Endocyclic extension of porphyrin π-system by interior functionalization of N-confused porphyrins

Internally alkynylated or cyanated N-confused porphyrins have been prepared, and these have been characterized by NMR, UV/Vis/NIR absorption, and X-ray analysis. The desired porphyrins have been synthesized by interconversion between an N-confused porphyrin and an N-fused porphyrin. In the case of terminal alkyne derivatives, intramolecular addition of a pyrrolic NH moiety to the triple bond occurred at ambient temperature to give etheno-bridged N-confused porphyrins. Significant bathochromic shifts in the absorbances of these compounds may be reasonably explained in terms of an increase in their HOMO energy levels due to effective overlap of the porphyrin π-orbital and the bridged alkene π-orbital. The corresponding rhodium(I) complexes have also been prepared, and these have been characterized by NMR and X-ray analysis.