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KOCA, ATIF

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Subject: Spectroelectrochemistry ×

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Now showing 1 - 10 of 87
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    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, Ulvi
    Metalloporphyrazines 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.
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    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 Altuntas
    We 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.
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    Electrochemical and in situ spectroelectrochemical monitoring of the interaction between cobaltphthalocyanines and molecular oxygen in aprotic media
    (ELSEVIER SCIENCE SA, 2011) KOCA, ATIF; Koca, Atif
    In 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.
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    1,4-Dithiaheterocycle-fused porphyrazines: Synthesis, characterization, voltammetric and spectroelectrochemical properties
    (ELSEVIER SCI LTD, 2009) KOCA, ATIF; Tuncer, Serap; Koca, Atif; Guel, Ahmet; Avciata, Ulvi
    Porphyrazines (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.
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    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, Atif
    Electrochemical 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.
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    PublicationOpen Access
    Synthesis, electrochemistry, and electrocatalytic activity of thiazole-substituted phthalocyanine complexes
    (2022-03-01) KOCA, ATIF; Demir F., Yenilmez H. Y., KOCA A., Bayır Z.
    We report the synthesis of non-peripheral metallophthalocyanines which carry four 4-(4-methoxyphenyl)-2-thiazole-2-thio units. H-1-NMR, FT-IR, UV-Vis, and MS data were acquired to characterize the synthesized compounds. Voltammetric and in situ spectroelectrochemical measurements shed light on the redox properties of the metallophthalocyanines (MPcs) in order to show the influence of the metal cations and thiazole-bearing substituents. In solution, the redox processes had an influence to the electrochromic responses, which were examined with in situ spectrocolorimetry. Phthalocyanines having cobalt (II), manganese (III), iron (III), and zinc (II) at the center yielded characteristic redox couples which are metal- and/or Pc-based and which are harmonious with the common redox properties of these types of compounds. In situ spectroelectrochemistry provided the information that MPc species underwent distinct color changes during electron transfer reactions. Electropolymerization of all complexes was performed on glassy carbon electrode, and the electropolymerized film of FePc was evaluated as an active electrocatalyst, in the alkaline medium, for oxygen evolution reaction (OER).
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    Synthesis, electrochemical, in situ spectroelectrochemical and in situ electrocolorimetric characterization of new metal-free and metallophthalocyanines substituted with 4-{2-[2-(1-naphthyloxy)ethoxy]ethoxy} groups
    (PERGAMON-ELSEVIER SCIENCE LTD, 2010) KOCA, ATIF; Acar, Irfan; Biyiklioglu, Zekeriya; Koca, Atif; Kantekin, Halit
    The synthesis of novel metal-free and metallophthalocyanines [Ni(II), Zn(II), Co(II), Cu(II)] were prepared by cyclotetramerization of a novel 4-{2-[2-(1-naphthyloxy)ethoxy]ethoxy}phthalonitrile and the corresponding metal salts (NiCl2, Zn(CH3COO)(2), CoCl2 and CuCl2). The structures of the target compounds were confirmed using elemental analysis, IR, H-1 NMR, C-13 NMR, UV-Vis and MS spectral data. Voltammetric and in situ spectroelectrochemical measurements show that while cobalt phthalocyanine complex gives both metal-based and ring-based redox processes, metal-free, and zinc phthalocyanines show only ring-based reduction and oxidation processes. All complexes decomposed and coated on the electrode as non-conductive film at positive potential window of the electrolyte. An in situ electrocolorimetric method has been applied to investigate color of the electro-generated anionic and cationic forms of the complexes. (C) 2010 Elsevier Ltd. All rights reserved.
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    Synthesis, characterization, EPR, electrochemical, and in situ spectroelectrochemical studies of salen-type oxovanadium(IV) and copper(II) complexes derived from 3,4-diaminobenzophenone
    (TAYLOR & FRANCIS LTD, 2013) KOCA, ATIF; Ercag, Ayse; Sahin, Musa; Koca, Atif; Bozkurt, Esat
    A new half unit and some new symmetrical or asymmetrical VO(IV) and Cu(II) complexes of tetradentate ONNO Schiff base ligands were synthesized. The probable structures of the complexes have been proposed on the basis of elemental analyses and spectral (IR, UVVis, electron paramagnetic resonance, ESI-MS) data. VO(IV) and Cu(II) complexes exhibit square pyramidal and square-planar geometries, respectively. The complexes are non-electrolytes in dimethylformamide (DMF) and dimethylsulfoxide. Electrochemical behaviors of the complexes were studied using cyclic voltammetry and square wave voltammetry. Half-wave potentials (E-1/2) are significantly influenced by the central metal and slightly influenced by the nature of substituents on salen. While VO(IV) complexes give VOIV/VOV redox couples and a ligand-based reduction process, Cu(II) complexes give only a ligand-based reduction. In situ spectroelectrochemical studies were employed to determine the spectra of electrogenerated species of the complexes and to assign the redox processes. The g-values were calculated for all these complexes in polycrystalline state at 298K and in frozen DMF (113K). The evaluated metalligand bonding parameters showed strong in-plane sigma-bonding for some Cu(II) complexes.
