Zn(II), Ni(II), Cu(II), and Fe(III) complexes of potentially bimetalating tris(pyridine- and imidazole-appended) picket-fence naphthylporphyrins withbenzyl ether spacers: Implications for cytochrome c oxidase active-site modeling

Two new unsymmetrical pick-et-fence naphthylporphyrin ligands, I and 2, and several of their metalated porphyrinato complexes have been synthesized as precursor model compounds for the binuclear (Fe/Cu) cytochrome c oxidase ( CcO) active site. 1 and 2 have a naphthylporphyrin superstructure that has been specifically incorporated to confer long-term configurational stabilit y to the atropisomeric products. The two picket-fence porphyrin ligands als o bear covalently linked, axially offset tris(heterocycle) coordination sit es for a copper ion, much like, that found in the native enzyme. Monometall ic porphyrin complexes [M = Zn(II), Ni(II), Cu(II), and Fe(III)] of the pyr idine-appended ligand 1 have been prepared and spectroscopically and magnet ically characterized. An unusual monomeric iron(IE) hydroxo porphyrin compl ex was isolated upon workup of the compound formed under ferrous sulfate/ac etic acid reflux conditions. There is general difficulty in forming binucle ar complexes of 1, which is attributed to the conformational flexibility of the benzyl ether type picket spacers. The potential of ligands such as I a nd 2 for future CcO active-site modeling studies is considered.