Chemical Communications Blog

The molecule will readily adjust the size of its opening to accommodate its guest

Chemists in the US have successfully isolated the first anion of a distinctive type of pincer molecule, known as a buckycatcher, and confirmed the extraordinary flexibility it has for encapsulating guest molecules.

The buckycatcher in this study (C₆₀H₂₈) consists of a tetrabenzocyclooctaraene tether that links two corannulene (the smallest and most studied buckybowl) pincers. In previous attempts to isolate this molecule, researchers have had difficulties with solvate formation, as solvents fill the large empty cleft that the buckycatcher uses to encapsulate guest molecules. However, Marina Petrukhina, and co-workers at the University at Albany, State University of New York, have finally managed to elucidate the structure of this rather interesting molecule by developing and carrying out a rather arduous solvent-free method that involved growing the crystals in a vacuum over several months.

The buckycatcher’s flexibiliy has been suggested before, but Petrukhina‘s team provide the first experimental evidence for the adjustability of the tetrabenzocyclooctaraene tether that connects its coranulene pincers and allows them to move closer or further apart to catch guest species.

Read the full article in Chemistry World»

Read the original journal article in ChemComm:
An unsolvated buckycatcher and its first dianion
Alexander V. Zabula, Yulia V. Sevryugina, Sarah N. Spisak, Lesya Kobryn, Renata Sygula, Andrzej Sygula and Marina A. Petrukhina  
Chem. Commun., 2014, Advance Article, DOI: 10.1039/C3CC49451A, Communication

Researchers in Japan have developed the fastest known synthetic route for preparing crystalline microporous solids. The method is currently being scaled-up to meet the increasing demand for these versatile materials in industrial applications.

AlPO4-5 has been commercialised as a vapour adsorbent for refrigerators

Crystalline microporous solids are an important class of inorganic material that impact our everyday lives. Their ordered structures contain arrays of channels and voids several nanometres across, enabling them to selectively and reversibly absorb molecules based on their shapes and sizes. This has led to their widespread use as catalysts, molecular sieves and gas sensors. Research into their potential use as hydrogen storage materials for mobile energy applications is also ongoing.

However, microporous solids often crystallise slowly and typically require several hours to several weeks of hydrothermal treatment to achieve satisfactory yields, limiting their applications on industrial scales. Now, a collaborative effort from the University of Tokyo and the Mitsubishi Chemical Group has led to an ultra-fast method for preparing the aluminophosphate AlPO₄-5. A combination of rapid heating and crystal seeding completes the synthesis within one minute.

Read the full article in Chemistry World»

Read the original journal article in ChemComm:
One-minute synthesis of crystalline microporous aluminophosphate (AlPO4-5) by combining fast heating with a seed-assisted method
Zhendong Liu, Toru Wakihara, Daisuke Nishioka, Kazunori Oshima, Takahiko Takewaki and Tatsuya Okubo  
Chem. Commun., 2014, Advance Article, DOI: 10.1039/C3CC49548E, Communication

Scientists based in the US have developed a new strategy to simplify the chemical synthesis of complex carbohydrates.

TFA simultaneously cleaves all protecting groups from the precursors to form the desired oligosaccharides in quantitative yields

Oligosaccharides are polymeric carbohydrates consisting of a small number of monosaccharide monomers. They are essential to all cellular organisms, playing vital roles in cell recognition and signalling.

Automated methods are routinely used to prepare biomacromolecules such as peptides and nucleic acids, but similar strategies in oligosaccharide synthesis are far less developed. Oligosaccharides contain a large number of hydroxyl groups which normally have to be protected orthogonally, i.e. in such a way that they can be unmasked independently of one another. This poses a great challenge to chemists and has hindered progress towards automated carbohydrate synthesis.

Classical protecting groups for hydroxyl groups include benzyl ethers, which are generally removed via hydrogenolysis or dissolving metal reduction, and acetate, benzoate or pivaloate esters, which are cleaved using base-catalysed hydrolysis. While these reactions are well established, a high level of training in practical organic chemistry is required to carry them out, in contrast to deprotection in automated peptide synthesis, which can be as simple as shaking the protected molecule with an acidic or basic solution.

