Phthalocyanine-related Macrocycles: Cross Cyclotetramerisation Products from 3,4-Dicyanothiophenes, 2,3-Dicyanothiophene and 3,6-Dialkylphthalonitriles

Examples of the novel tribenzo[b,g,l]thiopheno[3,4-q]porphyrazine and tribenzo[b,g,l]thiopheno[2,3-q]porphyrazine ring systems have been obtained by cross cyclotetramerisation reactions of 3,6-dialkylphthalonitriles with 3,4-dicyanothiophenes and 2,3-dicyanothiophene respectively. Dibenzodithiopheno[2,3]porphyrazines and benzotrithiopheno[2,3]porphyrazines have also been recovered. Octaoctyl tribenzo[b,g,l]thiopheno[3,4-q]porphyrazine, in particular, shows a strongly split Q-band absorption in the far red region of the spectrum, one component of which is highly bathochromically shifted relative to the corresponding band in octaoctyl phthalocyanine. The compounds, most of which exhibit columnar liquid crystal behaviour, form even, transparent spin-coated films which exhibit a broad band absorption envelope, in some instances extending from 600 nm to beyond 800 nm. Reaction of 2,3-dicyanothiophene with a 2,5-dialkyl-3,4-dicyanothiophene, the latter in excess, gives a product mixture rich in macrocycles derived predominantly from involvement of the former.