L. Zh. Guseva

Acid-base properties of sterically strained tetraethyltetramethylporphyrin derivatives

Acid dissociation constants in acetonitrile were determined for cationic forms of sterically strained tetraethyltetramethylporphyrin derivatives. These compounds are more basic than their unstrained analog because of deformations of the porphyrin macroring, that increase the electron density on tertiary nitrogen atoms of the reaction center and make them more accessible for reaction.

A new procedure for the spectrophotometric determination of nitrogen(II) oxide in solutions

A new simple and reliable procedure was developed for the spectrophotometric determination of nitrogen(II) oxide. The procedure is based on the determination of excess oxygen after its reaction with NO. Alkaline solutions of thiourea dioxide were used for the determination of oxygen. It was found that the decomposition of an alkaline solution of thiourea dioxide under aerobic conditions is accompanied by the formation of dithionite, and its concentration is proportional to the concentration of oxygen in the solution. The absorbance of the resulting dithionite was measured at 315 nm. The solutions obeyed Beer’s law at oxygen concentrations of 1 × 10−5−1.5 × 10−3 M. The analytical range for NO was 1 × 10−5−1.5 × 10−3 M. The proposed procedure was also used for the determination of nitrogen(II) oxide in aqueous-ethanolic solutions.

N(II) oxide coordination to Co complexes with water-soluble porphyrin

Novel, water-soluble metalloporphyrin of zwitterionic type (Co complex with 5,10,15,20-tetra(4N-carboxymethylenepyridyl)porphyrin tetrabromide) was synthesized and its interaction with N(II) oxide was studied. IR and electronic absorption spectra were analyzed. Alcoholic solutions of this complex saturated with NO were found to contain all three types of coordinated ligands, i.e., NO, NO+, and NO−.

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.

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.

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.

Coordination dimer based on zinc octaethylporphyrin and meso -pyridyl-substituted porphyrin

New dimeric porphyrin was synthesized as a result of coordination interaction between 2,3,7,8,12,13,17,18-octaethylporphyrinatozinc(II) and 5-(3,5-di-tert-butylphenyl)-2,8,12,18-tetraethyl-3,7,13,17-tetramethyl-15-(pyridin-4-yl)porphyrin. The new compound was characterized by spectral and TLC data, and equilibrium constant for the formation of molecular ensemble was determined.

Coordination of nitrogen(II) oxide by metal prophyrins

The equilibrium constants have been determined for the extra coordination of nitrogen(II) oxide and its metabolite formed in biochemical reactions (the nitrite ion) by cobalt complexes of porphyrins with various structures in ethanolic and aqueous solutions with near-physiological pHs. The far higher values of the thermodynamic stability constants of (NO)CoP nitrosyl complexes compared to those for nitrite complexes argue for a considerable covalence of the Co-NO bond.

Coordinating Properties of Co(II) and Zn(II) Complexes with Sterically Hindered Porphyrins

Cobalt(II) and zinc(II) complexes with 5,15-di(o-methoxyphenyl)-3,7,13,17-tetramethyl-2,8,12,18-tetra-n-buthylporphyrin and its capped analogues, where the MN4 reaction site is shielded by bridging groups containing m-phenylene and dimethoxy-substitutedp-phenylene fragments, were synthesized. Equilibrium constants of additional coordination of pyridine and N-methylimidazole by these metalloporphyrins were determined at 298 K. It was found that steric distortion of the porphyrin core destabilizes extra complexes.