Tetrakis(thiadiazole)porphyrazines. 1. Syntheses and Properties of Tetrakis(thiadiazole)porphyrazine and Its Magnesium and Copper Derivatives

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 species. Deuteration of TTDPzH2 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.