Person: KOCA, ATIF
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KOCA
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ATIF
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Publication Metadata only Synthesis, characterization, electrochemistry and spectroelectrochemistry of novel soluble porphyrazines bearing unsaturated functional groups(ELSEVIER SCI LTD, 2012) KOCA, ATIF; Tuncer, Serap; Koca, Atif; Gul, Ahmet; Avciata, UlviMetalloporphyrazines with a 2-methyl-2-pentenyl group fused to each pyrrole unit were synthesized starting with the corresponding unsaturated dicarbonitrile derivative. The new compounds were characterized by elemental analysis together with FTIR, (1)H-NMR, and UV-Vis spectroscopy and via voltammetric and spectrochemical methods. Electrochemical and spectroelectrochemical measurements demonstrate that while metal-free and magnesium porphyrazines gave common porphyrazine (Pz) ring-based electron-transfer reactions, incorporating redox active metal center, Co(II), into the porphyrazine core extended the redox activity of the ring system with reversible metal-based reduction and oxidation couples of the metal center in addition to the common Pz ring-based electron transfer processes. The unsaturated functional groups of the porphyrazines did not alter the common electrochemical behavior of the complexes. An in situ electrocolorimetric method, based on the 1931 CIE (Commission Internationale de l'Eclairage) system of colorimetry, was applied to investigate the color of the electro-generated anionic and cationic forms of the complexes for possible electrochromatic applications. (C) 2011 Elsevier Ltd. All rights reserved.Publication Metadata only Voltammetric, spectroelectrochemical, and electrocatalytic properties of thiol-derivatized phthalocyanines(PERGAMON-ELSEVIER SCIENCE LTD, 2008) KOCA, ATIF; Osmanbas, Omer A.; Koca, Atif; Ozcesmeci, Ibrahim; Okur, Ali Ihsan; Gul, AhmetVoltammetric and spectroelectrochemical properties and electrocatalytic activities of thiol-derivatized phthalocyanine complexes for hydrogen production have been investigated. Voltammetric and spectroelectrochemical measurements show that while cobalt phthalocyanine complexes (CoPc) present well defined metal-based and ring-based redox processes, all other complexes give only ring-based reduction and oxidation processes. The redox processes are generally diffusion-control led, reversible and one-electron transferred processes. The complexes bearing tetra(acetoxyethylthio) substituents represents aggregation tendency in DCM solution. Cobalt and nickel phthalocyanines are easily electrodeposited on the GCE working electrode during the repeating cycles of positive potentials. Electrocatalytic activities of electrodeposited complexes indicated that Cope catalyzed the proton reduction via the electro-reduced [Co'Pc2-](1-) and/or [Co'Pc3-](2-) species depending on the pH of the aqueous solution. (C) 2008 Elsevier Ltd. All rights reserved.Publication Metadata only Electrochemical, spectroelectrochemical, and dielectric properties of metallophthalocyanines bearing redox active cobalt and manganese metal centres(ELSEVIER SCIENCE SA, 2017) KOCA, ATIF; Uzunmehmetoglu, Hilal Zengin; Yenilmez, H. Yasemin; Kaya, Kerem; Koca, Atif; Altindal, Ahmet; Bayir, Zehra AltuntasWe report herein the synthesis of symmetrical metallophthalocyanines having cobalt, zinc, and manganese as the metal ions, and having tetrakis(4-phenyl-1,3-thiazole-2-thiolate) groups substituted at the peripheral positions of the phthalocyanine. Electrochemical responses of the complexes were determined with voltammetric and in situ spectroelectrochemical measurements. Cobalt and mu-oxo manganese phthalocyanines (CoPc and mu-oxo MnPc) illustrated metal-based electron transfer reactions in addition to the Pc based reactions.-oxo-manganese phthalocyanine exhibited completely different redox properties than those of the monomeric manganese phthalocyanine. Thiazole substituents of the complexes caused oxidative electropolymerisation of the complexes on the working electrode. Electropolymerised-oxo manganese phthalocyanine catalyzed oxygen evolution reaction (OER) in basic aqueous solution. The ac behaviour of the tetrasubstituted metallophthalocyanines was studied by impedance spectroscopy technique over a temperature range of 300-450 K and frequency of 100 Hz-13 MHz. The results show that the new compounds exhibit abnormally high dielectric constants even at room temperature. It was concluded that Maxwell-Wagner polarisation is an appropriate model to explain the behaviour of the dielectric function at low frequencies. Frequency dependent measurements revealed that the compounds exhibits non-Debye type relaxation behaviour. (C) 2017 Elsevier B.V. All rights reserved.Publication Metadata only Electrochemistry of novel tetra peripherally and non-peripherally substituted phthalocyanines bearing morpholine groups(ELSEVIER SCIENCE SA, 