Multicomponent Redox Catalysts for Reduction of Large Biological Molecules Using Molecular Hydrogen as the Reductant

One-electron reduction of the large biological molecules horse heart cytochrome c, sperm whale myoglobin, and horseradish peroxidase using H₂ as the reductant can be catalyzed by two-component, high surface area heterogeneous catalysts. The catalysts can be prepared by first functionalizing high surface area Si0₂ with a polycationic polymer into which is dispersed MCl₄^2-(M = Pd, Pt). Reduction with H₂ yields elemental Pd or Pt dispersed in the polymer. The particles are finally functionalized with a redox polymer derived from hydrolysis of Si(OR)₃ groups of an N,N'-dialkyl-4,4'-bipyridinium- or from a cobalticenium-based monomer. The two components of the heterogeneous catalysts are the buried noble metal capable of activating the H₂ and the redox polymer, which can equilibrate both with the noble metal and with the large biological molecule. Reduction of the large biological molecules in aqueous solution can be effected at room temperature and 1 atm H₂ using the catalysts under conditions where the biological materials would not be reducible with H₂ alone or when the noble metal alone would be used as the catalyst.