A. S. Semeikin

Thermal oxidative degradation of the functionally substituted 2,2′-dipyrrolylmethenes hydrobromides and difluoroborates

Thermal oxidative decomposition of samples of crystalline hydrobromide and borofluoride complexes (BODIPY) of a series of 2,2′-dipyrrolylmethenes (HL) was studied by means of thermogravimetry in an atmosphere of air oxygen. An increase in the degree and symmetry of substitution, aromaticity, and the length of the substituents in 4,4′-positions of the pyrrole ligand rings increases stability of the BODIPY-dyes to oxidative degradation. A comparative analysis of the influence of structural factors on the thermolability of hydrobromdes (HL·HBr), d-metal (ML2) and boron(III) complexes with 2,2′-dipyrrolylmethenes was carried out.

Synthesis, physicochemical and coordination properties of 5,15-diphenyltetramethyltetraethylporphyn nitro derivatives

The 5,15-diphenyl-3,7,13,17-tetramethyl-2,8,12,18-tetraethylporphyrin nitro derivatives containing the nitro groups in the meso-positions of the porphyn ring and/or para-positions of phenyl rings were synthesized. Porphyrins were characterized by electron absorption, 1H NMR, and IR spectra. The purity and individuality of the synthesized compounds was proved by TLC and elemental analysis. Kinetic parameters of complexation reactions of the synthesized porphyrins with copper acetate in pyridine and in the mixed solvent benzene-acetic acid (7:3) depend on the degree of deformation of the tetrapyrrole cycle, on the solvation effects and electronic effects of the nitro groups.

Phenyl-substituted porphyrins: III. Relative reactivity in the nitration reaction

Study on the nitration of phenyl-substituted porphyrins showed that protonation of the porphyrin macroring does not affect the relative reactivity of the meso- and β-positions and phenyl groups.

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.

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.

A molecular receptor based on the 2,3,7,8,12,13,17,18-octaethyl-21,23-dimethylporphyrin for detection of fluoride ions: Synthesis, spectral and complexation properties

Abstract2,3,7,8,12,13,17,18-Octaethyl-21-methylporphyrin and 2,3,7,8,12,13,17,18-octaethyl-22,23-dimethylporphyrin monotriflate based on the former were synthesized. Basic and complexing properties of these compounds were studied by the method of spectrophotometric titration in acetonitrile-perchloric acid and acetonitrile-tetrabutylammonium fluoride systems at 298 K. It was established that in the system of acetonitrile-perchloric acid the cationic forms of 2,3,7,8,12,13,17,18-octaethyl-21-methylporphyrin do not form complexes with fluoride ions, whereas 2,3,7, 8,12,13,17,18-octaethyl-22,23-dimethylporphyrin monotriflate forms complexes of 1:1 composition with the fluoride ions. The protonation constant of 2,3,7,8,12,13,17,18-octaethyl-21-methylporphyrin and the stability constant of the complex of 2,3,7,8,12,13,17,18-octaethyl-22,23-dimethylporphyrin with fluoride ions in acetonitrile at the standard temperature were determined.

Synthesis and properties of (1,2,3,7,9-pentamethyldipyrrolylmethen-8-yl)-(1,2,3,7,8-pentamethyldipyrrolylmethen-9-yl)methane and bis(1,2,3,7,9-pentamethyldipyrrolylmethen-8-yl)trifluoromethylmethane dihydrobromides

Abstract(1,2,3,7,9-pentamethyldipyrrolylmethen-8-yl)(1,2,3,7,8-pentamethyldipyrrolylmethen-9-yl)-methane and bis(1,2,3,7,9-pentamethyldipyrrolylmethen-8-yl)trifluoromethylmethane hydrobromides were synthesized and characterized spectrally (1H NMR, IR, electron absorption spectra). A comparative study was performed of the effect of the bonding site (α- or β-position of the dipyrrolylmethene) with the methane structural fragment connecting two dipyrrolylmethene chromophores, and trifluoromethyl group on the spectral properties of the molecules of compounds dissolved in organic solvents of different nature and their resistance to thermal oxidative degradation.

Electrochemical properties and spectrophotometry of membranes based on holmium tetraphenylporphyrinchloride

Protolytic properties of holmium tetraphenylporphyrinchloride were studied by the method of two-phase spectrophotometric titration with potentiometric monitoring of pH of the medium. Apparent constants of the heterophase reaction of the exchange of an anion for the hydroxide ion were determined. It was found that the membranes based on holmium tetraphenylporphyrinchloride with dibutyl phthalate as a solvent-softener are selective to ions of alkaline earth metals (Ca2+ and Ba2+) in the region of pH > 7 over the concentration range from 1 up to 1×10−4 M. Selectivity coefficients were determined by two independent methods: the method of biion potentials and the method of mixed solutions. The found selectivity series coincides with traditional Hofmeister series for cations.

Study of acidity and coordination properties of 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetraphenylporphyrin in the system of 1,8-diazabicyclo[5.4.0]undec-7-ene-acetonitrile

Spectrophotometric titration method was used to study the acidic properties of 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetraphenylporphyrin in the presence of a deprotonated agent, 1,8-diazabicyclo[5.4.0] undec-7-ene, in acetonitrile. The spectral characteristics of the ionized forms and combined ionization constant for the first and second stages were revealed. The reaction of complex formation between the dianionic forms of 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetraphenylporphyrin and zinc acetate was studied.