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The main factors governing the dimer–monomer self-assembly in 6H-1,4-diazepinoporphyrazines are shown.

Octaaryl-substituted Si(iv) corrolazine complexes, obtained by reductive ring contraction reaction of the appropriate SiPzAr8, exhibit high ability for single oxygen generation. The crucial role of acid in the Pz → Cz transformation is revealed.

Novel electron-deficient low-symmetry perhalogenated azaanalogues of subphthalocyanine, [Cl2F8N2subPc] and [Cl4F4N4subPc], were prepared by mixed co-cyclotrimerization of tetrafluorophthalonitrile and 5,6-dichloropyrazine-3,4-dicarbonitrile in p-xylene in the presence of BCl3. They were characterized by MALDI mass-spectrometry, UV-VIS, IR, [Formula: see text]C, and [Formula: see text]F NMR spectroscopy, and the molecular structure of [Cl2F8N2subPc] was established by single crystal X-ray diffraction. The spectral-luminescence and redox properties of [Cl2F8N2subPc] and [Cl4F4N4subPc] as well as peculiarities of their electronic structure are compared with the corresponding symmetrically substituted compounds - perfluorosubphthalocyanine, [F[Formula: see text]subPc], and hexachlorotripyrazinosubporphyrazine, [Cl6N6subPc]. Consecutive substitution of one and two tetrafluorobenzene fragments by dichloropyrazine units leads to stabilization of the frontier [Formula: see text]-molecular orbitals and widening of the HOMO–LUMO gap. As a result, electron-affinity of the macrocycle is increased and the first reduction potentials are increasingly shifted in the less negative region from -0.43 V for [F[Formula: see text]subPc] to -0.31 V for [Cl2F8N2subPc], -0.19 V for [Cl4F4N4subPc], and the maxima of the Q-band is shifted hypsochromically from 573 nm to 565 and 553 nm, respectively. Preliminary photoelectrical measurements indicate that novel compounds can be used as acceptor materials in non-fullerene photovoltaic cells.

Anionic crystalline complexes of free-base tetrapyrazinoporphirazines with alkyl- and phenanthrene-substituents have been isolated. Their structures and properties have been studied and discussed.

Phosphorus(v) tetrapyrazinocorrolazines having HO groups in the para-position of axial aryloxy ligands exhibit a pH-switchable PET effect and can be used for the development of solvent- and pH-sensitive fluorophores and photosensitizers.

Novel MgII porphyrazine 3 bearing four appended seven-membered tert-butyl substituted 1,4-diazepine rings was prepared via Linstead macrocyclization of 5,7-di-tert-butyl-6[Formula: see text]-1,4-diazepine-2,3-dicarbonitrile 2, obtained by condensation of diaminomaleonitrile and 2,2,6,6-tetramethylheptanedione-3,5 (1) in anhydrous ethanol in the presence of P2O5. The structure of the dinitrile precursor 2 was established by single crystal X-ray work. 1H NMR study revealed that the 1,4-diazepine ring is present in the 6[Formula: see text] tautomeric form both in the dinitrile precursor 2 and the MgII complex 3. The inversion of the tert-butyl substituted diazepine ring occurs more easily than in the case of aryl and alkenyl substituted species. Although porphyrazine 3exhibit some tendency to aggregation in low-polar solvents the presence of bulky tert-butyl substituents stabilizes the monomeric form and hinders formation of H-bonded dimers characteristic for aryl and styryl substituted analogues.

The interest in functional supramolecular systems for the design of innovative materials and technologies, able to fundamentally change the world, is growing at a high pace. The huge array of publications that appeared in recent years in the global literature calls for systematization of the structural trends inherent in the formation of these systems revealed at different molecular platforms and practically useful properties they exhibit. The attention is concentrated on the topics related to functional supramolecular systems that are actively explored in institutes and universities of Russia in the last 10–15 years, such as the chemistry of host–guest complexes, crystal engineering, self-assembly and self-organization in solutions and at interfaces, biomimetics and molecular machines and devices. The bibliography includes 1714 references.

