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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.

The chloroiron(III) complex of 2,8,12,18-tetrabutyl-3,7,13,17-tetramethyl-5,10-diazaporphyrin, [(Cl)FeMBDAP], was prepared and studied by X-ray crystallography and by solution (1)H NMR and UV-vis measurements. In the crystal structure of hemisolvate [(Cl)FeMBDAP] x 0.5CHCl(3), two nonequivalent [(Cl)FeMBDAP] units containing Fe1 and Fe2 are arranged in pi-dimers with considerable overlap on their concave sides. Axial chloride bonded to Fe2 is solvated by hydrogen bonding with CHCl(3). Parameters of the coordination pyramid have typical values for the spin-mixed (S = 3/2 / 5/2) Fe(III) complexes in the case of Fe1 and are characteristic for the pure intermediate-spin state for Fe2 (displacement from the (N(Pyr))(4) planes - 0.385 and 0.290 A and the average N(Pyr)-Fe bond lengths -1.992 and 1.954 A for Fe1 and Fe2, respectively). Effective magnetic moments in CHCl(3) and CH(2)Cl(2) capable of specific solvation of chloride by hydrogen bonding (4.5-4.6 micro(B) at 298 K) are indicative about mixed intermediate/high-spin state S = 3/2 / 5/2, with the S = 3/2 contribution increasing upon lowering of the temperature (4.02 micro(B) in CD(2)Cl(2) at 193 K). In nonsolvating CCl(4), C(6)D(6), and THF-d(8), the mu(eff) values are consistent with the predominantly high-spin state at ambient temperature (5.5-5.75 micro(B) at 298 K) and almost pure S = 5/2 state at low temperature (ca. 5.9 micro(B) in THF-d(8) below 270 K). Downfield isotropic shifts from 35 to 50 ppm are observed for alpha-alkyl protons and upfield shifts from -5 to -15 ppm for meso-CH protons, which is characteristic for the presence of the intermediate-spin state. The splitting of signals of the diastereotopic alpha-CH(2) protons is increased with growth of the S = 3/2 state contribution from 1.5 to 4 ppm in nonsolvating to 11 ppm in specifically solvating solvents at 298 K and further to 31 ppm at 193 K (in CD(2)Cl(2)). In the presence of DMSO addition and in methanol solution, the single CH(2) signal is observed at 25-28 ppm, and the meso-CH resonance is also shifted downfield to ca. 30 ppm, indicating the formation of six-coordinated complexes [(DMSO)(2)FeMBDAP](+) and [(MeOH)(2)FeMBDAP](+), the latter having the mu(eff) value of 4.92 micro(B) at 291 K is a spin-mixed species. The electron spin resonance spectra recorded at 77 K indicates that in frozen glasses in CD(2)Cl(2) and THF molecules in the high-spin state (g( perpendicular) approximately 6) and the predominantly intermediate-spin state (g( perpendicular) approximately 4.2-4.3) coexist together.

