A series of metal complexes of tetrakis-2,3-[5,6-di(2-pyridyl)pyrazino]porphyrazine, [Py(8)TPyzPzH(2)], having the general formula [Py(8)TPyzPzM].xH(2)O (M = Mg(II)(H(2)O), Mn(II), Co(II), Cu(II), Zn(II); x = 3-8) were synthesized by reaction of the free-base macrocycle with the appropriate metal acetate in pyridine or dimethyl sulfoxide under mild conditions. Clathrated water and retained pyridine molecules for the Mn(II) and Co(II) species are easily eliminated by heating under vacuum, the water molecules being recovered by exposure of the unsolvated macrocycles to air. Magnetic susceptibility measurements and EPR spectra of the materials in the solid state provide basic information on the spin state of the Cu(II), Co(II), and Mn(II) species. Colloidal solutions caused by molecular aggregation are formed in nondonor solvents (CH(2)Cl(2), CHCl(3)), a moderately basic solvent (pyridine), and an acidic solvent (CH(3)COOH), with the extent of aggregation depending on the specific solvent and the central metal ion. UV-vis spectral monitoring of the solutions after preparation indicates that disaggregation systematically occurs as a function of time leading ultimately to the formation of clear solutions containing the monomeric form of the porphyrazine. Cyclic voltammetry and thin-layer spectroelectrochemistry show that each compound with an electroinactive metal ion undergoes four reversible one-electron reductions, leading to formation of the negatively charged species [Py(8)TPyzPzM](n-) (n = 1 - 4). The stepwise uptake of four electrons is consistent with a ring-centered reduction, but in the case of the cobalt complex a metal-centered (Co(II) --> Co(I)) reduction occurs in the first process and only three additional reductions are observed. No oxidations are observed in pyridine or CH(2)Cl(2) containing 0.1 M tetrabuthylammonium perchlorate (TBAP). The nonlinear optical properties (NLO) of the species [Py(8)TPyzPzM] (M = 2H(I), Cu(II), Zn(II), Mg(II)(H(2)O)) have also been examined with nanosecond pulses at 532 nm in dimethyl sulfoxide solution. Reverse saturable absorption is shown by all of the [Py(8)TPyzPzM] species, which exhibit distinct behavior depending on the nature of M and extent of aggregation.

The structures of the acid-paste-prepared α-form of cobalt phthalocyanine (α-PcCo) and of its corresponding β-form (β-PcCo) have been refined through X-ray powder diffraction using the Rietveld method. The α-polymorph is triclinic, space group P1̄, cell parameters a = 12.090(8) Å, b = 3.754(2) Å, c = 12.800(9) Å, α = 88.96(6)°, β = 90.97(6)°, γ = 95.09(7)°, and Z = 1; the β-form is monoclinic, space group P21/a, cell parameters a = 14.5982(9) Å, b = 4.7937(3) Å, c = 19.4348(11) Å, β = 120.782(3)°, and Z = 2. α-PcCo consists of columnarly arranged molecules, those of adjacent columns being aligned parallel to each other, whereas a nearly perpendicular arrangement is present in β-PcCo. α-PcCo also differs from the α-forms of PcH2 and PcPt in which an angle of ca. 125° is observed between molecules of closely contacting chains. From the refined peak-profile parameters of the powder pattern a crystallite size of ∼150 Å has been estimated for α-PcCo, a value approaching that of nanocompounds. The isothermal α → β phase transition has been followed in-situ real-time by means of EDXD at two different temperatures, 152 and 250 °C. Calorimetric data indicate two different behaviors of the rate constant in the temperature ranges 182.5−220 and 220−270 °C leading to values of the empirical activation energy, E a, of 36.6(16) and 14.8(9) kcal/mol, respectively. However the various DSC runs lead to values of the phenomenological n parameter in the range 2.34−2.68 (indicating an isokinetic two-dimensional growth). According to the combined EDXD and DSC data a three-step model for the α → β PcCo phase transition may be proposed:  (1) disordering of adjacent layers of PcCo molecules from their original α-type arrangement; (2) crystallization of the β-form from the disordered phase through rearrangement of the layers of the phthalocyanine units; (3) crystal growth of the β-phase from the nuclei to an average particle size of ∼ 2500 Å, as indicated by the fitted peak-profile parameters. No evidence of the occurrence of intermediate ordered phases was observed.

The new macrocycle tetrakis(thiadiazole)porphyrazine, TTDPzH 2 , has been prepared, in CF 3 COOH, from its corresponding Mg(II) derivative, [TTDPzMg(H 2 O)]‚CH 3 COOH, 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 CF 3 COOH. An alternative preparation allows the Cu(II) complex to be obtained from the metal-free macrocycle and Cu(OCOCH 3 ) 2 in pyridine. Like the Mg(II) complex, TTDPzH 2 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. TTDPzH 2 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 species. Deuteration of TTDPzH 2 has allowed assignments of the NH stretching and bending vibrations. The UV-visible solution spectra in different media all exhibit intense absorptions in the Soret-band (300-400 nm) and Q-band (600-700 nm) regions, showing strong resemblance to those of their corresponding phthalocyanine analogues. A detailed analysis of the spectral behavior allows the electronic structure of the TTDPz macrocyclic ring to be adequately depicted. IntroductionSome of the most recent research work on the synthesis, chemical-physical characterization, and reactivity of metal phthalocyanines developed by our and joint laboratories has shown the capacity of different diphthalocyanine molecular units, i.e., Pc 2 M (M ) Ti(IV), Sn(IV)), 1 (PcFe) 2 C, 2 and (PcRu) 2 , 3 to result in the formation of linearly elongated electrically conductive materials upon oxidation with I 2 or O 2 , and the role played by the metal centers and by the close π-π contacts of the adjacent Pc rings in the efficiency of charge transfer along the chained systems has been thoroughly examined. 1-3 We have now started an investigation on porphyrazine (Chart 1a) and substituted porphyrazines and their metal derivatives, a class of materials far less studied, though recently the object of growing interest, 4 than their closely related phthalocyanine 5 (Chart 1b) and porphyrin analogues, 6 and have focused our attention on the synthesis of tetrakis(thiadiazole)porphyrazine, TTDPzH 2 (Chart 2a) and its selenium analogue and their metal derivatives as well, because electron-rich and soft substituents such as S or Se inserted into the proximity of the central