Azaphthalocyanines – from Synthesis through Photochemical and Photophysical Properties to Emerging Applications

Abstract

Azaphthalocyanines are macrocyclic compounds closely related to synthetic dyes – phthalocyanines. They are synthesized by cyclotetramerization of corresponding pyrazine-2,3-dicarbonitriles. Several approaches to synthesis of azaphthalocyanines, both precursors and final pro­ducts, are discussed. Interesting structure-properties relationships were found in several studies. These studies were mainly focused on photophysical and photochemical pro­perties of azaphthalocyanines showing how to design the structure of these compounds in order to maximize singlet oxygen production, fluorescence or other deactivation pathways of excited states.  Intramolecular charge transfer, an uncommon relaxation channel for azaphthalocyanines is explained. Several applications including photodynamic therapy, dark quenchers of fluorescence and sensors are discussed in relation to the structure-properties relationships.