Monometallic derivatives of tetrakis(1,2,5-thiadiazole)porphyrazine, [TTDPzH2], with main group tervalent metal ions having the formulae [TTDPzMX] (TTDPz = tetrakis(1,2,5-thiadiazole)porphyrazinato dianion; M = Al(III), X = Cl-, Br-, OH-; M = Ga(III), X = Cl-, OH-; M = In(III), X = AcO-) were prepared and investigated by single-crystal X-ray analysis and IR and UV-vis spectroscopy as well as cyclic voltammetry and spectroelectrochemistry. The complexes [TTDPzMX] (M = Al(III), X = Cl-, Br-; M = Ga(III), X = Cl-) were obtained by direct autocyclotetramerization of the precursor 3,4-dicyano-1,2,5-thiadiazole in hot quinoline in the presence of MX3 salts (M = Al(III), Ga(III); X = Cl-, Br-) and were hydrolized to form the corresponding hydroxide derivatives, [TTDPzMOH]. The In(III) complex, [TTDPzIn(OAc)], was obtained from the free-base macrocycle [TTDPzH2] with In(OH)(OAc)2 in CH3COOH. A single-crystal X-ray study was made at 173 K on the two isostructural species [TTDPzMCl] (M = Al(III), Ga(III)), which have space group P, with a = 12.470(14), b = 12.464(13), and c = 13.947(12) angstroms, alpha = 70.72(3), beta = 79.76(3), and gamma = 90.06(3) degrees, V = 2009.3(3) angstroms3, and Z = 4 for [TTDPzAlCl] and a = 12.429(3), b = 12.430(3), and c = 13.851(3) angstroms, alpha = 70.663(6), beta = 79.788(8), and gamma = 89.991(9) degrees, V = 1983.3(7) angstroms3, and Z = 4 for [TTDPzGaCl]. Square pyramidal coordination exists about the M(III) centers, with Cl- occupying the apical position (Al-Cl = 2.171(5) and Ga-Cl = 2.193(1) angstroms). Al(III) and Ga(III) are located at distances of 0.416(6) and 0.444(2) angstroms from the center of the N4 system. The molecular packing consists of stacked double layers with internal and external average interlayer distances of 3.2 and 3.3 angstroms, respectively. IR spectra show nu(Al-Cl) at 345 cm(-1) for [TTDPzAlCl], nu(Al-Br) at 330 cm(-1) for [TTDPzAlBr], and nu(Ga-Cl) at 382 cm(-1) for [TTDPzGaCl]. The UV-vis spectra in weakly basic (pyridine, DMF, DMSO) and acidic solvents (CF3COOH, H2SO4) show the typical intense pi --> pi transition bands in the Soret (300-400 nm) and Q-band regions (640-660 nm), the bands evidencing some dependence on the nature of the solvent, particularly in acidic solutions. Cyclic voltammetry, differential pulse voltammetry, and thin-layer spectroelectrochemical measurements in pyridine and dimethylformamide of the species [TTDPzMX] indicate reversible first and second one-electron reductions, whereas additional ill-defined reductions are observed at more negative potentials. The examined species are much easier to reduce than their phthalocyanine or porphyrin analogues as a result of the remarkable electron-attracting properties of the TTDPz macrocycle which contains annulated strongly electron-deficient thiadiazole rings.

The synthesis and general chemical physical characterization of the following new classes of complexes derived from tetrakis(thiadiazole)porphyrazine (TTDPzH(2)), i.e., [(TTDPz)M(DMSO)(2)] (M = Mn(II), Fe(II)), [(TTDPz)M](H(2)O)(2), and [(TTDPz)M] (M = Mn(II), Fe(II), Co(II), Ni(II), Zn(II)) are reported. The IR spectra in the region 4000-200 cm(-)(1) show for all the species typical modes of the TTDPz skeleton and specific absorptions of the thiadiazole ring. The UV-visible spectra in different media show the expected absorptions in the Soret and Q-band regions. Inspection of the IR spectra of the two six-coordinate adducts [(TTDPz)M(DMSO)(2)] and of their corresponding species containing DMSO-d(6) clearly indicate that DMSO is O-bonded to the central metal in both species (nu(SO) located at 918 and 940 cm(-)(1) for the Fe(II) and Mn(II) species, respectively), differently from the findings for DMSO (S-bonded) in the Fe(II) and Ru(II) phthalocyanine analogues. The complexes [(TTDPz)M](H(2)O)(2) and [(TTDPz)M] are all tetracoordinate species, the water molecules for the hydrated species being very likely only weakly ligated at the peripheral thiadiazole rings of the macrocycle. Some additional information on the oxidation and spin state of the complexes has been achieved by Mössbauer spectra (Fe) and room-temperature magnetic susceptibility measurements, and data at hand are compared, when allowed, with those of the parallel classes of metal phthalocyanine complexes.

The new macrocycle tetrakis(thiadiazole)porphyrazine, TTDPzH2, has been prepared, in CF3COOH, from its corresponding Mg(II) derivative, [TTDPzMg(H2O)]·CH3COOH, which, in turn, is obtained by the reaction of magnesium(II) propylate and 3,4-dicyano-1,2,5-thiadiazole. The Mg(II) complex is also used for the preparation of the Cu(II) derivative, TTDPzCu, by reaction with copper acetate in CF3COOH. An alternative preparation allows the Cu(II) complex to be obtained from the metal-free macrocycle and Cu(OCOCH3)2 in pyridine. Like the Mg(II) complex, TTDPzH2 and TTDPzCu are obtained as solvated species (carboxylic acid, water). Practically complete elimination of the solvent molecules can be achieved by heating the species under vacuum (10-2 mmHg) at 300−310 °C, only the Mg(II) complex retaining water. TTDPzH2 and TTDPzCu can also be obtained by sublimation under vacuum (10-2 mmHg, 400−450 °C) from the parent solvated complexes. IR spectra in the range 4000−200 cm-1 allow easy identification of the different spe...