Pavel A. Stuzhin

The chemistry of porphyrazines: an overview

The main synthetic approaches for the preparation of porphyrazines are outlined. In addition, some structural and spectroscopic properties, especially the UV-vis absorption profiles emanating from their peripheral functionalization, the modification of the tetraazaporphyrin skeleton or the arrangement of macrocycles in a supramolecular manner, are discussed. Cyclotetramerization of appropriate dinitrile derivatives or modification of peripheral substituents on porphyrazines constitute the main synthetic routes. Moreover, the use of special templates, as well as different intermediates or nonpyrrolic precursors, are tools for the attainment of azaporphyrin analogues of distinct nature and unusual characteristics.

Tetrakis(selenodiazole)porphyrazines 1: Tetrakis(selenodiazole)porphyrazine and its Mg(II) and Cu(II) Derivatives. Evidence for their Conversion to Tetrakis(pyrazino)porphyrazines through Octaaminoporphyrazines

The new phthalocyanine-like macrocycle tetrakis(selenodiazole)porphyrazine, TSeDPzH2, and its Mg(II) and Cu(II) complexes have been prepared and their general, spectroscopic (IR, UV-vis), and magnetic properties investigated. It has been observed that the peripheral selenodiazole rings of the TSeDPz skeleton can be opened by the action of H2S, with release of the Se atoms and formation of a new macrocycle, i.e. octaaminoporphyrazine, which is easily converted into tetrakis(pyrazino)porphyrazine derivatives.

Azaporphyrins and Phthalocyanines as Multicentre Conjugated Ampholites

Molecules of azaporphyrins combine two acidic pyrrole-type NH groups and several basic centres—two internal pyrrolenine nitrogen atoms and from one to four meso-nitrogen atoms—in one highly conjugated aromatic system. The acid–base properties of such unique multicentre ampholites have been the subject of numerous studies and discussions. Along with a short critical historical review the paper presents the latest results of a systematic investigation of the influence of successive aza substitution on the spectral properties and thermodynamic stability of the acid–base forms of azaporphyrins.

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.

Theoretical AM1 study of acidity of porphyrins, azaporphyrins and porphyrazines

The structure-acidity relationship in the series of non-substituted, meso- or β-substituted and β,β-annulated porphyrins and porpyrazines have been studied using the AM1 method with unrestricted Hartree-Fock basis set. With this purpose, heats of formation have been determined for the geometry optimized structures of the free base macrocycles and corresponding monoanions and dianions formed by deprotonation. Calculated first deprotonation enthalpy values show correlation with available experimental pK1a values and can be used for prediction of acidity. For porphyrazines bearing electron-withdrawing substituents or π-deficient annulated heteroarens the dianions have lower heats of formation than the corresponding neutral species and such porphyrazines are easily deprotonated upon dissolution in basic solvents (pyridine, DMF). For porphyrazines with annulated 5-member heteroarens it is predicted that deprotonation of peripheral NH groups should occur more easily than deprotonation of the internal NH groups. The influence of different types of annulation of 5- and 6-membered heteroarens to the porphyrazine core on the stability of the macrocyclic system and its acidity are also discussed.

Iron octaphenyltetraazaporphyrins: synthesis and characterization of the five-coordinate complexes of iron(III) (XFeIIIOPTAP; X=F, Cl, Br, I, HSO4)

Abstract Five-coordinate complexes of iron with octaphenyltetraazaporphine (H2OPTAP) containing halide or hydrosulfate as an axial acido-ligand (XFeIIIOPTAP; X=F, Cl, Br, I, HSO4) have been synthesized by treatment of the μ-oxo dimer, O(FeIIIOPTAP)2, or of the anionic dihydroxo complex [(HO)2FeIIIOPTAP]− with the corresponding acid HX. UV-Vis, IR, 1H NMR and Mossbauer spectroscopy methods and magnetic susceptibility measurements have been used for the characterization of these complexes. Magnetic moment (μeff=3.44 for chloro and 2.98 for bromo complex at r.t.), Mossbauer parameters (δFe=0.24−0.29 mm s−1 and ΔEQ=2.8-3.6 mm s−1 at 82 K) and the character of the paramagnetic shifts of the phenyl proton resonances (o-Ph 5.4–6.1 ppm, m-Ph 10.6–11.6 ppm and p-Ph 3.1–3.5 ppm in CHCl3 at r.t.) are consistent with an intermediate spin state ( S= 3 2 ) of iron in these complexes. The origin of the absorption bands in the UV-Vis and IR spectra is discussed and their assignment is proposed. A comparison with the corresponding five-coordinate complexes of porphyrins and phthalocyanine is made.

