Porphyrazines, or tetraazaporphyrins, are
tetrapyrrole macrocycles similar to
porphyrins and
phthalocyanines. Pioneered by
Sir R. Patrick Linstead as an extension of his work on phthalocyanines, porphyrazines differ from porphyrins in that they contain -meso nitrogen atoms, rather than carbon atoms, and differ from phthalocyanines in that their β-pyrrole positions are open for substitution. These differences confer physical properties that are distinct from both porphyrins and phthalocyanines.
Synthesis
Porphyrazines are prepared by magnesium templated cyclization of maleonitriles. Cross-cyclization with
phthalonitrile or diiminoisoindole derivatives is possible introducing a flexibile synthetic route that has led to the synthesis of porphyrazines with peripheral
heterocyclic rings,
heteroatom substituents (S, O, N), peripherally bound metal atoms, and mixed -benzo porphyrazine systems.
[Miwa, H., Ishii, K., Kobayashi, N., Electronic Structures of Zinc and Palladium Tetraazaporphyrin Derivatives Controlled by Fused Benzo Rings. ''Chemistry - A European Journal'', 2004,10, 4422–4435.]
Optical properties
Porphyrazines are most well known for their intense electronic absorption throughout the
UV,
visible, and
NIR spectral regions. Electronic absorption spectra for porphyrazines are similar to those of phthalocyanines, with an intense
Soret band Soret may refer to:
Persons
* Charles Soret (1854–1904), a chemist, and son of Jacques-Louis Soret
**Thermophoresis, also known (particularly in liquid mixtures) as the Soret effect, named for him
* Frédéric Soret (1795–1865), a physicist an ...
(λ ≈ 300 - 400 nm) and Q-band (λ > 600 nm).
Porphyrazines exhibit
fluorescence from the first excited
singlet state (S
1 → S
0) at visible and NIR wavelengths which is typical of tetrapyrrole macrocycles. Dual-emission from organic fluorophores is
not common but, as observed in phthalocyanines, violet emission from an upper excited state (S
2 → S
0) is observed in porphyrazines.
References
{{Reflist
Tetrapyrroles