RAF graças a National Science Foundation (CHE-0844946) para apoio a este trabalho.

1. Síntese de SMI 2 (0,1 M) <ol><li> Chama secar de 50 ml balão de fundo redondo e lave-o com argônio. Adicionar uma barra de agitação e cobrir o recipiente com septos. Pesar de metal samário (0,2 g, 1,3 mmol) e adicionar ao frasco, o frasco de lavagem mais uma vez com árgon. </li><li> Adicionar 10 ml seco, tetra-hidrofurano completamente desgaseificado (THF) seguido por cristais de iodo (0,254 g, 2,0 mmol). Adicionar um balão de árgon através do septo, o que mantém uma pressão positiva de atmosfera de Ar na reacção. </li><li> Agita-se vigorosamente a solução à temperatura ambiente durante mais 3 h. Como SMI 2 é gerado a solução passa através de uma variedade de alterações de cor; laranja seguido de amarelo (45 min), e verde (1 hr), que, eventualmente, se transforma em azul. </li><li> A final da marinha de cor azul é indicação de que isoladamente samário ionizado formou. A fim de assegurar a conversão completa, agita-se a solução durante pelo menos 3 horas antes de utilizar SMI 2 em síntese. </li></ol> 2. SaMarium Barbier Reação hexametilfosfórica-Adição (HMPA) <ol><li> Para fazer com que a SMI 2-HMPA complexo, tomar a SMI preparada de fresco 2, sob árgon (10 ml, 0,1 M, 1,0 mmol) e adicionar 1,75 ml de HMPA (10 equiv., 10 mmol) através de uma seringa, gota a gota, sob atmosfera de árgon. Um profundo formas de cor púrpura. </li><li> Separadamente em um frasco limpo, seco, sob árgon, iodododecane add (0,45 mmol, 110 uL), 3-pentanona (0,45 mmol, 48 ul) e 2 ml de THF seco. </li><li> Adicionar a mistura gota a gota uma solução de substrato para o complexo SMI 2 / HMPA. </li><li> Dentro de 5 min de agitação, a cor púrpura começará a procurar turva, indicando o final da reacção. </li><li> Depois da reacção estar completa, a solução de expor ao ar para extinguir lo; após agitação a cor muda para amarelo mais. </li><li> A reacção é em seguida manipulada por lavagem com cloreto de amónio aquoso saturado. Adicionar a solução para um funil de separação e adicionar éter dietílico (5 ml). Após agitação vigorosa removera camada orgânica superior, adicionar mais éter dietílico. Extrair da camada aquosa mais duas vezes e, em seguida, combinam todas as camadas orgânicas. </li><li> Lava-se a camada orgânica com uma solução saturada de tiossulfato de sódio aquoso. Remover a camada aquosa inferior, seguido por lavagem com água e, em seguida, a lavagem final com solução salina. Obter a camada orgânica superior e adicionar sulfato de magnésio para absorver qualquer quantidade de água presente último na solução. </li><li> Filtrar a solução através de um tampão de Florisil, a fim de remover o excesso de HMPA. </li><li> Concentra-se a solução num evaporador rotativo para se obter Barbier produto. O produto foi identificado por GCMS e RMN de 1H 23. </li></ol> 3. Samário Barbier Reaction-Ni (acac) 2 Catalisador <ol><li> Pesar Ni (acac) 2 (1% mol, 0,01 mmol, 0,0026 g) e adicionar a um frasco limpo, seco, contendo 3 ml de THF desgaseificado, sob atmosfera de árgon. Adicionar o Ni (acac) 2 solução através de uma seringa a uma s recentemente preparadalução de 0,1 M SMI 2 (1,0 mmol, 10 ml). </li><li> Separadamente em um frasco limpo, seco, sob árgon, iodododecane add (0,45 mmol, 110 uL), 3-pentanona (0,45 mmol, 48 ul) e 2 ml de THF seco. </li><li> Adicionar gota a gota, a solução de substrato para a SMI 2 / mistura Ni. </li><li> Dentro de 15 minutos de agitação, a cor azul se dissipar para formar uma cor verde-amarela que indica o final da reacção. </li><li> Depois da reacção estar completa, a solução de expor ao ar para extinguir lo; após agitação a cor muda para amarelo mais. Trabalhar-se a reacção através de lavagem com 0,1 M aq. Ácido clorídrico (3 ml). Adicionar a solução para um funil de separação e adicionar éter dietílico (5 ml). </li><li> Lava-se a camada orgânica, utilizando o protocolo descrito anteriormente com uma solução aquosa de tiossulfato de sódio a água e salmoura, e depois seca-se sobre sulfato de magnésio. Concentra-se a solução para se obter o produto Barbier. O produto pode ser identificado por GCMS e RMN de 1H 28. </sse&gt; </li></ol>

