News

The team of Richard Walton and his collaborators (contact: Franck Millange, Institut Lavoisier, Université de Versailles, UMR 8180, 78035 Versailles (France)) esed high intensiity synchrotron X-rays in situ diffraction observations of the solvothermal crystallisation of metal-organic frameworks (MOFs) constructed from transition- metals and carboxylate ligands. The study reveals that while some show classical nucleation-growth crystallisation, others are formed via metastable transient phases. These are among the first experimental data concerning the crystallisation mechanism of porous MOFs, materials currently at the focus of intense research activity for applications in separation and catalysis.http://dx.doi.org/10.1002/anie.200905627

The team studied the binding mode adopted by picolinamide derivatives in organometallic Os^II and Ru^II half-sandwich complexes and showed that it can lead to contrasting cancer cell cytotoxicity. N-Phenyl picolinamide derivatives (XY) in Os^II (1, 3−5, 7, 9) and Ru^II (2, 6, 8, 10) complexes [(η⁶-arene)(Os/Ru)(XY)Cl]ⁿ⁺, where arene = p-cymene (1−8, 10) or biphenyl (9), can act as N,N- or N,O-donors. Electron-withdrawing substituents on the phenyl ring resulted in N,N-coordination and electron-donating substituents in N,O-coordination. Dynamic interconversion between N,O and N,N configurations can occur in solution and is time- and temperature- (irreversible) as well as pH-dependent (reversible). The neutral N,N-coordinated compounds (1−5 and 9) hydrolyzed rapidly (t_1/2 ≤ min), exhibited significant (32−70%) and rapid binding to guanine, but no binding to adenine. The N,N-coordinated compounds 1, 3, 4, and 9 exhibited significant activity against colon, ovarian, and cisplatin-resistant ovarian human cancer cell lines (3 4 > 1 > 9). In contrast, N,O-coordinated complexes 7 and 8 hydrolyzed slowly, did not bind to guanine or adenine, and were nontoxic. http://dx.doi.org/10.1021/jm900731j

Final year PhD student Julie Ann Lough (Prof. Sadler's group) won Best Female at this year's BBC Radio 1 Student Radio Awards (www.studentradioawards.co.uk). She was shorlisted to the final 6 from hundreds of entries nationwide in October and on Tuesday the 24th of November in a lavish event with many of the countries top radio personalities she received the award of Best Female Presenter. The award was presented by Huw Stephens and the event hosted by Fearne Cotton and Scott Mills  (BBC Radio 1 presenters). Julie Ann has only being doing student radio for a year and so winning an award of this prestige is a massive achievement. Her regular show "Late Night Chat with Julie Ann" can be heard on Sundays from 9 - 11pm on RaW-1251AM (radio.warwick.ac.uk). This award entitles Julie Ann to present a show on BBC Radio1 and a weeks work experience in a GLOBAL Radio station.

Her award winning entry can be heard here 

Ioana Dumitrescu, Patrick R. Unwin and Julie V. Macpherson make the cover of Chem.Commun with their feature article on Electrochemistry at carbon nanotubes (CNTs): It is a large and growing field, but one in which there is still uncertainty about the fundamental activity of CNTs as electrode materials. On the one hand, there are many reports which focus on the favourable electrochemical properties of CNT electrodes, such as enhanced detection sensitivity, electrocatalytic effects and reduced fouling. On the other hand, other studies suggest that CNTs may be no more electroactive than graphitic powder. Furthermore, it has been proposed that the catalytic nanoparticles from which CNTs are formed may dominate the electrochemical characteristics in some instances. A considerable body of the literature presumes that the CNT sidewall is inert and that edge-plane-graphite-like open ends and defect sites are responsible for the electron transfer activity observed. In contrast, studies of well characterised single-walled nanotube (SWNT) electrodes, either as individual tubes or as two-dimensional networks, suggest sidewall activity. This review highlights how the various discrepancies in CNT electrochemistry may have arisen, by taking a historical view of the field and identifying crucial issues that still need to be solved. When assessing the behaviour of CNT electrodes, it is vitally important that careful consideration is given to the type of CNT used (SWNT or multi-walled), the quality of the material (presence of impurities), the effect of chemical processing steps in the fabrication of electrodes and the experimental arrangements adopted. Understanding these key features is an essential requirement to develop a fundamental understanding of CNT electrochemistry, to allow a wide range of electroanalytical applications, and to move the field forward rationally. As part of this process, high resolution electrochemical and electrical imaging techniques are expected to play a significant role in the future, as well as theoretical developments which examine the fundamentals of electron transfer at different types of CNTs and their characteristic surface sites. http://dx.doi.org/10.1039/b909734a

