The synthesis, photochemical and photophysical properties of zinc aryloxy- and alkyloxy azaphthalocyanines

Octasubstituted zinc tetrapyrazinoporphyrazines bearing butyloxy, octyloxy, 2,6-diisopropylphenoxy and 4-(hydroxymethyl)phenoxy substituents were synthesized from the corresponding 5,6-disubstituted pyrazine-2,3-dicarbonitriles using Zn(quinoline)2Cl2 in yields varying from 14 to 44%. The reaction procedure proved to be efficient for the synthesis of both alkyloxy- and aryloxy- substituted zinc tetrapyrazinoporphyrazines and did not require strictly anhydrous conditions. Optimal cyclotetramerization conditions were identified for each derivative, in terms of reaction temperature, as overheating cleaved the ether bond leaving a vacant OH group on the macrocycle. The photochemical and photophysical properties of the synthesized compounds were investigated in pyridine. Singlet oxygen quantum yields (ΦΔ) ranged from 0.49 to 0.61 and high fluorescence quantum yields (ΦF) of ∼0.30 were observed for non-aggregated compounds.