Nanoplasmonic Photoluminescence Spectroscopy at Single‐Particle Level: Sensing for Ethanol Oxidation

Surface plasmon resonances of metal nanoparticles have shown significant promise for the use of solar energy to drive catalytic chemical reactions. More importantly, understanding and monitoring such catalytic reactions at single‐nanoparticle level is crucial for the study of local reaction processes. Herein, using plasmonic photoluminescence (PL) spectroscopy, we describe a novel sensing method for catalytic ethanol oxidation reactions at the single‐nanoparticle level. The Au nanorod monitors the interfacial interaction with ethanol during the catalytic reaction through the PL intensity changes in the single‐particle PL spectra. The analysis of energy relaxation of excited electron–hole pairs indicates the relationship between the PL quenching and ethanol oxidation reaction on the single Au nanorod.     

Integrating bimetallic AuPd nanocatalysts with a 2D aza-fused π-conjugated microporous polymer for light-driven benzyl alcohol oxidation

Efficient catalytic system with low energy consumption exhibits increasing importance due to the upcoming energy crisis.Given this situation,it should be an admirable strategy for reducing energy input by effectively utilizing incident solar energy as a heat source during catalytic reactions.Herein,aza-fused7 r-conjugated microporous polymer(aza-CMP)with broad light absorption and high photothermal conversion efficiency was synthesized and utilized as a support for bimetallic AuPd nanocatalysts in light-driven benzyl alcohol oxidation.The AuPd nanoparticles anchored on aza-CMP(aza-CM P/Au_xPdy)exhibited excellent catalytic performance for benzyl alcohol oxidation under 50 mW/cm^2 light irradiation.The improved catalytic performance by the aza-CMP/Au_xPdy is attributed to the unique photothermal effect induced by aza-CMP,which can promote the catalytic benzyl alcohol oxidation occurring at Au Pd.This work presents a novel approach to effectively utilize solar energy for conventional catalytic reactions through photothermal effect.     

Design,synthesis, characterization and catalytic performance of a new cellulose‐based magnetic nanocomposite in the one‐pot three‐component synthesis of α‐aminonitriles

A sulfonated magnetic cellulose‐based nanocomposite was prepared and characterized using scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, X‐ray diffraction and Fourier transform infrared spectroscopy. Then, it was used as a green nanocatalyst for the synthesis of α‐aminonitriles by a one‐pot three‐component condensation reaction of aldehydes or ketones, amines and trimethylsilylcyanide in ethanol at room temperature. The reaction procedure is simple, yields are very high, reaction time is very short and the catalyst can be easily separated from the reaction mixture and reused in subsequent reactions without significant loss of catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Iodine Catalyzed Three-component Strecker-type Synthesis of α-Aminonitriles from Aldehydes, Amines and Tributyltin Cyanide

A simple and efficient one-pot method has been developed for the synthesis of a-aminonitriles from aldehydes, amines and tributyltin cyanide in the presence of a catalytic amount of iodine with high yields. The reactions proceeded smoothly at room temperature via very simple procedure.     

Recent Progress in Application of Graphene Supported Metal Nanoparticles in C−C and C−X Coupling Reactions

The carbon‐carbon and carbon‐heteroatom bonds catalytic formation is among the most significant reactions in organic synthesis which extensively applied for synthesis of natural products, heterocycles, dendrimers, biologically active molecules and useful compounds. This review provides the latest advances in the preparation of graphene supported metal nanoparticles and their application in the catalytic formation of both carbon‐carbon (C−C) and carbon‐heteroatom (C−X) bonds including the Suzuki, Heck, Hiyama, Ullmann, Buchwald and Sonogashira coupling reactions. Numerous examples are given concerning the use of these catalysts in C−C and C−X coupling reactions along with the reliable and simple preparation methods of these catalysts, their characterization and catalytic properties and also the recycling possibilities.     