By cyclotrimerization of tert-butyl substituted pyrazine-2,3-dicarbonitrile in the presence of boron trichloride, two positional isomers ([Formula: see text] and [Formula: see text] symmetry) of the corresponding boron(III) tripyrazinosubporphyrazines were first obtained and efficiently separated by column chromatography. The new compounds were characterized by MALDI mass-spectrometry, UV-visible and 1H NMR spectroscopy. A Q-band in the electronic absorption spectra for both fractions was observed at [Formula: see text]530 nm, which is typical for tripyrazinosubporphyrazines. The fluorescence quantum yield for the regioisomer with lower symmetry ([Formula: see text] is 1.5 times higher than for the more symmerical [Formula: see text] species ([Formula: see text] = 0.37 and 0.28, respectively). Comparative spectrophotometric study of the basic properies reveals that hexaaza substitution in benzene rings of tert-butyl substituted subphthalocyanine decreases the basic properties of meso-nitrogen atoms.

Chlorophyll dyes are widely spread in nature, and some of their semisynthetic analogs are available on the market. It is, therefore, very tempting to use these molecules in artificial photoconverting systems such as solar cells, thus avoiding problems with a labor-intensive synthesis of new photoactive components, their toxicity, biocompatibility and photostability. However, similar to a situation when mimicking a bird's flight does not necessarily lead to creation of a reliable aircraft, the attempts to make photovoltaically effective mimics of, for example, chlorophyll-based photosynthetic antenna have not so far ended up in commercial breakthroughs. This particularly concerns multilayer thin-film cells with planar or bulk molecular heterojunction(s), the type of devices that have been demonstrating a significant growth in power conversion efficiency over the past few decades. In this review we focus on those aspects of optical, self-assembling and bulk electrical properties of chlorophyll-type dyes that are of importance in solid-state photovoltaics. Starting from the very basics and tracing the developments in this field retrospectively, we come to a conclusion that the morphology of thin solution-processed films is a critical problem that arises immediately at the stage of manufacturing of a laboratory prototype. The measures that have been taken to date to improve the mobility of charge carriers both in the chlorophyll aggregates and throughout the photoconductive layer seem insufficient by comparison with their more successful counterparts like phthalocyanines.

The geometrical and electronic structures of iron and cobalt metal complexes of porphyrazine and tetra(1,2,5-thiadiazole)porphyrazine in ground and low-lying excited electronic states were determined by DFT calculations and the complete active space (CASSCF) method with following accounting dynamic correlation by multiconfigurational quasidegenerate second-order perturbation theory (MCQDPT2). A geometrical structure of D[Formula: see text] symmetry has been obtained for all four complexes. According to data obtained by the MCQDPT2 method, the complexes of cobalt and iron possess the ground states 2A[Formula: see text] and 3A[Formula: see text], respectively, and wave functions of the ground states have the form of a single determinant. It is shown that the crystal field theory (CFT) can be used to describe the sequence of electronic states of the investigated complexes. The nature of the bonds between metal atoms and nitrogen atoms has been described using the analysis of the electron density distribution in the frame of Bader’s quantum theory of atoms in molecule (QTAIM).

Electronic and geometric structures of metal-free, Al, Ga and In complexes with tetrapyrazinoporphyrazine (TPyzPA) and octachlorotetrapyrazinoporphyrazine (TPyzPACl8) were investigated by density functional theory (DFT) calculations and compared in order to study the effect of chlorination on the structure and properties of these macrocycles. The nature of the bonds between metal atoms and nitrogen atoms was described using the NBO-analysis. Simulation and interpretation of electronic spectra were performed with the use of time-dependent density functional theory (TDDFT). A description of calculated IR spectra was carried out based on the analysis of the distribution of the potential energy of normal vibrational coordinates.

The electronic and molecular structures of metal-free tetrabenzoporphyrin (H2TBP) and its complexes with zinc, cadmium, aluminum, gallium and indium were investigated by density functional theory (DFT) calculations with a def2-TZVP basis set. A geometrical structure of ZnTBP and CdTBP was found to possess D4h symmetry; AlClTBP, GaClTBP and InClTBP were non-planar complexes with C4v symmetry. The molecular structure of H2TBP belonged to the point symmetry group of D2h. According to the results of the natural bond orbital (NBO) analysis, the M-N bonds had a substantial ionic character in the cases of the Zn(II) and Cd(II) complexes, with a noticeably increased covalent contribution for Al(III), Ga(III) and In(III) complexes with an axial –Cl ligand. The lowest excited states were computed with the use of time-dependent density functional theory (TDDFT) calculations. The model electronic absorption spectra indicated a weak influence of the nature of the metal on the Q-band position.

