Phthalorubines: Fused-Ring Compounds Synthesized from Phthalonitrile.

A series of dibenzo[a,f][1,3,5]triazino[2,1,6-cd] pyrrolizine compounds have been synthesized from phthalonitriles by a facile intramolecular cyclization process using "half-phthalocyanine" precursors, and they were characterized by X-ray crystallography, 1 H NMR spectroscopy, UV/Vis, and theoretical calculations. These compounds have spectroscopic profiles similar to phthalocyanines and porphyrins, although their inner-core structures and coordination types are totally different. They can be regarded as a new class of aromatic fused-ring compounds. The low-energy absorption of these new fused-ring compounds are located at around 600 nm. Such a low-energy π-π* transition is scarce in aromatic compounds having a similar molecular size. According to the nomenclature of phthalocyanines, these types of compounds have been named phthalorubines (Prs).