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Outstanding organocatalysis – An article collection

13 Jun 2012

Catalysts are key to some of the most important reactions on the planet; a world without the Haber process or catalysts to crack crude oil is difficult to imagine. Not to mention the enzymatic reactions that are crucial to all life on earth.

Organocatalysts are an important class of catalyst and consist of carbon-based molecules often functionalised with oxygen, sulfur, nitrogen or phosphorus. They have shown promise in a range of reactions including hydrogenation, Diels-Alder, Michael and Mannich reactions, and are of particular interest in asymmetric reactions.

To help keep you up-to-date with the latest in cutting-edge organocatalytic research we have made the following articles free to access until 9^th July. After reading all these there will be little you won’t know about the exciting world of organocatalysis!

Click here for the full list of free articles

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Mirrors to improve dye sensitised solar cell performance

11 Jun 2012

Mirror-like nanoparticles can boost the efficiency of solar cells. Scientists in Australia coated a solar cell’s TiO₂ photoanode with cubic cerium oxide nanoparticles. The nanoparticles’ large mirror-like facets are good at scattering light back onto the TiO₂ nanoparticles, resulting in a 17.8% improvement in the power conversion efficiency compared to regular dye sensitised solar cells.

Link to journal article
Cubic CeO₂ Nanoparticles as Mirror-like Scattering Layer for Efficient Light Harvesting in Dye-Sensitized Solar Cells
Lianzhou Wang
Chem. Commun., 2012, DOI: 10.1039/c2cc32239k

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Personal glucose sensors can be adapted to detect cancer too

06 Jun 2012

Personal glucose sensors (PGS) can be used to detect cancer, say Chinese scientists.

The team loaded magnetic beads with invertase (an enzyme that catalyses the hydrolysis of sucrose to glucose) and an antibody. The beads acted as a label for a lung cancer biomarker that had been captured on an antibody-coated ELISA plate. By monitoring the production of glucose from sucrose with a PGS, they could indirectly measure the amount of the biomarker down to the sub-nanogram per millilitre level.

Link to journal article
Personal glucose sensor for point-of-care early cancer diagnosis
Jiao Su, Jin Xu, Ying Chen, Yun Xiang, Ruo Yuan and Yaqin Cha
Chem. Commun., 2012, Accepted Manuscript, DOI: 10.1039/C2CC32729E

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Easy synthesis of nanocups and nanopatches

29 May 2012

Graphical abstract: Facile synthesis of functional Au nanopatches and nanocups A gold nanocup – it sounds like something a posh fairy might drink out of. But actually, metal nanocups are promising particles for sensing and nanoelectronics thanks to their plasmon coupling and light scattering properties. Until now, they have been difficult to make but Jinlong Gong at Tianjin University, China, Zhihong Nie, at the University of Maryland, USA, and colleagues have developed a new easy route suitable for large scale synthesis.

The team used a template-free, liquid-liquid interfacial reaction to build up the gold cups round polymer particles. These so called ‘patchy particles’ are themselves attractive as building blocks for nanostructures due to the directional interactions between the metal patches. Removing the polymers using organic solvent revealed the nanocups with diameters as small as 76 nm. The team demonstrated that the cups can enhance surface enhanced Raman scattering intensity up to the order of 10⁸.

Find out more – download Gong’s ChemComm communication

Want to learn more about surface enhanced Raman spectroscopy? Check out the ChemComm web theme >

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Chiral Control for the Future?

24 May 2012

Tragedies such as the thalidomide scandal led to a re-think as to how pharmaceutical drugs are tested and examined before their sale to the public. Prior to this, racemic mixtures were often administered yet sometimes only one enantiomer of the compound gave the therapeutic properties while the other caused serious side effects. For this reason, huge interest developed in controlling reactions so that only enantiomer would be formed – not a trivial task for the many millions of molecules tumbling around in a round bottom flask! Such is the significance of this problem that the 2001 Nobel Prize for Chemistry was awarded to Sharpless, Noyori and Knowles for work in this field.

