Opposing influences of ruffling and doming deformation on the 4-N cavity size of porphyrin macrocycles: the role of heme deformations revealed.

Ruffle- and dome-type porphyrins were developed as model systems to investigate the role of deformation mode and degree of distortion in heme. Their crystal structures revealed that as the degree of distortion increases, cavity size can be contracted in the ruffle mode and expanded in the dome mode, and the size of cavity can exceed the limit of free metal ions from the fourth period (see scheme).