Pavel A. Tarakanov

A highly stable double-coordinated 2-hydroxy-tri(tert-butyl)-substituted zinc phthalocyanine dimer: synthesis, spectral study, thermal stability and electrochemical properties

A highly stable J-type dimer based on 2-hydroxy-tri(tert-butyl)-substituted zinc phthalocyanine with specific supramolecular architecture was investigated by UV-visible and fluorescence spectroscopy and by cyclic voltammetry to show strong π–π interactions and coordination between hydroxy-groups and Zn2+ central metal ions. The possibility of controlling the fluorescent properties of the obtained complex by using different solvents is demonstrated, which, along with the high thermal stability according to the thermoanalytical study, may increase practical applicability of supramolecular dimeric phthalocyanine compounds.

Porphyrazines with annulated diazepine rings 4: Synthesis and properties of MgII tetradiazepinoporphyrazine carrying exocyclic styryl fragments

A novel tetradiazepinoporphyrazine MgII complex bearing eight peripheral styryl substituents, [St8TDzPAMg(H2O)] (St = -CH=CHAr, where Ar = 4-methoxyphenyl) was prepared by template cyclotetramerization of the corresponding precursor — 5,7-distyryl substituted diazepino-2,3-dicarbonitrile — in the presence of MgII butoxide in n-butanol. UV-visible and 1H NMR spectral data indicate that the complex is strongly aggregated in non-coordinating solvents (dichloromethane, chloroform, benzene), it is dimeric in pyridine, whereas it is predominantly monomeric in dimethylsulfoxide and dimethylformamide. The fluorescence response is high for solutions in which the monomeric form is prevalent, but it is strongly quenched as the content of the dimer is increased. Evidence was obtained that dimerization occurs due to intermolecular hydrogen bonding between acidic CH2 groups in the diazepine ring (6H form) of one molecule with meso- and/or diazepine N atoms of another molecule, dimerization being also contributed by the presence of chlatrated water. In the presence of fluoride anions the dimer is destroyed with formation of the monomeric species, which is changed to the 1H form upon heating, as indicated by 1H NMR spectra.

Novel A3B-type tert-butyl-substituted tribenzodiazepinoporphyrazine: Synthesis, spectral properties and DFT study

Novel A3B-type 8(9),13(14),18(19)-tri-tert-butyl-2(5),4(7)-bis(4-tert-butylphenyl)tribenzo[g,l,q]-6H-1,4-diazepino[2,3-b]porphyrazine, which has high solubility in organic solvents, was obtained by template co-condensation of 2,3-dicyano-5,7-bis(4-tert-butylphenyl)-6H-1,4-diazepine and 4-tert-butylphthalonitrile. It was characterized by UV/Vis, (1)H, (13)C NMR spectroscopy, and MALDI-TOF/TOF mass spectrometry. We have demonstrated for the first time using fluorescence spectroscopy measurements and quantum-chemical calculations that the complicated UV/Vis spectrum of A3B-type tribenzodiazepinoporphyrazine is due to the formation of stable H-type aggregates.

The first synthesis of sandwich-type complex based on tetradiazepinoporphyrazine ligand

Sandwich-type complex based on tetradiazepinoporphyrazine ligand — bis{tetrakis(5,7-di(4-tert-butylphenyl)-6H-1,4-diazepino)[2,3-b,g,l,q]porphyrazinato}lutetium — was synthesized for the first time. The structure of the compound has been confirmed by UV-vis/NIR, 1H NMR spectroscopy, and MALDI-TOF mass spectrometry data. The introduction of annulated diazepine heterocycles to porphyrazine molecule significantly changes macrocycle reactivity and results in sandwich-type complex under conditions used for the selective synthesis of lanthanide(III) monophthalocyanines.

Cerium bis(tetradiazepinoporphyrazinate): synthesis and peculiarities of spectral and electrochemical behavior

Bis{tetrakis(5,7-bis(4-tert-butylphenyl)-6H-1,4-diazepino)[2,3-b,g,l,q]porphyrazinato} cerium has been prepared for the first time via two alternative synthetic pathways: template macrocyclization of 5,7-bis(4-tert-butylphenyl)-6H-1,4-diazepine-2,3-dicarbonitrile and direct complexation employing its cyclic tetramer, a free-base porphyrazine ligand. A combination of HRMS, UV-Vis, FT-IR and NMR spectroscopic methods allowed the identification of the tetravalent oxidation state of cerium ion in the double-decker obtained. Unlike Pc2CeIV (Pc2− = phthalocyaninate anion), the compound revealed a complicated UV-Vis spectrum that demonstrated a strong solvent dependence. A comparative electrochemical study of the cerium complex and the corresponding free-base ligand was carried out. Ligand-centered processes are diffusion controlled, whereas Ce4+/3+ transformation is characterized by slow electron transfer kinetics. This is as a result of poor accessibility of the metal center to an electrode surface due to the presence of bulky ligands, as well as a considerable structural rearrangement of the sandwich molecule.

New metalloporphyrazines as active components of membranes of anion-selective electrodes

Nickel(II), manganese(III), and magnesium(II) porphyrazines are synthesized and investigated as active electrode components of polyvinyl chloride plasticized membranes for ion-selective electrodes (ISE). The potentiometric response of membranes based on metalloporphyrazines doped with 1,3-dihexadecylimidazolium chloride (ionic additive) relative to benzylpenicillin and iodide anions is studied. It is found that the introduction of the ionic additive significantly improves the electrochemical characteristics of the ISE: the slope of the electrode function in benzylpenicillinate solutions is (58 ± 7) mV/dec and cmin = 7 × 10−5 M, and in iodide solutions, (55 ± 2) mV/dec and cmin = 6 × 10−6 M. It is shown that the ISE based on manganese(III) porphyrazine with an ionic additive can be used to determine iodide in Iodinol preparation.

Cobalt(II) porphyrazine as an active component of iodide-selective electrodes

Cobalt(II) porphyrazine is synthesized and studied as an active component of a polyvinyl chloride plasticized membrane ion-selective electrodes (ISEs). It is established that regardless of their structure, ISEs are sensitive to iodide. The introduction to the ISE of an ionic additive, ionic liquid 1,3-dihexadecylimidazolium chloride, significantly improves the electrochemical characteristics: the slope of the electrode function reaches −(57 ± 1) mV/dec, cmin = 8.3 × 10–6 M. Solid-state screen-printed electrodes the surfaces of which are modified by a 1: 4 mixture of cobalt(II) porphyrazine and ionic liquid 1,3-dihexadecylimidazolium chloride demonstrate satisfactory electrochemical characteristics: the slope of the electrode function is −(56 ± 4) mV/dec and cmin = 2.5 × 10–5 M. The potentiometric selectivity of the ISEs for iodide is studied. It is found that the effect of lipophilic interfering ions is significantly lower for solid state ISEs than for plasticized membrane electrodes.