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In this work the oxidation and reduction reactions of MnIII–Coproporphyrin-I (MnIII-CPI) have been studied and four forms of manganese–CPI complexes have been characterized. This complex was observed to be highly reactive (at basic pH) towards Mn(II), hypochlorite, hydrogen peroxide and oxone, forming [MnIV(O)CPI(OH)]− that was unstable and, after a short time, formed again [MnIIICPI(OH)2]−. With an excess of NaClO, a further oxidation of the complex [MnIV(O)CPI(OH)]−, provoked a significant spectral change for the [MnV(O)CPI(OH)] formation that showed, in the time, a partial polymerization. [MnIIICPI(OH)2]− was reduced by sodium dithionite to form the very unstable complex of [MnIICPI(OH)]− that successively degraded with Mn(II) release.

The reaction of 3,8,13,18-tetramethyl-21H,23H-porphine-2,7,12,17-tetrapropionic acid or coproporphyrin-I (CPI) with the elements of 11 group have been studied. CPI is an anionic porphyrin that slowly reacts with copper ion to form Cu II CPI and with silver ions to form Ag II CPI, Ag III CPI complexes and colloidal silver. Gold ions do not form complexes with CPI, but, in the main, colloidal gold and some CPI- N -oxide. The kinetics of the reactions with copper and silver were spectrophotometerically studied and the rate constants were calculated. The identification and characterization of this water-soluble anionic porphyrin and its metal complexes have been performed by electrospray mass spectrometry (ESI-MS) that proved to be an excellent method for these determinations. The multiple charged parent ions for metal free ligand and their metal complexes were identified.

When dropping mercury electrode (DME) dipped in ultrapure water, thoroughly deaerated with pure hydrogen, is irradiated with UV light, we can observe a cathodic photocurrent in the non-faradaic region of the polarographic curve, in the absence of scavengers of hydrated electrons. Newly we have followed the effect on photocurrent of initial very small additions of alkali metal chlorides to pure water. By repeated experiments, we could show that first additions of the alkali metal halides increase the photocurrent and that the already known suppression of photocurrent by addition of halides begins only after the halide concentration exceeds ca 10-4 mol l-1. We could show for the first time that in ultrapure water and dilute electrolyte solutions, the photocurrent follows a modified seven-halves law. The extent of the positive effect of small additions of alkali metal halides on photocurrent depends on the nature of each alkali metal cation. The reason for this specificity is discussed.

ABSTRACT The use of potassium tetrakis(1H-pyrazolyl)borate KB(Pz)4 as a mobile phase additive for reverse phase High Performance Liquid Chromatography of metal chelating compounds was investigated. The reason for its superiority over previously employed eluent modifiers is described.

A reproducible current-voltage curve of pure water, obtained with the dropping mercury electrode (DME), contains a 1-2 V wide region where no faradaic processes take place. This region consists of three distinct parts according to different orientations of water molecules and their interactions with the mercury surface. On irradiation of the DME by UV and visible light a cathodic photocurrent is produced in the negative part of the nonfaradaic region, which increases with increasing voltage. The photocurrent appears in water in the absence of scavengers of hydrated electrons, and its magnitude is of the same order as that of the current due to photoemission of electrons into solutions of electrolytes containing scavengers. Additions of electrolytes decrease and ultimately suppress this kind of photocurrent. We explain the photocurrent by the effect of an electric field of the extended electrode double layer on the return of hydrated electrons, generated by photoemission, back to the electrode. Re...

We synthesized the Cu(ii) and Zn(ii) complexes of the 2,7,12,17- tetrapropionic acid of 3,8,13,18-tetramethyl-21H,23H porphyrin (coproporphyrin-I) and successfully employed them as sensitizers in dye-sensitized solar cells. Copper(ii) coproporphyrin-I exhibits a power conversion efficiency of 3.8% measured under irradiation of AM 1.5G full sunlight (100 mW cm-2). © The Royal Society of Chemistry 2010.

Sulphur and sulphide ions react in (K,Na)SCN eutectic melt with the formation of polysulphide. The electrolytic oxidation of SCN(-) at 155 degrees forms S(4) which gives S(2-)(5) with S(2-); at 165 degrees the sulphur electrogenerated is S(2) that reacts according to S(2) + S(2-) = S(2-)(3). The equilibrium constants of these reactions have been obtained by voltammetric measurements. The formation of S(2) at 155 degrees by irradiation from a xenon lamp was confirmed. The S(2) reacts with S(2-) to give S(2-)(3), and the equilibrium constant for this reaction is the same as that found for the reaction at 165 degrees .

Summary The electrodic oxidation of thiocyanate melt with different platinum electrodes giving different products is discussed. The formation of (SCN)3− species and the complicated electrodic reduction is reported. The cyclic voltammetry study of sulphide gives evidence of a coupled electrodic reaction at 155 and 165°C. The behaviour of the polysulphide has been studied by means of the same technique at 155°C.

The electrochemical oxidation of selenocyanate in ammoniate solution was studied by potentiostatic, voltammetric, and galvanostatic measurements on Pt electrodes. The formation of both an anodic deposit, possibly a (SeCN) x matrix with trapped (SeCN) − 3 , and a soluble species, (SeCN) − 3 , was observed at current densities below 0.3 mA cm −2 . At higher current densities only deposit formation was observed. A theoretical treatment and experimental evidence are given for the kinetic mechanism of deposit formation. The mechanism explains the impossibility experienced in both obtaining a massive deposit and enhancing its photoelectrochemical properties.

Summary The solubility and the electrochemical behaviour of water at bright platinum microelectrodes have been studied in (Na,K) acetates (46.3 mol % CH3COONa) eutectic melt in the temperature range 250–290°C. The Henry's law constant has been found to be K=1.21×10−3 mol kg−1 Torr−1 at 250°C while the enthalpy of the process is −10.2±0.3 kcal mol−1. The water reduction (H2O+ea1/2H2+OH−) has been found to be a diffusion controlled process proceeding reversibly at bright platinum electrodes. By means of chronopotentiometry the water diffusion coefficient is DH2O=1.34×10−5 cm2 s−1 at 250°C while the Arrhenius activation energy for diffusion is +9.5±0.5 kcal mol−1.

Nitrite is converted completely to nitrogen by sulfamic acid, the excess of which is determined after conversion to ammonia by acid hydrolysis. Equal aliquots of sample are treated with increasing amounts of sulfamic acid, and potentials are measured after the hydrolysis. Nitrite in the range 1.5 × 10 -5 –2 × 10 -2 mol l -1 can be determined with errors less than 2%.

The voltammetric behavior of Pb(II), Cd(II), Tl(I) and Ni(II) in fused acetamide at 87°Chas been studied. The measurements have been carried out using normal polarography and cyclic voltammetry either with mercury or platinum electrodes. Only Tl(I) reduction occurs reversibly while all the other cations show some degree of irreversibility.

The feasibility of the titration of some cations in molten sodium thiocyanate-potassium thiocyanate mixture with electrolytically generated sulphide ions has been tested at 443 K. Quantitative data are given for the titration of cadmium, mercury and zinc ions.

The anodic deposit on platinum electrodes in thiocyanate melts is a complex mixture of species which, depending on experimental conditions, undergoes various chemical reactions terminated by complete polymerisation.

A layer of sulphur produced on a platinum electrode by anodic electrodeposition from an alkali thiocyanate melt gives a marked photoeffect with visible light in solution or in melts containing S2– ions.