-LUMO energies and electrostatic surface mapping of the complex were calculated and the results were discussed with the capacitive properties of the complex. Electrochemical analysis by cyclic voltammetry (CV) of the complex shows reversible redox peaks about platinum center. The complex was used as an electrode material for the capacitor device and result is promising that the highest performance of complex 3 was found as 10.22 F/g. (C) 2018 Elsevier Ltd. All rights reserved.Öğe Density Functional Theory Studies of Some Barbiturates on Lipophilicity(2021) Serin, Sümeyra; Bayri, AliThis paper deals with the evaluation of lipophilicity expressed by logPow parameter of ten barbiturate derivatives generally used as sedative-hypnotics based on Density Functional Theory (DFT) calculations. All geometry optimizations and frequency calculations have been carried out by using DFT/B3LYP/ 6-311++G (d,p) basis set in gas phase and also in water and n-octanol phases. Gibbs free energies of solvation for studied barbiturates were calculated to predict logPow. The correlation between the calculated logPow values and available data in literature has been examined. Root mean square error (RMSE), mean square error (MSE), mean absolute deviation (MAD) and mean absolute percentage error (MAPE) statistics were utilized in measuring predictive accuracy (forecast performance) of DFT method used in this study. Accordingly, the reasonable results have been obtained in estimating the partition coefficient of the mentioned ten barbiturate derivatives by DFT/B3LYP/6-311++G (d,p)method. The lipophilicity tendency of the studied barbiturates was interpreted with the help of the calculated quantum chemical descriptors such as HOMO energy (EHOMO), LUMO energy (ELUMO), molecular volume (Vm), electrophilicity index (?). ELUMO, Vm, and ? descriptors gave reasonable results rather than EHOMO. Also, the 3D molecular lipophilicity potential (MLP) maps that display the accumulative lipophilic contributions of each atom in studied barbiturates were visualized.Öğe HIGH PROBABILITY OF LARGE ORBITAL ANGULAR MOMENTUM CONTRIBUTION TO THE MAGNETIC MOMENT OF COBALT(II) ION IN NEWLY REPORTED MACROCYCLIC COMPLEX CONTAINING AMIDE, IMINE AND SECONDARY AMINE FUNCTIONS(Walter De Gruyter Gmbh, 2008) Bayri, Ali; Aytekin, OezlemThe magnetic moments of Co+2 complexes in newly reported macrocyclic complexes containing amide, imine, and secondary amine functions are investigated by a semi-theoretical approach for various geometrical situations. It is found that in order to obtain the observed room temperature magnetic moments, some of the parameters, related to the geometry of the complexes, should be varied in the magnetic Hamiltonian. The calculations and experiments obtained from the literature suggest that the environments of complexes are low field distorted octahedral. It is also suggested that while the probability of orbital contribution to the magnetic moment is high, the probability of ferromagnetic interactions between two cobalt(II) ions in a dimeric unit is quite low.Öğe Investigation of hybrid-capacitor properties of ruthenium complexes(Wiley-Hindawi, 2019) Altin, Serdar; Oz, Erdinc; Altundag, Sebahat; Bayri, Ali; Roisnel, Thierty; Dorcet, Vincent; Bruneau, ChristianRu complexes were successfully produced, and their structural properties were investigated using FTIR, Raman, and single crystal XRD patterns. The HOMO, LUMO, Eg, and electronic surface potential (ESP) values of the molecules were calculated by a Gaussian program. The complexes were used for producing hybrid capacitor cells as electrode materials. According to electrochemical analysis, complex 2 showed the best CV graph between -1 V and +1 V and had the highest current value and hysteresis area when compared with the other complexes. The performance analysis and the capacity fade of the cells were investigated. The first capacity values of the complexes were 57.5, 22.1, 16.9, and 0.0021 F/g for complexes 1, 2, 3, and 4, respectively. The capacitive mechanism of the cells as relates to molecular interactions was also investigated. We suggested that the ESP values of the molecules were directly related to the capacitive performance of the cells. In addition to this, the best cycling performance was obtained for complex 2, which has the lowest Eg value among the complexes. We speculate that the charged regions on the complex materials have a crucial role in the increasing the capacitance of the cells.