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    Synthesis, electrochemical, in situ spectroelectrochemical and in situ electrocolorimetric characterization of new phthalocyanines peripherally fused to four flexible crown ether moieties
    (PERGAMON-ELSEVIER SCIENCE LTD, 2009) KOCA, ATIF; Biyiklioglu, Zekeriya; Koca, Atif; Kantekin, Halit
    Novel Ni(II), Zn(II), Co(II) and Cu(II) phthalocyanines with four peripheral 4-[methyleneoxy(18-crown-6)] groups have been synthesized via the cyclic tetramerization of 4-[{(18-crown-6)-yl}methyleneoxy]phthalonitrile and the corresponding metal salts (NiCl2, Zn(CH3COO)(2), CoCl2 and CuCl2). The thermal stabilities of the metal-free and metallophthalocyanine compounds were determined by thermogravimetric analysis. The structures of the target compounds were confirmed using elemental analysis, IR, H-1-NMR, C-13-NMR, UV-Vis and MS spectral data. Voltammetric and in situ spectroelectrochemical measurements show that while the cobalt phthalocyanine complex gives both metal-based and ring-based redox processes, the metal-free, nickel, zinc and copper phthalocyanines show only ring-based reduction and oxidation processes. An in situ electrocolorimetric method has been applied to investigate the color of the electro-generated anionic and cationic forms of the complexes. (C) 2009 Elsevier Ltd. All rights reserved.
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    PublicationOpen Access
    Non-peripheral tetra methoxylated pyrazoline bearing Co-II, Cu-II and (MnCl)-Cl-III phthalocyanines: Syntheses, electrochemistry and spectroelectrochemistry
    (2022-08-01) BUDAK, ÖZLEM; KOCA, ATIF; Yalazan H., KANTEKİN H., BUDAK Ö., KOCA A.
    The novel and highly soluble cobalt(II), copper(II) and manganese(III) phthalocyanines ((Pc-Co, Pc-Cu, and Pc-Mn) bearing 3-(5-(3,5-dimethoxyphenyl)-1-phenyl-4,5-dihydro-1H-pyrazol-3-yl)phenol have been synthesized and characterized by FT-IR, NMR, UV-Vis and mass spectroscopic methods. Additionally, electrochemical and spectroelectrochemical properties of these phthalocyanine compounds were investigated. Due to the redox inactivity of the Cu2+ central cation of (Pc-Cu), Pc based reductions and oxidation processes are recorded. [(CoPc2-)-Pc-II]/[(CoPc2-)-Pc-I](1-) and [(CoPc2-)-Pc-II]/[(CoPc2-)-Pc-III](1+) couples for the central metal redox reactions, and [(CoPc2-)-Pc-I](1-)/[(CoPc3-)-Pc-I](2-), [(CoPc3-)-Pc-I](2-)/[(CoPc4-)-Pc-I](3-) and [(CoPc2-)-Pc-III](1+)/[(CoPc1-)-Pc-III](2+) couples for the Pc based reduction and oxidation are observed respectively with (Pc-Co). Like (Pc-Co), (Pc-Mn) also illustrated metal-based reduction processes, [Cl1--(MnPc2-)-Pc-III]/[Cl1--(MnPc2-)-Pc-II](1-) and [Cl1--(MnPc2-)-Pc-II](1-)/[Cl1--(MnPc2-)-Pc-I](2-) in addition to the Pc based [Cl1--(MnPc2-)-Pc-I](2-)/[Cl1--(MnPc3-)-Pc-I](3-), [Cl1--(MnPc3-)-Pc-I](3-) /[Cl1--(MnPc4-)-Pc-I](4-) and [Cl1--(MnPc2-)-Pc-III]/[Cl1--(MnPc1-)-Pc-III](1+) redox couples were also recorded. These redox mechanisms were supported with the characteristic spectral changes observed during the in-situ spectroelectrochemical measurements. Especially metal-based electron transfer changes caused distinct spectral and color changes, which are the desired properties of the complexes for the possible opto-electrochemical applications. (C) 2022 Elsevier B.V. All rights reserved.