扫描电化学显微镜在电催化表面反应分析中的现代应用

能源和环境问题成为制约未来可持续发展的关键问题之一,因此,针对不同电催化反应设计电催化剂变得越来越重要.电催化剂因其能量效率高、制备简单和易操作等优点,而应用于可再生能源的相关反应(如水分解和人工光合作用)中.明确不同反应电催化剂的设计原理,深入理解其在相关反应中的催化机理,可进一步优化催化剂性能.本文综述了扫描电化学显微镜(SECM)应用于电催化反应的历程、关键方法以及一些代表性的工作,阐明了电催化剂的工作机理以推进电催化剂的设计.本文还介绍了为提高SECM的空间分辨率而尝试的纳米尺寸电极方面的新进展,分享了纳米电极在以前研究无法涉及的单一催化实体方面的应用.     

Rate-limiting steps, rate-determining parameters, and apparent activation energy of stepwise reactions, 2. Simple stepwise consecutive catalytic reactions linear in respect to intermediates

The paper considers the application of a recently suggested mathematically correct approach for determining the rate-limiting steps, rate-determining parameters as well as the apparent activation energy for the steady occurrence of simple stepwise consecutive catalytic reactions which are linear in respect to catalytic intermediates. Under consideration are situations of both the small and large coverage of the surface with catalytic intermediates. This revised version was published online in June 2006 with corrections to the Cover Date.     

Tetraloop‐like Geometries Could Form the Basis of the Catalytic Activity of the Most Ancient Ribooligonucleotides

The origin of the catalytic activity of ancient oligonucleotides is a largely unexplored field of contemporary science. In the current work we use molecular dynamics simulations to investigate the plausibility of tetraloop‐like overhang geometries to initiate transphosphorylation reactions that lead to ligation and terminal cleavage in simple, Watson–Crick (WC) complementary oligoC/oligoG sequences observed experimentally. We show a series of examples of known tetraloop architectures, which can be adopted by the unpaired overhangs of short oligonucleotide sequences for a sufficiently long time to enable chemical reactions that lead to simple ribozyme‐like catalytic activity. Thus, our computations demonstrate that the role of non‐WC interactions at the emergence of the most ancient catalytic oligonucleotides could be more significant than ever believed.     

Copper(I) oxide nanoparticles supported on magnetic casein as a bio‐supported and magnetically recoverable catalyst for aqueous click chemistry synthesis of 1,4‐disubstituted 1,2,3‐triazoles

Copper(I) oxide nanoparticles supported on magnetic casein (Cu₂O/Casein@Fe₃O₄NPs) has been synthesized as a bio‐supported catalyst and was characterized using powder X‐ray diffraction, transmission electron microscopy, energy dispersive X‐ray and Fourier transform infrared spectroscopies, thermogravimetric analysis and inductively coupled plasma optical emission spectrometry. The catalytic activity of the synthesized catalyst was investigated in one‐pot three‐component reactions of alkyl halides, sodium azide and alkynes to prepare 1,4‐disubstituted 1,2,3‐triazoles with high yields in water. The reaction work‐up is simple and the catalyst can be magnetically separated from the reaction medium and reused in subsequent reactions.     

Redox‐Active Ligands in Catalysis

Nature’s use of redox‐active moieties combined with 3d transition‐metal ions is a powerful strategy to promote multi‐electron catalytic reactions. The ability of these moieties to store redox equivalents aids metalloenzymes in promoting multi‐electron reactions, avoiding high‐energy intermediates. In a biomimetic spirit, chemists have recently developed approaches relying on redox‐active moieties in the vicinity of metal centers to catalyze challenging transformations. This approach enables chemists to impart noble‐metal character to less toxic, and cost effective 3d transitional metals, such as Fe or Cu, in multi‐electron catalytic reactions.     