Öğe Investigation of potential hybrid capacitor property of chelated N-Heterocyclic carbene Ruthenium(II) complex(Elsevier Science Sa, 2018) Akkoc, Mitat; Oz, Erdinc; Demirel, Serkan; Dorcet, Vincent; Roisnel, Thierry; Bayri, Ali; Bruneau, ChristianThe synthesis of chelated ruthenium(II) complex type Ru(eta(6)-HMB) (NHC) Cl (NHC = N-heterocyclic carbene, HMB = hexamethylbenzene) is presented. The ruthenium(II)-NHC complex 6 was obtained in good yield and was fully characterised by NMR spectroscopy, X-ray diffraction and HRMS analysis. Electrochemical analysis by cyclic voltammetry (CV) revealed reversible redox behaviour at the ruthenium centre in 6. DFT studies and the catalytic activity of complex 6 on transfer hydrogenation reaction of aryl ketones are also presented. The potential hybrid capacitor applications of Ru-NHC complex is discussed and reported firstly in the literature. It was found that the highest performance was found at 20.1 F/g, which is a promising result for energy storage applications. (c) 2018 Elsevier B.V. All rights reserved.Öğe Investigation of Ti-substitution effects on structural and electrochemical properties of Na0.67Mn0.5Fe0.5O2batterycells(Wiley-Hindawi, 2020) Altin, Serdar; Altundag, Sebahat; Altin, Emine; Oz, Erdinc; Harfouche, Messaoud; Bayri, AliTi-substituted Na(0.67)Mn(0.5)Fe(0.5)O(2)powders were fabricated by quenching at high temperatures, and the structural properties were investigated by Fourier transform infrared (FTIR), Scanning Electron Microscope (SEM), X-ray powder diffraction (XRD), and X-ray absorption spectroscopy (XAS) measurements. According to XRD analysis, it was not observed any impurity phases and it was found that the lattice constants of the powders were slightly increased by Ti content. The change in the valence state of both Mn and Fe ions was investigated by X-ray absorption near edge structure (XANES), and it was found that Ti-substitution caused a decrease in the valance state of Fe in Na0.67Mn0.5Fe0.5O2. Fourier transform (FT) of XANES showed that the local structure around the metal ions changed with the addition of Ti ions. The cycling voltammetry (CV) graphs of Ti-substituted cells were almost the same as the pure sample, which may not change the cycling mechanism in the cells. According to galvanostatic cycling measurements at room temperature, the best performance was obtained with Ti-substitution of 0.06 to 0.09 in the structure. The effect of environmental temperature in the battery cells was investigated at 10 degrees C to 50 degrees C, and it was found that the battery performance depends on the environmental temperatures.Öğe Investigations of the capacity fading mechanism of Na0.44MnO2via ex situ XAS and magnetization measurements(Royal Soc Chemistry, 2018) Altin, Serdar; Oz, Erdinc; Altin, Emine; Demirel, Serkan; Bayri, Ali; Avci, SevdaNa-ion batteries represent a promising complementary alternative to Li-ion batteries due to their high energy density and natural abundancy of Na. However, these batteries have short cycle life and extensive research activities on these batteries are required to understand the mechanism of such drawbacks. In this report, we investigate the capacity fading mechanism of Na(0.44)MnO(2)via ex situ X-ray diffraction, X-ray absorption spectroscopy, Fourier transform infrared spectroscopy and magnetization measurements. Our results show that the unit cell volume, the effective mass of Mn-O bonds, the number of Mn4+ ions and the effective magnetic moment decrease upon repeated cycling. We propose that some Mn4+ ions in the octahedral environment become Mn3+ ions in a square pyramidal environment, causing oxygen release upon cycling. Any free oxygen in the battery is expected to react with the electrolyte and cause capacity fade.Öğe Magnetic and thermoelectric properties of B-substituted NaCoO2(Springer Heidelberg, 2015) Altin, Emine; Oz, Erdinc; Demirel, Serkan; Bayri, AliWe report the structural, electrical, thermal and magnetic properties of NaCo1-xBxO2 from 300 K down to 5 K. XRD analysis shows that B ions successfully incorporate in the crystal structure for x < 0.25. The resistivity of the samples increases with increasing B content and the transport mechanism change for x = 0.5. The highest thermopower value is obtained for x = 0.5 sample, and the thermoelectric behavior at low temperature is explained by Mott approximation. The experimentally obtained thermal conductivity data are analyzed by this model including the carrier thermal term, kappa(c), and the lattice thermal conductivity term, kappa(L). We found that phonon-phonon interaction and point defect contribution to kappa are affected by the B content and the temperature. The Co valance states are analyzed by Heike formula, and the effective magnetic moment is determined by these values. The chi-T curves of the samples are fitted by Curie-Weiss law, and the obtained mu(eff) values match well with the theoretically calculated values (0.9 mu(B)/Co). We observed a strong correlation between magnetic properties and thermopower.