Water-soluble sulfophenyl substituted P(v) corrolazines are effective photosensitizers in aqueous solutions. Fluorescence quenching accompanying the acid ionization of the central P(OH)2 moiety can be used for the development of pH-sensors.

Novel near-IR-absorbing porphyrazines, tetrakis-(5,7,7-trimethyl-6,7-dihydro-1H-1,4-diazepino)porphyrazines (Me12Dz4PzMgII and Me12Dz4PzH2) and their cyclohexyl derivatives (Cy8Dz4PzMgII and Cy8Dz4PzH2), were prepared by template cyclotetramerization of the corresponding 6,7-dihydro-1H-1,4-diazepine-2,3-dicarbonitriles in the presence of magnesium or lithium butoxides. The resulting macrocycles were characterized using IR, MALDI TOF, 1H NMR, and UV-Vis-spectroscopy and cyclic voltammetry. The presence of the electron acceptor imino and donor secondary amino groups in the fused 6,7-dihydro-1H-1,4-diazepine rings leads to strong polarization of the π-chromophore and shifts the Q band maxima in the near IR region (710–740 nm for the MgII complexes, and 750–770 nm for the metal free macrocycles). The NH-groups in the diazepine fragments participating in intramolecular charge transfer (ICT) strongly quench the fluorescence. Spectrophotometric titration, 1H NMR measurements and quantum chemical molecular modeling indicate that protonation of the diazepine rings which occurs on the imino nitrogen atoms switches off the ICT effect and increases the fluorescence quantum yields by 2–4 times.

The thin film properties of the new hexachloro-pyrazinosubporphyrazine compound, Cl6-pSubPz, were studied in comparison with those of an effective molecular acceptor, hexachloro-substituted subphthalocyanine, Cl6-SubPc. The latter compound is widely used in organic photovoltaics as electron acceptor (n-type layer). It was shown that with high-vacuum sublimation Cl6-pSubPz forms stable, smooth and highly textured films on many functional inorganic surfaces. The position of the main electronic absorption band (Q-band) of this compound in the visible range coincides with the maximum of the solar spectrum. Specific conductivity of the sublimed films of both studied compounds lies in the same range, but its thermal activation energy for Cl6-pSubPz is two times higher than for Cl6-SubPc.

The autocyclotetramerization of the precursor 2,3-dicyano-5,6-di(2'-pyridyl)pyrazine [(CN)2Py2Pyz] in the presence of MCl3 compounds (M = AlIII, GaIII) leads to the formation of the new mononuclear porphyrazine complexes [Py8TPyzPzMCl]·xH2O (Py8TPyzPz = tetrakis-2,3-[5,6-di(2-pyridyl)pyrazino]porphyrazinato anion). From these species, the hydroxide analogues [Py8TPyzPzMOH]·xH2O were obtained by contact with hot water, and their corresponding pentanuclear species [(PdCl2)4Py8TPyzPzMCl]·xH2O could be easily formed by the reaction with PdCl2. Physicochemical characterization of the mono- and pentanuclear macrocycles was based on elemental analysis, and mass, powder X-ray, and IR spectra. UV-vis spectral studies of the mononuclear species in solutions of DMF, DMSO, or pyridine (c ≈ 10-5-10-6 M) indicate (mainly in DMF and DMSO) the initial presence of aggregation, in some cases accompanied by the concomitant occurrence for the complex of a one-electron reduction. While disaggregation into a single species evolves spontaneously over time, the -1 charged species, eventually also found present, can be brought back to its neutral form by addition of a slight amount of HCl, the final spectrum showing the presence of the starting neutral species in its pure monomeric form. Similar aspects were faced also for the parent pentanuclear complexes. Cyclic voltammetry experiments, conducted for the mono-/pentanuclear complexes in DMF and DMSO (c ≈ 10-4 M), exhibit progressive one-electron reductions (1 → 4) characterized by E1/2 values (V vs SCE) positioned to significantly less negative values than those known for the phthalocyanine (Pc) analogues, these data confirming the previously already proven higher electron-deficient character of the MII derivatives of the Py8TPyzPz macrocycle with respect to Pc. The role of the present new series of AlIII and GaIII macrocyclic species to act as photosensitizers for the generation of singlet oxygen, 1O2, the cytotoxic agent in the anticancer treatment known as photodynamic therapy (PDT), has been explored in DMF/HCl. Among the quantum yields ΦΔ, the value found for the GaIII complex [Py8TPyzPzGaCl] (0.68), practically coincident with that observed for the TTDPz analogue (0.69), is well above those of most porphyrazines analogues (ΦΔ = 0.4-0.6), a result encouraging further research work for potential applications in the biochemical field.

