The structure of the dicobalt “face-to-face” porphyrin with two four-atom amide bridges [Co2(FTF4)] has been determined by single-crystal X-ray diffraction methods. This compound is the first synthetic molecule that catalyzes the direct four-electron reduction of O2 to H2O in acidic media. The Co2(FTF4) molecule exhibits crystallographically imposed twofold symmetry, and hence the amide bridge is disordered. The crystal is composed of only one enantiomeric pair, d, 1-anti. The two porphyrin rings of the compound are stacked almost exactly over each other; the shear displacement of the two metal centers is only 0.13 Å. These two porphyrin rings, interplanar distance 3.54 Å, are twisted by approximately 40° with respect to each other. The cobalt atom is slightly displaced out of the mean porphyrin plane toward the diporphyrin cavity and the Co-Co distance is 3.417 (4) Å. This structure is compared with those of other cofacial porphyrin dimers. Possible O2 binding modes in this compound are also discussed. Crystallographic data: monoclinic, C2/c, Z = 4, a = 14.365 (9) Å, b = 14.923 (10) Å, c = 27.182 (18) Å, β = 95.94 (1)°, V = 5795 Å3 at -150 °C, 2971 unique data, 215 variables, R(F) (Fo2 > 3σ(Fo2)) = 0.084.
ASJC Scopus subject areas
- Colloid and Surface Chemistry