Volume 8 Issue 6, June 2016

Chemistry education and research in Africa is challenging — a fact that is clearly reflected by publication metrics. Yet this is far from the full story on a continent that has youth on its side, a cultural link to chemistry through its strong interest in plants and indigenous medicine, and an increasing number of ways forward.

Mauricio Erben, a researcher at the National University of La Plata and the National Scientific and Technical Research Council, talks to Nature Chemistry about his experience of research in Argentina, and how it is inherently linked to the country's political climate.

Early theories suggested the possibility of atomically thin boron layers, but electron-deficient boron favours multicentre bonds and assembles into various polymorphs, making the synthesis of such layers challenging. Now, in two independent experiments, the deposition of atomic boron has offered this long-sought material on a silver platter.

The critical step in water splitting is the formation of a peroxo bond; the mechanism, thought to involve oxyl radical formation, remains elusive. Now, experiments reveal a distinct bond vibration directly connected to an oxyl radical that is simultaneously coupled to both the semiconductor electronic states and the motion of the surrounding water.

The low-complexity-protein, liquid phases of membraneless organelles have now been established to selectively partition biomolecules. The specialized microenvironment that they provide differs chemically from the surrounding medium and enables specific nucleic-acid remodelling reactions.

Natural products are a prime source of innovative molecular fragments and privileged scaffolds for drug discovery and chemical biology. Advanced machine-learning approaches can help analyse and design synthetically accessible, natural-product-derived, compound libraries and provide insight into the high selectivity of such compounds.

Molecular machines that assemble polymers in a programmed sequence are fundamental to life. Now, synthetic machinery built from DNA has been used to execute a molecular program that produces peptides, or olefin oligomers, with a defined sequence. The oligomeric product is linked to a double-stranded DNA product that records the sequence of reactions that were executed.

Water oxidation on titanate surfaces is thought to occur via an oxyl-radical intermediate (Ti­–O^•), which precedes O–O bond formation, and for which there is indirect evidence. Using ultrafast infrared spectroscopy and theoretical calculations of photocatalytic water oxidation at the n-SrTiO₃/aqueous interface, the oxyl radical has now been detected through its subsurface vibration.

Naturally occurring DNA polymerases can amplify DNA efficiently via PCR, but they cannot utilize C2′-modified substrates to make non-natural nucleic acids. Such C2′-modified nucleic acids are of interest as they are resistant to nucleases. Now, a Stoffel fragment DNA polymerase has been evolved to transcribe C2′-modified DNA from a DNA template, reverse transcribe C2′-modified DNA back into DNA, and PCR-amplify C2′-modified DNA.

A variety of two-dimensional materials have been reported in the past few years, yet single-element systems—such as graphene and black phosphorus—have remained rare. 2D allotropes of boron have long been predicted and recently investigated. Two boron sheets have now been grown on a Ag(111) surface by molecule beam epitaxy that exhibit significant chemical stability against oxidation.

Membraneless organelles form as liquid droplets inside cells. These bodies are effectively a separate organic phase, with unique biochemical properties. Now, the solvent interior of membraneless organelles has been shown to have a significant effect on the properties and structure of biomolecules. In addition to selectively partitioning and trafficking proteins, they can melt DNA without using ATP.

Designing improved catalysts is predicated on understanding how they work. Now, by positioning three ruthenium centres in a macrocyclic framework, a remarkable acceleration of catalytic water oxidation has been achieved. Detailed mechanistic studies revealed that the catalyst operates through the ‘water nucleophilic attack’ pathway—similar to the natural oxygen-evolving cluster of photosystem II.

The preferential oxidation of CO is a potentially efficient means of purifying industrial hydrogen, however, no catalytic systems are known with sufficiently high activity and selectivity. Now Au/Al₂O₃ catalysts are shown to have outstanding activity and selectivity when both the feed flow-rate and the amount of surface water are carefully controlled.

Macrocyclic oligomers are a unique structural class of compounds in which the ring size and structure can be tuned through the precise control of the primary sequence. Now, it has been shown that oligothioetheramide (oligoTEA) macrocycles can be synthesized using a one-pot acid-catalysed cascade reaction. Preliminary results indicate that cationic oligoTEAs are promising bactericidal agents.

Few-layer black phosphorus (BP) is a promising semiconductor, but it is highly reactive and susceptible to ambient degradation. Covalent functionalization with aryl radicals has now been shown to significantly improve the stability of exfoliated BP, as well as the performance of BP-based electronic devices through a controllable p-type doping effect.

The influence of the thermodynamic driving force for photoinduced electron-transfer between single-walled carbon nanotubes and fullerene derivatives has been investigated. The Marcus inverted region and small reorganization energies were observed for this model organic heterojunction. Small reorganization energies aid in minimizing energy losses for solar conversion to electricity or fuels.

The choice of ligand used in a reaction can drastically influence the overall outcome. Using a combination of classic physical organic chemistry and modern mathematical modelling, phosphine ligand effects are probed. The methods described provide the groundwork for future mechanistic studies of this ubiquitous ligand class.

Polymers that are both elastic and self-healing are desirable for a variety of applications, but often rely on hydrogen bonding which makes them moisture-sensitive. Now, by incorporating metal–ligand interactions with different bond strengths into flexible polymer backbones, an elastomer has been devised that combines high stretchability and high dielectric strength with autonomous self-healing and mechanical actuation capabilities.

Photoresponsive wet- and dry-type actuators can be built up from rotaxane-like structures through the polycondensation of four-armed polyethylene glycols with [c2]daisy chains comprised of cyclodextrin rings and azobenzene side chains. The response of the dry-type (xerogel) actuator to UV light was found to be more than 10,000 times faster than the wet-type (hydrogel) actuator.

Bohrium behaves just as a group 7 element should — but this is in fact surprising, Philip Wilk explains.