2020) KOCA, ATIF; Akyuz, Duygu; Demirbas, Umit; Akcay, Hakki Turker; Koca, Atif; Kantekin, HalitMorpholine bearing phthalonitriles (3a and 3b) and peripherally and non-peripherally tetra substituted TiOPc and CuPc complexes (4a-5b) were prepared. Electrochemical responses of metallophthalocyanines were analysed and compared with each other in order to determine the influence of Cu2+ and TiO2+ metal centers and peripherally or non-peripherally substituents of the complexes. While CuPcs illustrated common Pc based reduction processes, TiOPcs showed extraordinary reduction peaks. During the oxidation processes, all complexes were electropolymerizable and metal centers and nonperipherally or peripherally substituents considerably affect electropolymerization processes. However, it was clearly seen that changing the positions of the substituents did not extensively influence the reduction processes. (C) 2020 Elsevier B.V. All rights reserved.Publication Metadata only Asymmetric N2O2 complexes of iron(III) and nickel(II) obtained from acetylacetone-S-methyl-thiosemicarbazone: synthesis, characterization and electrochemistry(TAYLOR & FRANCIS LTD, 2015) KOCA, ATIF; Kaya, Busra; Koca, Atif; Ulkuseven, BahriIron(III) and nickel(II) complexes from acetylacetone-S-methyl-thiosemicarbazone were synthesized and characterized. The thiosemicarbazidato structures of N2O2 are N-1-acetylacetone, N-4-salicyl/3-methoxy/5-bromo-/3,5-dichlorosalicylidene. The square-pyramidal iron(III) and square-planar nickel(II) complexes of N-1-acetylacetone-N-4-3-methoxy thiosemicarbazidato were determined by X-ray diffraction. Electrochemical characterizations of the complexes were carried out by using cyclic voltammetry and square wave voltammetry. While nickel(II) complexes only give ligand based reduction and oxidation reactions, iron(III) complexes give reversible Fe-III/Fe-II reduction in addition to the ligand based processes. Changing of the substituents on the ligand, shifts the redox processes and also affects the stabilities of the electrogenerated species. With respect to the reduction potential of Fe-III/Fe-II couple, the most easily reduced complex was 3,5-dichloro substituted complexes and the most difficult to reduce was the 3-methoxy substituted one.Publication Metadata only Synthesis, X-ray crystal structures, thermal and electrochemical properties of thiosemicarbazidatodioxouranium(VI) complexes(ROYAL SOC CHEMISTRY, 2010) KOCA, ATIF; Sahin, Musa; Koca, Atif; Ozdemir, Namik; Dincer, Muharrem; Buyukgungor, Orhan; Bal-Demirci, Tulay; Ulkuseven, BahriThe stable uranyl complexes, [UO2(L)C9H19OH], were obtained from 3,5-dichlorosalicyl-(L-I) and salicyl-aldehyde-S-propyl-thiosemicarbazones (L-II) with substituted-salicylaldehyde in nonyl alcohol. The structures of the complexes have been characterized by elemental analysis, IR, H-1 NMR, conductivity, magnetic moment measurements, cyclic voltammetry, thermal gravimetric analysis and single crystal X-ray diffraction technique. The U(VI) centre is seven-coordinated in a distorted pentagonal bipyramidal geometry. The relative orientations of the nonyl alcohol and S-propyl group in the title complexes are completely different due to different crystal packing. Electrochemical behaviors of the thiosemicarbazone ligands and the uranyl complexes were studied using cyclic voltammetry and square wave voltammetry. Redox processes of the compounds are significantly influenced by the central metal ions and the nature of substituents on the thiosemicarbazones, which are important factors in controlling the redox properties. In situ spectroelectrochemical studies were employed to determine the colors and spectra of electro-generated species of the complexes.Publication Metadata only Novel 4-(2-(benzo[d]thiazol-2-yl)phenoxy) substituted phthalocyanine derivatives: Synthesis, electrochemical and in situ spectroelectrochemical characterization(ELSEVIER SCIENCE SA, 2014) KOCA, ATIF; Nas, Asiye; Kantekin, Halit; Koca, AtifIn this study, the new tetra peripherally 4-(2-(benzo[d]thiazol-2-yl)phenoxy)-substituted metal-free (4), zinc(II) (5), lead(II) (6), cobalt(II) (7) and copper(II) (8) phthalocyanine derivatives, which are organosoluble, have been synthesized for the first time and their structures characterized by using electronic absorption, infrared spectroscopy, nuclear magnetic resonance spectroscopy, elemental analysis and mass spectra. Voltammetric characterization of the phthalocyanine derivatives (4-7) was performed with cyclic voltammetry and square wave voltammetry. Cobalt phthalocyanine (7) gave metal based electron transfer reactions in addition to the phthalocyanine ring based reduction and oxidation reactions. Although lead phthalocyanine (6) illustrated reversible reduction process during the voltammetric measurements, it was de-metallized and thus it turned back to the metal free phthalocyanine during the in situ spectroelectrochemical measurements under the