Atıf Koca

Photocatalytic hydrogen production by direct sun light from sulfide/sulfite solution

Abstract The photocatalytic hydrogen production from a sulfide/sulfite solution is one of the photocatalytic processes that have been of interest recently for hydrogen production. Different types of semiconductor photocatalysts have been prepared and tested for this purpose. In this paper, photocatalysts CdS/ZnS that were prepared by a different coprecipitation technique was studied with and without n-Si in sulphide/sulphite solution irradiated with direct sunlight at laboratory level. From the study of variation in composition of CdS/ZnS, 2:1(by weight) composition was found to be very efficient for hydrogen production. The rate of hydrogen liberation was achieved by addition of n-Si. The maximum hydrogen has been produced with the photocatalyst CdS/ZnS/n-Si (2/1/1.4–1.6%). The recorded maximum hydrogen evolution rate was 35.5 ml h −1 g −1 in 250 ml 0.24 M Na 2 S and 0.35 M Na 2 SO 3 solution.

Synthesis, characterization and electrochemistry of novel differently octasubstituted phthalocyanines

Abstract We describe the complete synthesis of differently substituted multifunctional metallo phthalocyanines (MPcs) (M=Ni, Zn, Co) bearing four 2′-aminophenylsulfanyl or 2-aminophenoxy moieties and four chloro atoms on peripheral positions. The synthesis started from the corresponding anhydrous metal salts and differently substituted [4-(2′-aminophenylsulfanyl)-5-chlorobenzene-1,2-dicarbonitrile] (2a) and [4-(2-aminophenoxy)-5-chlorobenzene-1,2-di-carbo nitrile] (2b), and the products were separated by HPLC. These multifunctional amino substituents serve as strong binding sites for further reactions after phthalocyanine formation, such as Schiff-bases, and provide solubility of the phthalocyanines in organic solvents (THF, CHCl3 and CH2Cl2). The newly synthesized compounds have been characterized by elemental analysis, FTIR, 1H NMR, MS (EI and FAB), UV–Vis and atomic absorption spectroscopy. Electrochemical studies reveal that CoPc (6a) has two metal and four ligand-based redox processes while NiPc (4a) and ZnPc (5b) show three ligand-based reduction processes.

Synthesis, spectroscopy and redox properties of a novel (E–E) vic-dioxime and its mono-, di- and trinuclear complexes bearing an 18-membered N2O2S2 macrocyle

Abstract A new 18-membered ligand, 2,3-dibromo-6,7,13,14,15,16,22,23-octahydro 14, 15-bis(hydroxyimino)-tribenzo [e,k,q] [1,4,10,13,7,16] diazadioxadithiacyclooctadecine (LH4) containing three different heteroatoms (N, O, S) has been prepared from 1,2-bis (2′-amino phenylsulfanylethoxy)-4,5-dibromobenzene and cyanogen di-N-oxide. Mononuclear (LH3)2M, where M=Ni(II), Cu(II), Co(II), Fe(II) binuclear (LH)2(UO2)2(OH)2 and trinuclear (LH)2M3, where M=Cu (II), Co (II) complexes of LH4 have been obtained with a metal:ligand ratio 1:2, 2:2 and 3:2, respectively, through N,N-coordinating or N, N, S, S-coordinating in the presence of a base, as do most of the vic-dioximes. 1H NMR, IR, UV–Vis and MS data are presented. The cyclic voltammetric (CV) measurements of the newly synthesized compounds were measured. Voltammetric results showed that oxime-containing ligands stabilize Ni(III), Fe(III), Co(III) and Cu(III). The Fe(II) complex displayed a different behavior with respect to other complexes. This indicated that both Fe(III) and Fe(I) species are stable while oxime containing ligands tend to stabilize only one of the oxidized forms of the metal center of the complexes. Differently, ligand based reduction was recorded only with the Ni(II) complex.

