Structure analysis of a gigantic macrocyclic molecule

Expanded porphyrins, porphyrin analogues bearing more than five pyrrole rings, show many interesting features that normal porphyrins do not have. For instance, while a normal porphyrin has a planar framework, expanded porphyrins exhibit twisted structures stabilized by hydrogen bonds between pyrroles as a consequence of their flexible backbones. Because a larger macrocycle becomes more flexible, structural prediction of huge twisted porphyrinoids is difficult, and their precise structure elucidation requires SCX analysis. However, only few example of SCX analysis of huge twisted aromatic compounds with more than 10 pyrrole rings have been reported.