Xinyu Liu and Yao Li at the University of Pittsburgh have developed a series of acid-cleavable PMB- and NAP-capped 4-hydroxybutanoic acid and 2-(hydroxymethyl)benzoic acid ester-type protecting groups that act as surrogates of acetate and benzoate. Trifluoroacetic acid (TFA) in toluene can simultaneously cleave all of these groups during the final stage of an oligosaccharide assembly to emulate the synthetic efficiency traditionally reserved for peptide chemistry.

Read the full article in Chemistry World»

Read the original journal article in ChemComm:
Tunable Acid-Sensitive Ester Protecting Groups in Oligosaccharide Synthesis
Yao Li and Xinyu Liu  
Chem. Commun., 2013, Accepted Manuscript, DOI: 10.1039/C3CC49205B, Communication

A modular LHC built on the DNA three-way junction
Markus Probst, Simon M. Langenegger and Robert Häner
Chem. Commun., 2014, 50, 159-161
DOI: 10.1039/C3CC47490A, Communication

Free to access until 19th January 2014

One pot synthesis of cyclohexanone oxime from nitrobenzene using a bifunctional catalyst
Paula Rubio-Marqués, Juan Carlos Hernández-Garrido, Antonio Leyva-Pérez and Avelino Corma
Chem. Commun., 2014, Advance Article
DOI: 10.1039/C3CC47693F, Communication

Free to access until 19th January 2014

Recent advances in cooperative bimetallic asymmetric catalysis: dinuclear Schiff base complexes
Shigeki Matsunaga and Masakatsu Shibasaki
Chem. Commun., 2014, Advance Article
DOI: 10.1039/C3CC47587E, Feature Article

Free to access until 19th January 2014

From assembled metal–organic framework nanoparticles to hierarchically porous carbon for electrochemical energy storage
Arlin Jose Amali, Jian-Ke Sun and Qiang Xu
Chem. Commun., 2014, Advance Article
DOI: 10.1039/C3CC48112C, Communication

Free to access until 19th January 2014

Nitrogenase: a general hydrogenator of small molecules
Ian Dance
Chem. Commun., 2013, 49, 10893-10907
DOI: 10.1039/C3CC46864J, Feature Article

Free to access until 19th January 2014

In situ atomic imaging of coalescence of Au nanoparticles on graphene: rotation and grain boundary migration
Jong Min Yuk, Myoungho Jeong, Sang Yun Kim, Hyeon Kook Seo, Jihyun Kim and Jeong Yong Lee
Chem. Commun., 2013, 49, 11479-11481
DOI: 10.1039/C3CC46545D, Communication
From themed collection Structure and chemistry of materials from in-situ electron microscopy

Free to access until 19th January 2014

THAT’S NOT ALL! Click here for more free HOT ChemComm articles for December!!

Carriers that release hydrophobic substances at cell membranes but do not enter the cells themselves could be the foundation for a new way to deliver drugs into cells, according to a team of scientists in Germany.

  

Mailänder and his team tested their approach using biodegradable poly-L-lactide nanoparticles that fleetingly touch the cell’s phospholipid layer for around 100ms to release their cargo, in this case a hydrophobic dye that was left to stain the cell membrane, before quickly detaching from the cell – hence the term ‘kiss-and-run.’ They later found that the dye, representing water-insoluble drug cargo, was ultimately stored as lipid droplets within the cell.

Read the full article in Chemistry World»

Read the original journal article in ChemComm:
Drug delivery without nanoparticle uptake: delivery by a kiss-and-run mechanism on the cell membrane
Daniel Hofmann, Claudia Messerschmidt, Markus B. Bannwarth, Katharina Landfester and Volker Mailänder  
Chem. Commun., 2014, Advance Article, DOI: 10.1039/C3CC48130A

Bacterial toxins that undergo unique cell interactions have been used to perform logic functions by researchers in Germany. In a similar way to how we store letters and words on computer disks, these proteins provide a new approach to storing information within whole cells.

