(5,10,15,20-Tetra(4-pyridil)porphinato)manganes(III) acetate modified by four mu(3)-oxo-triruthenium acetate clusters: synthesis, characterization, electrochemical behavior and catalytic activity

A novel supermolecule constituted by four mu(3)-oxo-triruthenium acetate cl usters coordinated to manganese(III)-meso -tetra(4-pyridil)porphyrin acetat e ([MnTPyP]CH3COO) has been synthesized. Characterization has been performe d by UV-Vis and H-1 NMR spectroscopy. The electrochemical behavior (cyclic voltammetry and spectroelectrochemistry) in N,N'-dimethylformamide has been analyzed in terms of five redox processes: three related to peripheral clu sters (Ru-IV,Ru-III,Ru-III/Ru-III,Ru-III,Ru-III/Ru-III,Ru-II,Ru-II) and two centered on the Mn-porphyrin core ((MnP)-P-III/(MnP)-P-II/(MnP2-)-P-II). A direct comparison has been performed between MnTCP and MnTPyP as catalysts for the cyclooctene and cyclohexane oxidation reactions. The improved sele ctivity exhibited by the supramolecular catalyst for cyclohexane oxidation has been ascribed to electronic effects on the oxomanganese(V) porphyrin sp ecies induced by the four peripheral clusters, in the formal (RuRuRuIII)-Ru -IV-Ru-III oxidation state. (C) 2000 Elsevier Science S.A. All rights reser ved.