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KOCA, ATIF

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End date: 2009 × Start date: 2002 ×

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    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, Ahmet
    Voltammetric 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.
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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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    A new redox-active multisite ligand: synthesis, spectroscopy and electrochemistry of its mono and dinuclear complexes, and the interaction of (E,E)M (M = Ni) complex with Pd-II and Ag-I
    (PERGAMON-ELSEVIER SCIENCE LTD, 2004) ÖZKAYA, ALİ RIZA; Kandaz, M; Koca, A; Ozkaya, AR
    A novel redox active (E,E)-dioxime ligand, S,S-bis-[2(2'-ferrocenemethylaminobenzyl)]-dithioglyoxime (LH2), containing ferrocene and flexible aminobenzenesulfanyl-moieties on the periphery has been synthesized from 2-(2'-ferrocenemethylamino)benzenethiol. which was obtained by the reduction of 2,2-pyridylbenzothiazolidine with a large excess of NaBH4. Mononuclear (LH)(2)M (M = Ni-II, Cu-II, Co-II, Fe-II and Mn-II), homodinuclear (LH)(2)(UO2)(2)(OH)(2) and heterotrinuclear (LH)(2)MM'X-2(n) (M = Ni-II and M' = Pd-II, X = Cl-, n = 4 and M' = Ag-1, X = NO3-, n = 2) complexes have been obtained with the metal:ligand ratios of 1:2, 2:2 and 3:2. respectively. Flexible ferrocenemethylaminobenzenesulfanyl moieties bearing two different heteroatoms, -S and -N, on the periphery of the vic-dioxime serve as weak binding sites for Pd-II and Ag-I ions. The detection of H-bonding in all complexes except the uranyl complex by IR revealed square-planar MN4 coordination of the mono- and trinuclear complexes. The MN4 coordination of the Ni-II complex was also determined by the H-1 NMR spectroscopy. The structures of the complexes were characterized by elemental analysis, H-1 NMR, IR, MS, UV-Vis spectral and cyclic voltammetry. The voltammetric analyses of the complexes showed metal, ligand, and ferrocene based signals. The redox chemistry of the complexes exhibited both M-I and M-III oxidation states of the central metals of the complexes. (C) 2004 Published by Elsevier Ltd.
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    Electrochemical investigation on porphyrazines with peripheral crown-ether groups
    (SPRINGER WIEN, 2003) KOCA, ATIF; Koca, A; Saglam, OG; Gul, A
    In this study, the electrochemical properties of novel porphyrazines with eight crown ether substituents appending on the periphery through flexible chains were investigated by using cyclic voltammetry and controlled potential coulometry. Cyclic voltammetry measurements showed that the metal free porphyrazine gave all of the six possible redox reactions of common porphyrazine derivatives. Cobalt porphyrazine exhibited a metal-based reduction and a metal-based oxidation processes followed by two ligand-based reduction and two oxidation processes. I-p vs. nu(1/2) plots of redox processes of the two compounds indicated the diffusional mass transfer mechanism of the complexes. Copper porphyrazine gave an oxidation process having adsorption properties and three reduction reactions. The variations of peak current ratios of electrochemical reactions for all three complexes with scan rate showed that electron transfer processes of complexes were followed by reversible or irreversible chemical reactions. Aggregation and sandwich adduct formation properties of complexes were determined by CV measurements. Peak potentials of redox processes for all complexes were shifted towards positive potentials by addition of alkali metal cations. Addition of K+ formed sandwich type adducts with 15-crown-macrocycles diminishing aggregation of planar molecules by intramolecular rather than intermolecular complexation.
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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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    Synthesis and electrochemical characterization of biphenyl-malonic ester substituted cobalt, copper, and palladium phthalocyanines
    (PERGAMON-ELSEVIER SCIENCE LTD, 2007) KOCA, ATIF; Sener, M. Kasim; Koca, Atif; Guel, Ahmet; Kocak, Makbule Burkut
    Phthalocyanines with four biphenyl-malonic ester groups on the periphery were synthesized by cyclotetramerization of 4-(1,1-dicarbethoxy-2-(4-biphenyl)-ethyl)-phthalonitrile. The new compounds were characterized by elemental analyses, FT-IR, H-1 NMR, C-13 NMR, UV-Vis, and MASS spectral data. Electrochemical behaviors of novel Co(II), Cu(II), and Pd(II) phthalocyanines were investigated by cyclic voltammetry, potential differential pulse voltammetry, and applied potential chronocoulometry techniques. While Cu(II) and Pd(II) phthalocyanines give up to four common phthalocyanine ring reductions, Co(II) phthalocyanine gave two ligand-centered and two metal-centered redox processes. HOMO-LUMO gap of the complexes are comparable with the reported MPc papers. (c) 2006 Elsevier Ltd. All rights reserved.
