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The singlet oxygen luminescence method and the photochemical methods using 1,3-diphenylisobenzofuran (DPBF) or bilirubin ditaurate (BDT) as chemical quenchers were employed to determine the single oxygen quantum yields (Φ_Δ) of different phthalocyanines and tris(2,2″-bipyridyl)ruthenium(II) dichloride in dimethylformamide (DMF) or aqueous micellar solution of 0.1 M CTAC (cetyltrimethylammonium chloride). Additionally, a perylenetetracarboxylic acid diimide derivative was examined in DMF. In a series of tetrasulfonated phthalocyanines (PTS) the following order was found: ZnPTS > GaPTS > AlPTS ≈ H₂PTS > CoPTS. In general, the singlet oxygen quantum yields are higher in DMF than in 0.1 M CTAC/H₂O. The results obtained with the photochemical systems are comparable with those obtained by the photophysical method.

The photochemical DPBF method results in absolute values of Φ_Δ. However, in micellar solution, chain reactions occur when DPBF is used as chemical quencher in the photo-oxidative process. This problem can be overcome by adding sodium thiosulphate which is able to destroy the endoperoxide initially formed. BDT can be used as quencher in different solvents to determine Φ_Δ relative to a photosensitizer with known singlet oxygen quantum yield in the respective solvent.

In comparison to the chemical methods the luminescence method exhibits the advantage that side reactions of the quencher are excluded. But normally the Φ_Δ values obtained are relative to a reference, since absolute determinations need much larger efforts.

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.

The present contribution summarizes the most recent results on the synthesis and chemical physical characterization of the new classes of porphyrazine macrocycles having annulated five- and seven-membered heterocyclic rings, i.e. tetrakis(thiadizole)porphyrazine, TTDPzH₂, tetrakis(selenodiazole)porphyrazine, TSeDPzH₂, tetrakis-2,3-(5,7dipheny-6H-1,4-diazepino)porphyrazine, Ph₈DzPzH₂, and a number of their metal derivatives, prepared by using, respectively, 3,4-dicyano-1,2,5-thiadiazole, 3,4-dicyano-1,2,5-selenodiazole, and 5,7-diphenyl-2,3-dicyano-6H-1,4-diazepine as monomeric precursors. The available information indicates that, owing to the presence of electron rich and soft atoms (S, Se) inserted in the proximity of the porphyrazine core, the TTDPz and TSeDPz macrocycles, closely resembling their phthalocyanine analogues in terms of structural and electronic features and physical behaviour (solubility, thermal stability, vaporizability, etc.), might be promising new materials for applicative properties. Particularly interesting is the operated peripheral ring opening of the TSeDPz macroxycle leading to the formation of octaaminoporphyrazine, followed by its conversion to a tetrakis(pyrazino)porphyrazine. The macrocycles containing the Ph₈DzPz skeleton, due to the presence of the external non planar diphenyldiazepine units, appear to exhibit a distinct physical behaviour, which can be probably modulated by appropriate alternative substitutions in the 5, 6, and 7 positions of the diazepine rings.

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.

This paper summarizes what was discussed in a lecture at the IXth International Conference on Porphyrin Chemistry held in Suzdal (Russia) in September 2003. The development of porphyrin chemistry in former Soviet Union countries and over the world are discussed. Some ideas which were cultivated during three conditional porphyrin periods (1930-1960, 1960-1980 and 1980-2000) are also discussed.

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 pK_1a 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.

A series of new porphyrazines with oligo(ethylene oxide) thioalkoxy side chains has been synthesized. Study of the phase transitions reveals the absence of liquid crystallinity. Due to the ethylene oxide moieties, the solubility in a variety of solvents is dramatically increased. This allowed the first study of solvent effects on the photophysical properties (absorption and emission) in water and chloroform. The complexation of the porphyrazines with the redox couple LiI/I₂ has been studied. No effect on the aggregate formation has been observed in solution, while in a film incorporation of an increased amount of LiI/I₂ leads to a disturbance of the aggregates. At temperatures up to 100°C the porphyrazine - LiI/I₂ complexes are stable in the liquid phase, but from 115°C onwards, small crystallites of LiI are formed in the isotropic liquid.