Сyclotrimerization of pyrazine-2,3-dicarbonitrile and its phenyl substituted derivative in the presence of BCl3 in p-xylene leads to azaanalogues of subphthalocyanine dye. Non-substituted tripyrazinosubporphyrazine [Pyz3sPABCl] was formed only in trace amounts allowing only limited spectral study in solution. Hexaphenyl substituted derivative [Ph6Pyz3sPABCl] was isolated as chlorboron(III) complex and fully characterized by 1H, 13C, 11B NMR, IR, electronic absorption and emission spectroscopy, cyclovoltammetry and its structure was established by single crystal X-ray diffraction. Pyrazine fused subporphyrazines exhibit strong absorption bands at 300–310 and 530–550 nm. The phenyl substituted derivative [Ph6Pyz3sPABCl] has an additional intense charge transfer band at 390 nm and can be reversibly reduced at −0.81 V (vs Ag/AgCl in MeCN). The influence of pyrazine rings on the geometrical and electronic structural features and spectral properties of subporphyrazine dye was also studied using DFT and TD DFT methods. Experimental and theoretical results evidence that fusion of pyrazine rings leads to stabilization of the frontier π-molecular orbitals and endows the macrocycle with enhanced electron deficiency. Pyrazine fused subporphyrazines can be considered as perspective dyes intensively absorbing in the 300–600 nm range for applications as n-type materials in organic electronics.

Reaction of (2,3,9,10,16,17,23,24-octabutylphthalocyaninato)lanthanide(iii) acetylacetonates ((Bu)PcLn(acac), 1a-c, Ln = Lu (a), Eu (b), La (c)) with a tetrakis(5,7-bis(4-tert-butylphenyl)-6H-1,4-diazepino)[2,3-b,g,l,q]porphyrazine ligand ((tBuPh)DzPzH(2), 2) produced sandwich compounds ((tBuPh)DzPz)Ln(Pc-Bu) (3a-c), which represent the first heteroleptic double-deckers incorporating both Pc and DzPz decks. A combination of high-resolution mass spectrometry, UV-Vis/NIR, MCD, and H-1 NMR spectroscopy, and square-wave voltammetry provided unambiguous characterization of target complexes 3 indicating that their spectral and electrochemical properties are generally intermediate with respect to their homoleptic relatives. Based on the data of solution-state H-1-H-1 NMR (COSY, NOESY) correlation spectroscopy supported by DFT calculations, a dimerization tendency of compounds 3 proportional to the Ln(iii) ion size was found. The spectroelectrochemical study of 3 and the corresponding homoleptic double-deckers revealed a pronounced tendency to aggregation of the one-electron oxidized forms of DzPz-containing double-decker complexes compared to homoleptic Pc(2)Ln compounds.

Although subphthalocyanines (SubPcs) possess advantageous fluorescence properties and serve as an amazing tool to attach a recognition sensor moiety to the axial position, a limited number of switchable SubPcs have been described so far. Isosteric aza-replacement is known to improve sensing properties in closely related phthalocyanine families; however, pyrazino[2,3-b,g,l]subporphyrazines (SubPyzPzs) have not yet been investigated for use in sensing applications. Therefore, this project focuses on the synthesis and sensing abilities of pH-sensitive SubPcs and SubPyzPzs on the principle of photoinduced electron transfer (PET). 4-Dimethylaminophenoxy (for acidic pH) or 4-hydroxyphenoxy (for basic pH) groups were employed as pH-sensitive axial ligands. Electrochemical studies revealed improvements in the electron-accepting properties of SubPyzPzs (Ered-0.56 V vs. SCE) in comparison to those of SubPcs (Ered-1.0 V vs. SCE). Hydroxy groups on the axial phenoxy ligands of SybPyzPzs and SubPcs have been found to act as donors for PET. The sensing properties under basic conditions could not be studied, since all the SubPcs and SubPyzPzs decomposed under basic conditions, SubPyzPzs were more susceptible to this process. On the other hand, compounds with 4-dimethylaminophenoxy groups as axial ligands showed great potential for sensing applications. These compounds were nonfluorescent (ΦF < 0.01) in acetone due to efficient PET, while their fluorescence steeply increased by two orders of magnitude upon the addition of trifluoroacetic acid, reaching a ΦF value of up to 0.17 (λem range of 563-590 nm). These compounds maintained their sensing properties in aqueous medium after incorporation into microemulsions. The most basic derivative showed pKA = 2.95 with ΦF = 0.10 in the ON state (fluorescence enhancement factor = 46, λem = 577 nm).

