N-Fused Porphyrin: A Maverick Member of the Porphyrin Family

Fusion is a relatively new concept to produce unique members of the porphyrin family. A representative compound formed by fusion is N-fused porphyrin, which is synthesized from N-confused porphyrin. N-Fused porphyrin has an unusually narrow HOMO–LUMO energy gap and exhibits absorption in the near infrared region up to 1100 nm. Moreover, N-fused porphyrin serves as a versatile mono-negative tridentate ligand, which can bind a variety of metal centers tightly. While inner-core fusion is rare in tetrapyrrolic porphyrinoids, it becomes more common in expanded porphyrins, where a variety of novel structures are produced unanticipatedly.