O. G. Khelevina

Azaporphyrins: structure of the reaction centre and reactions of complex formation☆

Abstract X-ray, spectral (UV-visible, nuclear magnetic resonance and photoelectron spectroscopy) data and quantum-chemical calculation results for porphyrins, phthalocyanines and azaporphyrins are compared and conclusions about the influence of aza substitution on the geometry of CN skeleton and on the state of NH bonds in porphyrin-type ligands are made. The studies of kinetics of metal ion incorporation in azaporphyrins are reviewed and the effect of the ligand structure, nature of metal salt and solvent on the complex formation reaction is discussed.

Modification of β‐positions in porphyrazines by substitution reactions

Peripheral modification of the porphyrazine macrocycle is an important synthetic approach to β-substituted porphyrazine derivatives, especially those which cannot be obtained via direct template cyclotetramerization of maleodinitriles and other similar synthons. The paper presents the last results of the systematical investigation of the reactivity of unsubstituted porphyrazine (tetraazaporphine) in the reactions of electrophilic and radical substitution in pyrrole rings (bromination, chlorination, chloromethylation, nitration and sulfonation) and nucleophilic substitution reactions of chloro-, bromo- and sulfo-substituted porphyrazines.

Rhodium(III) and Iridium(III) Complexes with Octaphenyltetraazaporphine: Synthesis and Study of Their Acid Forms in Proton-Donor Media

The Rh(III) and Ir(III) complexes with octaphenyltetraazaporphine (X)MOPTAP (M = Rh, X = HSO4, OH; M = Ir, X = HSO4) are synthesized and their specific acid–base interactions in the CF3COOH–CH2Cl2 and H2SO4–CH3COOH systems are studied. The quantitative characteristics of equilibria between the acid and basic forms are obtained. The stability constants рK1 of the first acid forms, in which one of the meso-N atom is protonated, for hydrosulfate (HSO4)MOPTAP complexes in the H2SO4–CH3COOH mixture are equal to –0.54 (Rh) and 0.0057 (Ir). The Ir complexes have more basic meso-N atoms due to more strong π-backbonding effect of coordination and, therefore, the second protonation stage (рK2 = –4.25) could be also observed. In the CF3COOH–CH2Cl2 mixture, the basic properties of the meso-N atoms are levelled out. For (HSO4)RhOPTAP рK1 = 1.35, while for (HSO4)IrOPTAP рK1 = 1.24 and рK2 = 0.45.

Acid base interactions of octaphenyltetrapyrazinoporphyrazine and its complex with lutetium(III) in proton-donor media

Acid base interactions of octaphenyltetrapyrazinoporphyrazine and its complex with lutetium(III) in acetic and trifluoroacetic acid media were studied, and parameters characterizing equilibria between the acid and base forms were determined. Acid-base interactions of octaphenyltetrapyrazinoporphyrazine involve primarily nitrogen atoms in the pyrazine fragments, while its lutetium(III) complex undergoes protonation at the meso-nitrogen atoms.

Synthesis and spectral properties of the Co2+ and Co3+ complexes with octaaryltetraazaporphyrins

Complexes Co2+ and Co3+ with octaphenyltetraazaporphyrin, octa(4-bromphenyl)tetraazaporphyrin and octa(4-nitrophenyl)tetraazaporphyrin were obtained and identified. The influence of the composition of reaction medium on the oxidation processes of the complexes Co2+ → Co3+ in DMF was revealed and the optimum conditions of formation of the corresponding compounds were determined.

Kinetic Stability of Indium(III) Complexes with Azaporphyrins in Aqueous Sulfuric Acid

Stability of chloro(octaphenyltetraazaporphinato)indium(III) and chloro(2,8,12,18-tetrabutyl-3,7,13,17-tetramethyl-5,15-diazaporphinato)indium(III) in 90-98 % aqueous sulfuric acid was studied. Kinetic parameters of solvoprotolytic dissociation of the complexes were determined, and a mechanism of the reaction was proposed. Diaza substitution results in more stable complexes than tetraaza substitution. The state of chloro(2,8,12,18-tetrabutyl-3,7,13,17-tetramethyl-5,15-diazaporphinato)indium(III) in a proton-donor medium was studied to show that the acid-base interaction involves one by one two meso-nitrogen atoms. Dissociation constants of the resulting acid forms were determined.

Complex formation of magnesium(II) with octaaryltetraazaporphyrins in pyridine

Complex formation of magnesium with octaphenyltetraazaporphyrin, octakis[p-(chloromethyl)phenyl]tetraazaporphyrin, and octakis[p-(dodecylsulfamoyl)phenyl]tetraazaporphyrin from corresponding ligands and magnesium acetate in pyridine and pyridine-diethylamine was studied. Increase in the basicity of the medium favors a much faster reaction. Some suggestions concerning the mechanism of the reaction were made.

State of the Rare Earth Elements Tetapyrazinoporphyrazinate Complexes in Protic Media

The acid-base interactions of tetrapyrazinoporphyrazine erbium(III) and lutetium(III) complexes in the media based on acetic and trifluoroacetic acids were investigated. The quantitative characteristics of equilibria between the acid-base forms were revealed. The structure of the acid forms was suggested. The reaction of solvoprotolytic dissociation of the octaphenyltetrapyrazinoporphyrazine lutetium(III) complex in CH3COOH-H2SO4 medium was studied and a scheme of the reaction mechanism was proposed.

Acid-base interactions of benzo-annelated porphyrazines in proton-donor media

Acid-base interactions of benzo-annelated trifluoromethylphenylporphyrazines in media based on acetic and trifluoroacetic acids were studied. The quantitative characteristics of the equilibria between acid-base species were obtained. Variation of the porphyrazine structure leads to changes not only in the macroring basicity, but also in the structure and order of formation of acidic species depending on the nature of the proton-donor medium.

Acid-Base Interactions of Benzoannelated Porphyrazines in a Dichloromethane-Trifluoroacetic Acid Solution

Acid-base interactions of benzoannelated trifluoromethylphenylporphyrazines in a CH2Cl2-CF3COOH medium were studied. The stability constants of the acid forms were determined and assumptions were made concerning their structure. It was shown that successive introduction of benzene rings into a porphyrazine molecule enhances the macrocycle basicity.