<ol>
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Um procedimento simples para a geração de SMI solução 2 e sua aplicação em síntese orgânica utilizando dois dos aditivos mais comuns é apresentado aqui. Os dois exemplos descritos retratar a importância do entendimento mecanicista da reação para afinar a reatividade da SMI 2. O conhecimento do esteio do mecanismo de reacção permite a utilização deste reagente de ser adaptados por químicos sintéticos de acordo com as exigências da sua reacção. Este redutor electrão único homogénea é fácil de manusear e podem ser comprados a partir de fontes comerciais. Embora o protocolo acima é para a frente quando feita sob condições inertes, alguns dos procedimentos de resolução de problemas comuns são: (a) assegurar que o THF é devidamente desgaseificado e seco, (b) se o metal Sm teve uma exposição prolongada a ar que pode ter um oxidado fora da camada, moer o metal com um almofariz e um pestal para expor a superfície de metal limpa, (c)chama-secar todo o material de vidro e arrefecer sob atmosfera de árgon, (d) árgon é preferido sobre atmosfera inerte de azoto, como o mais tarde tem sido mostrado para interagir com o metal, (e) A presença de excesso de Sm-metal ajuda a manter a concentração de SMI 2, (f) resublime os cristais de iodo.

<table border="1"><tbody><tr><td> Nome do reagente </td><td> Companhia </td><td> Número de catálogo </td><td> Comentários (opcional) </td></tr><tr><td> Samário de metal </td><td> Acros </td><td> 29478-0100 </td><td> Malha -40, 99,9% (base metais) </td></tr><tr><td> THF </td><td> OmniSolv </td><td> TX0282-1 </td><td> Purificada através inovador sistema de purificação de Tecnologias de solvente. Em alternativa, pode ser desgaseificado através do método de livre-bomba-descongelação </td></tr><tr><td> Iodo </td><td> Alfa Aesar </td><td> 41955-22 </td><td> Cristais Resublimed, 99,8% </td></tr><tr><td> Iodododecane </td><td> Acros </td><td> 25009-0250 </td><td> 98% </td></tr><tr><td> 3-pentanona </td><td> Alfa Aesar </td><td> AAA15297-AE </td><td> 99% </td></tr><tr><td> HMPA </td><td> Alderich </td><td> H11602 </td><td> 98%; Destilar de CaO em árgon </td></tr><tr><td> Nii 2 </td><td> Alfa Aesar </td><td> 22893 </td><td> 99,5% (base metais) </td></tr></tbody></table>

preparation and use of samarium diiodide (smi2) in organic synthesis: the mechanistic role of hmpa and ni(ii) salts in the samarium barbier reaction

