Strapped Porphyrins and Hemoprotein Models

This is a long lasting research axis which started prior to the resolution of the X-ray structure of cytochrome c Oxidase in 1995.

Fig. 1. (left) Cytochrome c oxidase (CcO) active site,1 (center) phenanthroline strapped zinc-copper complex2 and (right) a functional CcO model ligand in the form of a Zn complex.3

Some thirty years ago, based on the information from EXAFS measurements on the enzyme, a phenanthroline strapped porphyrin was designed4 to simultaneously bind zinc or iron in the porphyrin and copper in the phenanthroline. Nowadays, the phenanthroline strapped porphyrins are equipped with charged polar substituents and combined with cyclodextrins5 for the development of water soluble hemoprotein models.6

Aside from providing several efficient mimics of cytochrome c oxidase using iron-copper complexes of the ligands represented in Figure 1 (center and right),7 the phenanthroline strapped zinc-porphyrin has exhibited peculiar binding features that led to the development of self-assembled porphyrin wires.8

  1. « Structures of metal sites of oxidized bovine heart cytochrome c oxidase at 2.8 » A  by Yoshikawa et al. Science, 269, 1069-1074.
  2. Electrocatalytic reduction of oxygen with phenanthroline-trapped porphyrins J. Porph. Phthalocyanines (2007), 11, 212-221.
  3. Toward Generic Models of Hemoproteins Org. Lett. (2009), 11, 2487-2490.
  4. A highly rigid capped porphyrin J. Org. Chem. (1992), 57, 1015-18.
  5. Hydrogen bond directed molecular recognition in water in a strapped-porphyrin-cyclodextrin assembly J. Porph. Phthalocyanines (2019), 23, (4/5), 569-574
  6. A water-soluble supramolecular complex that mimics the heme/copper hetero-binuclear site of cytochrome c oxidase Chem. Sci. (2018), 9, (7), 1989-1995; Modelling haemoproteins: porphyrins and cyclodextrins as sources of inspiration Chem. Commun. (Feature Article) (2019), 55, (97), 14558-14565.
  7. Comparative studies in series of cytochrome c oxidase models  J. Inorg. Biochem. 2012, 108, 196–202; A question of flexibility in cytochrome c oxidase models Inorg. Chim. Acta (2017), 468, 232-238.
  8. From Models of Hemoproteins to Self-Assembled Molecular Wires ChemPlusChem (2017), 82, 584-594.