Porphyrazines with Annulated Diazepine Rings, 1 Synthesis and Characterization of Tetrakis‐2,3‐(5,7‐diphenyl‐6H‐1,4‐diazepino)porphyrazine and Its MgII, CuII, and ZnII Complexes – X‐ray Crystal Structure of 2,3‐Dicyano‐5,7‐diphenyl‐6H‐1,4‐diazepine

A new class of porphyrazine macrocycles carrying peripheral diazepine rings, i.e. tetrakis-2,3-(5,7-diphenyl-6H-1,4-diazepino)porphyrazine [Ph2DzPzH2](H2O)4, and its metal derivatives of formula [Ph2DzPzM](H2O)x=2–7 [M = MgII(H2O), CuII, ZnII] have been prepared and characterized. Single crystal X-ray work on the monomeric precursor 5,7-diphenyl-2,3-dicyano-6H-1,4-diazepine, Ph2(CN)2Dz, and NMR spectra (CDCl3, (CD3)2SO) and UV/Vis spectra in solution of different media (basic, neutral, acid) of the monomer and its macrocyclic derivatives have provided information on the conformational flexibility of the diazepine ring as well as on the structural and electronic features of the entire porphyrazine skeleton.

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.

Synthesis and Spectroscopic Properties of Low-Symmetry Tribenzoporphyrazines with Annulated 6H-1,4-Diazepine Ring

Template co-condensation of 2,3-dicyano-5,7-diphenyl-6H-1,4-diazepine 1 with 10-fold molar excess of phthalodinitrile 2 in the presence of MgII propoxide or butoxide in the corresponding alcohol leads to a mixture of MgII-diazepinoporphyrazines 3–6 from which the low symmetry 3:1 species 3, which contains three annulated benzene and one 1,4-diazepine rings, is separated by column chromatography as the aquo complex, [2,4-diphenyltribenzo[b,g,l][1,4]diazepino[2,3-q]porphyrazinato(aquo)magnesium(ii)], [Bz3DzPzMg(H2O)]. The complex 3 can be demetalated in acetic or trifluoroacetic acids under mild conditions with formation of the corresponding free-base [Bz3DzPzH2] 3a. This latter is also formed by co-cyclotetramerization of the same precursors 1 and 2 in the presence of sodium ethoxide in ethanol or lithium butoxide in butanol followed by demetalation of the intermediate disodium or dilithium salts in acid medium. The constitution and structure of the obtained compounds were established on the basis of elemental analysis, mass spectrometry, and 1H NMR spectra. The variable temperature 1H NMR measurements provide evidence that in porphyrazines 3 and 3a the 1,4-diazepine ring exists predominantly in the 6H-form over a wide temperature range. The free energy of activation for the inversion of the 1,4-diazepine ring determined for 3 is 45.6 ± 1.7 kJ mol–1. Solution UV-visible spectra measurements in acidic media (CH2Cl2/CF3COOH) provide evidence that the MgII complex 3 is easily protonated on the meso-N atom of the porphyrazine macrocycle followed by slow demetallation with formation of the free base 3a in its neutral form or as a species protonated on the diazepine ring.

First tellurium-containing phthalocyanine analogues: strong effect of tellurium on spectral, redox and conductivity properties of porphyrazines with annulated chalcogenodiazole ring(s)

The first tellurium-containing phthalocyanine analogues have been prepared and spectroscopically characterised: the Mg(II) complex of tetra(1,2,5-telluradiazolo)porphyrazine and a low-symmetry tert-butyl substituted Mg(II) tribenzoporphyrazine with one fused 1,2,5-telluradiazole ring. It was observed that the introduction of Te atom(s) reduces the energy of the Q-transition, facilitates the reduction of the macrocycle and strongly increases the conductivity of thin films.