S. V. Zaitseva

Synthesis and coordination properties of the zinc complex of dimeric porphyrin in reactions with imidazole, 2-methylimidazole, and the pyridine in benzene

Dimeric porphyrin(2,6-bis[15′-(3″,5″-di-tert-butylphenol)-3′,7′,13′,17′-tetramethyl-2′,8′,12′,18-tetraethylporphin-5′-yl]-4-tert-buthylphenol) and its binuclear zinc complex were obtained from 4,4′-dimethyl-3,3′-diethyldipyrrolylmethane, 2,6-diformyl-4-tert-butylphenol and 3,5-di-tert-buthylbenzaldehyde. Coordina-tion properties of dimeric zincporphyrin in the intermolecular reaction with nitrogen-containing bases (imidazole, 2-methylimidazole, and pyridine) in benzene were studied. Geometry and electronic structure of the zincporphyrin and its molecular complexes were calculated by a quantum-chemical method. Energy characteristics of the intermolecular reaction of the dimeric zincporphyrin with bases were determined. The calculated energies of the central metal atom interaction with the nitrogen atom of an extra-ligand agree well with the stability of the Zn-porphyrin molecular complexes. The influence of the deformation distortions of the porphyrin ligand on the strength of the metal-extra-ligand σ-bond was established.

Complexes of zinc 5,15-di(ortho-methoxyphenyl)octaalkylporphyrinate with nitrogen-containing bases

The formation of molecular complexes of zinc 5,15-di(ortho-methoxyphenyl)-2,8,12,18-tetramethyl-3,7,13,17-tetrabutylporphyrinate (ZnP) with nitrogen-containing bases L (L is imidazole, 2-methylimidazole, pyridine, 3,5-dimethylpyrazole, or dimethylformamide) in benzene is studied by spectrophotometry and computer simulation. The nature of an additional molecular ligand affects the stability of the macrocyclic complex (L)ZnP. The stability constant of this complex increases linearly with an increase in the basicity of the extra ligand and is proportional to the shift of the main absorption bands in the electronic spectra (Q(0–1), B (Soret band)). The molecular structures of zinc porphyrinate and its extra complexes are optimized by the PM3 quantum-chemical method. Their geometric and energy parameters are calculated. Correlations between the calculated energies of interaction of the central metal atom with the nitrogen atom of the extra ligand and the stability of (L)ZnP are found. The dependence of the zinc-extra ligand bond strength on the basicity of the additional molecular ligand is determined on the basis of the experimental and calculated data. The coordination properties of the compound under study are found to be affected by steric strains.

Reduction of (chloro)-μ-nitrido-bis[(tetra-tert-butyl-phthalocyaninato)iron(IV)] with organic N-bases

The interaction of (chloro)-μ-nitrido-bis[(tetra-tert-butyl-phthalocyaninato)iron(IV)] Cl(FePc)2N with organic N-bases L as electron–donors (L = diethylamine, imidazole, 1-methylimidazole, 2-methylimidazole) with the formation of one-electron reduced species (L)PcFeIII–N=FeIVPc(L) was investigated in benzene at 298 K by UV-visible spectroscopy. The reaction was established to be stepwise process including fast reversible axial binding of two substrate molecules onto iron cations followed by slow one-electron metal-centered reduction. The results of IR, ESI-MS and EPR study support the formation of final product with Fe+3–N =Fe+4 unit and two substrate molecules in the first coordination sphere. The reaction kinetics was studied, the pre-equilibrium constants Keq and rate constants k were obtained. The Keq and k values were found to be linearly correlated with basicity of substrates pKa. The possibility of the transition Fe4+→ Fe3+ is promoted by electron–donor properties of substrate combined with the pre...

Reactions of (Hydroxo)(tetrakis(3,5-dicarboxy)-and (Hydroxo)(tetrakis(4,5-dicarboxy)phthalocyaninato)aluminum(III) with Sulfuric Acid: Simulation and Kinetic Experiments

The interaction of the octacarboxy-substituted aluminum(III) phthalocyanines (hydroxo)(tetrakis(3,5-dicarboxy)- and (hydroxo)(tetrakis(4,5-dicarboxy)phthalocyaninato)aluminum(III) with sulfuric acid is reported. It has been demonstrated by computer simulation (PM3 method) and by studying the dependence of the electronic absorption spectra of the complexes in sulfuric acid on the acidity of the medium that ((OH)AlPc(4-COOH)4(5-COOH)4 has three protonated forms (mono-, di-, and trication) both in the gas phase and in concentrated sulfuric acid and (OH)AlPc(3-COOH)4(5-COOH)4 has three protonated forms in the gas phase and two ones in concentrated sulfuric acid. The destruction kinetics of the aluminum(III) phthalocyanines in hot sulfuric acid is investigated. A destruction mechanism is suggested in which the rate-limiting step is the dissociation of an Al-N bond and the transition state consists of one aluminum(III) phthalocyanine molecule and one hydronium ion. A stability series is established for a set of differently carboxy-substituted aluminum(III) phthalocyanines. The major factors in the stability of the complexes are the negative inductive effect and the number of carboxyl groups.

Coordination properties of (chloro)aluminum-5,15-diphenyloctaalkylporphyrin in the reactions with small organic molecules

The reactions of aluminum porphyrinate ((Cl)AIP) with organic molecules L (imidazole, pyridine, pyrimidine, and pyrazine) in benzene were studied using spectral and quantum-chemical methods. The structures and stabilities of the molecular complexes (Cl)Al(L)nP in solutions were determined. The influence of the nature of the macrocyclic ligand and organic base on the coordination properties of aluminum porphyrinate was observed. The degree of deformation of the metalloporphyrin and its molecular complexes was estimated. A good correlation between the experimental and calculated characteristics

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.

Coordination properties of μ-carbidodimeric iron(IV) 2,3,7,8,12,13,17,18-octapropyltetraazaporphyrinate and 5,10,15,20-tetraphenylporphyrinate in reactions with nitrogen-containing bases

The equilibria of μ-carbidodimeric iron(IV) 2,3,7,8,12,13,17,18-octapropyltetraazaporphyrinate and 5,10,15,20-tetraphenylporphyrinate in reactions with nitrogen-containing bases in an inert solvent were studied spectrophotometrically. The equilibrium constants of the studied processes and the compositions of molecular complexes were determined. The effect of the electronic and conformation factors of a macrocycle and the nature of the base on the equilibrium constant was pointed out. A comparative analysis of the substrate specificity of the studied compounds was performed.

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.

Intermolecular interactions of (5,15-diphenyl-3,7,13,17-tetramethyl-2,8,12,18-tetrabutylporphyrinato)manganese acetate with small organic molecules

The coordination properties of (5,15-diphenyl-3,7,13,17-tetramethyl-2,8,12,18-tetrabutylporphyrinato)-manganese(III) acetate toward small organic molecules in an inert solvent medium were studied. The values of the equilibrium constants of the process and the composition of the molecular complex were determined. The influence of the electronic and conformational factors of macrocycle on the value of the equilibrium constant was found. The geometry of isolated molecules of manganese porphyrinate and its molecular complexes was optimized by the quantum-chemical PM3 method. The structure of the reaction products favorable by the energy was theoretically found. A good agreement between the calculated and experimental data was obtained.