Electrochemical characterization of Co(II) and Pd(II) phthalocyanines carrying diethoxymalonyl and carboxymethyl substituents

In this study, electrochemical behaviors of Co(II) and Pd(II) phthalocyanines carrying tetrakisdiethoxymalonyl and Pd(II) phthalocyanine carrying tetrakiscarboxymethyl substituents at the peripheral positions are investigated by cyclic voltammetry and applied potential chronocoulometry techniques. Cyclic voltammetric studies show that, while Pd(II) phthalocyanines carrying diethoxymalonyl and carboxymethyl substituents give up to three common phthalocyanine ring reductions, Co(II) phthalocyanine carrying diethoxymalonyl substituents gives a metal-centered oxidation and a metal-centered reduction and three ligand-centered reduction and a ligand-centered oxidation processes. First reduction processes of both the PdPc complexes have shoulders. This different voltammetric behaviors of Pd(II) phthalocyanines carrying carboxymethyl and diethoxymalonyl substituents results from interaction of this distinctive substituents with the phthalocyanine ring π electron system and interaction with the different solvent systems. Observation of the splitting of the first reduction process of Pd(II) phthalocyanines carrying diethoxymalonyl and carboxymethyl substituents suggests the aggregation of the complex. Very small diffusion coefficient of the complexes with respect to Co(II) phthalocyanine also confirms the existence of the aggregation of the complex during the electrochemical studies. Effects of the substituents and the solvent media are clearly observed from the differences of the voltammograms of Pd(II) phthalocyanines carrying diethoxymalonyl and carboxymethyl substituents in DMSO and THF solvent media, respectively.

Functional alcohol-soluble double-decker phthalocyanines: synthesis, characterization, electrochemistry and peripheral metal ion binding

In this study we report the preparation, physical characterization and electrochemistry of peripherally functionalized substituted ionophore double-decker lanthanide phthalocyanines, lanthanide bis-[(4,4″,4″,4‴)-tetrakis-(6-hydroxyhexylthio)phthalocyaninates], {M[Pc(S-C6H13OH)4]2} (M = PrIII, YbIII, and LuIII). All benzenes on the double-decker phthalocyanines are functionalized with hydroxyhexylsulfanyl moieties for potential use as metal ion binding and surface anchors. The double-decker phthalocyanines synthesized from the anhydrous metal salts {Ln(acac)3} and the corresponding 4-(6-hydroxyhexylthio)-1,2-dicyanobenzene exhibit ion-specific optical changes in the presence of Ag+ and Pd2+. Thio donors of the complexes coordinate to Ag+ and Pd2+ to give 4:1 metal-phthalocyanine complexes. Newly synthesized lanthanide double-decker phthalocyanines are soluble in methanol (MeOH), ethanol (EtOH), tetrahydrofuran (THF), dimethylformamide (DMF), dimethylsulfoxide (DMSO), chloronapthalene, quinoline and less soluble in i-PrOH and acetonitrile. Electrochemical studies reveal that all lanthanide-base complexes undergo ligand-based redox processes. The smaller HOMO-LUMO gaps of the complexes indicate the existence of strong π-orbital interactions between the rings of the sandwich. The newly synthesized compounds have been characterized by elemental analysis, FTIR, 1H and 13C NMR, MS (ESI and Maldi-TOF), UV-vis and EPR spectral data.

Synthesis and electrochemical properties of porphyrazines with annulated 1,4-dithiaheterocycles

Abstract Porphyrazines (M=H, Mg, Zn or Cu) with 2,3-trimethyleneoxy-2,3-dihydro-1,4-dithiin or 2-ethoxy-2,3-dihydro-1,4-dithiin groups fused to each pyrrol unit have been synthesised starting with the corresponding unsaturated dicarbonitrile derivative. The elemental analysis and IR, 1 H NMR, UV–Vis and mass spectral data have been used to characterise the new compounds. Electrochemical investigations have shown that metal insertion into the porphyrazine core and substituents having high electron donating ability shift the ring centred reduction processes towards negative potentials.

Synthesis, in situ spectroelectrochemistry and in situ electrocolorimetry of electrochromic octakis(chloroethylsulfanyl) phthalocyaninatomanganese(III) chloride

In this study, the syntheses of octakis(hydroxyethylsulfanyl) phthalocyaninatomanganese(III) chloride and its chlorinated derivative, octakis(chloroethylsulfanyl) phthalocyaninatomanganese(III) chloride, and successive electrochemical investigations of the latter were reported. The voltammetric studies of the complex revealed that it exhibits three one-electron reduction processes and a one-electron oxidation process. In situ spectroelectrochemical studies were performed to decide the origin of the redox processes which are assigned to MnIIIPc2−/MnIIPc2−, MnIIPc2−/MnIPc2−, MnIPc2−/MnIPc3− and MnIIIPc2−/MnIIIPc1− couples, respectively. The presence of oxygen significantly affected the in situ spectroelectrochemical behavior of the complexes due to the formation of μ-oxo MnPc species. 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 electrogenerated anionic and cationic forms of the complex, which shows solvatochromic properties of the complex in solution. The possible polyelectrochromic application on solid state was suggested due to the color changes from brown to greenish blue and from brown to light yellow of a MnPc-coated thin film on ITO.