Octakis(pentafluorophenyl)porphyrazinatozinc(II), [ZnPAF40], has been prepared by template cyclotetramerization of perfluorinated α,β-dicyanostylbene in the presence of ZnCl2 in a melt. Influence of perfluorination of phenyl rings on spectral, electrochemical and acid-base properties of porphyrazine macrocycle is revealed by comparison with octaphenylporphyrazinatozinc(II), [ZnPA], which was prepared similarly from trans-α,β-dicyanostylbene. B3LYP DFT calculations show that perfluorination of phenyl rings stabilizes the frontier molecular orbitals of the porphyrazine macrocycle and slightly increases the HOMO-LUMO gap. As a result the reduction of the macrocycle is strongly facilitated and observed for [ZnPAF40] at 0.26 V vs Ag/AgCl, by 0.56 V in the less negative region as compared to [ZnPA]. Perfluorination leads to hypsochromic shift of the Q-band (lowest ππ* transition) in the electronic absorption spectra from 633 nm for [ZnPA] to 623 nm for [ZnPAF40] and increases the fluorescence quantum yield ФF from 0.12 to 0.19, respectively (values in THF). [ZnPAF40] has higher efficiency in generation of singlet oxygen (ФΔ = 0.60) than [ZnPA] (ФΔ = 0.37) (in THF). Introduction of 40 fluorine atoms decreases the basicity of the porphyrazine macrocycle almost by 3 orders of magnitude according to spectrophotometric titration study in CH2Cl2-CF3COOH medium.

This review is devoted to the scientific achievements of the departments of organic chemistry in higher schools of Russia within the past decade.

Two low-symmetry analogues of perfluorinated subphthalocyanine bearing 1,2,5-thiadiazole ring(s) instead one or two benzene rings were synthesized by cocyclotrimerization of tetrafluorophthalonitrile and 1,2,5-thiadiazolo-3,4-dicarbonitrile in the presence of dichlorophenylboron(III) in chlorobenzene. New subporphyrazines have being characterized by mass-spectrometry, NMR spectroscopy ( 1 H, 11 B, 19 F), electronic absorption and emission spectra. Reduction of the symmetry of the suborphyrazine π-chromophore lifts degeneracy of the LUMO and leads to a split Q-band in the visible region (∼540–550 and ∼570–580 nm). New absorption band due to charge transfer between the subporphyrazine core and fused π-electron deficient 1,2,5-thiadiazole rings appears at 390–420 nm.

The review describes the history of development of organic chemistry in higher schools of Russia over a period of 170 years, since the emergence of organic chemistry in our country till now.

The influence of the chalcogen atom (X) on the molecular and electronic structures for the series of Mg[Formula: see text] tetra(1,2,5-chalcogenadiazolo)porphyrazines [TXDPzMg] (X [Formula: see text] O, S, Se, Te) and their monoaqua complexes [TXDPzMg(OH[Formula: see text]] was studied using DFT methods (B3LYP and PBE0 functionals) with cc-pVTZ basis sets. The chalcogen atom X changes strongly the geometry of the fused 1,2,5-chalcogenadiazole rings, but has only a weak influence on the dimensions of the coordination cavity of the porphyrazine macrocycle in [TXDPzMg] leading to its slight expansion in the sequence S < Se < Te < O. The electron density distribution was considered in terms of the natural bond order (NBO) and the natural population analysis (NPA). The frontier molecular orbitals are destabilzed along with the decrease of electronegativity of the chalcogen atoms. The a[Formula: see text] and e[Formula: see text] orbitals (HOMO and LUMO) are mainly localized on atoms constituting the internal 16-membered macrocycle, while the chalcogen atoms have the strongest effect on the composition of the filled [Formula: see text]-MOs having the a[Formula: see text] symmetry – 2a[Formula: see text] and lower lying 1a[Formula: see text] orbitals. The Gouterman type a[Formula: see text] orbital with predominant localization on the nitrogen atoms of the internal 16-membered macrocycle is 2a[Formula: see text] for the O- and S-containing complexes and for the Se- and Te-analogs it becomes 1a[Formula: see text], while the higher lying 2a[Formula: see text] orbital resides mainly on the fused heterocycles (Se/Te and C[Formula: see text] atoms). The lowest excited states have been calculated for [TXDPzMg] and used for the explanation of the peculiarities and tendencies observed in the experimental electronic absorption spectra available for the S, Se- and Te-containing Mg[Formula: see text] complexes.

