Poly-phenylene jacketed tailor-made dendritic phenylazomethine ligand for nanoparticle synthesis.

Synthesizing metal clusters with a specific number of atoms on a preparative scale for studying advanced properties is still a challenge. The dendrimer templated method is powerful for synthesizing size or atomicity controlled nanoparticles. However, not all atomicity is accessible with conventional dendrimers. A new tailor-made phenylazomethine dendrimer (DPA) with a limited number of coordination sites (n = 16) and a non-coordinating large poly-phenylene shell was designed to tackle this problem. The asymmetric dendron and adamantane core four substituted dendrimer (PPDPA16) were successfully synthesized. The coordination behavior confirmed the accumulation of 16 metal Lewis acids (RhCl3, RuCl3, and SnBr2) to PPDPA16. After the reduction of the complex, low valent metal nanoparticles with controlled size were obtained. The tailor-made dendrimer is a promising approach to synthesize a variety of metal clusters with desired atomicity.

Highly Accurate Synthesis of Quasi-sub-nanoparticles by Dendron-assembled Supramolecular Templates.

Quasi-sub-nanomaterials (1-3 nm) have been predicted to exhibit unique properties originating from the gray structures considered both bulk solids and molecules, while their synthesis is extremely difficult. The present study describes a new template synthesis method for quasi-sub-nanosized materials using a combination of coordination chemistry and polymer chemistry. Utilizing self-assembly of guest basic phenylazomethine dendron units onto host acidic core units with six tritylium cations, the dendron-assembled supramolecules were constructed easily and quantitatively without costly techniques. This huge supramolecular capsule accumulating multiple acidic rhodium salts in its basic ligands enabled a precise synthesis of rhodium particles via formation of multinuclear complexes. The obtained particles (Rh84 , ≈1.5 nm) have particle sizes within 1-3 nm range and were larger than conventional sub-nanoparticles (Rh14 , ≈0.85 nm), therefore the precise template synthesis of quasi-sub-nanoparticles was successfully demonstrated.

Selective Hydroperoxygenation of Olefins Realized by a Coinage Multimetallic 1-Nanometer Catalyst.

The science of particles on a sub-nanometer (ca. 1 nm) scale has attracted worldwide attention. However, it has remained unexplored because of the technical difficulty in the precise synthesis of sub-nanoparticles (SNPs). We recently developed the "atom-hybridization method (AHM)" for the precise synthesis of SNPs by using a suitably designed macromolecule as a template. We have now investigated the chemical reactivity of alloy SNPs obtained by the AHM. Focusing on the coinage metal elements, we systematically evaluated the oxidation reaction of an olefin catalyzed by these SNPs. The SNPs showed high catalytic performance even under milder conditions than those used with conventional catalysts. Additionally, the hybridization of multiple elements enhanced the turnover frequency and the selectivity for the formation of the hydroperoxide derivative. We discuss the unique quantum-sized catalysts providing generally unstable hydroperoxides from the viewpoint of the miniaturization and hybridization of materials.