A relationship between the size of metal particles and their catalytic activity has been established over a nanometer scale (2-10 nm). However, application on a subnanometer scale (0.5-2 nm) is difficult, a possible reason being that the activity no longer relies on the size but rather the geometric structure as a cluster (or superatomic) compound. We now report that the catalytic activity for the oxygen reduction reaction (ORR) significantly increased when only one atom was removed from a magic number cluster composed of 13-platinum atoms (Pt13). The synthesis with an atomic-level precision was successfully achieved by using a dendrimer ligand as the macromolecular template strictly defining the number of metal atoms. It was quite surprising that the Pt12 cluster exhibited more than 2-fold catalytic activity compared with that of the Pt13 cluster. ESI-TOF-mass and EXAFS analyses provided information about the structures. These analyses suggested that the Pt12 has a deformed coordination, while the Pt13 has a well-known icosahedral atomic coordination as part of the stable cluster series. Theoretical analyses based on density functional theory (DFT) also supported this idea. The present results suggest potential activity of the metastable clusters although they have been "missing" species in conventional statistical synthesis.

Magic Number Pt 13 and Misshapen Pt 12 Clusters: Which One is the Better Catalyst? -Ptn (n = 12, 13) clusters are synthesized with atomic-level precision by using a dendrimer ligand as the macromolecular template. Addition of NaBH4 in MeOH to CHCl3/MeCN solutions of PtCl and fourth-order dendritic phenylazomethine with either a tetraphenylmethane or a triphenylpyridylmethane core successfully yields Pt12 and Pt 13 clusters, respectively. The Pt clusters are characterized by ESI-TOF-mass and EXAFS measurements, and by DFT calculations. The catalytic activity of the Pt12 clusters for the oxygen reduction reaction is more than twice that of the Pt13 clusters. -(IMAOKA, T.; KITAZAWA, H.; CHUN, W.-J.; OMURA, S.; ALBRECHT, K.; YAMAMOTO*, K.; J. Am. Chem. Soc. 135 (2013) 35, 13089-13095, http://dx.doi.org/10.1021/ja405922m ; Chem. Resour. Lab., Tokyo Inst. Technol., Yokohama 226, Japan; Eng.) -W. Pewestorf 01-009

Sediment oxygen demand (SOD) and chemical composition of the profundal zone ( ≥ 80 m water depth) of the northern part of the North Basin of Lake Biwa, Japan were analysed to identify the mechanism of formation of large-scale oxygen-deficient waters. Sediment core samples for SOD measurements were taken from five stations

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