A novel modular approach to triazole-functionalized phthalocyanines using click chemistry.

A novel, elegant, and significantly improved protocol for the synthesis of a protected octaacetylene phthalocyanine is described. Inexpensive, mild, and environmentally benign iodination of 1,2-dibromobenzene and subsequent optimized chemoselective palladium-catalyzed cyanation are employed to effectively build up the key intermediate 4,5-dibromophthalonitrile in two steps. Introduction of the tert-butyldimethylsilyl-protected acetylene moieties via a Sonogashira cross-coupling provides the desired phthalonitrile precursor that, after cyclization, yielded the protected octaacetylene phthalocyanine. Subsequently, in situ deprotection and "clicking" are employed as a highly efficient and quantitative route to a novel class of octatriazole-functionalized phthalocyanines. The ability of such triazole-derived phthalocyanines to form well-defined supramolecular structures upon doping with zinc(II) triflate is demonstrated.