The three components of the enterotoxin must bind to the cell membrane in a specific order to activate the logic gate

Synthetic biologists have already modified the genetic code of cells to create biocircuits capable of performing specific Boolean logic functions, for example AND gates and OR gates, for sensing, diagnostics and therapeutics. These genetic logic gates require sophisticated and extensive modifications of the cell DNA. Now, Erwin Märtlbauer and his team at the University of Munich have developed a comparably simple approach where proteins interact with the membrane of whole cells to produce a variety of combinatorial and sequential logic operators.

A unique enterotoxin protein made up of three components that must individually bind in a specific order to the cell membrane to cause cell death is central to Märtlbauer’s system. By using this sequential binding as the input of the logic gate and cell death as the output the team have created a logic operator with memory that is similar to a keypad lock, where unless the right key is pressed in the right order nothing will happen.

Read the full article in Chemistry World»

Read the original journal article in ChemComm:
Ordered self-assembly of proteins for computation in mammalian cells
Kui Zhu, Jianzhong Shen, Richard Dietrich, Andrea Didier, Xingyu Jiang and Erwin Märtlbauer  
Chem. Commun., 2014, Advance Article, DOI: 10.1039/C3CC48100J

After years of trying, scientists have finally isolated 1,4-oxazine.¹ Among the many possible 6-membered fully unsaturated parent heterocycles containing one group 15 and one group 16 atom, 1,4-oxazine is the first to be generated and spectroscopically characterised. The closest molecule to be made in the past was a monosubstituted oxazine.² Now, Alan Aitken and colleagues at the University of St Andrews in the UK have used flash vacuum pyrolysis to remove the N–tert-butoxycarbonyl group from the previous attempt and taken the synthesis all the way to 1,4-oxazine. Unsurprisingly, being a non-aromatic system, 1,4-oxazine is very unstable. 

Libraries of small molecules are central to screening processes in biomedical research and this work could aid wider efforts attempting to expand those libraries by developing synthetic routes to nitrogen-containing heterocyclic scaffolds. 

You can read this article in Chemistry World» 

Read the original journal article in ChemComm:
1,4-Oxazine
R. Alan Aitken, Kati M. Aitken, Philip G. Carruthers, Marc-Alexandre Jean and Alexandra M. Z. Slawin  
Chem. Commun., 2013,49, 11367-11369, DOI: 10.1039/C3CC47801G

pH-Triggered Au-fluorescent mesoporous silica nanoparticles for 19F MR/fluorescent multimodal cancer cellular imaging
Shizhen Chen, Yuqi Yang, Haidong Li, Xin Zhou and Maili Liu
Chem. Commun., 2013, Advance Article
DOI: 10.1039/C3CC47324D, Communication

Free to access until 15th December 2013

Nitrogenase: a general hydrogenator of small molecules
Ian Dance
Chem. Commun., 2013,49, 10893-10907
DOI: 10.1039/C3CC46864J, Feature Article

Free to access until 15th December 2013

Epoxidation of bromoallenes connects red algae metabolites by an intersecting bromoallene oxide – Favorskii manifold
D. Christopher Braddock, James Clarke and Henry S. Rzepa
Chem. Commun., 2013,49, 11176-11178
DOI: 10.1039/C3CC46720A, Communication

Free to access until 15th December 2013

Differential interference contrast microscopy imaging of micrometer-long plasmonic nanowires
Ji Won Ha, Kuangcai Chen and Ning Fang
Chem. Commun., 2013,49, 11038-11040
DOI: 10.1039/C3CC46871B, Communication
From themed collection Structure and chemistry of materials from in-situ electron microscopy

Free to access until 15th December 2013

Stereocontrolled synthesis of the oxathiabicyclo[3.3.1]nonane core structure of tagetitoxin
Hitomi Yamada, Masaatsu Adachi and Toshio Nishikawa
Chem. Commun., 2013,49, 11221-11223
DOI: 10.1039/C3CC46949B, Communication

