Double-sided porphyrinatoiron( 11) complexes bearing covalently bound axial imidazole, 5-[2-(5imidazolylvaleryloxy) -6-(piva1oyloxy)phenyll -1 0.1 5,20-tris[2.6-bis(pivaloyloxy)phenyl] porphyrinatoiron(//) and 5-[2-(3.3-dimethylbutyryloxy) -6-(5-imidazolylvaleryloxy)phenyl] -1 0.1 5,20-tris[2,6bis(3,3-dimethylbutyryloxy)phenyl] porphyrinatoiron (11).have been synthesized. On the basis of their absorption and 'H NMR spectra, the axial imidazole group is co-ordinated. The complexes reversibly form stable dioxygen adducts in toluene at 25 "C, and the kinetics of binding of 0, and CO has been investigated. When embedded in phospholipid unilamellar vesicles, the complexes possess the ability to transport dioxygen in an aqueous medium. The binding affinity of the pivaloyloxy derivative [P+(O,) = 27 Torr] is equal to that of a red blood cell suspension and the half-life of the dioxygen adduct formed was 1.5 d under physiological conditions (pH 7.4,37 "C).

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The amphiphilic tetraphenylporphin derivative having four dialkylglycerophosphocholine groups on both sides of the ring plane (octopus-porphyrin) forms spherical monolayered vesicle membranes in water with diameters of ca. 100 nm; the vesicle constituted by octopus-porphyrinatoiron(ii)/l -dodecyl-2-methylimidazole (DMlm) can reversibly bind dioxygen at 25 "C.