Electropolymerized Manganese Tetraaminophthalocyanine Thin Films onto Platinum Ultramicroelectrode for the Electrochemical Detection of Peroxynitrite in Solution

Peroxynitrite, ONOO^? also so‐called PON, is a very powerful oxidant and cytotoxic agent produced in biological systems by the recombination of nitric oxide and superoxide anion radical. Most of the techniques for assaying PON (chemiluminescence, fluorescence, UV‐visible spectroscopy, immunochemistry and EPR ) use indirect methods relying on measurements of secondary species. We report in this study the calibration of a chemically modified Pt ultramicroelectrode by electropolymerized manganese tetraaminophthalocyanine film (MnTAPc) for the determination of PON in aqueous solution. The obtained result allows showing for the first time a real‐time calibration curve of the amperometric determination of stable PON in aqueous solution. The sensitivity of the sensor is 14.6 nA mM^?1 and its detection limit is 5 μM.     

Tuning the redox properties of metalloporphyrin- and metallophthalocyanine-based molecular electrodes for the highest electrocatalytic activity in the oxidation of thiols

In this work we discuss different approaches for achieving electrodes modified with N(4) macrocyclic complexes for the catalysis of the electrochemical oxidation of thiols. These approaches involve adsorption, electropolymerization and molecular anchoring using self assembled monolayers. We also discuss the parameters that determine the reactivity of these complexes. Catalytic activity is associated with the nature of the central metal, redox potentials and Hammett parameters of substituents on the ligand. Correlations between catalytic activity (log i at constant E) and the redox potential of catalysts for complexes of Cr, Mn, Fe, Co, Ni and Cu are linear with an increase of activity for more positive redox potentials. For a great variety complexes bearing the same metal center (Co) correlations between log i and E(o') of the Co(II)/Co(I) couple have the shape of an unsymmetric volcano. This indicates that the potential of the Co(II)/Co(I) couple can be tuned using the appropriate ligand to achieve maximum catalytic activity. Maximum activity probably corresponds to a DeltaG of adsorption of the thiol on the Co center equal to zero, and to a coverage of active sites by the thiol equal to 0.5.     

Low temperature heat capacity and magnetic properties of UF3

The low temperature heat capacity of UF(3) has been measured using an adiabatic low temperature calorimeter in the temperature range from 10 to 350 K. These data are complemented at the lowest temperature region with data obtained with a Quantum Design PPMS-14 device in the temperature range from 0.5 to 20 K. Good agreement between both techniques has been found, and from these experimental results the absolute entropy of UF(3) at 298.15 K has been determined as 126.8 ± 2.5 J K(-1) mol(-1). On the basis of the specific heat data and the magnetization measurements performed on a SQUID device, a transition at 1.59 K attributed to Curie temperature of a ferromagnetic transition has been found in this study. This observation makes UF(3) a unique compound with an unusually low ferromagnetic ordering temperature.     

Electrochemical Characterization of Self‐Assembled Monolayer of a Novel Manganese Tetrabenzylthio‐Substituted Phthalocyanine and Its Use in Nitrite Oxidation

Manganese phthalocyanine MnPc(SPh)₄ has been synthesized and used to form self assembled monolayers on gold electrodes. The well packed SAM monolayer was characterized by analyzing the blocking of a number of Faradic processes by cyclic voltammetry, evaluating the electrical characteristics of the modified electrode by electrochemical impedance and imaging the modified surface by electrochemical scanning microscopy. Finally, MnPc(SPh)₄‐SAM modified electrode displayed an electrocatalytic behavior toward the oxidation of nitrite.