: Figure 1: Preparation of chiral-at-copper complexes

Many of the methods to obtain this selectivity focus on controlling the orientation of the molecule by building a bulky pocket around the reaction site. Doing so means a reaction can only occur on one side and, as a result, only one enantiomer is created. While this technique has been shown to work well, an alternative approach is to create a reaction site which itself can control the orientation of the molecule. It is exactly this that Paul Newman, Kingsley Cavell and Benson Kariuki at Cardiff University have achieved.

The idea behind the concept is that the reaction site itself is a more efficient way of transferring the control of the chirality. To do this they have created a ‘chiral-at-metal’ Cu(I) complex (Figure 1) which is itself very rare due to the instability of these types of compounds. The characterisation of such an exciting complex is certainly worthy of rapid communication but I hope to see further papers on this work in the near future, giving us an insight into how well this complex performs as a catalyst and how effective it is at transferring chirality. Over time, the catalyst will surely undergo many subtle alterations to improve its performance but only time will tell if this is truly going to be the most effective method of controlling chirality.

Keen to read more? Download this ChemComm article here.

Posted on behalf of Ruaraidh McIntosh, Chemical Communications web writer.

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First synthesis of potential sleeping sickness drug lead

22 May 2012

Researchers from the University of Oxford have completed the first synthesis of (±)-hydroxyanthecotulide, an antiparasitic molecule that displays a number of other interesting biological activities.

David Hodgson’s group used their previously developed Cr(II)-catalysed allylation reaction to construct the molecule’s carbon skeleton. Alcohol 1 was constructed in a single step and then oxidised to aldehyde 2, which was used crude in an allylation reaction with 3 to give the anti-product (5) in good yields and high levels of diastereoselectivity.

The desired enone functionality was revealed by a Meyer-Schuster rearrangement of 5, which proceeded in excellent yield with in situ desilylation occurring under the reaction conditions.

¹H and ¹³C NMR spectra of 6a were then compared with spectra of an authentic sample of (±)-hydroxyanthecotulide. Discrepancies in this spectral data encouraged the researchers to synthesise syn–6b, by inversion of the C-4 secondary alcohol.

Gratifyingly, the spectra of syn-(±)-hydroxyanthecotulide (6b) was found to match data for the authentic sample and HPLC analysis provided further evidence to confirm that natural (±)-hydroxyanthecotulide, possesses syn-stereochemistry.

This research enabled the synthesis of both anti– and syn-(±)-hydroxyanthecotulide in 5 and 7 steps respectively, and may provide an attractive synthetic route for access to analogues of this biologically relevant family of molecules.

Download the full communication to find out more >

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REMINDER: ChemComm-RSC Prizes and Awards Symposium in Oxford on Wednesday

21 May 2012

Don’t miss out on Wednesday’s ChemComm–RSC Prizes & Awards Symposium jointly organised with the RSC Dalton Division!

Date: Wednesday 23rd May 2012
Location: Inorganic Chemistry Laboratory lecture theatre, South Parks Road, University of Oxford, UK
Time: 11am – 6.45 pm

The purpose of this event is to bring together scientists in a stimulating and friendly environment to recognise the achievements of individuals in advancing the chemical sciences and also to foster collaborations. The symposium will appeal to academic and industrial scientists with an interest in inorganic and supramolecular chemistry. Attendance at the symposium is FREE OF CHARGE and student participation is strongly encouraged.

