Sergey M. Kuzmin

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 (H2T(p-NH2Ph)P) and 5,10,15,20-tetrakis(3′-aminophenyl)porphyrin (H2T(m-NH2Ph)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 oxidation peak current monitoring. The antioxidant properties of porphyrins were estimated in terms of binding constants. The strong effect of NH2 group position on the superoxide scavenging activity are shown: the H2T(p-NH2Ph)P (kb = 12.7 × 102 mol-1) demonstrates the significant superoxide scavenging activities whereas H2T(m-NH2Ph)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.

The coulometric approach to the superoxide scavenging activity determination: The case of porphyrin derivatives influence on oxygen electroreduction

The electrochemical and antioxidant properties of 5,10,15,20-tetrakis(3′-hydroxyphenyl)porphyrin (H2T(m-OHPh)P) and 5,10,15,20-tetrakis(4′-hydroxyphenyl)porphyrin (H2T(p-OHPh)P) were tested by the cyclic voltammetry (CV) method. It is shown that in dimethylsulfoxide (DMSO) the electroreduction processes of oxygen and porphyrins are under diffusion control. The electroreduction of H2T(m-OHPh)P and H2T(p-OHPh)P with potentials about -1 V are irreversible due to the chemical step (EC process) which leads to products with oxidation potentials about -0.5 V. Additionally in case of oxygen and porphyrin coreduction, both H2T(m-OHPh)P and H2T(p-OHPh)P influence the O2•- electrosynthesis. The nonlinear dependence of the O2•- peak current vs. porphyrin concentrations makes the available amperometric approach unsuitable for antioxidant activity estimation. To solve this problem, the coulometric parameters were calculated. The excellent linearity of the coulometric response of superoxide ion vs. porphyrins concentration was demonstrated for a wide concentration range. On the basis of coulometric responses, we constructed a parameter which separated the radical scavenging activity and variation of oxygen electroreduction. The superoxide scavenging activities of H2T(m-OHPh)P and H2T(p-OHPh)P were determined using the developed approach. The effect of OH group position on the superoxide scavenge activity is shown: H2T(p-OHPh)P has a higher activity (slope = 0.75 L.mmol-1) than H2T(m-OHPh)P (slope = 0.60 L.mmol-1).

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 (O2•−). The activation effect of the dissolved oxygen becomes evident in porphyrin interaction with the superoxide anion radical (O2•−) 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 ...

Structures and properties of porphyrin-based film materials part I. The films obtained via vapor-assisted methods

This review is devoted to porphyrin-based film materials. Various technological and scientific applications of ones are close to surface and interface related phenomena. In the part I of review the following topics are discussed the recent progress in field of submonolayers, monolayers and multilayers films on the vapor-solid interfaces, including results on (i) conformational behavior of adsorbed molecules, (ii) aggregation and surface phases formation, (iii) on-surface coordination networks, and (iv) on-surface chemical reactions. The examples of combined approaches to developing materials and porphyrin-based film materials application are also presented.

Hydroxyalkyloxy substituted tetraphenylporphyrins: Mechanism and superoxide scavenging activity

The novel electrochemical approach based on coulometric response of electro-generated superoxide (O2•−) was used to determine scavenging properties of 2H-5,10,15,20-tetrakis (4-hydroxyphenyl)porphyrin (H2T(4-OHPh)P); 2H-5,10,15,20-tetrakis[4-(2-hydroxyethyloxy)phenyl]porphyrin (H2T(4-OH(CH2)2OPh)P); 2H-5,10,15,20-tetrakis[4-(4-hydroxybutyloxy)phenyl]porphyrin (H2T(4-OH(CH2)4OPh)P); Zn-5,10,15,20-tetrakis[4-(4-hydroxyethyloxy)phenyl]porphyrin (ZnT(4-OH(CH2)2OPh)P) superoxide. It has been identified that the porphyrins under study possess good antioxidant properties. The analysis of possible interactions between porphyrins and superoxide anion-radical has shown that high values of superoxide scavenging activity of tetraphenylporphyrins with alcohol chains can be explained by the nucleophilic attack of O2•− on the C–C bonds of alcohol.