Reversible Binding of Dinitrogen and Dioxygen by a Ruthenium Picnic-Basket Porphyrin

Article abstract of DOI:10.1021/ja00219a024

We recently reported the synthesis and characterization of ruthenium picnic-basket porphyrin carbonyl complexes.These synthetic tetraarylporphyrins bear a rigid superstructure that defines a molecular cavity on one face of the porphyrin macrocycle.Photolysis of these carbonyl complexes in a coordinating solvent results in formation of bis-solvent complexes.The bis(pyridine) complex has been structurally characterized.General methods to control axial ligation in these ruthenium picnic-basket porphyrins are presented.A transient pentacoordinate ruthenium picnic-basket porphyrin, which reversibly binds both dinitrogen and dioxygen within the protected cavity has been prepared.The N2 and O2 complexes have been characterized by UV-visible, 1H NMR, and IR spectroscopies.The diamagnetic dioxygen complex shows ν(16O-16O) at 1103 cm^-1 and thus is described as containing coordinated superoxide ion.A correlation between dioxygen binding and the Ru(III/II) potential was observed.