Synthesis, X-ray crystal structure, UV/Visible linear and nonlinear (optical limiting) spectral properties of symmetrical and unsymmetrical porphyrazines with annulated 1,2,5-thiadiazole and 1,4-diamyloxybenzene moieties

Co-cyclization of 1,2,5-thiadiazole- 3,4-dicarbonitrile and 3,6-diamyloxyphthalodinitrile in the presence of magnesium or lithium amylate in amyl alcohol leads to mixtures containing the Mg derivatives of the symmetrical species tetrakis(1,2,5-thiadiazolo)- porphyrazine, (S4)PzH2 , and tetrakis( 1,4-diamyloxybenzo)porphyrazine, (A4)PzH2 , and the low-symmetry macrocycles bearing peripheral 1,2,5-thiadiazole and 1,4-dipentyloxybenzene rings in the ratio 3:1, 2:2 (cis and trans), and 1:3, that is, (SA3)PzH2, (S2A2)PzH2 , (SASA)PzH2 , and (S3A)PzH2 , respectively. The basic Mg materials were converted to the corresponding freebase macrocycles by treatment with CF3COOH. The species were separated from the mixtures by chromatography, either as Mg complexes or demetalated materials. With results on (S4)PzH2 and (SA3)PzH2 in hand, including crystallographic work on the latter, a general chemical physical investigation has been carried out of all the symmetrical and unsymmetrical free-base macrocycles. The structures of the species (S2A2)PzH2 and (A4)PzH2 . were elucidated by single- crystal X-ray crystallography. The effect of the progressive variation of the macrocyclic structure along the series, from the symmetrical (S4)PzH2 to its symmetrical partner (A4)PzH2 via the low-symmetry 3:1, 2:2 (cis and trans), and 1:3 macrocycles, was studied by IR, 1H NMR, and UV/Vis linear and nonlinear (optical limiting) measurements. The results are interpreted on the basis of intra- and intermolecular interactions between the electron-deficient 1,2,5- thiadiazole and the electron-donating 1,4-dipentyloxybenzene moieties.