Embora inicialmente considerado um reagente esotérico, SMI 2 tornou-se uma ferramenta comum para químicos orgânicos sintéticos. SMI 2 é gerado através da adição de iodo molecular para samário metálico em THF. 1,2-3 É um redutor de electrões suave e seletivo e sua versatilidade é um resultado da sua capacidade de iniciar uma ampla variedade de reduções incluindo CC-bond formar e cascata ou reações seqüenciais. SMI 2 pode reduzir uma grande variedade de grupos funcionais, incluindo sulfóxidos e sulfonas, os óxidos de fosfina, epóxidos, halogenetos de alquilo e de arilo, carbonilos, e ligações duplas conjugadas. 2-12 Uma das características fascinantes de smi-2-reacções mediadas é a capacidade de manipular o resultado de reacções através da utilização selectiva de co-solventes ou aditivos. Na maioria dos casos, os aditivos são essenciais para o controlo da taxa de redução e as reacções de quimio-ou estereosselectividade da. 13-14 Aditivos commonly utilizada para afinar a reatividade da SMI dois podem ser classificados em três grandes grupos: (1) Lewis bases (HMPA, outros doadores de electrões ligantes quelantes, éteres, etc), fontes (2) de prótons (álcool, água, etc ), e (3) aditivos inorgânicos (Ni (acac) 2, FeCl 3, etc.) 3 Compreensão do mecanismo da SMI 2 reacções e o papel dos aditivos permite a utilização de todo o potencial do reagente em síntese orgânica. A reacção de Sm-Barbier é escolhido para ilustrar a importância sintético e papel mecanístico de dois aditivos comuns: HMPA e Ni (II) nesta reacção. A reacção de Sm-Barbier é semelhante à reacção de Grignard tradicional com a única diferença sendo que o alquil-carbonilo, um halogeneto, e redutor Sm são misturados simultaneamente em uma panela. 1,15 Exemplos de reacções mediadas por Barbier Sm com uma variedade de parceiros de acoplamento têm sido relatados, 1,3,7,10,12 e foram utilized em passos-chave para a síntese de grandes produtos naturais. 16,17 Estudos anteriores sobre o efeito dos aditivos sobre a SMI 2 reacções têm mostrado que HMPA aumenta o potencial de redução de 2 por SMI coordenação ao metal samário centro, produzindo um mais poderoso, 13-14,18 estericamente impedidos redutor 19-21 e, em alguns casos, que jogam um papel importante na transferência de electrões de correio passos subsequentes facilitando de formação de ligação de eventos. 22 Na reacção de Sm-Barbier, HMPA tem sido demonstrado que, adicionalmente, ativar o halogeneto de alquilo através da formação de um complexo de um passo de pré-equilíbrio 23. Ni (II) sais são um aditivo catalítico usado com freqüência em Sm-mediadas transformações. 24-27 Embora fundamental para o sucesso, o papel mecanicista de Ni (II) não era conhecido nestas reações. Recentemente, foi demonstrado que reduz a SMI 2 Ni (II) para Ni (0), e a reacção é então realizada através organometallic química Ni (0) 28. Estes estudos mecanísticos realçar que, embora o produto Barbier mesma é obtida, a utilização de aditivos diferentes nos dois SMI reacção altera drasticamente a via mecanicista da reacção. O protocolo para a execução destes dois SMI iniciadas reacções é descrito.

A Figura 1 ilustra a reacção de samário Barbier. Sem aditivos a reacção mediada por Sm leva 72 horas; rendendo 69% do produto desejado, com os restantes materiais de partida, sendo. Com a adição de 10 ou mais equiv. de HMPA a reacção é praticamente quantitativa e completa dentro de alguns minutos. 15,23 Com a adição de 1 mol% de Ni (acac) 2, a reacção fica completa dentro de 15 min, com um rendimento de 97% 28. Quando é adicionado HMPA SMI 2, desloca o co-solvente de THF coordenado para formar 2 - (SMI HMPA) 4. Com a adição de HMPA ainda mais (6-10 equiv.), Os iões iodeto são deslocadas para a esfera exterior (Figura 2). 19-21 Estudos mecanísticos indicam que quando HMPA é usado na reacção de Sm-Barbier o co-solvente também interage com o substrato de um halogeneto de alquilo, formando um complexo que se alonga a ligação carbono-haleto, activando a species tornando-o mais susceptível a redução de Sm (Figura 3). Através deste entendimento detalhado dos papéis de HMPA, de um mecanismo de reacção para o Sm-Barbier com HMPA foi proposta (Figura 4). 23 O complexo de halogeneto de alquil-HMPA formado num passo de pré-equilíbrio é reduzido por Sm / HMPA para formar o radical na etapa determinante da velocidade. O radical sofre redução adicional para formar uma espécie organosamarium que acopla com o carbonilo e em cima de protonação produz o produto final. No caso do aditivo de Ni (II), SMI 2, inicialmente reduz Ni (II) de Ni (0), preferencialmente, sobre a redução de ambos os substratos. Com base em estudos cinéticos e mecanísticos o seguinte mecanismo foi proposto (Figura 5). Após 28 redução por SMI 2, insere o Ni solúvel (0) para a ligação das espécies halogeneto de alquilo formando uma espécie de organo-níquel. Motivados pela natureza altamente oxophilic de Sm (III)<html> , Transmetalação para formar um intermediário organosamarium lançamentos Ni (II) de volta para o ciclo catalítico. O organosamarium seguida casais com o grupo carbonilo, e em cima de protonação forma o desejado álcool terciário. Observou-se também que o Ni (0) nanopartículas são formadas através de Sm-mediada redução de Ni (II), no entanto estas partículas foram considerados inactivos e a fonte de desactivação do catalisador. <img alt="Figura 1" fo:content-width="4in" fo:src="/files/ftp_upload/4323/4323fig1highres.jpg" src="/files/ftp_upload/4323/4323fig1.jpg" /> Figura 1. Samário reacção Barbier com iodododecane e 3-pentanona. <img alt="Figura 2" fo:content-width="4in" fo:src="/files/ftp_upload/4323/4323fig2highres.jpg" src="/files/ftp_upload/4323/4323fig2.jpg" /> Figura 2. SMI complexo 2-HMPA. &quot;fo: manter-together.within-page =&quot; ONTEÚDO sempre &quot;&gt; <img alt="Figura 3" fo:content-width="3.5in" fo:src="/files/ftp_upload/4323/4323fig3highres.jpg" src="/files/ftp_upload/4323/4323fig3.jpg" /> Figura 3. HMPA e complexo iodeto de alquilo. <img alt="Figura 4" fo:content-width="4.5in" fo:src="/files/ftp_upload/4323/4323fig4highres.jpg" src="/files/ftp_upload/4323/4323fig4.jpg" /> Figura 4. Mecanismo proposto para a reacção de Barbier samário com HMPA adicional. <img alt="Figura 5" fo:content-width="4in" fo:src="/files/ftp_upload/4323/4323fig5highres.jpg" src="/files/ftp_upload/4323/4323fig5.jpg" /> Figura 5. Mecanismo proposto para a reacção Barbier samário contendo Ni catalítica (II).

