Conversion of Mg-Li Bimetallic Alloys to Magnesium Alkoxide and Magnesium Oxide Ceramic Nanowires

Technologically important composites with enhanced thermal and mechanical properties rely on the reinforcement by the high specific strength ceramic nanofibers or nanowires (NWs) with high aspect ratios. However, conventional synthesis routes to produce such ceramic NWs have prohibitively high cost. Now, direct transformation of bulk Mg-Li alloys into Mg alkoxide NWs is demonstrated without the use of catalysts, templates, expensive or toxic chemicals, or any external stimuli. This mechanism proceeds through the minimization of strain energy at the boundary of phase transformation front leading to the formation of ultra-long NWs with tunable dimensions. Such alkoxide NWs can be easily converted in air into ceramic MgO NWs with similar dimensions. The impact of the alloy grain size and Li content, synthesis temperature, inductive and steric effects of alkoxide groups on the diameter, length, composition, ductility, and oxidation of the produced NWs is discussed.     

What do we know about the ionic liquid effect in catalyzed multicomponent reactions?: A critical review

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Coordination of the natural ligand lapachol to iron(II): synthesis,theoretical study and antiproliferative activity

Transition Metal Chemistry - Lapachol is a natural naphthoquinone known for having a variety of biological properties, and in recent years, it has been used in the synthesis of metal complexes with...     

A click-flipped enzyme substrate boosts the performance of the diagnostic screening for Hunter syndrome

We report on the unexpected finding that click modification of iduronyl azides results in a conformational flip of the pyranose ring, which led to the development of a new strategy for the design of superior enzyme substrates for the diagnostic assaying of iduronate-2-sulfatase (I2S), a lysosomal enzyme related to Hunter syndrome. Synthetic substrates are essential in testing newborns for metabolic disorders to enable early initiation of therapy. Our click-flipped iduronyl triazole showed a remarkably better performance with I2S than commonly used O-iduronates. We found that both O- and triazole-linked substrates are accepted by the enzyme, irrespective of their different conformations, but only the O-linked product inhibits the activity of I2S. Thus, in the long reaction times required for clinical assays, the triazole substrate substantially outperforms the O-iduronate. Applying our click-flipped substrate to assay I2S in dried blood spots sampled from affected patients and random newborns significantly increased the confidence in discriminating between these groups, clearly indicating the potential of the click-flip strategy to control the biomolecular function of carbohydrates.

Click-triggered flip of the conformation of a sulfated iduronyl azide afforded a superior enzyme substrate to screen for Hunter syndrome.     

Magnetization Slow Dynamics in Ferrocenium Complexes

The single-molecule magnet (SMM) properties of a series of ferrocenium complexes, [Fe(η⁵-C₅R₅)₂]⁺ (R=Me, Bn), are reported. In the presence of an applied dc field, the slow dynamics of the magnetization in [Fe(η⁵-C₅Me₅)₂]BAr_F are revealed. Multireference quantum mechanical calculations show a large energy difference between the ground and first excited states, excluding the commonly invoked, thermally activated (Orbach-like) mechanism of relaxation. In contrast, a detailed analysis of the relaxation time highlights that both direct and Raman processes are responsible for the SMM properties. Similarly, the bulky ferrocenium complexes, [Fe(η⁵-C₅Bn₅)₂]BF₄ and [Fe(η⁵-C₅Bn₅)₂]PF₆, also exhibit magnetization slow dynamics, however an additional relaxation process is clearly detected for these analogous systems.     

High Performance of Carbon Nanotube Refrigerators

Vapor‐compression dominates the market for refrigeration devices due to low cost and relatively high efficiency. However, the most efficient vapor refrigerants are either ozone depleting or global warming substances. Solid‐state cooling is a young field of research with promising results toward the development of new, efficient, and environment friendly technology for a new generation of refrigeration devices. One of these methods is based on the so‐called elastocaloric effect (ECE), which consists of a temperature variation of a system in response to the application of adiabatic stresses. Although most of the literature describes the study of ECE solid‐state cooling based on materials undergoing phase‐transitions, a study recently predicted that carbon nanotubes (CNTs) present ECE as large as 30 K for 3% of strain. This motivates research toward the development of nanorefrigerators. As nobody knows the efficiency of such an ECE‐based CNT nanorefrigerator, here, significantly high coefficient of performance values of 4.1 and 6.5, and extracted heat per weight as large as 40 J g^?1 are reported for a zigzag CNT nanorefrigerator operating in an Otto‐like thermodynamic cycle. This efficiency is shown to overcome that of some other ECE materials.     

A Phosphoramidite Analogue of Cyclotriphosphate Enables Iterative Polyphosphorylations

An iterative polyphosphorylation approach is described, which is based on a phosphoramidite (P‐amidite) derived reagent (c‐PyPA) obtained from the cyclization of pyrophosphate with a reactive diisopropylaminodichlorophosphine. This type of reagent is unprecedented as it represents a reactive P‐amidite without protecting groups. The reagent proved to be stable in solution over several weeks. Its utility is described in the context of iterative monodirectional and bidirectional polyphosphorylations. The ensuing functionalized cyclotriphosphate can be opened with a variety of nucleophiles providing ready access to diverse functionalized polyphosphate chains of defined length with several tags, including both P‐N and P‐O labels. Their interaction with exo‐ and endopolyphosphatases is described.