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    Functional fluoro substituted tetrakis-metallophthalocyanines: Synthesis, spectroscopy, electrochemistry and spectroelectrochemistry
    (ELSEVIER SCIENCE SA, 2008) KOCA, ATIF; Gunsel, Armagan; Kandaz, Mehmet; Koca, Atif; Salih, Bekir
    In this study, electron-withdrawing fluoro-functional ligand and its tetrakis 2,9,16,23-4-(2,3,5,6-tetrafluoro)-phenoxy-phthalocyaninatometal (II) complexes, (ZnPcOBzF(16), CuPcOBzF(16) and CoPcOBzF(16)) (Bz: benzene) which are organo-soluble have been prepared. Their structures were confirmed by elemental analysis, FT-IR, H-1 NMR, UV/vis and MS (Maldi-TOF) spectral data. Electron-withdrawing fluorine atoms on 2,3,5,6-position of benzene at the peripheral sites increases the solubility of the tetrakis-metallophthalocyanines. The cyclic voltammetry and differential pulsed voltammetry of the complexes show that while CuPcOBzF(16) and ZnPcOBzF(16) give ligand-based reduction and oxidation processes, CoPcOBzF(16) gives both ligand and metal-based redox processes, in harmony with the common MPc complexes. Spectroelectrochemical measurements confirm the assignments of the complexes. (c) 2008 Elsevier B.V. All rights reserved.
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    Voltammetric and spectroelectrochemical properties of titanylphthalocyanines bearing catecholato and naphthalenediolato moieties
    (ELSEVIER SCIENCE SA, 2008) KOCA, ATIF; Koca, Atif; Arslanoglu, Yasin; Hamuryudan, Esin
    Detailed electrochemical characterization of catecholato-octakis(2-dimethylaminoethylsulfanyl phthalocyaninato) titanium(IV) and (2,3-naphthalenediolato)-octa-(2-dimethylaminoethylsulfanylphthalocyaninato) titanium(IV) derivatives has been carried out by cyclic voltammetry, differential pulse voltammetry, double potential step coulometry, controlled potential coulometry and spectroelectrochemical measurements. Cyclic and differential pulse voltammograms of the complexes are similar with two metal-based and two ligand-based reduction and two ligand-based oxidation couples. Capping of TiO core of octakis(2-dimethylaminoethylsulfanyl)phthalocyaninato oxotitanium(IV) with catecholato and naphthalenediolato changed the redox mechanism of the complexes. (2,3-naphthalenediolato)octa-(2-dimethylaminoethylsulfanylphthalocyaninato) titanium(IV) derivative is dimetallised during the negative potential sweeps. Spectroelectrochemical measurements confirm the metal- and ligand-based assignments of the redox couples. Distinctive voltammetric and spectroscopic changes during the titration with soft metal ions, Ag+ and Pd2+, shows the metal sensing and coordinating properties of the complexes. (c) 2008 Elsevier B.V. All rights reserved.
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    A water-soluble multisite ionophore ligand bearing pyridine and aminothiophenol functionality. Synthesis, spectroscopy and electrochemistry of its complexes, and peripheral reactivity of the (E,E)M (M = Ni) complex with Pd2+ and Ag+
    (SPRINGER, 2004) ÖZKAYA, ALİ RIZA; Kandaz, M; Ozkaya, AR; Koca, A
    The design, synthesis and coordination of a novel multisite vic-dioxime compound, LH2 containing flexible pyridine substituents and amitiophcnylsulfanyl moieties on the periphery, facilitating solubility in water as pyridinium hydrochloride salt are described. LH2 was prepared by the reaction between 2-(2-pyridylethylamino)-benzenethiol and (E,E)-dichloroglydioxime. Mononuclear [(E,E)M] (M = Ni-II, Cu-II. Co-II, Fe-II and Mn-II) and dinuclear uranyl (UO2II) complexes of LH2 were isolated and characterized with metal:ligand ratios of 1:2 and 2:2. respectively. The reaction of Na2PdCl4 . 3H(2)O and AgNo3 in DMF with the mononuclear complex, (LH)(2)Ni, resulted in the formation of the heterotrinuclear complexes [Pd2Ni(LH)(2)]Cl-4 and [Ag2Ni(LH)(2)](NO3)(2). The complexes were characterized by elemental analysis, H-1-n.m.r., u.v.-vis. spectroscopy, i.r., and MS (LSIMS). The redox properties of the complexes were studied by cyclic voltammetry.
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    Copper phthalocyanine complex as electrocatalyst for hydrogen evolution reaction
    (ELSEVIER SCIENCE INC, 2009) KOCA, ATIF; Koca, Atif
    In this work, we have sought economically viable methods for hydrogen evolution reaction (her). For this purpose, we have investigated the voltammetric and in situ spectroelectrochemical behavior of copper phthalocyanine complex and its electrocatalytic activity for her. In spite of the belief that the complexes bearing redox active metal center can catalyze hydrogen evolution reactions, copper phthalocyanine having ring-based redox processes shows excellent electrocatalytic activity. (C) 2009 Elsevier B.V. All rights reserved.