EDOT-Functionalized Calix(4)pyrrole for the Electrochemical Sensing of Fluoride in Water

A new calix[4]pyrrole compound bearing an electropolymerizable EDOT substituent (1) was synthesized, and its electrochemical behavior was investigated. The anion sensor ability of 1 was also studied in solution and in the solid state. Compound 1 interacts with halide ions selectively in solution, which illustrates its possible application as an anion sensor. To test possible practical applications, 1 and EDOT were electropolymerized on an ITO electrode, and this electrode was used as an effective fluoride anion sensor in the solid state.

Both alcohol and halogenated solvents soluble soft-metal sensor functional phthalocyanines: synthesis, electrochemistry, spectroelectrochemistry

In this study, we report a novel both alcohol and haloganated solvent soluble selective ionophore functional ligand and its β-substituted 2(3),9(10),16(17),23(24)-tetrakis(1-hydroxyhexan-3-ylthio)-phthalocyanines, M{Pc[S-CH(CH2CH2CH3)(CH2CH2OH)]4}, (Pc: Phthalocyanine) (M = Zn, Cu, Co), where -OH indicates peripheral functionality. Pcs exhibiting both hydrophobic and hydrophilic character were characterized spectroscopically (FT-IR, 1H and 13C NMR, MS (MALDI-TOF) and UV-vis), electrochemically and spectroelectrochemically. The complexes were soluble in both polar solvents, such as MeOH and EtOH, and non-polar solvents such as CHCl3, CH2Cl2, benzene, toluene, and even hexane. Absorption spectral changes of the functional MPcs during addition of AgI and PdII soft-metal ions are evaluated by monomer-oligomer and even polymer formations technique and monitored for in situ monitoring technique in the UV-vis spectroscopy. The binding process results in considerable blue-shift in the absorption spectra of MPcs. According to continuous variation method, the ligand:metal ratio was found ca. 1:1 and 1.5:1 for total concentration of 1.0 × 10-5M and 7.5 × 10-5M, respectively. Their electrochemical and spectroelectrochemical studies show that the complexes exhibited stable monoanionic M{Pc[S-CH(CH2CH2CH3)(CH2CH2OH)]4}1-, dianionic M{Pc[S-CH(CH2CH2CH3)(CH2CH2OH)]4}2- and monocationic M{Pc[S-CH(CH2CH2CH3)(CH2CH2OH)]4}1+ species during reduction and oxidation processes.

Electrochemical hydrogen peroxide sensor based on cobalt phthalocyanine captured in polyaniline film on a glassy carbon electrode

This work demonstrated preparation, characterization, and application of a cobalt phthalocyanine based enzymeless/mediatorless hydrogen peroxide sensor. The cobalt phthalocyanine (CoPc) was retained in polyaniline (PANI) film on a glassy carbon electrode during electrochemical polymerization of aniline and consequently a novel composite electrode (GCE/PANI/CoPc) for the electrochemical sensor application was constructed. The CoPc functionalized composite electrode, GCE/PANI/CoPc, was evaluated by voltammetry, electrochemical impedance spectroscopy, and UV-vis spectroscopy. The results displayed retaining of the CoPc molecules in the PANI film on the GCE electrode. Presence of CoPc in PANI increased conductivity of the composite on the electrode. Sensing performance of the GCE/PANI/CoPc composite electrode to H2O2 were evaluated in detail with respect to the selectivity, reproducibility, repeatability, stability, linear concentration range, and sensitivity with voltammetric and double potential step chronoamperometric techniques. The GCE/PANI/CoPc composite electrode gives a linear range for H2O2 between 2 and 18 μM H2O2 with sensitivities of 1.55 A.M-1 during the cathodic SWV scan and with sensitivities of 4.01 A.M-1 during the anodic SWV scan. A direct application of the sensor was performed in a real working condition, for the detection of hydrogen peroxide produced from the reaction between the glucose and glucose oxidase enzyme.