All-Aza <i>meso</i>-Benzo-Fused Triphyrins(2.1.1): Large Bathochromic Shift and Intensified Absorption via π‑Extended Conjugation

The topology that would be dependent on the effectiveness of π-electron coupling is significantly tuned by the strong conjugation that exists in fused systems. Side or linear fusion of unsaturated and conjugated hydrocarbons can have a significant effect on the π-electron cloud that is accessible in the final structure. The syntheses of three all-aza benzene-annulated triphyrins(2.1.1) were revealed. Because of the π extension, the lowest-energy Q band is not only red-shifted by more than 100 nm but also intensified to a great extent, indicating 18π-aromatic characteristics.