Yu. B. Ivanova

Synthesis and basic properties of bisporphyrinocalix[4]arene

A bisporphyrinocalix[4]arene was prepared, and its basicity was examined spectrophotometrically. The protonation of tetrapyrrole fragments of the porphyrinocalixarene conjugate in the ethanol-sulfuric acid system occurs in two steps and is described by the Hammett equation. The ionization constants and the concentration intervals of the formation of the mono-and dicationic forms of the bisporphyrinocalixarene were determined.

Porphyrin halide ion receptor

Formation of 1:1 and 1:2 complexes of mono-and dications of octaalkylporphyrin with halide ions in acetonitrile at 298 K was studied by spectropotentiometric titration. The stability constants of the complexes were determined.

The acid properties of dodecasubstituted porphyrins with a chemically active NH bond

The NH acid properties of nonplanar dodecasubstituted porphyrins (H2P) were studied by the spectropotentiometric and spectrophotometric methods and by semiempirical quantum-chemical calculations. The reaction of H2P with a weak organic base DMSO proceeded with the formation of the H-associated form DMSO⋯H⋯PH or DMSO⋯H⋯P⋯H⋯DMSO. Strong bases KOH[222] and [NR4]OH reacted with the formation of mono-(HP−) or dianionic (P2−) forms. An increase in NH acidity along the series tetraphenylporphin < tetraphenyltetrabenzoporphin < β-octaethyltetraphenylporphin < dodecaphenylporphin < β-octabromotetraphenylporphin was to a great extent caused by the polarization of molecules, which accompanied saddle-nonplanar distortions of their structure, rather than β-substituent electronic effects. The quantitative characteristics obtained using the suggested system of criteria of the chemical activity of NH bonds (1H NMR spectral, kinetic, and quantum-chemical criteria) linearly correlated with H2P acid dissociation constants and could be used for alternative estimation of the acidity of tetrapyrrole compounds.

Formation of phthalocyanines deprotonated forms and their interaction with Zn Ions in the system 1,8-diazabicyclo[5.4.0]undec-7-ene-acetonitrile at 298 K

The formation of deprotonated forms of tetra(t-butyl)phthalocyanine ((H2tButPc) and octa(pentoxy)-phthalocyanine (H2OAmPc) in the system acetonitrile-1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) at 298 K was studied by the method of spectrophotometric titration. With increasing DBU concentration sequential formation occurs of both mono- and douby deprotonated forms. The introduction of pentoxy groups into the fused benzene rings leads to a significant decrease in the acidity of the tetrapyrrole macrocycle compared with the tert-butyl substitution. The interaction of douby deprotonated forms of the phthalocyanines with zinc diacetate leads to the formation of metal complexes, the chelation constant of the latter is shown to correlate with the acidity of NH-protons in the nucleus of the macrocycle. For the chelation of more acidic tetra(t-butyl)-phthalocyanine an equimolar concentrations of zinc diacetate is sufficient, while the less acidic octa(pentoxy)-phthalocyanine requires almost 6-fold excess.

Spectrophotometric study of 2,3,12,13-tetrabromo-5,10,15,20-tetraphenylporphyrin in the system 1,8-diazabicyclo[5.4.0]undec-7-ene-acetonitrile at 298 K. Deprotonation of the pyrrole rings and complex formation with Zn(OAc)2

Acid-base and complexing properties of 2,3,12,13-tetrabromo-5,10,15,20-tetraphenylporphyrin in the system 1,8-diazabicyclo[5.4.0]undec-7-ene-acetonitrile were studied at 298 K by spectrophotometric titration. The titration of 2,3,12,13-tetrabromo-5,10,15,20-tetraphenylporphyrin with 1,8-diazabicyclo[5.4.0]-undec-7-ene was accompanied by successive deprotonation of the pyrrole nitrogen atoms with formation of the corresponding mono- and dianions, and the acid dissociation constants were determined. Complex formation of doubly deprotonated 2,3,12,13-tetrabromo-5,10,15,20-tetraphenylporphyrin with zinc acetate was studied.

