O. R. Simonova

Effect of metal cation surrounding on the redox properties of aluminum porphyrinate in the reaction with organic peroxide

Intermolecular interaction of aluminum(III) 5,15-di(o-methoxyphenyl)-2,8,12,18-tetrabutyl-3,7,13.17-tetramethylporphyrinate chloride with bis(1-methyl-1-phenylethyl)peroxide has been studied by spectral and modeling methods; the reaction kinetics and mechanism have been elucidated. Effect of nature of the metal outer coordination sphere on the reaction rate has been examined. Geometry parameters of the initial molecules and the intermediates have been simulaed by the PM3 method, and their distortion has been estimated. The intermediates formation is accompanied by increased steric strain of the macrocycle.

Influence of imidazole on the kinetics of oxidation of 5,15-di(ortho -methyloxyphenyl)-2,3,7,8,12,13,17,18-octamethylporphyrin with organic peroxides in o-xylene

The structure of zinc 5,15-di(ortho -methyloxyphenyl)-2,3,7,8,12,13,17,18-octamethylporphyrin was studied by spectrophotometry and computer simulation. Its properties in the reaction with organic peroxides in o-xylene in the presence of imidazole were studied at 295 K. The apparent and true rate constants for this process were calculated. The metalloporphyrin chromophore was found to decompose completely during the interaction of the zinc porphyrin (ZnP) with peroxides. The influence of imidazole on the reaction rate was revealed. The geometric characteristics of the optimized ZnP structure and intermediates of the oxidation were obtained by the PM3 quantum-chemical method. The deformational strains in the ZnP macrocycle were found to increase during the reaction.

Reaction of μ-carbido-dimeric iron(IV) octapropyltetraazaporphyrinate with dicumene peroxide and tert-butyl peroxide in benzene

We report the results of our studies into the oxidation reactions of μ-carbido-dimeric iron(IV) octapropyltetraazaporphyrinate with organic peroxides. Kinetic parameters have been determined, and a possible scheme of the process suggested. The nature of peroxide has been shown to influence the rates of redox transformations. The reaction has been shown to generate the μ-carbido-dimeric iron(IV) octapropyltetraazaporphyrinate radical cation through the dissociation of the О–О bond in the peroxide coordinated to the iron atom. The reaction product enters an aggregated state over time, and readily recovers the initial form in the presence of a nitrogen-containing base.

Structure and properties of (Ac)Fe(III)-5,15-diphenyl-3,7,13,17-tetramethyl-2,8,12,18-tetrabutylporphyrin in the reaction with organic peroxides in benzene: The effect of imidazole on reaction kinetics

The kinetics of the reaction between (Ac)Fe(III)-5,15-diphenyl-3,7,13,17-tetramethyl-2,8,12,18-tetrabutylporphyrin and dicumene peroxide in benzene at 295 K was studied with the purpose of further studying the effect of the conformational and electronic factors of nonplanar metalloporphyrinates on redox properties using a combination of computational and spectrophotometric methods. The molecular structures of reagents and intermediates of the studied reaction were optimized by the PM3 quantum-chemical method. The obtained characteristics were analyzed, and the distortion of a macrocycle was established to considerably increase in the reaction of iron(III) porphyrinate with peroxides. The intermediate molecule was found to be sterically hindered and extremely unstable. The kinetic characteristics of the reaction were obtained spectrophotometrically. The nature of a metal atom and the distortion of a macrocycle were established to have some effect on the process rate. The introduction of imidazole into a reaction mixture and the variation of concentration of a base were shown to produce some changes in the composition of reagents and the kinetics of the process. A good agreement between experimental and calculated data was observed.

Reaction of (Ac)Co-5,15di( ortho -methyloxyphenyl)-2,8,12,18-tetramethyl-3,7,13,17-tetrabutylporphyrin and its molecular complex with organic peroxides in xylene

The reaction of cobalt porphyrinate with organic peroxides in o-xylene has been studied using spectrophotometric titration, and its kinetic parameters have been determined. Imidazole has been shown to influence the process rate. A comparative analysis of the kinetic parameters of peroxide decomposition involving cobalt(III) porphyrinate and its zinc analogue has been carried out. A PM3 quantum-chemical method was used to optimize discrete molecules of the reagents and reaction intermediates, and their geometric parameters have been derived. Steric hindrances in the cobalt porphyrinate macrocycle and a considerable enhancement of distortion have been noticed to occur upon its reaction with a peroxide molecule.

