Expanded phthalocyanine analogues: synthesis and characterization of new triazole-derived annulenes containing six heterocyclic subunits.

A series of heteroannulenes 3a-f containing four subunits of isoindole, two 1,2,4-triazole moieties, and six aza bridges have been synthesized by dimerization of the corresponding metallated, three-unit intermediates 5a-f. All these 28 pi-electron triazolephthalocyanine derivatives coordinate two metal ions within their central cavity and are the first examples of expanded heterophthalocyanines. Spectroscopic properties of these macrocycles show evidence for extended conjugation and antiaromaticity. The nature of the metal ions plays a definite role in the electronic properties of these derivatives.