Investigation of Acidic and Coordination Properties of Octabromo-Substituted Porphyrins in the System of 1,8-Diazabicyclo[5,4,0]unde-7-ene-Acetonitrile

Acidity and metal ion coordination are described for three porphyrin derivatives, different in their macrocycle conformation and electronic substitution effects due to bromine substitution in pyrrole rings and trifluorometyl or phenyl groups in meso-positions. Combination of these facts allows modulating both steric and electronic effects on the macrocycle π-conjugated system. The role of electronic substitution effects in the macrocycle deprotonation and metal ion complex formation is found dominating with comparable resonance and inductive contributions, whereas non-planar conformation of reactive species contributes to the reaction rates to a lesser extent. The interaction of two single-electron (a_1ue_g) and (a_2ue_g) configurations is studied as a function of non-planar distortions of the molecular structure for the three tetrapyrrole compounds. The additive influence of disturbing factors on the configuration interaction of single-electron (a_1ue_g) and (a_2ue_g) configurations in the tetrapyrrole macrocycle is demonstrated.

     

Spectrophotometric Study of Acid-Base Properties of Sulfonated Derivatives of 5,10,15,20-Tetraphenyl-21-thiaand 5,10,15,20-Tetraphenyl-21-oxoporphyrins in the Ethanol–Sulfuric Acid System

Spectral and basic properties of heterosubstituted porphyrins of anionic type have studied by means of spectrophotometric titration in comparison with their structural analog — tetraphenylporphine tetrasulfonic acid. The parameters of electronic absorption spectra and concentration ranges of existence of the mono- and diprotonated forms of the studied ligands as well as the constants of basic dissociation have been determined. Comparative analysis of the effect of the reactive site modification and the medium composition on the basicity of the compounds has been performed.

     

Dissociation kinetics of cobalt and zinc β-octabromo-meso-tetraphenyl- and β-octaethyl-meso-tetraphenylporphyrin complexes

Kinetics of solvoprotolytic dissociation of zinc and cobalt porphyrin complexes with a porphyrin macrocycle distorted to different extents (β-octaethyl-meso-tetraphenylporphyrin and β-octabromo-meso-tetraphenylporphyrin) have been studied in binary proton-donating solvents. The main factor decreasing the stability of the porphyrin complexes is the distortion of the planar structure of the macrocycle. The reactivity of the cobalt porphyrins is governed by both structural and electronic effects.     

Surfactant-modified polypropylene as a catalyst for oxidation of mercaptans

Surface modification of polypropylene by soluble metallophthalocyanine was performed. The effect of pretreatment of polypropylene on the degree of surface anchoring of the macrocycle was shown. The catalytic activity of the hybrid materials produced in the oxidation reaction of sodium diethyldithiocarbamate was determined.     

Coordination of pyridine and piperidine by cobalt complexes of water-soluble porphyrin and phthalocyanines

The extracoordination reactions of nitrogen-containing bases pyridine and piperidine with cobalt complexes of water-soluble porphyrin and phthalocyanines were studied. The stability constants of the axial complexes of cobalt porphyrins and cobalt phthalocyanines with pyridine and piperidine were determined.     

Electronic and steric effects of substituents on the coordinating properties of porphyrins

Kinetics of the formation of zinc complexes of porphyrin with various substituents was studied in acetic acid and pyridine. The introduction of strong electron-withdrawing substituents (nitro groups) to the meso-positions of the porphyrin macrocycle was shown to change the reaction rate by an order of magnitude or less compared to the phenyl-substituted analogs. However, the introduction of a large number of bulky substituents leads to the deformation of the porphyrin ligand and thus affects much stronger the coordination properties of porphyrins, decreasing or increasing the rate of the complexation reaction by several orders of magnitude.     

Tetrapyrrole macrocycles complexes as a basis for the development of materials with a combined biological action

Extracoordination reactions of pyridine and piperidine nitrogen bases, and nitrite ion with cobalt complexes of water-soluble porphyrins and tetrasulfophthalocyanine were studied. A method for the modification of polymer systems by immobilization of coordination compounds of tetrapyrrole macrocycles on polymer substrates was developed. Bactericidal properties of the obtained composite films were revealed.     

Porphyrin acidity and metal ion coordination revisited: electronic substitution effects

Macrocycle acidity and Zn²⁺ ion coordination are reported for three porphyrin derivatives which differ in both steric and electronic substitution effects on the macrocycle π-conjugated system. The role of the electronic substitution effects in the macrocycle deprotonation and metal ion chelating was found to be dominating whereas the macrocycle nonplanar distortions contribute to the acidity and metal chelation rate of the studied porphyrins in less extent. The contributions of both resonance and inductive electronic substitution effects have been distinguished based on the relationship between the weighted sum of resonance and inductive Hammett constants and the acidity and metal ion chelation rate.     

Coordination properties of molecular and anionic forms of 5,10,15,20,21-pentaphenyl-2,3,7,8,12,13,17,18-octaethylporphyrin in acetonitrile

Acid and coordination properties of 5,10,15,20,21-pentaphenyl-2,3,7,8,12,13,17,18-octaethylporphine in 1,8-diazabicyclo[5.4.0]undec-7-ene–acetonitrile system at 298 K have been studied by spectrophotometric titration. It has been found that titration causes deprotonation of nitrogen atom of the pyrrole ring to produce monodeprotonated form. Acid dissociation constant of the compound in 1,8-diazabicyclo[5.4.0]undec-7-ene–acetonitrile system at 298 K has been determined. Complexation of molecular and deprotonated forms of the ligand with silver nitrate has been studied, kinetic parameters of the corresponding reactions have been obtained. Kinetics of silver complexation with the studied ligand by ionic and molecular mechanism has been analyzed.     

Coordination of nitrogen-containing ligands by Co complexes with tetra-and dodeca-substituted porphyrins

Capabilities of complexes with tetraphenylporphyrin, the derivative of tetrapyridiniumporphyrin, and with β-octabromine-meso-tetraphenylporphyrin to coordinate additional nitrogen-containing ligands are compared. The equilibrium constants of addition of extra ligands, namely, pyridine, piperidine, and N-methylimidazole, to the Co complexes with these porphyrins in ethanol solutions at 298 K are determined.