Combination of experimental and theoretical methods were used to study NH-acidity and related spectral properties of tetrapyrazinoporphyrazines – octaazaanalogues of phtalocyanines. The theoretical values of deprotonation enthalpy (DPE) in gaseous phase indicate that substitution of benzene rings in phthalocyanine by pyrazine fragments strongly enhances the NH-acidity of the macrocycle which can be further tuned by introduction of substituents in pyrazine rings. Spectrophotometric titration study of octaethyl substituted tetrapyrazinoporphyrazine, [Et 8 TPyzPAH 2 ], in organic solvents (CH 2 Cl 2 , THF and DMSO) has revealed that it is easily deprotonated not only in the presence of strong bases such as tetrabutylammonium hydroxide, but also in such proton-acceptor solvent as DMSO. The thermodynamic acidity constants (pK a1 = 7.77 and pK a2 = 7.80) determined for [Et 8 TPyzPAH 2 ] in DMSO solution using spectropotentiometric titration indicate that TPyzPA macrocycle has ∼ 1000 times stronger NH-acidity than phthalocyanine. Deprotonation of [Et 8 TPyzPAH 2 ] in pyridine solution is only possible in the presence of water playing a crucial role in formation of the dianion, which can be considered as a sensitive spectral sensor for water traces. Theoretical DFT B3LYB/631++G(p,d) study has confirmed that the dianion is only stabilized as bisaqua complex [TPyzPA(H 2 O) 2 ] 2− with complementary H-bonds between water molecule and N-atoms of two opposite pyrrole rings (N…HOH…N).

The review discusses the latest advances in the directed synthesis and application of macroheterocyclic compounds in science, engineering and technology, viz. as catalysts for various processes in photo- and electrocatalysis, optical chemosensors for metal cations, selective receptors of organic compounds, inductors and selectors, in nonlinear optics, organic electronics, as magnets, photosensitizers for PDT of a number of oncological diseases and for antimicrobial PDT, etc.

The autocyclotetramerization of the precursor 2,3-dicyano-5,6-di(2'-pyridyl)pyrazine [(CN)

The template cyclotetramerization of 1,2,5-thiadiazolo-3,4-dicarbonitrile in the presence of lithium n-butoxide in n-butanol leads to the Li(I) complex of tetrakis(1,2,5-thiadiazolo)porphyrazine. Various possible structures of dilithium and monolithium complexes have been considered by DFT/B3LYP molecular modelling using the cc-pvtz basis set, and their theoretical IR and UV-VIS spectra have been calculated. The experimental 7Li NMR, IR and UV-VIS spectra measurements show that the complex contains two inequivalent lithium atoms – one is coordinated to the macrocyclic dianion to form the anionic lithate complex [TTDPaLi]−, while the other forms the solvated countercation [Li(Solv)4]+. The lithate complex is stable in protic solvents, such as methanol, and is soluble in water to give aggregated solutions. Its demetallation occurs in the presence of acids (CH3COOH, CF3COOH, H2SO4). In aprotic solvents (DMF, DMSO), the acid-catalyzed formation of the [TTDPa]2− dianion is observed which is followed by the formation of the meso-protonated form {H[TTDPa]}− at higher acid concentrations. Both processes can be reversed by the addition of a lithium salt excess or neutralization of the acid. The fluorescence quantum yield for the lithate complex [TTDPaLi]− is much higher than that for the [TTDPa]2− dianion (0.34 and 0.01 in DMSO), and this can be used for detecting low concentrations of acids and Li+ in aprotic solvents (10−6–10−5 M). The first reversible reduction of the macrocycle in the anionic lithate complex (−0.94 V vs. SCE in DMSO) is ∼0.5 V more difficult than that in the complexes with divalent metals [TTDPaM] (M = MgII, ZnII, CuII).