KOtBu‐Catalyzed Michael Addition Reactions Under Mild and Solvent‐Free Conditions

Designed transition metal complexes predominantly catalyze Michael addition reactions. Inorganic and organic base‐catalyzed Michael addition reactions have been reported. However, known base‐catalyzed reactions suffer from the requirement of solvents, additives, high pressure and also side‐reactions. Herein, we demonstrate a mild and environmentally friendly strategy of readily available KO^tBu‐catalyzed Michael addition reactions. This simple inorganic base efficiently catalyzes the Michael addition of underexplored acrylonitriles, esters and amides with (oxa‐, aza‐, and thia‐) heteroatom nucleophiles. This catalytic process proceeds under solvent‐free conditions and at room temperature. Notably, this protocol offers an easy operational procedure, broad substrate scope with excellent selectivity, reaction scalability and excellent TON (>9900). Preliminary mechanistic studies revealed that the reaction follows an ionic mechanism. Formal synthesis of promazine is demonstrated using this catalytic protocol.     

Polymer‐anchored copper(II) complex: an efficient reusable catalyst for the synthesis of propargylamines

A new, heterogeneous, polymer‐supported copper(II) complex was prepared and characterized using various techniques, including Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X‐ray spectroscopy, atomic absorption spectroscopy and thermogravimetric analysis. This heterogeneous copper catalyst is efficient for the synthesis of propargylamines via a three‐component coupling reaction of aldehydes, amines and alkynes. The effect of solvent on the coupling reactions was investigated. Further, the catalyst can be easily recovered quantitatively by simple filtration and reused for a minimum number of cycles without significant loss of its catalytic activity. Copyright © 2014 John Wiley & Sons, Ltd.     

能源催化材料的电化学合成

电催化是发展可持续洁净能源技术的基础科学,是电化学能源转换和物质转化的关键环节.精准合成催化活性纳米结构是制约很多电催化反应走向实际应用的重要挑战.与湿化学合成、固相合成和气相沉积等传统方法相比,电化学合成是一种简单、快速、廉价及可控的高效催化材料制备方法,也是一种最为直接的一体化电极制备方法.本文综述了近年来利用电化...     

Bifunctional Heterogeneous Catalysis of Silica–Alumina‐Supported Tertiary Amines with Controlled Acid–Base Interactions for Efficient 1,4‐Addition Reactions

We report the first tunable bifunctional surface of silica–alumina‐supported tertiary amines (SA–NEt₂) active for catalytic 1,4‐addition reactions of nitroalkanes and thiols to electron‐deficient alkenes. The 1,4‐addition reaction of nitroalkanes to electron‐deficient alkenes is one of the most useful carbon–carbon bond‐forming reactions and applicable toward a wide range of organic syntheses. The reaction between nitroethane and methyl vinyl ketone scarcely proceeded with either SA or homogeneous amines, and a mixture of SA and amines showed very low catalytic activity. In addition, undesirable side reactions occurred in the case of a strong base like sodium ethoxide employed as a catalytic reagent. Only the present SA‐supported amine (SA–NEt₂) catalyst enabled selective formation of a double‐alkylated product without promotions of side reactions such as an intramolecular cyclization reaction. The heterogeneous SA–NEt₂ catalyst was easily recovered from the reaction mixture by simple filtration and reusable with retention of its catalytic activity and selectivity. Furthermore, the SA–NEt₂ catalyst system was applicable to the addition reaction of other nitroalkanes and thiols to various electron‐deficient alkenes. The solid‐state magic‐angle spinning (MAS) NMR spectroscopic analyses, including variable‐contact‐time ¹³C cross‐polarization (CP)/MAS NMR spectroscopy, revealed that acid–base interactions between surface acid sites and immobilized amines can be controlled by pretreatment of SA at different temperatures. The catalytic activities for these addition reactions were strongly affected by the surface acid–base interactions.     