Watch this Scientific Journal Video about Preparation and Use of Samarium Diiodide SmI2 in Organic Synthesis: The Mechanistic Role of HMPA and NiII Salts in the Samarium Barbier Reaction at JoVE.com

Preparation and Use of Samarium Diiodide SmI2 in Organic Synthesis: The Mechanistic Role of HMPA and NiII Salts in the Samarium Barbier Reaction

Um procedimento simples para a preparação de samário diiodeto (SMI<sub&gt; 2</sub&gt;) Em THF é descrito. O papel dos dois aditivos principais a saber hexametilfosforamida (HMPA) e Ni (acac)<sub&gt; 2</sub&gt; Sm em reacções mediadas é demonstrada no Sm-Barbier reacção.

Preparação e Uso de Samário diiodeto (SMI<sub&gt; 2</sub&gt;) Em Organic Synthesis: The Role mecanístico de HMPA e (II) de Ni Sais na Reacção Barbier Samário

Although initially considered an esoteric reagent, SmI2 has become a common tool for synthetic organic chemists. SmI2 is generated through the addition of ...

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Preparation and Use of Samarium Diiodide (SmI2) in Organic Synthesis: The Mechanistic Role of HMPA and Ni(II) Salts in the Samarium Barbier Reaction

32.6K visualizações.  Lehigh University. Um procedimento simples para a preparação de samário diiodeto (SMI 2) Em THF é descrito. O papel dos dois aditivos principais a saber hexametilfosforamida (HMPA) e Ni (acac) 2 Sm em reacções mediadas é demonstrada no Sm-Barbier reacção.

Vídeo: Preparation and Use of Samarium Diiodide SmI2 in Organic Synthesis: The Mechanistic Role of HMPA and NiII Salts in the Samarium Barbier Reaction

Synthesis, Cellular Delivery and In vivo Application of Dendrimer-based pH Sensors

The development of fluorescent indicators represented a revolution for life sciences. Genetically encoded and synthetic fluorophores with sensing abilities allowed the visualization of biologically relevant species with high spatial and temporal resolution. Synthetic dyes are of particular interest thanks to their high tunability and the wide range of measureable analytes. However, these molecules suffer several limitations related to small molecule behavior (poor solubility, difficulties in targeting, often no ratiometric imaging allowed). In this work we introduce the development of dendrimer-based sensors and present a procedure for pH measurement in vitro, in living cells and in vivo. We choose dendrimers as ideal platform for our sensors for their many desirable properties (monodispersity, tunable properties, multivalency) that made them a widely used scaffold for several biomedical devices. The conjugation of fluorescent pH indicators to the dendrimer scaffold led to an enhancement of their sensing performances. In particular dendrimers exhibit reduced cell leakage, improved intracellular targeting and allow ratiometric measurements. These novel sensors were successfully employed to measure pH in living HeLa cells and in vivo in mouse brain.

