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981.
In Situ Electrodeposition of an Asymmetric Sol–Gel Membrane Based on an Octadecyltrimethoxysilane Langmuir Film
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Maria Hitrik Prof. Ovadia Lev Prof. Daniel Mandler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(38):12104-12113
The unique properties of Langmuir film formation were utilized in assembling a thin skin of an asymmetric membrane. An octadecyltrimethoxysilane (ODTMS) Langmuir monolayer was formed at the air–water interface and served as the substrate for growing a bulky sol–gel polymer in situ. The latter was based on the electrochemical deposition of tetramethoxysilane dissolved in the water subphase by means of horizontal touch electrochemistry. The resultant asymmetric layer that consisted of a thin hydrophobic ODTMS Langmuir film connected to a bulk hydrophilic sol–gel network was studied in situ and ex situ by using various techniques, such as cyclic voltammetry, electrochemical impedance spectroscopy (EIS), scanning electron microscopy, transmission electron microscopy (TEM), and goniometry. We found that a porous hydrophilic film grew on top of a hydrophobic layer as was evident from TEM, contact angle, and EIS analyses. The film thickness and film permeability could be controlled by changing the deposition conditions such as the potential window applied and its duration. Hence, this method offers an alternative approach for assembling asymmetric films for various applications 相似文献
982.
Comparative Studies of Thermally Induced Homolytic CarbonCarbon Bond Cleavage Reactions of Strained Dicarba[2]ferrocenophanes and Their Ring‐Opened Oligomers and Polymers
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Andrew D. Russell Prof. Joe B. Gilroy Prof. Ian Manners 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(14):4077-4085
Reactivity studies of dicarba[2]ferrocenophanes and also their corresponding ring‐opened oligomers and polymers have been conducted in order to provide mechanistic insight into the processes that occur under the conditions of their thermal ring‐opening polymerisation (ROP) (300 °C). Thermolysis of dicarba[2]ferrocenophane rac‐[Fe(η5‐C5H4)2(CHPh)2] (rac‐ 14 ; 300 °C, 1 h) does not lead to thermal ROP. To investigate this system further, rac‐ 14 was heated in the presence of an excess of cyclopentadienyl anion, to mimic the postulated propagating sites for thermally polymerisable analogues. This afforded acyclic [(η5‐C5H5)Fe(η5‐C5H4)‐CH2Ph] ( 17 ) through cleavage of both a Fe?Cp bond and also the C?C bond derived from the dicarba bridge. Evidence supporting a potential homolytic C?C bond cleavage pathway that occurs in the absence of ring‐strain was provided through thermolysis of an acyclic analogue of rac‐ 14 , namely [(η5‐C5H5)Fe(η5‐C5H4)(CHPh)2‐C5H5] ( 15 ; 300 °C, 1 h), which also afforded ferrocene derivative 17 . This reactivity pathway appears general for post‐ROP species bearing phenyl substituents on adjacent carbons, and consequently was also observed during the thermolysis of linear polyferrocenylethylene [Fe(η5‐C5H4)2(CHPh)2]n ( 16 ; 300 °C, 1 h), which was prepared by photocontrolled ROP of rac‐ 14 at 5 °C. This afforded ferrocene derivative [Fe(η5‐C5H4CH2Ph)2] ( 23 ) through selective cleavage of the ?H(Ph)C?C(Ph)H? bonds in the dicarba linkers. These processes appear to be facilitated by the presence of bulky, radical‐stabilising phenyl substituents on each carbon of the linker, as demonstrated through the contrasting thermal properties of unsubstituted linear trimer [(η5‐C5H5)Fe(η5‐C5H4)(CH2)2(η5‐C5H4)Fe(η5‐C5H4)(CH2)2(η5‐C5H4)Fe(η5‐C5H5)] ( 29 ) with a ?H2C?CH2? spacer, which proved significantly more stable under analogous conditions. Evidence for the radical intermediates formed through C?C bond cleavage was detected through high‐resolution mass spectrometric analysis of co‐thermolysis reactions involving rac‐ 14 and 15 (300 °C, 1 h), which indicated the presence of higher molecular weight species, postulated to be formed through cross‐coupling of these intermediates. 相似文献
983.
