Articles in 2012

Liposomes are a leading drug-delivery platform in cancer chemotherapy. Now they can be used to destroy cancer cells through a method that converts chemical energy to mechanical force. These localized disruptions can cause cell death while minimizing the collateral damage to neighbouring cells.

A collection of articles in this issue focuses on the ability to selectively perform a reaction at just one specific site in a complex molecule that contains many other similarly reactive sites.

The complexity of living systems makes attempts to gain a molecular-level understanding of them a unique and inspiring challenge. This Review summarizes progress in the development of bioorthogonal reaction-based fluorescent probes used to follow the spatial and temporal dynamics of biologically important analytes within living systems.

The lithium–O₂ battery can theoretically provide energy densities that greatly exceed that of Li-ion, but it requires more efficient catalysts (or ‘promoters’) than carbon for oxygen reduction and evolution. Here, we report a tailor-made mesoporous metallic oxide that results in high reversible capacities and operates over many cycles.

Oxatriquinane is a remarkably stable alkyl oxonium ion, despite the fact that its carbon–oxygen bond lengths are 1.54 Å. The robust nature of this fused tricyclic molecule enabled the addition of increasing steric bulk to the system, culminating in a tri-tert-butyloxatriquinane with a record 1.62 Å C–O bond distance.

The discovery and synthesis of inorganic clusters can be both time consuming and limited by a lack of reproducibility. An automated flow process coupled with multiple batch crystallization has now been successfully used to rapidly screen and scale-up the syntheses of inorganic clusters, including polyoxometalates and manganese-based single-molecule magnets.

Xenon is an inert element at ambient conditions but may become reactive under pressure. It has now been predicted that pressure stabilizes increasing oxidation states of Xe atoms (from Xe⁰ to Xe²⁺ to Xe⁴⁺ to Xe⁶⁺), and thus a series of compounds — XeO, XeO₂ and XeO₃ — become thermodynamically stable at megabar pressures.

The selective dissociation and formation of different functional groups in a single organic molecule may prove useful for making nanoscale devices and offer new opportunities for studying changes in electronic structure. It has now been shown that bond-selective chemistry can be induced and visualized at the submolecular level in a complex thiol-based molecule using a scanning tunnelling microscope.

Supramolecular gels whose properties can be tuned through non-covalent interactions — typically metal coordination or hydrogen bonding — are attracting attention in various fields. Researchers have now shown that halogen bonding is also strong enough to be relied on; it interferes with competitive, gel-inhibitory hydrogen bonding to induce co-gelation between two urea-based components.

A {U₁₂Mn₆} wheel-shaped cluster that has been assembled through cation–cation interactions exhibits single-molecule-magnet behaviour. Single-molecule magnets are promising for magnetic storage devices at the nanoscale, and the observation of magnetic bistability with an open hysteresis loop and high relaxation barrier in this 5f–3d complex suggests that uranium-based compounds could be useful components.

Site-selective functionalizations of complex small molecules can generate targeted derivatives with exceptional step-efficiency, but general strategies for maximizing selectivity in this context are rare. Investigations with the ion-channel-forming natural product amphotericin B have revealed that site-selectivity can be tuned by simply modifying the electronic nature of the reagents.

Hydroxyl radicals (OH) are important in many chemical systems, including combustion and atmospheric reactions, however experimentally measuring their velocities in specific internal quantum states has proved difficult. Now differential cross-sections for inelastic scattering of fully state-specified OH with He and Ar have been observed for the first time using velocity-map imaging in a crossed-molecular-beam arrangement.

The precise pairing of cysteine residues in proteins is routinely achieved in nature. However, the comparable pairing within polypeptides is a long-standing challenge for the preparation of multicyclic species. Here, a straightforward approach to direct the inter-/intramolecular pairing of cysteine residues within peptides using a minimal CXC motif is presented.

Templated atomic layer deposition (ALD) is used to create oxide ‘nanocavities’ on the surface of catalyst particles. Subnanometre-nm films containing nanocavities act as sieves for the underlying catalyst, resulting in high selectivities for the smaller of two reactants in competitive oxidations or reductions.

Efficient hydrogen-evolving catalysts comprising readily available elements are needed if hydrogen is to be adopted as a clean alternative to fossil fuels. Now, a diimine–dioxime cobalt complex has been covalently attached to a carbon nanotube electrode to yield an active and robust electrocatalyst for hydrogen generation (55,000 turnovers in seven hours) from aqueous solutions.