Synthesis, Cellular Delivery and In vivo Application of Dendrimer-based pH Sensors

Fluorescence sensors are powerful tools in life science. Here we describe a methodology to synthesize and use dendrimer-based fluorescent sensors to measure pH in living cells and in vivo. The dendritic scaffold enhances the properties of conjugated fluorescent dyes leading to improved sensing properties.

Síntese, Entrega Celular e<em&gt; In vivo</em&gt; Aplicação de sensores de pH à base de Dendrímero

The development of  fluorescent indicators represented a revolution for life sciences. Genetically  encoded and synthetic fluorophores with sensing ...

Química

Amide Coupling Reaction for the Synthesis of Bispyridine-based Ligands and Their Complexation to Platinum as Dinuclear Anticancer Agents

Amide coupling reactions can be used to synthesize bispyridine-based ligands for use as bridging linkers in multinuclear platinum anticancer drugs. Isonicotinic acid, or its derivatives, are coupled to variable length diaminoalkane chains under an inert atmosphere in anhydrous DMF or DMSO with the use of a weak base, triethylamine, and a coupling agent, 1-propylphosphonic anhydride. The products precipitate from solution upon formation or can be precipitated by the addition of water. If desired, the ligands can be further purified by recrystallization from hot water. Dinuclear platinum complex synthesis using the bispyridine ligands is done in hot water using transplatin. The most informative of the chemical characterization techniques to determine the structure and gross purity of both the bispyridine ligands and the final platinum complexes is 1H NMR with particular analysis of the aromatic region of the spectra (7-9 ppm). The platinum complexes have potential application as anticancer agents and the synthesis method can be modified to produce trinuclear and other multinuclear complexes with different hydrogen bonding functionality in the bridging ligand.

This protocol describes the use of amide coupling reactions of isonicotinic acid and diaminoalkanes to form bridging ligands suitable for use in the synthesis of multinuclear platinum complexes, which combine aspects of the anticancer drugs BBR3464 and picoplatin.

Acoplamento de amida de reacção para a síntese de ligandos baseados em Bispyridine e sua complexação com platina como agentes anticancerígenos dinucleares

Amide coupling reactions can be used to synthesize bispyridine-based ligands for use as bridging linkers in multinuclear platinum anticancer drugs. ...

Synthesis and Characterization of Functionalized Metal-organic Frameworks

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy.

Synthesis, activation, and characterization of intentionally designed metal-organic framework materials is challenging, especially when building blocks are incompatible or unwanted polymorphs are thermodynamically favored over desired forms. We describe how applications of solvent-assisted linker exchange, powder X-ray diffraction in capillaries and activation via supercritical CO2 drying, can address some of these challenges.

Síntese e caracterização de funcionalizados metal-organic frameworks

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and ...

Preparation and Use of Carbonyl-decorated Carbenes in the Activation of White Phosphorus

Here we present a protocol for the synthesis of two distinct carbonyl-decorated carbenes. Both carbenes can be prepared using nearly identical procedures in multi-gram scale quantities. The goal of this manuscript is to clearly detail how to handle and prepare these unique carbenes such that a synthetic chemist of any skill level can work with them. The two carbenes described are a diamidocarbene (DAC, carbene 1) and a monoamidoaminocarbene (MAAC 2). These carbenes are highly electron-deficient and as such display reactivity profiles that are atypical of more traditional N-heterocyclic carbenes. Additionally, these two carbenes only differ in their electrophilic character and not their steric parameters, making them ideal for studying how carbene electronics influence reactivity. To demonstrate this phenomenon, we are also describing the activation of white phosphorus (P4) using these carbenes. Depending on the carbene used, two very different phosphorus-containing compounds can be isolated. When the DAC 1 is used, a tris(phosphaalkenyl)phosphane can be isolated as the exclusive product. Remarkably however, when MAAC 2 is added to P4 under identical reaction conditions, an unexpected carbene-supported P8&#160;allotrope of phosphorus is isolated exclusively. Mechanistic studies demonstrate that this carbene-supported P8allotrope forms via a [2+2] cycloaddition dimerization of a transient diphosphene which has been trapped by treatment with 2,3-dimethyl-1,3-butadiene.

