Expanded Phthalocyanine Analogues: Synthesis and Characterization of New Triazole-Derived Annulenes Containing Six Heterocyclic Subunits

Abstract

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.

Triazoleporphyrazines: A New Class of Intrinsically Unsymmetrical Azaporphyrins

“…We have hence synthesized a variety of triazolehemiporphyrazines, [3] and have studied their optical and liquid crystalline properties. [3] Furthermore, we have prepared heterobinuclear and heterotrinuclear phthalocyanine-hemiporphyrazine hybrids with extended conjugation [6] and have reported the first examples of triazolehemiporphyrazine [7] and thiadiazolehemiporphyrazine, [8] expanded heteroannulenes with unusual coordination features, such as the ability to bind two or three metal ions, respectively, within their central cavities.…”

A Bottom-up Synthesis of Antiaromatic Expanded Phthalocyanines: Pentabenzotriazasmaragdyrins, i.e. Norcorroles of Superphthalocyanines

“…In contrast to the expanded porphyrins, the chemistry of expanded Pcs is quite limited. A small number of expanded Pcs have been reported . However, none of the reported expanded Pcs consist of pyrrole or isoindole units linked by nitrogen bridges, except in the case of super­phthalo­cyanines …”

Phenylene‐Bridged Expanded Porphyrazines

“…In contrast to the rich synthetic chemistry of expanded porphyrins, that of expanded analogues of porphyrazine, in which carbon atoms at the meso ‐positions are replaced with nitrogen atoms, has been rather limited, mainly because of the difference in the synthesis of porphyrazine from that of porphyrin. As rare examples, expanded porphyrazines containing heterocycles can be synthesized from mixed condensation reactions of 1,3‐diiminoisoindoline and thiadiazolediamine or a self‐condensation reaction of a [2+1]‐type acyclic precursor prepared from 1,3‐diiminoisoindoline and triazolediamine . These expanded porphyrazine molecules can be trivially named after the numbers of two component units, such as [4+2] and [3+3] expanded porphyrazines.…”