Chemical Science Blog

US chemists have made a new type of molecular bowl that binds strongly to C₇₀ fullerenes.

hexabenzocoronene

Colin Nuckolls, at Columbia University, New York, and colleagues joined together the proximal carbons of contorted hexabenzocoronenes using solution-based, palladium-catalysed chemistry. The resulting shallow bowl-shaped molecules bind C₇₀ very strongly and are also better than their hexabenzocoronene precursors at stabilising negative charge.

The unique optical, electronic and structural properties of these new bowl-shaped polycyclic aromatic hydrocarbons provide opportunities to create new organic materials, novel host-guest complexes and improved photovoltaics, says Nuckolls.

Bowled over by this research? Read the Edge article and tell us what you think below.

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If you thought squid only belonged in the depths of the ocean, think again. SQUID, or superconducting quantum interference device, has been used to study single-molecule magnets (SMMs) in solution, which could help us store more information on hard drives in future.

As the demand for increased information storage continues to rise, scientists have turned to the development of new nanostructured materials, incorporating SMMs. These tiny magnets can store information depending on the charge and spin properties of their electrons. But until now, there have been few studies to examine how much of these molecules’ magnetic properties come from their molecular properties and how much comes from the way they are packed together in the solid-state. 

Using SQUID, which is a very sensitive device for detecting weak magnetic fields, Euan Brechin and colleagues have studied the spin properties of frozen solutions of two different hexanuclear manganese (Mn₆) complexes. The two compounds display different spin-relaxation properties in the solid-state, but similar spin-dynamics once in solution. Brechin believes the study demonstrates that the SMM behaviour is intrinsically a molecular effect that can be modulated in the solid-state by crystal packing strain effects.

Read the full story in the Chemical Science Edge article, which, like all Chemical Science articles, is free to download until the end of 2011.

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40 years after it was first isolated, UK scientists have identified the biosynthetic genes of an important antibiotic, offering insights into its poorly understood biosynthetic pathway.

Tunicamycin antibiotics have attracted much attention (over 8000 citations) due to their unusual structure and potent inhibition of bacterial cell wall biosynthesis. Although they have been chemically synthesised, the lack of a sequence for the tunicamycin gene cluster (or any part of it) has left scientists puzzled over its biosynthetic pathway.

Now Benjamin Davis, at the University of Oxford, and colleagues have identified the tunicamycin biosynthesis genes in Streptomyces chartreusis, a soil bacterium, using genome sequencing and mining. Using this genetic insight, they have proposed the detailed biosynthetic pathway to this family of antibiotics.

The studies unlock a comprehensive and unusual toolbox of biosynthetic machinery with which to create variants of this natural product, says Davis. He anticipates this will lead to future therapeutic antibiotics with improved antibacterial activity and reduced cytotoxicity.

Find out more in Davis’ Chemical Science Edge article, downloadable for free. Access our free content any time, any place by registering for an RSC Publishing personal account today.

Phew! Other than the weather it has been a hot month here at Chemical Science. Here’s the monthly round up of the articles our referees thought were particularly exciting:

A couple of catalysts for coupling
Stephen Buchwald and colleagues report their studies on the use of two catalyst systems that provide the widest scope for palladium-catalysed C–N cross-coupling reactions to date. What were these systems? Find out in their Edge Article.

Frustrated about global warming?
Nitrous oxide is three times more potent a greenhouse gas than carbon dioxide and can hang around for over 150 years in the stratosphere. So Douglas Stephan and colleagues have been investigating how frustrated Lewis pairs interact with nitrous oxide with a view to converting the gas into a less environmentally harmful species. Read what they discovered in their Edge Article.

Additions to the molecular toolbox
The interaction of a sulfamate ester-derived metallonitrene with an allene generates a versatile intermediate with 2-amidoallylcation-like reactivity. In their Edge Article, Armin Stoll and Simon Blakey outline reactivity patterns for this novel dipolar species, demonstrating both [3 + 2] reactions with benzaldehyde, and unusual [3 + 3] annulation reactions with a variety of nitrones.

Economical extensions
The hydroxymethylation reaction is one of the most powerful and atom-economical one-carbon extension methods. Now Xiaoming Feng and colleagues have managed to hydroxymethylate unprotected oxindoles, which they say could provide practical and broadly applicable access to chiral linchpins bearing oxindoles. Find out how they did it in their Edge Article.

Mechanistic insights
Intermediates in gold(I)-catalysed cyclizations of enynes are not simple carbocations, say Antonio Echavarren and colleagues. They’ve investigated the mechanism of the gold-catalysed cyclopropanation of alkenes with 1,6-enynes, showing that it is stereospecific and mechanistically related to the Simmons-Smith reaction. Read all their insights in their Edge Article.

Let us know what you think of these articles by commenting below. And if you have your own hot research, submit it to Chemical Science today.

Nanowires that efficiently split water into oxygen and hydrogen could be an important step toward affordable chemical storage of solar power according to US scientists. 

Water and sunlight are highly abundant and nature uses these to make energy through photosynthesis. Despite intensive studies on artificial photolysis, making it as efficient as nature is proving difficult. Titanium dioxide electrodes are one way to split water under ultraviolet light but the efficiency is low as they are only able to absorb ultraviolet light and the amout of light converted to energy is low.

Now, Hongkun Park and colleagues, at Harvard University, have synthesised TiO₂ nanowires with high surface areas, deposited them on an electrode and found that chemically crosslinking them increases their optical density – allowing more light to be absorbed. This allows the light to energy conversion to be doubled compared to previous TiO₂ electrodes, says Park.

Doping the nanowire network with gold or silver nanoparticles allows the water splitting reaction to take place under visible light, adds Park. This could lead to a ten fold improvement in the catalysts ability to split water, he says.

‘Our work shows that the performance of a material can be enhanced by putting it in a nanostructured network, and this design can potentially be extended to many other materials to achieve the goal of highly efficient solar water-splitting,’ says Park.

Steve Dunn, an expert in materials chemistry, at the Centre for Materials Research, Queen Mary University of London comments, ‘This work is very interesting with the most significant new finding being the morphological change from using more traditional titania powders to using nanorods. The advantages of using titania, over other more exotic systems, is that the chemistry is well known, it is highly photostable, it is cheap and is also non-toxic.’

The group now plan to study water photoelectrolysis with other metal oxides, such as iron oxide, that can absorb visible light and to study how their efficiency is enhanced in a similar nanowire networks.

Carl Saxton

Want to find out more? Read the Chemical Science Edge article.

Metal catalysed asymmetric allylic alkylation (AAA) reactions have been an extensively studied and fruitful area of research in organic chemistry. The use of heteroatom-centered nucleophiles in this reaction is a powerful method for asymmetric C–X (X = heteroatom) bond formation.

In issue 4’s Perspective, Barry Trost and colleagues summarise developments and applications of metal catalysed AAA reactions employing heteroatom nucleophiles.

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Drug delivery technology has emerged as an important focus of biotechnological research and commercial enterprise. While much attention is focused on the design and effectiveness of drug delivery devices, the nature of their interaction with surrounding tissues – their biocompatibility – is crucial.

In the latest Chemical Science Mini review Daniel Kohane and Robert Langer discuss biocompatibility, specifically as it relates to drug delivery systems, which differ from other biomaterial-based devices by possibly containing large quantities of drugs with their own effects on tissues. Let us know your thought on this topic by commenting below.

If you are interested in writing a review for Chemical Science, please contact the Editorial Office.