Pyridino[3,4]tribenzoporphyrazines: edge-to-face versus face-to-face assemblies among phthalocyanine analogues

The metal-free and nickel derivatives of hexaoctylpyridino [3,4] tribenzoporphyrazine generate conventional face-to-face aggregates in solution, exhibit columnar mesophases and form columnar assemblies upon evaporation of solutions. By contrast, the zinc derivative forms alternative edge-to-face complexes through axial ligation of one molecule to the zinc atom of another, a process which inhibits mesophase behaviour and leads to new types of visible region absorption signatures.