Pyridyl-substituted porphyrins: II. Synthesis and basic properties of dipyridylporphyrins

Abstract5,15-Bis(pyridin-2-yl)-, 5,15-bis(pyridin-3-yl)-, and 5,15-bis(pyridin-4-yl)-substituted 3,7,13,17-tetramethyl-2,8,12,18-tetraethylporphyrins were synthesized, and their acid-base properties in ethanol-sulfuric acid were studied by spectrophotometric titration. Concentration ranges for the existence of mono- and dicationic forms of 5,15-dipyridylporphyrins and the corresponding ionization constants were determined. The effect of pyridine fragments on the basic properties of alkyl-substituted porphyrins was discussed.

Pyridyl-substituted porphyrins: I. Synthesis and basicity of monopyridylporphyrins

Abstract13,17-Diethyl-2,3,7,8,12,18-hexamethyl-5-(pyridin-2-yl)porphyrin, 13,17-diethyl-2,3,7,8,12,18-hexamethyl-5-(pyridin-2-yl)porphyrin, and 13, 17-diethyl-2,3,7,8,12,18-hexamethyl-5-(pyridin-4-yl)porphyrin were synthesized, and their basic properties were studied by spectrophotometric titration in the system ethanol-sulfuric acid. Concentration ranges for the existence of mono- and dicationic forms of meso-pyridyl-substituted porphyrins and the corresponding ionization constants were determined.

Influence of substituents structure and their electronic effects on acid-base and complexing properties of 5,10,15,20-tetranitro-2,3,7,8,12,13,17,18-octaethylporphyrin

Abstract5,10,15,20-Tetranitro-2,3,7,8,12,13,17,18-octaethylporphyrin has been prepared, and its acid-basic properties have been studied in acetonitrile by titration with 1,8-diazabicyclo [5.4.0]undec-7-ene and perchloric acid. The substituted porphyrin ability towards complex formation with zinc acetate has been studied in acetonitrile and acetonitrile, 1,8-diazabicyclo [5.4.0]undec-7-ene media. Spectral properties of neutral and ionic forms of 5,10,15,20-tetranitro-2,3,7,8,12,13,17,18-octaethylporphyrin and its zinc complex have been determined; constants of acid and basic ionization of the ligand have been estimated. Kinetic parameters of the porphyrin complex formation with zinc via molecular and ionic mechanism have been analyzed. The substituents effect on the studied properties is discussed.

Synthesis and Basic Properties of Tetra-tert-butyltetrabenzo- 5,10,15-triazaporphyrin

Abstract22,72,122,172-Tetra-tert-butyltetrabenzo-5,10,15-triazaporphyrine was synthesized, and its basic properties were studied by spectrophotometric titration. It was found that in the system ethanol-sulfuric acid nitrogen atoms in the tetrapyrrole macroring undergo protonation in three steps. The corresponding ionization constants and concentration ranges for mono-, di-, and tricationic forms of the examined compound were determined.

Dependence of the basic properties of meso-nitro-substituted derivatives of β-octaethylporphyrin on the nature of substituents

Spectrophotometric titration is used to study the basic properties of a series of porphyrins with a continuously increasing degree of macrocycle deformation resulting from the introduction of strong electron-withdrawing substituents: 2,3,7,8,12,13,17,18-octaethylporphyrin (I), 5-nitro-2,3,7,8,12,13,17,18-octaethylporphyrin (II), 5,15-dinitro-2,3,7,8,12,13,17,18-octaethylporphyrin (III), 5,10,15-trinitro-2,3,7,8,12,13,17,18-octaethylporphyrin (IV), and 5,10,15,20-tetranitro-2,3,7,8,12,13,17,18-octaethylporphyrin (V). It is found that the values of logKb (total basicity constants) obtained for the investigated compounds consistently diminish with an increase in the number of meso-substituents: 11.85 (I) > 10.45 (II) > 10.31 (III) > 10.23 (IV) > 9.56 (V). It is shown that two opposing factors, the steric and electronic effects of the substituents, change the basic properties of the above series of compounds.