Synthesis and spectral properties of tetrapyrazinoporphyrazinato metal complexes derived from sterically hindered phenol

Abstract

Dedicated to Prof. Nouria Al-Awadi on the occasion of her 55th anniversary AbstractThe synthesis of metal-containing tetrapyrazinoporphyrazines (azaphthalocyanines) bearing eight bulky substituents at the peripheral positions is described. The key precursor is prepared using a nucleophilic aromatic substitution reaction between a sterically hindered phenol and 5,6-dichloropyrazine-2,3-dicarbonitrile. Thus, azaphthalocyanine (AzaPc) derived from 2,6-isopropylphenol possesses substituents that are forced by steric constraints to adopt a non-planar conformation which drastically enhances the solubility of the macrocycles and inhibits efficient cofacial interaction of the macrocycles even in the solid state as evaluated by UV-Vis and 1 H NMR spectroscopic techniques. The intense absorption in the red visible region and photostability of these highly soluble and non-aggregated complexes enhance the dynamic activity and make these complexes potentially suitable for PDT.