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    Öğe
    Cobalt(II)/(III) complexes bearing a tetradentate thiosemicarbazone: Synthesis, experimental and theoretical characterization, and electrochemical and antioxidant properties
    (Wiley, 2020) Kaya, Busra; Akyuz, Duygu; Karakurt, Tuncay; Sahin, Onur; Koca, Atif; Ulkuseven, Bahri
    New cobalt complexes,Co1andCo2, were synthesized starting from acetylacetone-S-methylthiosemicarbazone. The square planar cobalt(II) and octahedral cobalt(III) complexes were characterized by FT-IR, UV-visible,H-1 NMR, and X-ray diffraction spectroscopies and mass spectrometry. Frontier orbitals of the complexes were theoretically obtained to better understand the complex structures and intermolecular interactions. The electrochemical behaviors ofCo1andCo2were investigated and the results were evaluated by comparing with each other and with similar published compounds to determine their possible usage in various electrochemical technologies, such as energy storage devices, electrocatalysts, and electrosensors. Metal-based oxidation at around 0 V and metal-based reduction at around -1.0 V indicated that these complexes are valuable for the proposed applications. By determining the trolox equivalent antioxidant capacity and the radical scavenging activity of the cobalt complexes, the compatibility between the antioxidant qualification, redox, and theoretical calculation results was discussed.
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    Öğe
    Electrochemical and spectroelectrochemical properties of thiadiazole substituted metallo-phthalocyanines
    (Pergamon-Elsevier Science Ltd, 2016) Demirbas, Umit; Akyuz, Duygu; Barut, Burak; Bayrak, Riza; Koca, Atif; Kantekin, Halit
    4-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.
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    Öğe
    Synthesis and electrochemical characterization of tetra-(5-chloro-2-(2,4-dichlorophenoxy)phenol) substituted Ni(II), Fe(II) and Cu(II) metallophthalocyanines
    (Elsevier Science Sa, 2016) Demirbas, Umit; Kobak, Rabia Zeynep Uslu; Barut, Burak; Bayrak, Riza; Koca, Atif; Kantekin, Halit
    The synthesis and characterization of novel nitrile compound (3) and peripherally tetra 5-chloro-2-(2,4-dichlorophenoxy)phenol substituted nickel(II) (4), iron(II) (5) and copper(II) (6) phthalocyanines were accomplished for the first time in this study. Electrochemical characterizations of the complexes were carried out with voltammetric and in situ spectroelectrochemical measurements. CuPc and NiPc showed common Pc based electron transfer reactions. Small potential differences were observed between the redox responses of these complexes due to the different effective nuclear charges of the metal centers. [Cl1--(FePc2-)-Pc-III] complex gave metal and Pc based electron transfer reactions. While [Cl-1-Fe(III)pc(2-)] reduced to [Cl1--(FePc2-)-Pc-II](1-), [Cl1--(FePc2-)-Pc-I](2-), and [Cl1--(FePc3-)-Pc-I](3-) during reduction reactions, a metal based ([Cl1--(FePc2-)-Pc-III]/[Cl1--(FePc2-)-Pc-IV](1+)) and then a Pc based ([Cl1--(FePc2-)-Pc-IV](1+)/[Cl1--(FePc1-)-Pc-IV](2+)) oxidation reaction was observed the cathodic potential scans. Determination of the spectra, color of the electrogenerated MPc species and peak assignments of the complexes were determinated with in situ spectroelectrochemical measurements. (C) 2016 Elsevier B.V. All rights reserved.
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    Öğe
    Synthesis, characterization and investigation of electrochemical and spectroelectrochemical properties of peripherally and non-peripherally tetra 2-methyl-5-benzothiazole substituted nickel(II), copper(II) and cobalt(II) phthalocyanines
    (Elsevier Science Sa, 2017) Demirbas, Umit; Akyuz, Duygu; Bayrak, Riza; Barut, Burak; Koca, Atif; Kantekin, Halit; Degirmencioglu, Ismail
    In this study novel tetra 2-methyl-5-benzothiazole substituted peripherally nickel(II) (6), copper(II) (8), cobalt(II) (10) and non-peripherally nickel(II) (7), copper(II) (9), cobalt(II) (11) phthalocyanines were synthesized. These novel compounds were characterized by a combination of FT-IR, H-1 NMR and UVvis and MALDI-TOF mass spectroscopic techniques. Electrochemical measurements gave well illustrated redox responses for the Pc ring and/or metal center of the complexes. While MPc bearing redox inactive metal centers underwent [(MPc-2)-Pc-II]/[(MPc-3)-Pc-II](1-), [(MPc-3)-Pc-II](1-)/[M(II)Pc(-)4](2-), [(MPc-4)-Pc-II](2-)/[(MPc-5)-Pc-II](3-) and [(MPc-2)-Pc-II](1-)/[(MPc-1)-Pc-II](1+) redox couples. (CoPc)-Pc-II illustrated [(CoPc-2)-Pc-II]/[(CoPc-2)-Pc-I](1-), [(CoPc-2)-Pc-I](1-)/[(CoPc-3)-Pc-I](2-), [(CoPc-3)-Pc-I](2-)/[(CoPc-4)-Pc-I](3-) and [(CoPc-2)-Pc-II]/[(CoPc-2)-Pc-II](1+) redox couples respectively during reduction and oxidation processes respectively. Position of the substituents altered the chemical and electrochemical reversibility of the redox processes. While the substituents were non-peripheral position, the complexes aggregated and both of the redox processes of the aggregated and nonaggregated species were observed, incorporation of the substituents to peripheral position decreased aggregations of the complexes, therefore MPcs substituted at peripheral positions illustrated well resolved reversible redox reactions. In situ spectroelectrochemical results illustrated that electrogenerated MPc species had distinct color differences.