Carbenaporphyrins: A Missing Ligand in N-Heterocyclic Carbene Chemistry

The successful synthesis of a carbenaporphyrin ligand based on carbazole and triazolylidene (CTP) is reported. Instead of a macrocyclic aromatic or antiaromatic character, the aromaticity of each heterocyclic moiety is preserved, which results in optical properties different from porphyrins, e.g. fluorescence. In Li⁺ and Sc³⁺ complexes the ligand reveals striking geometric similarity to porphyrins, but is stronger electron donating.