Öğe Magnetic Properties and Environmental Temperature Effects on Battery Performance of Na0.67Mn0.5Fe0.5O2(Wiley-V C H Verlag Gmbh, 2021) Altin, Serdar; Bayri, Ali; Altin, Emine; Oz, Erdinc; Yasar, Sedat; Altundag, Sebahat; Harfouche, MessaoudHerein, a modified solid state synthesis of Na0.67Mn0.5Fe0.5O2 and the results of a detailed investigation of the structural and magnetic properties via Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis are reported. The magnetic properties of Na0.67Mn0.5Fe0.5O2 do not fit the Curie-Weiss law and a model regarding the spin configuration of the Mn and Fe ions and a possible ferrimagnetic order is suggested. Electrochemical measurements and ex situ structural analysis of the cathode material confirm the reversible structural transitions for the cells charged up to 4.0 V. Environmental temperature-dependent electrochemical measurements reveal a strong temperature dependence of both, the initial capacity and the capacity retention. Ex situ SEM, FTIR, and XRD studies on the battery membrane verify the formation of a Na2CO3 phase on the membrane, which blocks the Na ion diffusion through membrane pores and is responsible for the capacity fade for this compound.Öğe Magnetochemistry of some trinuclear Co(II) thiocarboxylates(World Scientific Publ Co Pte Ltd, 2008) Bayri, Ali; Aytekin, Ozlem; Sulu, Mustafa; Karakaplan, MustafaThis study discusses the magnetic behavior of some trinuclear Co(II) thiocarboxylates complexes. From the detailed theoretical investigation, it is suggested that, although the reported magnetic moments seem to be due to the spin and some orbital contributions, there may be some intramolecular ferromagnetic exchange interactions among the paramagnetic centers.Öğe Mikrobiyal Yakıt Hücresinde Grafen Kaplı Nikel-Titanyum (NiTi) Alaşımının Anot Elektrotu Olarak Kullanılması(2019) Taşkan, Ergin; Bulak, Selman; Taşkan, Banu; Şaşmaz, Merivan; Gürtekin, Engin; Bayri, AliBu çalışmada, grafen kaplı nikel-titanyum (NiTi) alaşımı üretilerek mikrobiyal yakıt hücresinde (MYH) anot elektrotuolarak kullanılmıştır. Çalışmada çift bölmeli bir MYH reaktörü sürekli modda işletilmiş ve elektrik üretim performansı detaylıbir şekilde araştırılmıştır. MYH reaktörünün ürettiği maksimum güç yoğunluğu 2043 mW/m2 olarak elde edilmiştir. Sistemintoplam iç direnci 437.7 ? olarak ölçülmüştür. İşletme süresi sonunda anot elektrotu yüzeyinden alınan SEM görüntülerindebiyofilm yapısında genellikle yuvarlak şekilli mikroorganizmaların mevcut olduğu tespit edilmiştir. Biyofilm numunesineuygulanan PCR-DGGE analizleri elektrot yüzeyinde Shewanella oneidensis ve Pseudomonas aeruginosa gibi elektriküretiminde etkin mikrobiyal türlerin mevcut olduğunu göstermiştir.Öğe Structural, magnetic, electrical, and electrochemical properties of Sr-Co-Ru-O: A hybrid-capacitor application(Wiley, 2018) Altin, Serdar; Bayri, Ali; Demirel, Serkan; Oz, Erdinc; Altin, Emine; Avci, SevdaIn this study, we report the synthesis of SrCo1-xRuxO3- nominal compositions, where x=0.0-1.0, using solid-state reaction technique. XRD analysis confirms the structure of x=0 sample as hexagonal Sr6Co5O15. As the Co ions are substituted by Ru, a two-phase structure (hexagonal R32 and orthorhombic Pbnm) emerges up to x0.5. As the Ru content is increased further, the hexagonal R32 phase disappears completely and an orthorhombic Pbnm phase becomes the main phase. SEM images show that grain size of the samples decreases with increasing Ru content. Temperature-dependent electrical conductivity studies indicate upon Ru substitution in the nominal SrCo1-xRuxO3- compounds, resistivity decreases due to appearance of metallic SrRuO3 phase. The cyclic voltammogram (CV) of the samples show capacitive properties upon Ru substitution. The cycle measurements of the capacitors yield promising results for potential supercapacitor applications.