Density functional theory studies of negishi alkyl-alkyl cross-coupling reactions catalyzed by a methylterpyridyl-Ni(I) complex

Density functional theory calculations were done to examine the potential energy surfaces of Ni(I)-catalyzed Negishi alkyl-alkyl cross-coupling reactions by using propyl iodide and isopropyl iodide as model alkyl electrophiles and CH 3ZnI as a model alkyl nucleophile. A four-step catalytic cycle involving iodine transfer, radical addition, reductive elimination, and transmetalation steps were characterized structurally and energetically. The reaction mechanism for this catalytic cycle appears feasible based on the calculated free energy profiles for the reactions. The iodine transfer step is the rate-determining step for the Ni(tpy)-CH 3 (tpy = 2,2'6',2'-terpyridine) reactions with alkyl iodides. For secondary alkyl electrophiles, the oxidative addition intermediate, Ni(III), prefers to undergo decomposition over reductive elimination, whereas for the primary alkyl electrophiles, Ni(III) prefers to undergo reductive elimination over decomposition based on comparison of the relative reaction rates for these two types of steps. In addition, thermodynamic data were employed to help explain why the yield of the coupled product is very low from the Ni(II)-alkyl halide reactions with organozinc reagents.     

Pd–Schiff base complex supported on Fe3O4 magnetic nanoparticles: A new and highly efficient reusable catalyst for C–C bond formation in water

A protocol is introduced for the preparation of a new cage‐like Pd–Schiff base organometallic complex supported on Fe₃O₄ nanoparticles (Fe₃O₄@Schiff‐base‐Pd). The structure of the nanomagnetic catalyst was comprehensively characterized using Fourier transform infrared (FT‐IR) spectroscopy, X‐ray diffraction (XRD), energy‐dispersive X‐ray spectroscopy, Brunauer–Emmett–Teller measurements, scanning electron microscopy (SEM), transmission electron microscopy, X‐ray mapping, thermogravimetric analysis, vibrating sample magnetometry and inductively coupled plasma atomic emission spectroscopy. In the second stage, the catalytic activity of this catalyst was studied in the Suzuki and Heck cross‐coupling reactions in water as a green solvent. In this sense, simple preparation of the catalyst from commercially available materials, high catalytic activity, simple operation, short reaction times, high yields and use of green solvent are some advantages of this protocol. Finally, the nanocatalyst was easily recovered, using an external magnet, and reused several times without significant loss of its catalytic efficiency. In addition, the stability of the catalyst after recycling was confirmed using SEM, XRD and FT‐IR techniques.     

Understanding Reaction Dynamics in Coordination Chemistry—Application of High Pressure Techniques

In order to understand the dynamics of chemical reactions in general, detailed information on electronic, structural and kinetic properties is required. The key questions on how chemical reactions actually occur can in many cases only be answered in terms of information obtained from kinetic studies. In conventional kinetic studies of chemical reactions in solution, the variables usually selected include concentration, acidity, solvent, and temperature. In recent years, pressure has become an additional selected variable in such studies. It enables the measurement of the volume of activation and the construction of reaction volume profiles and thus assists in the elucidation of the underlying mechanism; it also completes the comprehension of reaction kinetics by adding another kinetic parameter that the suggested reaction mechanism must account for. Furthermore, the volume of activation is the only transition state property that can be correlated with the corresponding ground state property in an experimentally simple manner. In this paper, the insights so gained in our understanding of the dynamics of reactions involving coordination complexes will be presented. Such reactions are of fundamental interest to chemists since they often form the basis of catalytic, biological, environmental and energy related processes. Any additional information that will add to the understanding of the reaction dynamics is therefore of exceptional importance.     

Simple cross-section model for elementary reactions

A simple reaction cross-section model has been obtained. It consists of hard spheres where the mass of the products has been introduced via angular momentum conservation. For exothermic reactions the cross section shows a maximum, providing that a threshold energy is present. The model has been applied to the alkali-atom—alkyl-oxide reactions, giving a simple understanding of the systematic trend of the cross section and the energy dependence of its maximum.     

Quantum energy flow during molecular isomerization

Intramolecular energy flow greatly influences molecular isomerizations, particularly when the energy barrier to reaction is low, as in catalytic and biochemical reactions. We discuss here a simple quantum mechanical theory that describes the extent and rate of vibrational energy flow in molecules, and apply it for the first time to predict rates of isomerization. We consider trans-cis photoisomerization of stilbene, which has been extensively studied experimentally. Vibrational flow in stilbene plays a crucial role in moderating isomerization; the rate both in supersonic jets and low pressure gases is well described by the theory treating quantum flow.