ABSTRACT
Colloidal platinum nanoparticles with diameters of 2-5 nm on carbon supports are currently regarded as the best catalysts for the oxygen reduction reaction. However, the particle size is limited by the conventional preparation methods that are used to synthesize small platinum particles; the inherent activity of ultrasmall nanoparticles has not yet been revealed. We present a practical synthesis for ultrafine subnanometre platinum clusters using a spherical macromolecular template with no disorder in molecular weight or structure. The template, a phenylazomethine dendrimer, offers control of the number of metal complexes in an assembly through stepwise complexation, allowing the complexes to accumulate in discrete nano-cages. Subsequent reduction of Pt(IV) chloride to Pt(0) results in the formation of platinum clusters composed of a defined number of atoms. As a result of exceptionally small particle size, the clusters exhibit very high catalytic activity for the four-electron reduction of oxygen molecules.
ABSTRACT
[structure: see text] A new type of phenylazomethine dendrimer with a tetraphenylmethane core was synthesized by a convergent method. The properties of the dendrimer were confirmed by thermal, rheological, TEM, and AFM measurements. A stepwise radial complexation was clearly observed with SnCl(2).
Subject(s)
Azo Compounds/chemistry , Azo Compounds/chemical synthesis , Dendrimers/chemistry , Dendrimers/chemical synthesis , Porphyrins/chemistry , Porphyrins/chemical synthesis , Toluene/chemistry , Molecular Structure , Tin Compounds/chemistryABSTRACT
[structure: see text] Novel phenylazomethine dendrimers having a cyclam core were synthesized by the convergent method. The dendrimers showed selective coordination with zinc chloride on the cyclam ring and with tin chloride on the imine groups. The metal cyclam exhibits a metal-assembling function to provide a multinuclear hetero metal complex.