applied potentials. Spectroelectrochemical measurements were performed to assign the redox processes and spectroscopic responses of the electrogenerated species. (C) 2014 Elsevier B.V. All rights reserved.Publication Metadata only Electrochemical and in situ spectroelectrochemical monitoring of the interaction between cobaltphthalocyanines and molecular oxygen in aprotic media(ELSEVIER SCIENCE SA, 2011) KOCA, ATIF; Koca, AtifIn this study, voltammetric and spectroelectrochemical measurements of cobaltphthalocyanines (CoPc) bearing different substituents were performed in aprotic solvents to determine the mechanism of interaction between CoPc and molecular oxygen. Metal-based redox processes of the cobaltphthalocyanine complexes indicate their possible electrocatalytic activities toward many target species. Different substituents of the complexes affect the peak characters and assignments of the processes. Presence of O-2 in the electrolyte system influences oxygen reduction reaction and the electrochemical and spectral behaviors of the complexes, which indicate homogeneous electrocatalytic activity of the complexes for the oxygen reduction reaction. In situ electrocolorimetric method was applied to investigate color of the anionic and cationic forms of the complexes. Electrochemical and in situ spectroelectrochemical analysis indicate interaction of molecular oxygen with monoanionic [(CoPc-2)-Pc-1](1-) and presence of an equilibrium between the reactants [(CoPc-2)-Pc-1](1-) and O-2 and the intermediates [O-2(-)-(CoPc2-)-Pc-II](-) and [O-2(2-)-(CoPc2-)-Pc-II](2-). This equilibrium is disturbed in desired direction by changing the excitation signals of the voltammetric and spectroelectrochemical techniques. The intermediates are very unstable, regenerating the starting form of the catalyst and the products O-2(-) and O-2(2-). Interaction rate of O-2 with the complexes is significantly influenced with the steric and coordination properties of the substituents and solvent of the system. Voltammetric and spectroelectrochemical results indicate that homogeneous electrocatalytic ORR follows an inner sphere chemical catalysis process. (C) 2011 Elsevier B.V. All rights reserved.Publication Metadata only 1,4-Dithiaheterocycle-fused porphyrazines: Synthesis, characterization, voltammetric and spectroelectrochemical properties(ELSEVIER SCI LTD, 2009) KOCA, ATIF; Tuncer, Serap; Koca, Atif; Guel, Ahmet; Avciata, UlviPorphyrazines (M = H, Mg, Zn and Co) with a 2,3-dicyano-5-phenyl-5,6-dihydro-1,4-dithiin group fused to each pyrrole unit were synthesized and characterized starting with the corresponding unsaturated dicarbonitrile derivative. The voltammetric and spectroelectrochemical characterizations of the metallo-porphyrazines (M=2H(+), Mg2+, Zn2+ and Co2+) substituted with 2,3-dicyano-5-phenyl-5,6-dihydro-1,4-dithiin groups on peripheral positions are described. Cyclic voltammetry and differential pulse voltammetry studies showed that while metal-free, magnesium, and zinc porphyrazines represented well-defined one-electron ligand-based reductions and ligand-based one-electron oxidation couples, cobalt porphyrazine gave both metal-based and ligand-based reduction and oxidation couples. Assignments of the redox couples were confirmed by spectroelectrochemical measurements. (C) 2008 Elsevier Ltd. All rights reserved.Publication Metadata only Titanyl phthalocyanines: Electrochemical and spectroelectrochemical characterizations and electrochemical metal ion sensor applications of Langmuir films(ELSEVIER SCIENCE SA, 2013) KOCA, ATIF; Demir, Faruk; Erdogmus, Ali; Koca, AtifElectrochemical and spectroelectrochemical characterizations of titanyl phthalocyanines, which were peripheral (alpha-TiOPc) and nonperipheral (beta-TiOPc) tetra and octa substituted (octa-TiOPc) with 3,4-(methylendioxy)-phenoxy moieties were performed to determine their possible applications in different electrochemical technologies. Voltammetric and in situ spectroelectrochemical measurements illustrate that position and number of 3,4-(methylendioxy)-phenoxy substituents affect the redox behavior of the complexes. While alpha-TiOPc gives up to four reduction processes, beta-TiOPc and octa-TiOPc gives up to three reduction processes. While octa-TiOPc gives metal-metal-ring-ring reductions, alpha-TiOPc and beta-TiOPc complexes give metal-ring-ring-metal reduction mechanism. Solvent of the media also alter the electrochemical behavior of the complexes. In situ electrocolorimetric measurements shows distinct color differences among the electrogenerated anionic and cationic redox species, which indicates their possible applications in display technologies. Multiple and reversible, diffusion controlled and multi-electron redox reaction indicate possible usage of the complexes especially in electrosensing applications. The complexes sense Ag+ and Pd2+ ions in the solution and in the solid states. (C) 2013 Elsevier B.V. All rights reserved.