Free to access until 15th December 2013

Incorporation by coordination and release of the iron chelator drug deferiprone from zinc-based metal–organic frameworks
Andrew D. Burrows, Monika Jurcic, Luke L. Keenan, Rebecca A. Lane, Mary F. Mahon, Mark R. Warren, Harriott Nowell, Michael Paradowski and John Spencer
Chem. Commun., 2013,49, 11260-11262
DOI: 10.1039/C3CC45689G, Communication

Free to access until 15th December 2013

A mixed dicarboxylate strut approach to enhancing catalytic activity of a de novo urea derivative of metal–organic framework UiO-67
Paul W. Siu, Zachary J. Brown, Omar K. Farha, Joseph T. Hupp and Karl A. Scheidt
Chem. Commun., 2013,49, 10920-10922
DOI: 10.1039/C3CC47177B, Communication

Free to access until 15th December 2013

A new technique for the accurate and fast detection of amino acids has been developed by researchers in the US. The simple method, employing cucurbiturils and the lanthanide europium, could light the way to improvements in nutritional analysis and drug detection.  

Amino acids are essential building blocks for all living beings. Abnormal amino acid levels can indicate underlying health problems such as malnutrition, pancreatitis and Alzheimer’s disease. Conventional amino acid sensing techniques involve chromatography or electrochemical methods, which can be costly and must be performed by skilled operators.  

The method proposed by Pavel Anzenbacher Jr and coworkers at Bowling Green State University in Ohio analyses fluorescence signals when guest europium ions are displaced from an array of two cucurbituril host probes. One of the probes is cylindrical and prefers to bind smaller molecules in a host–guest fashion, whilst the other is a larger linear molecule that wraps around larger analytes.  

Probe fluorescence is quenched when an Eu ion is bound. When the Eu is displaced by an analyte, the fluorescence is "turned-on"

 Read the full article in Chemistry World»  

Read the original journal article in ChemComm:
“Turn-on” fluorescent sensor array for basic amino acids in water
Tsuyoshi Minami, Nina A. Esipenko, Ben Zhang, Lyle Isaacs and Pavel Anzenbacher  
Chem. Commun., 2014, Advance Article, DOI: 10.1039/C3CC47416J

Cobalt-based crystal surrounded by nickel-based crystal (top) and cobalt-based crystal surrounded by zinc-based crystal (bottom)

Scientists based in France are behind these peculiar looking crystals. Sylvie Ferlay, Mir Wais Hosseini and colleagues at the University of Strasbourg used a molecular tectonics strategy to prepare the crystals. In molecular tectonics, building blocks, called tectons, are designed to recognise each other so that they self-assemble into molecular networks when placed together.

Combining M²⁺ cations (where M = Co, Ni, Cu or Zn) with 2,4,6-pyridinetricarboxylic acid, bisamidinium dications and sodium hydroxide resulted in metal complexes that interconnected into single crystals of different colours depending on the metal cation. Single crystals based on one metal were then immersed in a solution containing the same ligand (2,4,6-pyridinetricarboxylic acid) and organic tectons (bisamidinium dications) and a different metal cation. The single crystals acted as seeds for the crystallisation of the coordination polymer of the different metal cation since the unit cells fitted almost perfectly to each other. Single crystals of one compound grew around the single crystal of another  to give a crystal within a crystal.

This crystal engineering strategy is a powerful tool for preparing crystalline materials with different crystalline domains, the researchers say. It just leaves us to wonder how many coloured stripes could be added on?

You can also read this article in Chemistry World

Read the original journal article in ChemComm:
Molecular tectonics: from crystals to crystals of crystals
Gabriela Marinescu, Sylvie Ferlay, Nathalie Kyritsakas and Mir Wais Hosseini  
Chem. Commun., 2013,49, 11209-11211, DOI: 10.1039/C3CC45205K