Oxidation kinetics of Zn-5,15 bis(ortho-methoxyphenyl)-2,3,7,8,12,13,17,18-octamethylporphyrin with organic peroxides in o-xylene

With the purpose of further investigation of the effect of the steric strain of the porphyrin macroring in metal porphyrins on their redox properties, kinetics of oxidation of Zn-5,15 bis(ortho-methoxyphenyl)-2,3,7,8,12,13.17,18-octamethylporphyrin with organic peroxides in o-xylene at 295°C were studied spectrophotometrically to show that this process leads to complete destruction of the complex. Kinetic characteristics (kef, kv) of the process were evaluated. The structure of the zinc porphyrin and its oxidation intermediates were obtained by quantum-chemical calculations. Steris strains in the metal prophyrin macroring were revealed and shown to enhance in the course of the reaction. An effect of the degree of deformational strain on the oxidation rate was noted.

Calibration characteristics of a glass electrode in dimethyl sulfoxide in the temperature range 298–318 K

The work presents the results of the temperature calibration of an electrode system and the tabulation of pH scale in DMSO against buffer solutions.

Influence of the macrocycle nature on the redox properties of vanadium porphyrinates in their reaction with an organic peroxide

The redox properties of vanadium 5,15-bis(о-methoxyphenyl)-3,7,13,17-tetrabutyl-2,8,12,18-tetramethyl-5,10,15,20-tetraphenylporphyrinates in the reaction with an organic peroxide, specifically dicumyl peroxide, were studied. The kinetic parameters of the reaction were determined and its possible mechanism was suggested. The coordinating capacity of vanadium porphyrinates with respect to dicumyl peroxide and imidazole and the stability of the resulting molecular complexes were estimated. It was shown that the nature of the macrocyclic ligand and the surrounding of the coordination center affect the rate of redox transformations. The isolated structures of the reagents and oxidation intermediates were optimized and their geometric parameters were obtained by the quantum-chemical РМ3 method. The calculation results revealed a high degree of deformation of the intermediate molecule, leading to macrocycle destruction.

Study of Intermolecular Interaction of Mg-5,15-Di(o-methoxyphenyl)-2,8,12,18-tetramethyl- 3,7,13,17-tetrabutylporphin with o-Xylene Organic Peroxides. Effect of Imidazole on the Reaction Kinetics

Using the method of spectrophotometric titration a reaction of magnesium porphyrinate with the o-xylene organic peroxides was investigated, the reaction mechanism and kinetic parameters were determined. The effect of imidazole on the rate of the reaction under investigation was demonstrated. The presence of steric strain in the magnesium porphyrinate macrocycle and its increase in the course of formation of intermediates was observed.

Kinetics of Zn-5,15-di(ortho-methyloxyphenyl)-2,8,12,18-tetramethyl-3,7,13,17-tetrabutylporphyrin oxidation by organic peroxides in o-xylene

A spectrophotometric and quantum chemical (PM3) study of the structure and properties of Zn-5,15-di(ortho-methyloxyphenyl)-2,8,12,18-tetramethyl-3,7,13,17- tetrabutylporphyrin (ZnP(I)) in its oxidation with organic peroxides in o-xylene at T = 295 K is presented. The kinetic parameters (kapp, kv) of this reaction are reported. The reactivities of strained zinc porphyrinates (ZnP(I), Zn-5,15-di(ortho-methyloxyphenyl)-2,3,7,8,12,13,17,18-octamethylporphyrin (ZnP(II)), and a zinc porphyrin with a 2,5-dimethoxyphenylene “cover” (ZnP(III))) are compared. The electronic and conformational properties of the macrocycle are significant factors in the interaction of the metalloporphyrins with the peroxides. The structures of the reactants and intermediates have been calculated by the PM3 method. The macrocycle of ZnP(I) has a distorted structure. The degree and type of distortion are estimated. When reacting with the peroxides, the metalloporphyrin changes its structure so that the macrocycle becomes still more strained, and this enhances its reactivity.