Catalysis on gold-nanoparticle-passivating monolayers

Clusters of gold atoms in the range 1–100 nm of diameter are unstable and tend to aggregate to form insoluble materials but become very stable once passivated with a monolayer of organic molecules typically anchored on the surface via an Au–S bond. The properties of this monolayer as a reaction loci constitute the topic of this overview of the recent literature. In analyzing the examples reported with functionalized monolayers we show how efficient catalysts these systems may become. Several data point out the occurrence of unusual reaction pathways and significant cooperativity between functional groups not observed not only in monomeric equivalent catalysts but also in other aggregation colloids like micelle and vesicles. The picture that emerges is that of a unique environment mimicking several features of enzymatic processes.     

The III Seminar on the Theoretical Problems of Catalysis and Russian-Japanese Seminar on Catalysis

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The III Seminar on the Theoretical Problems of Catalysis and Russian-Japanese Seminar on Catalysis     

Catalysis

A brief summary of very recently published works on vibrational spectroscopic studies of adsorbed molecules (a) on metal single crystals or evaporated films with low surface area and (b) on supported metal catalysts or metal oxide catalysts with large surface area is presented here. So far as (a) is concerned some new results of EELS, reflection-absorption IR spectroscopy and IR emission spectroscopy (with cooled monochromator or interferometer) are discussed. With regards to topic (b) absorption by the support materials (SiO₂, Al₂O₃, MgO, TiO₂, etc.) usually prevents access to the region below about 1200 cm^–1. Therefore we concentrate mainly on the methods (diffuse reflection, photoacoustic or emission spectroscopy) offering vibrational data in a wide frequency range. Some new developments in emission and FIR spectroscopy in our laboratory are discussed.     

稀土金属在不对称催化中的应用:从均相催化到异相催化

稀土金属的配位数较高,可通过容纳大型手性配体,构筑手性环境,催化不对称反应的定向发生,在工业生产特别是制药工程中具有重要应用价值.本文以Henry反应、Mannich反应和Strecker反应为例,总结回顾了稀土金属催化剂在此类反应中的设计思路、性能特点与应用前景,旨在展现稀土金属催化剂兼具融合均相催化与异相催化的优势...     

IDPi Catalysis

High acidity and structural confinement are pivotal elements in asymmetric acid catalysis. The recently introduced imidodiphosphorimidate (IDPi) Brønsted acids have met with remarkable success in combining those features, acting as powerful Brønsted acid catalysts and “silylium” Lewis acid precatalysts in numerous thus far inaccessible transformations. Substrates as challenging to activate as simple olefins were readily transformed, ketones were employed as acceptors in aldolizations allowing sub‐ppm level catalysis, whereas enolates of the smallest donor aldehyde, acetaldehyde, did not polymerize but selectively added a single time to a variety of acceptor aldehydes.     

Processive Catalysis

Nature’s enzymes are an ongoing source of inspiration for scientists. The complex processes behind their selectivity and efficiency is slowly being unraveled, and these findings have spawned many biomimetic catalysts. However, nearly all focus on the conversion of small molecular substrates. Nature itself is replete with inventive catalytic systems which modify, replicate, or decompose entire polymers, often in a processive fashion. Such processivity can, for example, enhance the rate of catalysis by clamping to the polymer substrate, which imparts a large effective molarity. Reviewed herein are the various strategies for processivity in nature’s arsenal and their properties. An overview of what has been achieved by chemists aiming to mimic one of nature’s greatest tricks is also included.