Enhanced electrochemical and electrocatalytic activity of a new supramolecular manganese-porphyrin species containing four bis(bipyridine)(aqua)ruthenium(II) complexes

A novel supramolecular species [MnTPyP{Ru(bipy)(2)H2O}(4)](PF6)(9) containing four cis-bis(bipyridine)(aqua)ruthenium(II) complexes attached to the peripheral pyridyl groups of meso-tetra(4-pyridyl)porphyrin manganese(III) (MnTPyP) has been synthesized, and employed as the precursor of a rather promising multinuclear oxo-transfer catalyst. This complex forms molecular films by dip coating. Such films are soluble in water, but can be stabilized by exchanging the PF6- anions by [Fe(CN)(6)](4-) or [Zn-TPPS](4-). They exhibit remarkable electrochemical and electrocatalytic activity, as demonstrated in the oxidation of nitrite ions. In this case, experimental evidence supports the involvement of electrochemically generated [O=Ru-IV](2+) groups in the oxidation reaction, reflecting the characteristic reactivity of high-valence metal-oxo complexes. (C) 2003 Elsevier B.V. All rights reserved.