The Knudsen effusion method with mass spectrometric control of the vapor composition was used to study the possibility of a congruent transition to the gas phase and to estimate the enthalpy of sublimation of metal-free tetrakis(1,2,5-thiadiazolo)porphyrazine and its nickel complex (H2TTDPz and NiTTDPz, respectively). The geometrical and electronic structure of H2TTDPz and NiTTDPz in ground and low-lying excited electronic states were determined by DFT calculations. The electronic structure of NiTTDPz was studied by the complete active space (CASSCF) method, following accounting dynamic correlation by multiconfigurational quasi-degenerate second-order perturbation theory (MCQDPT2). A geometrical structure of D2h and D4h symmetry was obtained for H2TTDPz and NiTTDPz, respectively. According to data obtained by the MCQDPT2 method, the nickel complex possesses the ground state 1A1g, and the wave function of the ground state has the form of a single determinant. Electronic absorption and vibrational (IR and resonance Raman) spectra of H2TTDPz and NiTTDPz were studied experimentally and simulated theoretically.

Novel subphthalocyanine-type dye with enhanced electron-affinity was prepared by trimerization of 5,6-dichloropyrazine-2,3-dicarbonitrile in the presence of BCl3 in p-xylene. The obtained perchlorinated pyrazine fused subporphyrazine [Cl6Pyz3sPA] was characterized by mass-spectrometry, 13C and 11B NMR, IR and UV-VIS spectroscopy, cyclovoltammetry. Its molecular structure was confirmed by single crystal X-ray diffraction. To elucidate the combined effect of hexaazasubstitution and peripheral chlorination in subphthalocyanines on their electronic structure and spectral features, DFT and TD DFT calculations (B3LYP/pcseg-2 basis set) were used. Fusion of the pyrazine fragments instead of benzene rings strongly enhances the electron affinity of the macrocycle due to stabilization of the LUMO. Thus, the first reduction potential is observed at −0.20 V vs Ag/AgCl, that is macrocycle in [Cl6Pyz3sPA] is 0.5 V more easily reduced than in the peripherally hexachlorinated subphthalocyanine [Cl6sPc], the most popular subphthalocyanine-type acceptor for organic photovoltaics. The HOMO-LUMO gap is increased, so that the maximum of the Q band corresponding to the lowest ππ* transition 2a2→1e* shifts hypsochromically by 36 nm and appears at 535 nm. A distinct feature of the peripherally chlorinated macrocycles is appearance of two bands in the UV-region (B1 at ~300 nm and B2 at ~340 nm) corresponding to the electronic transitions 1a1→1e* and 2a1→1e*, respectively. Azasubstitution decreases fluorescence quantum yield, ΦF = 0.20 for [Cl6Pyz3sPA] and 0.37 for [Cl6sPc] in CH2Cl2. Spectrophotometric titrations indicate that unlike [Cl6sPc], that undergoes consecutive protonation of three meso-nitrogens in CH2Cl2-CF3COOH-H2SO4 medium, the presence of pyrazine rings in [Cl6Pyz3sPA] and their involvement in the acid-base interaction decrease the basicity of nitrogens in the meso-positions. The obtained data along with the photoelectric tests on the sublimed thin films point out at the prospects of [Cl6Pyz3sPA] for the photovoltaic applications.

Complexes of octachloro substituted tetrapyrazinoporphyrazine with AlIII, GaIII and InIII (2a-c) were synthesized by direct melting of 5,6-dichloro-2,3-dicarbonitrile (1) with corresponding metal salt (AlIII chloride, GaIII and InIII hydroxydiacetates). Metal free macrocycle (3) was prepared by catalytic demetallation of the InIII complex 2c in the presence of chloride ions. Introduction of eight chlorine atoms to the peripheral positions of the TPyzPA macrocycle leads to a bathochromic shift of the Q band by 10–15 nm indicating narrowing of the HOMO–LUMO gap by 210–260 cm−1. The presence of eight electronegative chlorine atoms facilitates the reduction of the TPyzPA macrocycle leading to the considerable positive shift of the 1st reduction potentials for the metal complexes 2a-c (E1/2 ∼ −0.16 V versus Ag/AgCl in DMSO) and for the metal free macrocycle 3 (E1/2 = −0.04 V versus Ag/AgCl in DMSO).