Direct X‐ray Observation of Trapped CO2 in a Predesigned Porphyrinic Metal–Organic Framework
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Jacob A. Johnson Dr. Shuang Chen Tyler C. Reeson Dr. Yu‐Sheng Chen Prof. Xiao Cheng Zeng Prof. Jian Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(25):7632-7637
Metal–organic frameworks (MOFs) are emerging microporous materials that are promising for capture and sequestration of CO2 due to their tailorable binding properties. However, it remains a grand challenge to pre‐design a MOF with a precise, multivalent binding environment at the molecular level to enhance CO2 capture. Here, we report the design, synthesis, and direct X‐ray crystallographic observation of a porphyrinic MOF, UNLPF‐2, that contains CO2‐specific single molecular traps. Assembled from an octatopic porphyrin ligand with [Co2(COO)4] paddlewheel clusters, UNLPF‐2 provides an appropriate distance between the coordinatively unsaturated metal centers, which serve as the ideal binding sites for in situ generated CO2. The coordination of CoII in the porphyrin macrocycle is crucial and responsible for the formation of the required topology to trap CO2. By repeatedly releasing and recapturing CO2, UNLPL‐2 also exhibits recyclability. 相似文献
984.
Biofunctionalization of Multiwalled Carbon Nanotubes by Electropolymerized Poly(pyrrole‐concanavalin A) Films
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Dr. Vladislav Papper Dr. Kamal Elouarzaki Dr. Karine Gorgy Ayrine Sukharaharja Dr. Serge Cosnier Prof. Robert S. Marks 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(42):13561-13564
The synthesis and electropolymerization of a pyrrolic concanavalin A derivative (pyrrole‐Con A) onto a multiwalled carbon nanotube (MWCNT) deposit is reported. Glucose oxidase was then immobilized onto the MWCNT‐poly(pyrrole‐Con A) coating by affinity carbohydrate interactions with the polymerized Con A protein. The resulting enzyme electrode was applied to the amperometric detection of glucose exhibiting a high sensitivity of 36 mA cm?2 mol?1 L and a maximum current density of 350 μA cm?2. 相似文献
985.
Dr. Arlin Jose Amali Dr. Hideto Hoshino Dr. Chun Wu Dr. Masanori Ando Prof. Qiang Xu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(27):8279-8282
Highly photoluminescent carbon nanodots (CNDs) were synthesized for the first time from metal–organic framework (MOF, ZIF‐8) nanoparticles. Coupled with fluorescence and non‐toxic characteristics, these carbon nanodots could potentially be used in biosafe color patterning. 相似文献
986.
Highly Enantioselective Catalytic System for Asymmetric Copolymerization of Carbon Dioxide and Cyclohexene Oxide
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Yuan‐Zhao Hua Liu‐Jie Lu Pei‐Jin Huang Dong‐Hui Wei Prof. Ming‐Sheng Tang Prof. Dr. Min‐Can Wang Prof. Dr. Jun‐Biao Chang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(39):12394-12398
A new ligand can be easily prepared, and its intramolecular dinuclear zinc complexes act as a high performance catalyst for the asymmetric alternating copolymerization of cyclohexene oxide and CO2 under very mild conditions (1 atm CO2, room temperature), affording completely alternating polycarbonates with up to 93.8 % enantiomeric excess (ee) and 98 % yield. A high Mn value of 28 600 and a relatively narrow polydispersity (Mw/Mn ratio) of 1.43 were also achieved. 相似文献
987.
Development of a Halide‐Free Aluminium‐Based Catalyst for the Synthesis of Cyclic Carbonates from Epoxides and Carbon Dioxide
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Dr. Jose A. Castro‐Osma Prof. Michael North Dr. Xiao Wu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(46):15005-15008
Kinetic studies of the synthesis of glycerol carbonate from glycidol and carbon dioxide have been carried out. These showed that under suitable reaction conditions, bimetallic aluminium(salen) complex 4 is able to catalyse the conversion of epoxides into the corresponding cyclic carbonates without the need for a co‐catalyst. 相似文献
988.
