˜_•¶ƒŠƒXƒg

Šwp˜_•¶ 2011

Organogold Clusters Protected by Phenylacetylene

P. Maity, H. Tsunoyama, M. Yamauchi, S. Xie, T. Tsukuda*
J. Am. Chem. Soc., 133 (50), 20123-20125 (2011)

A new class of monolayer-protected Au clusters with Au-C covalent bonds (organogold clusters) was synthesized by ligating phenylacetylene (PhCßCH) to PVP-stabilized Au clusters. Matrix-assisted laser desorption ionization mass spectrometry revealed for the first time a series of stable compositions of the organogold (Au:C2Ph) clusters.


197Au Mössbauer Spectroscopy of Au25(SG)18- Revisited

Tatsuya Tsukuda*, Yuich Negishi, Yasushi Kobayashi, Norimichi Kojima
Chemistry Letters, , 40 (11), 1292-1293 (2011).

Reanalysis of the 197Au Mössbauer spectrum of Au25(SG)18 (SG = glutathionate) based on the structure determined by sinle crystal XRD analysis gave a reasonable fit, demonstrating that 197Au Mössbauer spectroscopy is a powerful tool for predicting the structural motifs of thiolate-protected Au clusters.

Size-Controlled Synthesis of Gold Clusters as Efficient Catalysts for Aerobic Oxidation

Hironori Tsunoyama, Yongmei Liu, Tomoki Akita, Nobuyuki Ichikuni, Hidehiro Sakurai, Songhai Xie. E, Tatsuya Tsukuda*
Catal. Surv. Asia, 15(4), 293-299 (2011).

This article summarizes our recent research on the size-controlled synthesis of Au clusters stabilized by a polymer or supported by a solid, and related work reported by others. Small Au clusters have excellent, size-specific catalytic activity in the aerobic oxidation of alcohols and alkanes.

Isolation and Structural Characterization of Magic Silver Clusters Protected by 4-(Tert-butyl)benzyl Mercaptan

Yuichi Negishi*, Rio Arai, Yoshiki Niihori and Tatsuya Tsukuda
Chem. Commun., 47 (20), 5693-5695 (2011).

Small silver clusters (average diameter of 1.2 nm) protected by 4-(tert-butyl)benzyl mercaptan (BBSH) were converted to stable, monodisperse clusters (2.1 nm) by a ripening process with excess amount of BBSH. Multiple characterizations of the isolated magic clusters revealed an approximate chemical composition of Ag~280(SBB)~120.

Synthesis and Characterization of Au102(p-MBA)44 Nanoparticles

Yael Levi-Kalisman, Pablo D. Jadzinsky, Nir Kalisman, Hironori Tsunoyama, Tatsuya Tsukuda, David A. Bushnell, and Roger D. Kornberg*
J. Am. Chem. Soc., 133 (9), 2976-2982 (2011).

The synthesis of Au102(p-MBA)44 nanoparticles on a preparative scale in high yield is described. Various analytical methods are shown to give results consistent with the composition and known structure of the particles, showing the preparation is essentially homogeneous, and attesting to the validity of the methods as well. Derivatization of the particles with proteins and DNA is demonstrated, and conditions are described for imaging individual particles by cryo-EM at low electron dose, close to focus, conditions optimal for recording high-resolution details.

Production of an Ordered (B2) CuPd Nanoalloy by Low-temperature Annealing under Hydrogen Atmosphere

Miho Yamauchi*, Tatsuya Tsukuda
Dalton Transaction, 40, 4842-4845 (2011).

CuPd (1/1) nanoalloys composed of disordered body-centered-cubic crystals (crystal size = 1.6 nm) were prepared by synchronous reduction of Cu and Pd precursor ions with NaBH4. In situ XRD measurement revealed that Cu and Pd atoms in the CuPd nanoalloys are arranged into an ordered B2 structure under exposure to H2 (5 kPa) at 373 K. Ordering of Cu and Pd atoms over a longer distance (up to 3.6 nm) was achieved by annealing the nanoalloys for a longer time under a H2 atmosphere.

Highly Selective Ammonia Synthesis from Nitrate with Photocatalytically Generated Hydrogen on CuPd/TiO2

Miho Yamauchi*, Ryu Abe, Tatsuya Tsukuda, Kenichi Kato, and Masaki Takata
J. Am. Chem. Soc., 133 (5), 1150-1152 (2011).

Body-centered-cubic type CuPd nanoalloys were synthesized by a chemical reduction method. Photocatalytic hydrogen evolution and nitrate reduction were simultaneously examined over CuPd nanoalloys deposited on TiO2 (CuPd/TiO2). The efficiency of hydrogen evolution over CuPd/TiO2 was better than that over Pd/TiO2. As for nitrate reduction, ammonia was selectively (78%) produced with hydrogen generated photocatalytically over CuPd/TiO2. The continuous generation of nascent hydrogen atoms on the surface of the CuPd nanoalloy, where Cu and Pd are homogeneously mixed, led to the high selectivity for ammonia.

Aerobic Oxidations Catalyzed by Colloidal Nanogold

Tatsuya Tsukuda*, Hironori Tsunoyama, and Hidehiro Sakurai
Chemistry-An Asian journal, 6, 736-748 (2011).

Recently, dispersions of gold nanoclusters in liquid media (colloidal nanogold) have been extensively used as quasi-homogeneous catalysts for various aerobic oxidation reactions. This review describes recent progress in such reactions, with a focus on our comprehensive studies on Au clusters (<2 nm) stabilized by poly(N-vinyl-2-pyrrolidone), and their participation in oxidation reactions of alcohols, a-hydroxylation reactions of benzylic ketones, and homocoupling reactions of organoboronates, as well as formal Lewis acidic reactions, such as intramolecular hydroalkoxylation and hydroamination reactions of nonactivated alkenes. Mechanistic studies have shown that a partial electron transfer from the Au clusters to O2 generates superoxide- or peroxide-like species and Lewis acidic centers, both of which play essential roles in the catalytic reactions.

Aerobic Oxidation of Cyclohexane Catalyzed by Size-Controlled Au Clusters on Hydroxyapatite: Size Effect in the Sub-2 nm Regime

Yongmei Liu, Hironori Tsunoyama, Tomoki Akita, Songhai Xie, and Tatsuya Tsukuda*
ACS Catalysis, 1, 2-6 (2011).

In this work, we synthesized gold clusters, Aun (n = 10, 18, 25, 39), with atomically-controlled sizes on hydroxyapatite (HAP) and studied the catalysis for aerobic oxidation of cyclohexane. These Aun/HAP catalysts could efficiently oxidize cyclohexane to cyclohexanol and cyclohexanone. The turnover frequency monotonically increased with an increase in the size, reaching values as high as 18500 h-1 Au atom-1 at n = 39, and thereafter decreased with a further increase in n up to n~85. This finding provides a fundamental insight into size-specific catalysis of gold in the cluster regime (diameter < 2 nm) and a guiding principle for rational design of Au cluster-based catalysts.

ƒy[ƒW‚̐擪‚Ö