V. B. Sheinin

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.

Synthesis and spectral characteristics of (tetrabenzoporphyrinato)chloromanganese(III)

A method is developed of synthesis of (tetrabenzoporphyrinato)chloromanganese(III) from tetrabenzoporphyrinatocadmium( II) (as a donor of the macrocyclic ligand) and the salts, manganese acetate MnAc2 and dichloromanganese MnCl2, in boiling dimethylformamide in the presence of atmosperic oxygen in 80% yield. It is found that under the conditions of the synthesis tetrabenzoporphyrinatomanganese(II) is formed which can be oxidized by the atmospheric oxygen to (tetrabenzoporphyrinato)chloromanganese(III). Absorption spectra in the visible and infrared regions, Rf and the data of elemental analysis characterizing the resulting compound are given.

Self-assembly of 2-hydroxy-tri-tert-butylphthalocyaninato zinc into J-type dimer: UV-vis, DFT and spectropotentiometric study

The role of the base nature during complexation of 2-hydroxy-9(10),16(17),23(24)-tri-tert-butyl-29H,31H-phthalocyanine ligand (1) with zinc acetate was studied by the UV-vis spectroscopy and DFT calculations. The latter allowed us to explain the selective formation of double-coordinated J-type dimer in the presence of lithium methoxide. Spectropotentiometry was used to study the nucleophilic properties of the dimeric complex in comparison with the corresponding monomer and has demonstrated the strong intramolecular interactions of macrocycles.

Physicochemical properties of an electroconductive film based on tetrakis(p-aminophenyl)porphine

A strong, optically transparent electroconductive polyporphyrin film is obtained during the electrooxidation of tetrakis(p-aminophenyl)porphine in dichloromethane on the surface of a platinum electrode. Analysis of electronic absorption and IR spectra indicates that tetrakis(p-aminophenyl)porphine is polymerized during electrooxidation via the formation of dihydrophenazine fragments. It is found that the film deposited on the electrode is insoluble in many organic solvents and mineral acids, is thermally stable when heated up to 200°C, and has a homogeneous surface with an even distribution of oligomer globules. It is found through differential scanning calorimetry that the compound deposited on the electrode is a partially crystalline polymer.

Synthesis and design of tetrapyrrole molecular receptors for alkali metal cations

Abstractmeso-Phenylporphyrins containing at the benzene ring a conformationally labile polyether fragment with a terminal pyridine ring were synthesized, and their spectral and physicochemical properties were studied. The relations found between the spectral parameters of the tetrapyrrole chromophore, on the one hand, and acid-base equilibria and complex formation with alkali metal cations, on the other, showed the possibility for design of porphyrin-based molecular ensembles possessing useful properties.

Calibration characteristics of a glass electrode in dimethyl sulfoxide in the temperature range 298–318 K

The work presents the results of the temperature calibration of an electrode system and the tabulation of pH scale in DMSO against buffer solutions.

The acid properties of benzodiamyloxyl and thiadiazole porphyrazine derivatives in the H2L-(K[2.2.2])OH-DMSO system

AbstractStep acid dissociation reactions of benzodiamyloxyl (X) and thiadiazole (Y) porphyrazine (H2PA) derivatives H2PA(X)4, H2PA(X)3(Y), H2PA(X)2(Y)2, H2PA(X)(Y)3, and H2PA(Y)4 were studied theoretically (MP3) and experimentally (spectropotentiometrically) in the H2L-(K[2.2.2])OH-DMSO system for the series H2P (porphin), H2P(μs-Pr)4, H2P(μs-Ph)4, H(N-Me)P(μs-Ph)4, H2TBP (tetrabenzoporphin), H2TBP(μs-Ph)4, H2PA (porphyrazine), H2PA(β-Ph)4, H2PC (phthalocyanine), and H2PC(t-Bt)4. The linear correlation pKa1298 = 0.32622ΔH° a1(g) − 94.62 (R = 0.998) was observed for H2PA and its symmetrical derivatives H2PA(β-Ph)4, H2PC, H2PC(t-Bt)4, H2PC(X)4, and H2PC(Y)4. Deviations of the proportionality factors in the pKa1298 = bH° a1(g) + A dependences from the theoretical value (2.303RT)−1 were explained by medium effects. Substituent effects on pKa1298 were divided into internal δ(Ri)int and external δ(Ri)ext (solvation) contributions. The compensation dependences δ(Ri)ext = −0.10911δ(Ri)int + 0.13 and δ(Ri)ext = −0.52969δ(Ri)int (correlation coefficients 0.998) were observed for simple (H2PA, H2TBP, H2P(μs-Ph)4, and H2P(μs-Pr)4) and complex (H(N-Me)P(Ph)4, H2TBP(μs-Ph)4, H2PA(β-Ph)4,H2PA(Y)4, H2PC, H2PC(t-Bt)4, and H2PC(X)4) porphin derivatives, respectively.

A Spectropotentiometric Study of Association Equilibria of Cationic Acids of Mesoporphyrin IX Dimethyl Ester with Iodide Ions in Acetonitrile

The association equilibrium of porphyrinium ions of mesoporphyrin IX dimethyl ester (H2MP) with iodide ions in acetonitrile was studied by spectropotentiometric titration. Two associates were revealed: (H4MP2+)(I-) and (H4MP2+)(I-)2; the electronic absorption spectra of these species were measured, and their formation constants were determined.

Thermodynamics of formation of porphyrin sponge in the etioporphyrin III-methanol system

The processes of dissolution and formation of porphyrin sponge in the etioporphyrin III (H2P)-methanol system at 298–318 K were studied by methods of isothermal saturation and quantitative vacuum sublimation. Recrystallization of H2P from methanol yields the porphyrin sponge H2P·3CH3OH as the equilibrium bottom phase. In the course of separation from the solution, the porphyrin sponge transforms into another polymorphous modification characterized by higher energy of stabilization with solvent molecules. In addition, a third desolvated phase, dissolving in methanol considerably more rapidly, is formed on the surface of air-dry H2P·3CH3OH crystals. The thermodynamic functions of the equilibrium between the porphyrin sponge and saturated H2P solution were determined.