Research articles

Small nanoparticles with controlled morphologies can be prepared for catalysis applications by colloidal methods using stabilizing ligands. A solvent-extraction method has now been described that removes the ligands without affecting the morphology of the nanoparticles, or their catalytic activity over a range of reactions.

Droplet microfluidics offer a convenient platform for high-throughput experimentation. It has been difficult, however, to rapidly and controllably vary concentration — a key process used in macro-scale experiments. Here, a droplet dilution module is described that traps a mother droplet and then repeatedly dilutes it releasing a series of droplets that define a digital concentration gradient.

Unexpected and significant isotope exchange is observed in the near-threshold photodissociation of isopically labelled acetaldehyde. Theoretical modelling indicates that, at the lowest energies considered, an average of 20 H- or D-shifts occur before dissociation — evidence for extensive isomerization.

The first chemical synthesis of solanoeclepin A is described. The novel 5-4-6-7-5-5 polycyclic architecture was constructed in a stereoselective manner via a cyclopentene annulation strategy, the intramolecular cyclization of an epoxy nitrile intermediate, and an intramolecular Diels–Alder reaction of a furan derivative.

The first total synthesis of conolidine — representing the first asymmetric synthesis of a C5-nor-stemmadenine — is described. The chemical synthesis proceeds in just nine steps and gives an 18% overall yield from a commercially available pyridine — an achievement that led to the discovery that (+)-, (–)- and (±)-conolidine are potent non-opioid analgesics.

One of the hurdles facing the development of effective catalysts to produce ammonia from nitrogen is the stability of the metal nitrides that form during the reaction. Now, the hydrogenolysis of nitride ligands with hydrogen is reported and attributed to PNP pincer ligand cooperativity.

Single-molecule magnets hold great promise for device miniaturization but the blocking temperatures at which they perform must first reach practical values. Now, the electronically diffuse N₂³⁻ radical bridge has been shown to endow two di-lanthanide complexes with good magnetic properties — a di-gadolinium complex displays a strong magnetic coupling and its di-dysprosium analogue a high blocking temperature.

The photocatalytic production of hydrogen from renewables such as ethanol and water could be a key means of future fuel production. There are few, if any, catalysts available for such a reaction, and our understanding of photocatalytic reactions generally remains poor. It is now demonstrated that gold–titania nanoparticles are effective catalysts for producing hydrogen from ethanol, and the rate is independent of gold particle size.

The development of an effective, cheap and robust water oxidation catalyst is crucial to the development of solar water-splitting technology. A manganese catalyst inspired by the water oxidizing centre of photosystem II is now shown to dissociate and reform into nanoparticles resembling the known natural oxidant mineral birnessite.

Spirooxindoles are important structural motifs found in an array of bioactive compounds. Here a Michael–aldol domino reaction for the construction of bispirooxindoles is presented, creating four stereocentres, including three quaternary carbon centres. Novel multifunctional organocatalysts have been developed for this transformation.

High operating temperatures in heterogeneous catalytic processes compromise energy efficiency, catalyst lifetime and product selectivity. Plasmonic silver nanoparticles are shown to couple thermal energy and a low-intensity photon flux to drive commercially important oxidation reactions at lower temperatures than conventional thermal processes.

Bimetallic core@shell nanoparticles often have properties that are different from those of single-metal or alloy nanoparticles. Here, a route to such nanoparticles that binds the second metal to the core surface prior to reduction is described. The unique catalytic properties of the nanoparticles are demonstrated in the selective production of chloroaniline.

Crystal growth in nature is controlled by biomolecules to produce precisely engineered crystal shapes. Now, facet-specific peptide sequences that have been rationally selected through a biomimetic evolution process are used as regulating agents for predictable synthesis of platinum nanocrystals with selectively exposed crystal surfaces.

Single-molecule magnets (SMMs) are multinuclear clusters whose behaviour typically relies on intramolecular spin-coupling interactions between neighbouring metal ions. A diuranium–arene complex has now been prepared that shows behaviour characteristic of an SMM without relying on this type of superexchange mechanism. This may enable the construction of SMMs that maintain their magnetism at higher temperatures.

The recoil of adsorbates away from and towards surfaces is well-known. Here, long-range recoil in the plane of the surface, which leads to reaction at a distance, is described. Surface reactions are shown to propel their physisorbed ethylenic products across the rough surface of Si(100) by up to 200 Å before re-attachment.

Enzyme-mediated oxidative cyclizations in nature are a powerful demonstration of the utility of selective C–H activation. Here, Rieske oxygenase-like enzymes RedG and McpG are shown to mediate regio- and stereodivergent carbocyclization of undecylprodigiosin to streptorubin B and metacycloprodigiosin, respectively. Understanding these remarkably selective C–H activations could inspire the design of biomimetic catalysts with similar capabilities.

The development of high-performance ‘smart’ catalysts will rely on the rational design of nanoscale metal–metal oxide interfaces. A tandem catalyst that has both CeO₂-Pt and Pt-SiO₂ interfaces is now reported, and is capable of catalysing sequential reactions to convert methanol into ethylene.

The intrinsically hybrid nature of metal–organic frameworks (MOFs) — microporous crystalline solids composed of metal ions and organic ligands — has been exploited to grow thin MOF films at the aqueous–organic interface of a biphasic reaction mixture. These materials exhibit selective permeability and can also be obtained as hollow capsules that have potential as microreactors.

Macromolecules with antimicrobial properties are promising materials for combating multi-drug-resistant microbes. Now, it has been shown that amphiphilic cationic polycarbonates that are biodegradable can self-assemble into micellar nanoparticles that can kill gram-positive bacteria, MRSA and fungi efficiently, even at low concentrations. Moreover, no significant toxicity is observed during in vivo studies in mice.

The reaction of enols and enolates with electrophiles is used extensively in synthesis. Here, protein engineering — substituting amino acid residues in an enzyme active site — is used to produce biocatalysts for the control of enolate chemistry. The adapted enzymes enable stereoselective C–C bond formation yielding N-heterocycles in high diastereomeric excess by the reaction of trisubstituted-enolates.