Novel Syntheses of Porphyrazine-Phthalocyanine Hybrids

Abstract

Abstract Porphyrazines Pzs, are intermediate structures between phthalocyanines and porphyrines, each bearing the same core but with phthalocyanines having benzo-fusion on each pyrrolic unit. Phthalocyanine and porphyrin hybrids, where mixtures of C and N bridges exist, have received significant attention over recent years, in part due to the synthetic breakthroughs achieved by our group at UEA. However, C/N hybrid systems are still rare, and C/N porphyrazine-phthalocyanine hybrids (mixed C/N bridges and partial benzo-fusion) are unknown, to the best of our knowledge. The research by the Cammidge group has reported a new synthetic pathway involving the use of an AB dimer intermediate (formed from an aminoisoindoline and phthalonitrile) for the synthesis of meso‐aryl tetrabenzotriazaporphyrins TBTAPs. In this study, we have employed a similar synthetic strategy to investigate and develop new porphyrazine hybrid derivatives. The synthesis described in Chapter 2 is based on the formation of key AB dimer intermediates from trans-2,3-diphenyldinitrile derivatives starting materials, which are reacted with aminoisoindoline precursors. This dimer undergoes self-condensation in the presence of a Magnesium or Zinc template to give mixtures of M-porphyrazine complexes (unsymmetrical and symmetrical Pzs ABBA, ABBB-Ar, ABBB-N and BBBB), which were isolated and purified. The work culminated in the successful synthesis, purification, and characterisation of a wide array of porphyrazine hybrids using NMR spectroscopy, MALDI-TOF mass spectrometry, X-ray crystallography, and UV-Vis absorption spectroscopy, and experimental details are recorded in Chapter 3. Of particular note is the first direct observation of benzyl elimination during macrocyclization. While this step has been inferred from other syntheses of related hybrids, the observation of a mono-benzofused, all-N hybrid proves this process can operate under the reaction conditions.