Facile Electrochemical Hydrogenation and Chlorination of Glassy Carbon to Produce Highly Reactive and Uniform Surfaces for Stable Anchoring of Thiolated Molecules
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Ahmed M. Debela Dr. Mayreli Ortiz Dr. Valerio Beni Prof. Dr. Ciara K. O'Sullivan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(25):7646-7654
Carbon is a highly adaptable family of materials and is one of the most chemically stable materials known, providing a remarkable platform for the development of tunable molecular interfaces. Herein, we report a two‐step process for the electrochemical hydrogenation of glassy carbon followed by either chemical or electrochemical chlorination to provide a highly reactive surface for further functionalization. The carbon surface at each stage of the process is characterized by AFM, SEM, Raman, attenuated total reflectance (ATR) FTIR, X‐ray photoelectron spectroscopy (XPS), and electroanalytical techniques. Electrochemical chlorination of hydrogen‐terminated surfaces is achieved in just 5 min at room temperature with hydrochloric acid, and chemical chlorination is performed with phosphorus pentachloride at 50 °C over a three‐hour period. A more controlled and uniform surface is obtained using the electrochemical approach, as chemical chlorination is observed to damage the glassy carbon surface. A ferrocene‐labeled alkylthiol is used as a model system to demonstrate the genericity and potential application of the highly reactive chlorinated surface formed, and the methodology is optimized. This process is then applied to thiolated DNA, and the functionality of the immobilized DNA probe is demonstrated. XPS reveals the covalent bond formed to be a C?S bond. The thermal stability of the thiolated molecules anchored on the glassy carbon is evaluated, and is found to be far superior to that on gold surfaces. This is the first report on the electrochemical hydrogenation and electrochemical chlorination of a glassy carbon surface, and this facile process can be applied to the highly stable functionalization of carbon surfaces with a plethora of diverse molecules, finding widespread applications. 相似文献
989.
Robert W. Hicklin Tania L. López Silva Prof. Paul J. Hergenrother 《Angewandte Chemie (International ed. in English)》2014,53(37):9880-9883
Fenestranes are an intriguing class of highly strained molecules possessing a quaternary carbon with bonds that deviate from the canonical tetrahedral geometry. Herein we report the discovery that the natural product pleuromutilin can be used as a structurally complex starting material for the synthesis of a series of bridged cis,cis,cis,cis‐[4.5.5.5]‐ and cis,cis,cis,cis‐[4.5.7.5]oxafenestranes through a carbocation rearrangement cascade. X‐ray crystallographic analysis of several cis,cis,cis,cis‐[4.5.5.5]oxafenestranes shows a significant planarization of the central tetracoordinate carbon atom and demonstrates the influence of bridgehead substituents and bridging rings on planarity. 相似文献
990.
Dr. Roman S. Erdmann Dr. Hideo Takakura Alexander D. Thompson Felix Rivera‐Molina Dr. Edward S. Allgeyer Prof. Dr. Joerg Bewersdorf Prof. Dr. Derek Toomre Prof. Dr. Alanna Schepartz 《Angewandte Chemie (International ed. in English)》2014,53(38):10242-10246
We report a lipid‐based strategy to visualize Golgi structure and dynamics at super‐resolution in live cells. The method is based on two novel reagents: a trans‐cyclooctene‐containing ceramide lipid (Cer‐TCO) and a highly reactive, tetrazine‐tagged near‐IR dye (SiR‐Tz). These reagents assemble via an extremely rapid “tetrazine‐click” reaction into Cer‐SiR, a highly photostable “vital dye” that enables prolonged live‐cell imaging of the Golgi apparatus by 3D confocal and STED microscopy. Cer‐SiR is nontoxic at concentrations as high as 2 μM and does not perturb the mobility of Golgi‐resident enzymes or the traffic of cargo from the endoplasmic reticulum through the Golgi and to the plasma membrane. 相似文献