Non-uniformly substituted phthalocyanines and related compounds: alkylated tribenzo-imidazolo 4,5)porphyrazines

The synthesis and properties of '3:1' phthalocyanines, in which three of the benzenoid rings are similarly substituted whereas the fourth is differently substituted or is replaced by a heteroaromatic ring, are overviewed with an emphasis on contributions from the group at the University of East Anglia. The synthesis of novel hepta-alkylated tribenzo-imidazolo[4,5]porphyrazines as metal-free derivatives by cross-condensation of 3,6-dialkylphthalonitrile and 1-alkyl-4,5-dicyanoimidazole is described. The compounds show Q band absorption at 701 and 660 nm. The Q band is thus hypsochromically shifted relative to the Q band absorption of the corresponding metal-free octa-alkylphthalocyanines and the metal-free hexa-alkylated derivatives of tribenzo-pyridino[3,4]-porphyrazines, tribenzo-thispheno[2,3]porphyrazines and tribenzo-thiopheno[3,4]porphyrazines. Examples of the tribenzo-irnidazolo [4,5]porphyrazines have been deposited as smooth, even and transparent spin-coated films with broad-band absorption in the region 600-750 nm. Copyright (C) 2000 John Wiley & Sons, Ltd.