The fabrication of micrometer-sized monodisperse highly porous polymer particles, of both spherical and rodlike shapes, using a simple microfluidic setup is demonstrated. Droplets were generated in a coflow device from a water-in-oil high internal phase emulsion (HIPE), hereby creating a water-in-oil-in-water (W/O/W) emulsion. The individual droplets of monomer HIPE were polymerized downstream in the channel through photopolymerization. The polymer particles produced via this strategy possess very large macropores in comparison with the more conventional porous polymer beads synthesized by inducing in situ phase separation throughout the polymerization process through the use of porogenic solvents. Epoxy-functionalized porous particles made using the HIPE microfluidic method showed superior performance in a consecutive azide and cycloaddition “click”−“click” modification procedure monitored by IR. Our microfluidic approach led to the successful miniaturization of monodisperse submillimeter spherical poly(HIPE) beads, down to diameters of 400 μm. More strikingly is the production of poly(HIPE) rods, which were obtained by using a viscous HIPE, which in coflow emulsification formed an unstable jet that broke up into rodlike sections. These rodlike droplets maintained their shapes throughout the microfluidic channel and did not relax back into spherical droplets, allowing for production of poly(HIPE) rods upon photopolymerization. The nonspherical shape in this case is not determined by confined channel geometries, which to the best of our knowledge is unprecedented as a strategy to produce nonspherical polymer particles with microfluidics.

The work was carried out in collaboration with prof. Filip du Prez's research team (University of Ghent, Belgium). First author and PhD student M. Talha Gokmen visited Stefan Bon's team at Warwick for a number of weeks to found the basis for the work reported.

 http://dx.doi.org/10.1021/ma9018679

Alzheimer's Peptide Aβ1-42, an amyoid beta peptide, is found in plagues in the brains of Alzheimer's disease patients, and accumulation of this very hydrophobic peptide is thought to be the direct cause of the disease. However, the reason for accumulation is not clear. A common theory is that the balance between production and degradation of this peptide is disrupted in the disease. One method whereby degradation of the peptide can be inhibited is by modification into a form which is resistant to enzymatic degradation (proteolysis). In peptides, isomerization of aspartic acid into isoaspartic acid (where the peptide bond is via the side-chain beta carbon rather than the normal backbone alpha carbon) is known to inhibit enzymatic degradation, and may be the elusive Alzheimer's "trigger", which results in decreased degradation and therefore accumulation of the peptide. Nadia Sargaeva of Prof.  Peter O'Connor's group has developed a new mass spectrometric method for detecting this isomerization and tested it out on the worst variant of the amyloid beta peptide, the full length version containing amino acids 1-42. 

Read the paper 

I. Hancox, K. V. Chauhan, P. Sullivan, R. A. Hatton, A. Moshar, C. P. A. Mulcahy and T. S. Jones

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We report a 60% increase in open circuit voltage (V_oc) and power conversion efficiency in a chloroaluminium phthalocyanine (ClAlPc)/fullerene (C₆₀) planar heterojunction photovoltaic device after insertion of a MoO₃ hole-extracting layer at the interface between the indium tin oxide (ITO) electrode and the ClAlPc donor layer, with an associated improvement in device stability. A similar improvement was observed in heterojunction devices based on mixed ClAlPc/C₆₀ layers. We propose that the improvements in device performance are due to the pinning of the ITO Fermi level to the valance band of the MoO₃ interlayer, where the latter is closely aligned with the highest occupied molecular orbital of ClAlPc.

 

http://dx.doi.org/10.1039/b915764f

Drugs made using unusual metals could form an effective treatment against colon and ovarian cancer, including cancerous cells that have developed immunity to other drugs, according to research at the University of Warwick and the University of Leeds.

