Synthesis and properties of azaphthalocyanines with 1,2,3,4-tetrahydropyrazino[2,3-b]pyrazine moiety

Abstract

New metal-free and zinc azaphthalocyanines (AzaPc) containing peripheral tetrahydropyrazino moiety were prepared from 5,8-disubstituted (ethyl, phenyl, benzyl) 5,6,7,8-tetrahydropyrazino-[2,3-b]pyrazine-2,3-dicarbonitriles. All investigated compounds exerted very low singlet oxygen production due to intramolecular charge transfer (ICT). Conjugation of the donor centers (nitrogens of the tetrahydropyrazino moiety) with peripheral aromatic ring (phenyl) decreased partially their ability to undergo ICT, most likely due to decreased electron density on the lone pair of the concerned nitrogens. AzaPc with peripheral benzyl substituents showed interesting aggregation behavior in toluene. Their apparent solutions were shown to be microsuspensions with particles size around 200 nm. These particles caused appearance of the new band at longer wavelengths in region 730-760 nm. © ISUCT Publishing.