Oxygen Reduction to Water by a Cofacial Dimer of Iron(III)–Porphyrin and Iron(III)–Phthalocyanine Linked through a Highly Flexible Fourfold Rotaxane

A μ-oxo-dinuclear iron complex of a supramolecular porphyrin–phthalocyanine conjugate was synthesized and its catalytic electrochemical oxygen reduction properties were investigated. In the conjugate, porphyrin and phthalocyanine units were connected to form a cofacial dimeric structure through a flexible fourfold rotaxane linkage, which was advantageous for accommodating small substrates between the iron centers. The conjugate showed efficient catalytic properties, at more positive potentials than those of other reported dinuclear porphyrinoid iron complexes, to selectively afford water through a four-electron reduction process.