The complex μ-oxo-bis[tetrakis(thiadiazole)porphyrazinato-aluminum(III)], [(TTDPzAl)₂O], has been obtained from the corresponding mononuclear Al(III) hydroxo-complex, [TTDPzAlOH], by refluxing a solution of this latter in α-chloronaphthalene or by heating the solid hydroxo species (250–300 °C) under vacuum (10^-2 mmHg). The complex, which appears as a stable species in air, shows a typical IR absorption at 983 cm^-1, assigned as ν_as(Al-O-Al). Contact with water determines disappearance of this absorption consequent to the formation of the related hydroxide. [(TTDPzAl)₂O], insoluble in most organic non-donor solvents, and very scarcely soluble in dimethylsulfoxide and dimethylformamide, shows some instability in pyridine, with probable breaking of the μ-oxo bridge and formation of the mononuclear hydroxide. Single crystals suitable for X-ray analysis were obtained by subliming [(TTDPzAl)₂O] under vacuum at 500 °C under a continuous N₂ flow. Crystal data for [(TTDPzAl)₂O], C₃₂Al₂N₃₂OS₈: a = 7.613(2) Å, b = 11.280(2) Å, c = 23.363(5) Å, β = 96.869(3)°, space group P2₁/c (n. 14), U = 1991.9(7) ų, Z = 2, R(F)^a = 0.0492, wR(F²) = 0.1024. The μ-oxo bridged complex has a central linear Al-O-Al bond system, with the Al(III) atoms displaced out of the respective N₄ square planar coordination sites by 0.441 Å and the two TTDPz planes lying in an eclipsed position, the overall structure of the complex approaching closely that of the related phthalocyaninato complex [(PcAl)₂O]. Intermolecular contacts, instead, are definitely different for the two species, the type found present in [(TTDPzAl)₂O] highly reminiscent of those of other previously reported "thiadiazoleporphyrazine" macrocycles, with the observed short inter-unit contacts between adjacent TTDPz macrocycles again determined by the presence in the TTDPz framework of the annulated peripheral (S, N)-containing heterocycles.

Starting from easily available thiophenols (PhSH (1a), 4-tert-butyl-PhSH (1b)) and oxalylchloride we have prepared 2,3-thianaphtenequinones 2a,b which were then successively converted to thianaphthene-2,3-dicarboxylic acids 4a,b their imides 10a,b, diamides 9a,b and finally to thianaphthene-2,3-dicarbonitriles 11a,b — the key precursors for the series of novel porphyrazines bearing four 2,3-annulated thianaphthene moieties. The free-bases 12a,b were obtained by cyclotetramerization of the dinitrile 11a,b in the presence of lithium in n-pentanol, while the reaction with magnesium(II) butoxide in n-butanol leads to the Mg(II) complex 13a. Complexes with Al(III) (14a,b), Ga(III) (14a,b) and In(III) (14a,b) were obtained by the template cyclotetramerization of the dinitriles 11a,b in a melt with the corresponding (hydroxy)acetates. Tetra(2,3-thianaphtheno)porphyrazine 12a and its metal complexes 13a–15a are only sparingly soluble in common organic solvents, the solubility is enhanced for their tert-butyl substituted derivatives 12b, 14b–16b. The study of the electronic absorbtion spectra has revealed that the extension of the porphyrazine π-chromophore by fusion of four thianaphthene fragments due to the angular type of their annulation (similar to that found in 1,2-naphthalocyanines) and negative inductive effect of the sulfur atoms has an effect on its spectral properties which is less than in the case of the isoelectronic naphthalene rings fusion and is comparable with the influence of four benzene rings in phthalocyanines.

The novel polyfluorinated thioalkyl-porfirazine 2,3,7,8,12,13,17,18-octakis(1,1,1,2,2,-3,3,4,4-nonafluorohexylthio)-5,10,15,20-21H,23H-porfirazine was synthesized to investigate the fluorine effect on self-aggregation, electrochemical, and spectral properties of this class of tetrapyrrole macrocycles. This compound showed an ordered and quite thermally stable columnar discotic mesophase, never seen in non-fluorinated symmetrically substituted “free-base” thioalkyl-porphyrazines, revealing a significant effect of fluorine on molecular self-assembling properties. An important effect of fluorination was also observed on the spectral and electrochemical properties of the molecule, giving rise to a hypsochromic shift in the 400–700 nm range of UV-vis absorption spectrum and to a marked cathodic shift of the reduction potentials in respect to the non-fluorinated analogs. DFT and TDDFT calculations has been undertaken to elucidate the origin of the observed behavior. Interestingly, HOMO, LUMO, and band-gap values together with its mesomorphic properties make this compound a promising material for organic photovoltaics.

Molecular templating is an attractive method to improve the crystallinity and control the molecular orientations of organic thin films. Here, we report on the templating effects of an organic $n$-type semiconductor, tetrakis(thiadiazole)porphyrazine (H₂TTDPz), on the structure and optical absorption of a $p$-type semiconductor, copper phthalocyanine (CuPc). X-ray diffraction measurements for the double layer thin films, CuPc/H₂TTDPz, indicate a face-on orientation of CuPc, which is replicating the structure of the H₂TTDPz thin films, even though the CuPc thin films usually form edge-on-type thin films. The optical absorption measurements show new low-energy transitions in the templated CuPc films.

Novel Mg^II 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$H$-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$H$ tautomeric form both in the dinitrile precursor 2 and the Mg^II 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.