Oxyquinoliziniporphyrins: Introduction of a Heterocyclic Dimension to Carbaporphyrinoid Systems.

Oxyquinoliziniporphyrins, novel carbaporphyrinoids that incorporate quinolizone units, were synthesized. These structures exhibit moderate diamagnetic ring currents that are greatly enhanced upon protonation. Addition of trifluoroacetic acid initially gave a monocation, but this was readily converted into a dicationic species. The aromatic character of the free base and protonated species was assessed by proton NMR, nucleus-independent chemical shift calculations, and anisotropy of induced ring current plots. Stable Ni(II) and Pd(II) complexes are also reported.