Person: KOCA, ATIF
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KOCA
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ATIF
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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 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 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.Publication Metadata only Thiosemicarbazide-based iron(III) and manganese(III) complexes. Structural, electrochemical characterization and antioxidant activity(PERGAMON-ELSEVIER SCIENCE LTD, 2019) KOCA, ATIF; Kaya, Busra; Kaya, Kerem; Koca, Atif; Ulkuseven, BahriNew iron(III) and manganese(III) complexes were synthesized by the condensation of 1-phenyl-1, 3-butanedione-S-propyl-thiosemicarbazone (I) with salicylaldehyde in the presence of iron(III) or manganese(II) ions. The complexes were characterised by analytical and spectroscopic methods. X-ray analysis displayed the square pyramidal environments of the iron and manganese ions. The electrochemical behaviors of the iron(III) (1a) and manganese(III) (1b) complexes were studied by cyclic voltammetry and square wave voltammetry in different solvents. Both complexes displayed metal-based electron transfer reactions in addition to ligand based irreversible reduction and oxidation processes, which were affected by the type of metal. Spectroelectrochemical methods were used to examine the electrogenerated species of the complexes and to define the redox processes. The total antioxidant capacity (as the TEAC value) and free radical scavenging activities (FRS%) of the compounds were determined. The TEAC values of 1 (2.78), to (1.63) and 1b (1.28) are higher than those of vitamin C (0.96). (C) 2019 Elsevier Ltd. All rights reserved.Publication Metadata only 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, EsatA 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.Publication Metadata only Electrochemical metal-ion sensors based on a novel manganese phthalocyanine complex(ELSEVIER SCIENCE SA, 2012) KOCA, ATIF; Ceken, Berna; Kandaz, Mehmet; Koca, AtifIn this paper, we investigated the electrochemical metal-ion sensor activity of a manganese phthalocyanine (MnPc). For this purpose, interactions of MnPc with various transition metal ions were examined in solution and in solid state. MnPc forms aggregates only with Ag+ and Hg2+ ions selectively among various transition metal ions in solution, which indicates possible application of the complex as a metal sensor. For practical application, MnPc was immobilized in a polymeric cation exchange membrane, Nafion, on a glassy carbon electrode and used as an electrochemical receptor element. Sensor properties of MnPc were potentiometrically and amperometrically characterized as metal ion sensor with respect to reproducibility, repeatability, stability, linear concentration range, and sensitivity. (C) 2012 Elsevier B.V. All rights reserved.Publication Metadata only Electrochemical and spectroelectrochemical characterizations of new tetra-substituted metallophthalocyanines bearing 4-(trifluoromethoxy)phenoxy groups on non-peripheral positions(SPRINGER WIEN, 2020) KOCA, ATIF; Farajzadeh, Nazli; Akyuz, Duygu; Koca, Atif; Kocak, Makbule BurkutIn this study, a series of non-peripherally tetra-substituted phthalocyanines [M = Zn(II), Co(II), and In(III)] was successfully prepared by cyclotetramerization of the phthalonitrile derivative bearing 4-(trifluoromethoxy)phenoxy group at 3-position. All newly synthesized compounds were characterized using spectroscopic methods, such as FT-IR, NMR, and UV-Vis spectroscopy. The effect of concentration on aggregation properties of the resulting phthalocyanines was investigated in different concentrations ranging from 4 x 10(-6)to 14 x 10(-6) M in THF. In addition, the spectral properties of the metallophthalocyanines were studied in various organic solvents. Besides, redox responses of metallophthalocyanines and their electro-optical responses were determined. Although {1(4),8(11),15(18),22(25)-tetrakis[4-(trifluoromethoxy)phenoxy]phthalocyaninato}cobalt(II) showed well-resolved reversible redox peaks depicting the anticipated electron transfer reactions, electrochemical investigation of its zinc(II) and indium(III) chloride analogs resulted in complex redox waves, and their chemical reversibility decreased with the aggregation of the complexes. The influence of the redox processes on the optical responses of metallophthalocyanines was studied with in situ spectroelectrochemistry measurements and the peak assignments and optical responses of the electrogenerated species were determined. [GRAPHICS] .Publication Metadata only Electrochemical and spectroelectrochemical properties of thiadiazole substituted metallo-phthalocyanines(PERGAMON-ELSEVIER SCIENCE LTD, 2016) KOCA, ATIF; Demirbas, Umit; Akyuz, Duygu; Barut, Burak; Bayrak, Riza; Koca, Atif; Kantekin, Halit4-Thiadiazole substituted phthalonitrile and peripherally tetra-substituted phthalocyanine Cu(II), Fe(II) and Ti(IV)O complexes have been synthesized for the first time. Electrochemical properties of these complexes were determined with voltammetric and in situ spectroelectrochemical measurements. CuPc has redox inactive Cu2+ center, therefore it gave three Pc based reduction and two Pc based oxidation processes. TiOPc and FePc complexes gave metal based redox processes in addition to Pc based redox reactions due to the redox activity of Ti4+O and Fe2+ metal centers. Although FePc also gave three reduction and two oxidation reactions, peak potentials of these processes are different than those of CuPc due to the different assignments of the redox reactions. TiOPc went to five reduction and one oxidation reactions. Assignments of the redox processes were carried out with in situ spectroelectrochemical measurements. Spectra and color of the electrogenerated redox species of the complexes were also determined with in situ spectroelectrochemical and in situ electrocolorimetric measurements. Distinct color differences between the electrogenerated redox species were observed, which indicated their possible electrochromic usages. (C) 2015 Elsevier B.V. All rights reserved.