Here, we present a protocol for the synthesis of two carbonyl-decorated carbenes. The protocol makes these interesting compounds readily available to chemists of all skill levels. In addition to the synthesis of these two carbenes, their use in the activation of white phosphorus is also described.

Preparação e Utilização de carbenos Carbonyl decorados na ativação de fósforo branco

Here we present a protocol for the synthesis of two distinct carbonyl-decorated carbenes. Both carbenes can be prepared using nearly identical procedures ...

Metal-free Synthesis of Ynones from Acyl Chlorides and Potassium Alkynyltrifluoroborate Salts

Ynones are a valuable functional group and building block in organic synthesis. Ynones serve as a precursor to many important organic functional groups and scaffolds. Traditional methods for the preparation of ynones are associated with drawbacks including harsh conditions, multiple purification steps, and the presence of unwanted byproducts. An alternative method for the straightforward preparation of ynones from acyl chlorides and potassium alkynyltrifluoroborate salts is described herein. The adoption of organotrifluoroborate salts as an alternative to organometallic reagents for the formation of new carbon-carbon bonds has a number of advantages. Potassium organotrifluoroborate salts are shelf stable, have good functional group tolerance, low toxicity, and a wide variety are straightforward to prepare. The title reaction proceeds rapidly at ambient temperature in the presence of a Lewis acid without the exclusion of air and moisture. Fair to excellent yields may be obtained via reaction of various aryl and alkyl acid chlorides with alkynyltrifluoroborate salts in the presence of boron trichloride.

The goal of this manuscript is to demonstrate a straightforward method for the preparation of ynones from acyl chloride and potassium alkynyltrifluoroborate salt starting materials. The one-pot reaction proceeds rapidly in the presence of boron trichloride without exclusion of air and moisture.

Síntese livre de metais de Ynones da Acil cloretos de potássio e sais Alkynyltrifluoroborate

Ynones are a valuable functional group and building block in organic synthesis. Ynones serve as a precursor to many important organic functional groups ...

Synthesis and Reaction Chemistry of Nanosize Monosodium Titanate

This paper describes the synthesis and peroxide-modification of nanosize monosodium titanate (nMST), along with an ion-exchange reaction to load the material with Au(III) ions. The synthesis method was derived from a sol-gel process used to produce micron-sized monosodium titanate (MST), with several key modifications, including altering reagent concentrations, omitting a particle seed step, and introducing a non-ionic surfactant to facilitate control of particle formation and growth. The resultant nMST material exhibits spherical-shaped particle morphology with a monodisperse distribution of particle diameters in the range from 100 to 150&#160;nm. The nMST material was found to have a Brunauer-Emmett-Teller (BET) surface area of 285 m2g-1, which is more than an order of magnitude higher than the micron-sized MST. The isoelectric point of the nMST measured 3.34 pH units, which is a pH unit lower than that measured for the micron-size MST. The nMST material was found to serve as an effective ion exchanger under weakly acidic conditions for the preparation of an Au(III)-exchange nanotitanate. In addition, the formation of the corresponding peroxotitanate was demonstrated by reaction of the nMST with hydrogen peroxide.

The surfactant mediated sol-gel synthesis of nanosized monosodium titanate is described, along with preparation of the corresponding peroxide modified material. An ion-exchange reaction with Au(III) is also presented.

Síntese e Reacção Química de nanosize monossódico Titanate

This paper describes the synthesis and peroxide-modification of nanosize monosodium titanate (nMST), along with an ion-exchange reaction to load the ...

Synthesis and Characterization of Supramolecular Colloids

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical properties for applications in photonics, drug delivery and coating technology. Here we present a new family of colloidal building blocks, coined supramolecular colloids, whose self-assembly is controlled through surface-functionalization with a benzene-1,3,5-tricarboxamide (BTA) derived supramolecular moiety. Such BTAs interact via directional, strong, yet reversible hydrogen-bonds with other identical BTAs. Herein, a protocol is presented that describes how to couple these BTAs to colloids and how to quantify the number of coupling sites, which determines the multivalency of the supramolecular colloids. Light scattering measurements show that the refractive index of the colloids is almost matched with that of the solvent, which strongly reduces the van der Waals forces between the colloids. Before photo-activation, the colloids remain well dispersed, as the BTAs are equipped with a photo-labile group that blocks the formation of hydrogen-bonds. Controlled deprotection with UV-light activates the short-range hydrogen-bonds between the BTAs, which triggers the colloidal self-assembly. The evolution from the dispersed state to the clustered state is monitored by confocal microscopy. These results are further quantified by image analysis with simple routines using ImageJ and Matlab. This merger of supramolecular chemistry and colloidal science offers a direct route towards light- and thermo-responsive colloidal assembly encoded in the surface-grafted monolayer.

