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A series of low-symmetry ZnII, MgII, and metal-free porphyrazine derivatives with one 1,2,5-chalcogenadiazole ring (with S, Se or Te) and three pyrazines bearing tert-butylsulfanyls were synthesized. The absorption maxima of ZnII complexes lay at 660, 674, and 707 nm for S, Se, and Te, respectively, indicating increasing contribution of the 1,2,5-chalcogenadiazole rings to the π-electronic system. Photophysical studies revealed that introduction of Se as a chalcogen and ZnII as a central metal causes an increase in the singlet oxygen quantum yield, reaching a value of 0.81, whereas the combination of S and MgII gives only 0.39. This takes place on the account of the fluorescence quantum yields that differ significantly from 0.072 (ZnII+Se) to 0.51 (MgII+S). These results demonstrated the two-dimensional heavy atom effect combining the role of the chalcogen (first dimension) as well as the central metal (second dimension). Attempts to prepare oxygen-containing isologues led to the formation of an unexpected side product.

Tetrapyrazinoporphyrazines (TPyzPzs), the heterocyclic azaanalogs of the phthalocyanine macrocycle, are known since 1937 and were intensively studied especially in the last fifteen years. Due to advances in the synthesis, peripherally substituted TPyzPzs and their innumerable metal derivatives have become one of the most easily accessible phthalocyanine analogues. External substituents endow these species with solubility in organic solvents or water, influence aggregation behavior, determine spectral, electrochemical, coordination, acid–base, catalytic and photochemical properties. Moreover, by the building of new exocyclic coordination sites, they enable formation of multimetallic porphyrazines. Aspects concerning the synthesis of precursors, TPyzPz macrocycles and their metal derivatives and the related available structural information are illustrated and discussed in detail in this review including also low-symmetry species, oligomeric and polymeric TPyzPzs and higher TPyzPz homologues with fused benzene and heteroaromatic rings.

Binuclear mu-oxo-bridged Fe(III) complexes of 2,3,7,8,12,18-hexamethyl-13,17-dibutyl-5-monoazaporphine [mu-O(FeMAP)(2)], and 3,7,13,17-tetramethyl-2,8,12,18-tetrabutyl-5,15-diazaporphine [mu-O(FeDAP)(2)] have been prepared and characterised using UV/Vis, IR and (1)H NMR spectroscopies. The stretching vibrations of the mu-oxo-bridge nu(as)(Fe-O-Fe) are observed at 880 cm(-1) for mu-O(FeMAP)(2) and at 871 cm(-1) for mu-O(FeDAP)(2). The structure of mu-O(FeDAP)(2) has been confirmed by the single-crystal X-ray diffraction study of its monobenzene solvate. The Fe1 and Fe2 atoms are displaced from the mean planes formed by the coordinating N-atoms by 0.572 and 0.565 angstrom, respectively, and are connected to one another through the mu-oxo-bridge. The average Fe1-N and Fe2-N bond lengths are 2.053 and 2.050 angstrom, and the Fe1-O and Fe2-O bond lengths are 1.777 and 1.776 angstrom, respectively. The Fe1-O-Fe2 angle is 152.1 degrees, which leads to a non-coplanar arrangement of the two adjacent macrocyclic units (tilt angle 26.3 degrees) allowing for the close approach of the solvating benzene molecule to the bridging oxygen atom with a mu-O center dot center dot center dot H(benzene) distance of 2.584 angstrom. Addition of acid HX leads to dissociation of the binuclear mu-oxodiiron complexes and formation of the mononuclear pentacoordinate Fe(III) complexes (X)FeMAP and (X)FeDAP (X = AcOH, HCl, etc). Analysis of the kinetic results obtained for the reactions of the mu-oxodiiron complexes of (aza)porphyrins with acetic acid in benzene solution indicates that the stability of the mu-oxo bridge towards acid dissociation is primarily determined by its steric accessibility; for species with flexible alkyl chains in beta-pyrrolic positions the stability is much lower than in the presence of shielding meso- or beta-phenyl groups.