Öğe SUYUN ŞİZOFRENİYE ETKİLERİNİN İKİ FARKLI NÖROTRANSMİTTER BAĞLAMINDA TEORİK OLARAK İNCELENMESİ(2022) Ayhan, Murat; Bayri, AliSuyun hayatımızdaki yeri ve sag?lıklı bir yas?am su?rmemiz ic?in suyun ne kadar o?nemli oldug?u herkes tarafından kabul go?ren bir gerc?ektir. Su gu?nlu?k hayatta ic?ecek olarak kullanılmasının yanında ayrıca c?es?itli yo?ntemler aracılıg?ıyla tedavi unsuru olarak da tercih edilmektedir. C?alıs?mamızda s?izofreni hastalarına etkiyen iki no?rotransmitter, dopamine (C8H11NO2) veserotonin (C10H12N2O) u?zerinde duruldu. Bu iki no?rotarsmitterin u?c? boyutlu c?izimleri gaussian programı aracılıg?ıyla yapıldı. Bu iki no?rotrasmitterin moleku?ller yapısının yeterli miktarda su ile etkiles?mesiyle meydana gelen deg?is?ikliklere bakıldı. Moleku?ller yapıların su ile etkiles?mesi ile bag? ac?ılarında ve bag? uzunluklarındaki deg?is?imler irdelenerek sinapsların elektrostatik ileti mekanizması ele alındı. No?rotransmitter iki yapının geometrik optizimazyonu Gaussian 09W programında HF (Hatree- Fock) hesaplama yo?ntemindeki TD-SCF metod ve LanL2DZ baz seti kullanılarak yapıldı. Geometrik optimizasyon sonucu olus?an moleku?llerin en yu?ksek dolu moleku?ler orbital (HOMO) ve en du?s?u?k bos? moleku?ler orbital (LUMO) deg?erlerinin hesaplamaları yapıldı. I?ki yapınında su bag?lanmadan o?nceki verileri ile bag?landıktan sonra elde edilen veriler kars?ılas?tırıldı. no?rotransmitterlerin bulundug?u ortamda su kaynaklı meydana gelen deg?is?imler irdelendi. Su ile etkiles?im sonucu seratoninde bulunan atomların arasındaki bag? uzunlukları artarken, atomlar arasındaki bag? ac?ıları da genellikle artıs? go?stermektedir. Buna kars?ın dopaminde tam tersi bir durum go?zlenmektedir. Su ile dopaminin etkiles?mesi sonucu dopamindeki atomların bag? uzunlukları genellikle artıs? go?sterirken, atomlar arasındaki bag? ac?ıları ise azalıs? go?stermektedir. Dopamin ve seratonin no?rotransmitterleri elektrostatik olarak birbirlerine go?re tersinir c?alıs?maktadır. Bu ise iki no?rotransmitterin beyin kimyasının is?leyis?ine etkilerinin farklı oldug?unu so?yleyebiliriz. Yeterli miktarda suyun dopamine ait reaksiyonları kolaylas?tırıcı etkisi 0.401eV civarında iken suyun seratonine ait reaksiyonları kolaylas?tırıcı etkisi 3.214eV civarında idi. Buradan da go?ru?ldu?g?u? u?zere yeterli miktarda su ile etkiles?ime giren seratonin, dopaminden yaklas?ık olarak sekiz kat daha fazla etkinlig?ini arttırdıg?ını bize so?ylemektedir.Öğe SYMMETRY FACTOR FOR ELECTRONIC CONFIGURATION IN Ca3Co4O9 SYSTEM(2015) Karaman, Nazlı; Bayri, AliAbstract: Bu çalışma, Ca3Co4O9 sisteminde yüksek sıcaklıklardaki Co iyonlarının elektronik konfigürasyonlarıyla ilgilenir. Bu sistemin manyetik davranışı 700 K civarında bir anomali gösterir. Bu anomalinin sistemdeki Co2+, Co3+ ve Co4+ iyonlarının spin durum geçişlerinden kaynaklandığı düşünülmektedir. Octahedral bir alandaki Co iyonlarının dalga fonksiyonlarının simetri özellikleri; Co4+ iyonlarının, Co3+ iyonlarından daha önce yüksek spin konfigürasyonunu tercih edeceğini göstermektedir. Ancak octahedral alandaki d orbitallerinin ligand alan yarılma enerjileri; Co3+ iyonlarının yüksek spin konfigürasyonlarının, Co4+ iyonlarının yüksek spin konfigürasyonlarından daha önce gerçekleşeceğini göstermektedir.Öğe Thermally Induced Spin State Transition in LiCoO2 and Its Effects on Battery Performance(Pergamon-Elsevier Science Ltd, 2017) Oz, Erdinc; Demirel, Serkan; Altin, Serdar; Altin, Emine; Bayri, Ali; Avci, SevdaLiCoO2 is the most widely used and extensively studied cathode material for Li-ion batteries. The studies based on the improvement of the performance have focused on the structural and electrochemical properties of LiCoO2. However, significantly less attention has been paid to its magnetic properties and their effects on battery performance. For the first time to our knowledge, we report a thermally induced magnetic spin state transition from low spin (LS) to intermediate spin (IS) at similar to 800 K in bulk LiCoO2 via magnetic susceptibility measurements. We quench the LiCoO2 from above the spin state transition temperature (similar to 810 K) into liquid nitrogen to preserve the IS state at room temperature. We use this quenched sample (q-LiCoO2) as an active cathode material. We observe a significant improvement (similar to 15% better capacity retention after 200 cycles at 1C) in cell performance of q-LiCoO2 compared to the ref-LiCoO2 which is used as a reference material. Our results show that it is possible to tailor the magnetic properties and electronic structure of cathode materials to achieve better battery performance. (C) 2017 Elsevier Ltd. All rights reserved.