A protocol for the synthesis and characterization of colloids coated with supramolecular moieties is described. These supramolecular colloids undergo self-assembly upon the activation of the hydrogen-bonds between the surface-anchored molecules by UV-light.

Síntese e Caracterização de Supramoleculares Colloids

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical ...

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the development of antibody drug conjugates (ADCs) and nanomedicine, fluorescent microscopy and systems chemistry. For many of these applications, specificity of the bioconjugation method used is of prime concern. The Michael addition of maleimides with cysteine(s) on the target proteins is highly selective and proceeds rapidly under mild conditions, making it one of the most popular methods for protein bioconjugation.
We demonstrate here the modification of the only surface-accessible cysteine residue on yeast cytochrome c with a ruthenium(II) bisterpyridine maleimide. The protein bioconjugation is verified by gel electrophoresis and purified by aqueous-based fast protein liquid chromatography in 27% yield of isolated protein material. Structural characterization with MALDI-TOF MS and UV-Vis is then used to verify that the bioconjugation is successful. The protocol shown here is easily applicable to other cysteine - maleimide coupling of proteins to other proteins, dyes, drugs or polymers.

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

This protocol details the important steps required for the bioconjugation of a cysteine containing protein to a maleimide, including reagent purification, reaction conditions, bioconjugate purification and bioconjugate characterization.

Síntese de Bioconjugados de proteínas<em&gt; via</em&gt; Química cisteína-maleimida

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the ...

Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level

We demonstrate a method for the synthesis of cyclic polymers and a protocol for characterizing their diffusive motion in a melt state at the single molecule level. An electrostatic self-assembly and covalent fixation (ESA-CF) process is used for the synthesis of the cyclic poly(tetrahydrofuran) (poly(THF)). The diffusive motion of individual cyclic polymer chains in a melt state is visualized using single molecule fluorescence imaging by incorporating a fluorophore unit in the cyclic chains. The diffusive motion of the chains is quantitatively characterized by means of a combination of mean-squared displacement (MSD) analysis and a cumulative distribution function (CDF) analysis. The cyclic polymer exhibits multiple-mode diffusion which is distinct from its linear counterpart. The results demonstrate that the diffusional heterogeneity of polymers that is often hidden behind ensemble averaging can be revealed by the efficient synthesis of the cyclic polymers using the ESA-CF process and the quantitative analysis of the diffusive motion at the single molecule level using the MSD and CDF analyses.

A protocol for the synthesis and characterization of diffusive motion of cyclic polymers at the single molecule level is presented.

Síntese de polímeros cíclicos e Caracterização do seu movimento difusivo no estado fundido na molécula de nível único

We demonstrate a method for the synthesis of cyclic polymers and a protocol for characterizing their diffusive motion in a melt state at the single ...

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from benzimidazolium salts. Detailed and generalized protocols are also presented for testing the catalytic activity of such complexes in arylation and Suzuki-Miyaura cross-coupling reactions. Representative results are shown for the catalytic activity of the four complexes in arylation and Suzuki-Miyaura type reactions. For each of the reactions investigated, at least one of the four complexes successfully catalyzed the reaction, qualifying them as promising candidates for catalysis of many carbon-carbon bond-forming reactions. The protocols presented are general enough to be adapted for the synthesis, purification and catalytic activity testing of new palladium N-heterocyclic carbene complexes.

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from benzimidazolium salts. The complexes were tested for catalytic activity in arylation and Suzuki-Miyaura reactions. For each reaction investigated, at least one of the four complexes successfully catalyzed the reaction.

Complexos de paládio N-heterocíclicos de carbeno: síntese a partir de sais de benzimidazólio e atividade catalítica em reações de formação de ligações carbono-carbono

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from ...