The study, published in the Journal of Medicinal Chemistry, showed that a range of compounds containing the two transition metals Ruthenium and Osmium, which are found in the same part of the periodic table as precious metals like platinum and gold, cause significant cell death in ovarian and colon cancer cells.  

The compounds were also effective against ovarian cancer cells which are resistant to the drug Cisplatin, the most successful transition metal drug, which contains the metal platinum.

  Dr Patrick McGowan, one of the lead authors of the research from the School of Chemistry at the University of Leeds, explains: “Ruthenium and Osmium compounds are showing very high levels of activity against ovarian cancer, which is a significant step forward in the field of medicinal chemistry.

Sabine H. van Rijt, lead researcher in the laboratory of Professor Peter Sadler in the Department of Chemistry at the University of Warwick, said:

“Most interestingly, cancerous cells that have shown resistance to the most successful transition metal drug, Cisplatin, show a high death rate with these new compounds.”

 Professor Sadler, at the University of Warwick, commented that he is “excited by the novel design features in these compounds which might enable activity to be switched on and off”.

Cisplatin was discovered in the 1970s and is one of the most effective cancer drugs on the market, with a 95% cure rate against testicular cancer.  Since the success of Cisplatin, chemists all over the world have been trying to discover whether other transition metal compounds can be used to treat cancer.

In this type of anti cancer drug transition metal atoms bind to DNA molecules which trigger apoptosis, or programmed cell death, in the cancerous cells.

The study is a collaboration between the universities of Warwick and Leeds and was funded by the Engineering and Physical Sciences Research Council  (EPSRC).

 For more information please contact:

Dr Patrick McGowan  at leeds +44 (0)113 343 6404, or email: p.c.mcgowan@leeds.ac.uk  

Sabine H. van Rijt and Professor Peter Sadler from the University of Warwick are available for interview via  Professor Peter Sadler +44 (0)24 76 523818 p.j.sadler@warwick.ac.uk

2-tert-Butyl-6-(4-fluorophenyl)pyridine reacts with K₂PtCl₄ via the activation of an sp² C−H bond to give a cyclometalated complex that contains a bifurcated agostic interaction. Rearrangement of this complex results in the activation of an sp³ C−H bond, and reaction eventually leads to a doubly cyclometalated complex where both sp² and sp³ C−H bonds have been activated. Deuterium exchange studies show that a delicate balance exists between the two cyclometalations.

http://dx.doi.org/10.1021/ja905046n

Stefan Bon's polymer colloids group and collaborators have two papers out in issue 20 of Soft Matter, one of which has made the cover. In the paper selected for the cover of Soft Matter Bon, Keddie and coworkers show that when you add a small amount of a "soft" polymer latex armored with nanosized clay discs to a waterborne pressure sensitive adhesive (PSA), its performance respresented via the tack adhesion energy improves with 70%, as a direct result of the supracolloidal structure. A true synergistic effect was discovered showing for the first time that the clay-armored supracolloidal structure of the hybrid particles was essential to achieve a superior balance of viscoelastic bulk properties.

The second paper, a collaboration between David Cheung and Stefan Bon, describes the behaviour of "Janus"-type nanoparticles at liquid-liquid interfaces. Using simulations they demonstrate the adhesion and rotational behavior of a colloidal particle which has two "sides" each having a preferential affinity for one of the two bulk phases. Cheung and Bon demonstrate marked differences in behavior predicted by continueous theories.

Giovanni Constantini and collaborators report in ACS Nano: The ion beam deposition (IBD) of rhodamine dye molecules on solid surfaces in high vacuum is explored in order to characterize the possibility of fabricating molecular coatings or nanostructures from nonvolatile molecules. Molecular ion beams with a well-defined composition are deposited on silicon oxide surfaces with a controlled kinetic energy. Photoluminescence spectroscopy and time-of-flight secondary ion mass spectrometry (TOF-SIMS) are employed in order to characterize the sample with respect to coverage, homogeneity, and the fraction of intact landed ions (soft-landing ratio). We find that homogeneous rhodamine films of defined composition can be produced at energies of 2−100 eV. The coverage is found to be proportional to the ion dose. Soft-landing is observed for energies up to 35 eV.  http://dx.doi.org/10.1021/nn900022p