The following distinguished scientists have agreed to speak:

Professor Manfred Scheer, University of Regensburg, Germany (ChemComm sponsored speaker) – Polyphosphorus Ligands in Supramolecular Chemistry
Professor Kay Severin, EPFL, Switzerland (ChemComm sponsored speaker) – Multicomponent Assembly of Molecular and Polymeric Nanostructures
Professor Andrew Cooper, University of Liverpool, UK (ChemComm sponsored speaker) – Porous Organic Cages: MOFs Minus the Metals?
Professor Lawrence Que, University of Minnesota, USA (Inorganic Mechanisms Award 2011 Winner) – C-H Bond Cleavage by High-Valent Non-haem Iron-Oxo Complexes
Professor Russell Morris, University of St Andrews, UK (Applied Inorganic Chemistry Award 2011 Winner) – Adsorption, storage and delivery of medically important gases in porous solids
Dr Jonathan Nitschke, University of Cambridge, UK (Corday-Morgan Prize 2011 Winner ) – Designing complexity and function within self-assembled chemical systems

To register for the symposium, please complete the online registration form.

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Nanoscopic electrochemical cells probe forests

16 May 2012

3D carbon nanotube forests are of particular interest in the electrochemical arenas of sensing and energy applications. Some researchers have suggested that it is necessary to use open-ended carbon nanotubes and carry out a pre-treatment or activation step to support fast electrochemistry, but is this always the case?

Patrick Unwin and co-workers set out to investigate. They prepared carbon nanotube forests using a chemical vapour deposition growth method. To probe the local electrochemical response of the forests, they used a nanoscopic double barrelled pipette tip, filled with supporting electrolyte and redox species. This allowed the team to interrogate the sidewalls and closed ends of the nanotubes that made up the forest with high spatial resolution.

Both sidewalls and the closed tube ends were capable of fast electron transfer proving that single walled carbon nanotubes do not require open ends for fast electrochemistry with outer sphere redox couples. This overturns the current consensus, based on averaged macro-sized measurements, that open ends dominate nanotube forest electrochemistry.

Without the requirement for pre-treatment or activation, electrochemical nanotube forest applications will be easier to achieve.

To find out more, download the ChemComm article today.

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Chiral confusion

15 May 2012

Scientists in Israel have shown that non-biological chiral crystals are much more abundant than previously thought and their findings could clear up a possible confusion over the term ‘chiral’.

‘Chiral’ describes an object whose mirror image cannot be superimposed, for example human hands are chiral. Chirality is important to understand and recognise, as the production of a chiral molecule can lead to both mirror images – or enantiomers – being produced, and these often have very different chemical properties. Chiral crystals selective for one enantiomer that could be used for separation or as catalysts are therefore highly sought.

Read the full article in Chemistry World

Link to journal article
On the abundance of chiral crystals
Chaim Dryzun and David Avnir
Chem. Commun., 2012, Advance Article, DOI: 10.1039/C2CC17727G

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Creating the first high-valent iron oxo phthalocyanines

04 May 2012

Phthalocyanines are important industrial oxidation catalysts that are cheap and easy to make but their mechanism remains unclear. Now a team of French and Russian scientists have made and characterised a key intermediate in the catalytic cycle, previously postulated but never obtained.

Pavel Afanasiev and Alexander Sorokin from the CNRS-Université Lyon, France, and colleagues prepared and characterised the first high-valent iron oxo species on the phthalocyanine platform.

They treated tetra-tert-butylphthalocyanine iron chloride with m-chloroperbenzoic acid to give what they later proved to be an Fe(IV) oxo species. Isolation of such a reactive species is extremely challenging so the team characterised the reaction mixture in situ shortly after mixing the reagents. This approach also removed the possibility of the molecule undergoing further transformation en route to the X-ray diffraction facility or NMR spectrometer.

: A DFT-optimized structure of the iron-oxo phthalocyanine complex

The team used at least eight different techniques – including mass spectrometry, UV-vis and EPR spectroscopy, density functional theory (DFT) and X-ray emission studies – in their incredibly thorough examination of the molecule, not only confirm its creation but to fully define many aspects of its electronic structure. These results provide a platform from which a better understanding of iron phthalocyanine catalysts can be developed.

Posted on behalf of Ruaraidh McIntosh, Chemical Communications web writer.

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