In situ CCD video and voltammetric studies on enhanced cathodic peak observed at a hanging mercury drop electrode during consecutive two one-electron redox reactions in aprotic solutions

Solvent and electrode influence on electrochemical forming of poly-Fe(III)-aminophenylporphyrin films

Fe(III)-complexes of amino-substituted tetraphenylporphyrins obtained from solutions in organic solvents: dichloromethane, ethanol, and dimethyl sulfoxide have been electropolymerized. The solvents’ effects on deposition and surface morphology of the obtained polyporphyrin film have been determined. It is only possible to obtain a polyporphyrin film from DMSO solutions through electrochemical activation of electropolymerization by a superoxide anion radical (O[Formula: see text]. The activation effect of the dissolved oxygen becomes evident in porphyrin interaction with the superoxide anion radical (O[Formula: see text] that is synthesized in DMSO thanks to the quasi-reversible redox process. The size of particles forming the film is lowest when the film is deposited from DMSO and highest when it is deposited from dichloromethane. Therefore, the ratio of polyporphyrin phase grain growth rate to the nucleation rate has the highest value when the film is deposited from dichloromethane. Such films have the most developed surfaces, while those deposited from ethanol are the smoothest. If the film is deposited on an ITO-electrode, the particles forming the surface are a little larger than in the case of deposition on Pt, which is explained by a slower nucleation on the ITO surface. FeClT([Formula: see text]-NH2Ph)P-based films obtained from ethanol and dichloromethane have negative photo-EMF values, which indicates that the [Formula: see text]-type films have semiconductor properties.

Substituent position influence on the electrochemical properties and antioxidant activity of tetra(aminophenyl)porphyrins

Free radicals and reactive oxygen species (ROS) are important intermediate products in physiological processes. In the healthy cell, they are generated and regulated by enzymes and low molecular weight antioxidants. Overproduction of ROS leads to a large list of diseases, so the determination of antioxidant activity of perspective natural and synthetic compounds is necessary for drugs development. In this paper cyclic voltammetry (CV) method was applied to the electrochemical and superoxide scavenging properties of 5,10,15,20-tetrakis(4′-aminophenyl)porphyrin ( H 2 T (p- NH 2 Ph ) P ) and 5,10,15,20-tetrakis(3′-aminophenyl)porphyrin ( H 2 T (m- NH 2 Ph ) P ) investigation. It is shown that the studied porphyrins have very similar electrochemical behavior and slight effect on the quantity of superoxide produced during first CV cycle therefore the estimation of superoxide scavenging properties may be performed by the [Formula: see text] oxidation peak current monitoring. The antioxidant properties of porphyrins were estimated in terms of binding constants. The strong effect of NH 2 group position on the superoxide scavenging activity are shown: the H 2 T (p- NH 2 Ph ) P (kb = 12.7 × 102 mol-1) demonstrates the significant superoxide scavenging activities whereas H 2 T (m- NH 2 Ph ) P (kb = 0.83 × 102 mol-1) — negligible. The most probable mechanism of superoxide scavenges explaining the observed differences are the H -atoms transfer due to N – H bond breaking in the aminophenyl substituent.