A series of new axially bis-coordinated (octaphenylporphyrazinato)ruthenium(II) complexes {[(Ph8Pz)RuL2], L = cyclohexyl isocyanide, CyNC, (1b); 4,4′-bipyridine, bpy, (2c); N-methylimidazole, CH3Im, (3a)} was prepared and characterized. The reaction of the bis-isocyanide adducts [(Ph8Pz)Ru(tBuNC)2] (1a) or [(Ph8Pz)Ru(CyNC)2] (1b) with monodentate N-heterocycles gave, under certain conditions, the mixed-ligand complexes [(Ph8Pz)Ru(Py)(tBuNC)] (4a), [(Ph8Pz)Ru(Py)(CyNC)] (4b) and [(Ph8Pz)Ru(CH3Im)(CyNC)] (3b). The reaction of 1a or 1b with an excess of bidentate 4,4′-bipyridine under the same conditions resulted in the formation of the corresponding dimeric species [(Ph8Pz)Ru(tBuNC)]2(μ-bpy) (2a) and [(Ph8Pz)Ru(CyNC)]2(μ-bpy) (2b) in high yield. The structures of all the complexes were unambiguously proved by 1H NMR spectroscopy, and the possibility of their self-assembly is discussed. All mixed-ligand compounds were also characterized by UV/Vis and IR spectroscopy, as well as elemental analysis. The 1H NMR spectra of these compounds are discussed in detail. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

A hybrid inorganic/organic heterojunction formed by p-type cuprous iodide CuI and n-type fullerene C60 was employed in the archetypal photovoltaic devices. The thickness of the p-CuI layer deposited on a molybdenum oxide (MoOx) anode buffer was optimized to achieve a higher efficiency, while the thickness of the n-C60 photoabsorber layer was fixed. In an attempt to obtain semitransparent devices, a trilayer MoOx/metal/MoOx cathode with a BCP underlayer was applied (metal = Ag or Mg, BCP = bathocuproine). The maximum photovoltage of such devices on a PET/ITO substrate was equal to 0.75 V for an average transparency of about 35% over the range of 380–1000 nm. Similar devices having a non-transparent Al cathode in conjunction with an Alq3 underlayer generate photovoltage of 0.82 V (Alq3 = tris-8-hydroxy­quinolinato-aluminum), which shows the important effect of hybrid junctions in multilayer organic-based devices.

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.

Cross cyclotetramerization of bis(4-tert-butylphenyl)fumaronitrile with 1,2,5-selenadiazole-3,4-dicarbonitrile in the presence of magnesium butoxide as template afforded a mixture of magnesium(II) porphyrazine complexes, from which magnesium complex of 5,6,8,9,11,12-hexakis(4-tert-butylphenyl)[1,2,5]selenadiazolo[3,4-b]porphyrazine was isolated by column chromatography and was subjected to demetalation on treatment with trifluoroacetic acid. The free ligand was found to undergo protonation at one meso-nitrogen atom in acid medium and deprotonation of one pyrrole ring to form monoanion by the action of bases. Reductive deselenation of the title compound with formation of vicinal diamino porphyrazine was studied by spectral and kinetic methods, and a mechanism involving two hydrosulfide ions was proposed.

Cross cyclotetramerization of trans-2,3-diphenylbutanedinitrile with 1,2,5-thia(selena)diazole-3,4-dicarbonitriles or phthalodinitrile in the presence of magnesium butoxide gave mixtures of Mg(II) porphyrazine complexes which were treated with trifluoroacetic acid to isolate unsymmetrical hexaphenyl-substituted 1,2,5-thia(selena)diazolo-and benzo-fused porphyrazines together with diphenyltribenzoporphyrazine. Their 1H NMR and electronic absorption spectra (in the UV and visible regions) were recorded. The effect of benzene and heteroring fusion on the electronic and steric structure and spectral properties of porphyrazine derivatives was studied in terms of the molecular orbital perturbation theory and semiempirical quantum-chemical calculations (AM1, PM3, ZINDO/S, CNDO/S).

Cross cyclotetramerization of 1,2,5-thiadiazole-3,4-dicarbonitrile and 4-tert-butylphthalodinitrile in the presence of magnesium butoxide gave a mixture of symmetric and asymmetric porphyrazine magnesium(II) complexes. One of these, (22(3),72(3),122(3)-tri-tert-butyltribenzo[b,g,l][1,2,5]thiadiazolo[3,4-q]-5,10,15,20-tetraazaporphyrinato)magnesium(II) (MgSBBB), was isolated by column chromatography and was treated with trifluoroacetic acid to obtain the corresponding free ligand (H2SBBB). The effect of the mode of heteroring fusion on the electronic absorption spectra of tribenzoporphyrazines was studied.