Articles in 2018

The polyoxoanion [P₂W₁₈O₆₂]⁶⁻ has been shown to reversibly accept up to 18 electrons upon reduction in aqueous solution. The resulting highly reduced solution can then be used either for the on-demand generation of hydrogen over a catalyst bed, or as a high-energy-density electrolyte in a redox flow battery.

The promise shown by metal–organic frameworks for various applications is somewhat dampened by their instability towards water. Now, an activated MOF has shown good hydrolytic stability owing to the presence of weak, sacrificial coordination bonds that act as a ‘crumple zone’. On hydration, these weak bonds are cleaved preferentially to stronger coordination bonds that hold the MOF together.

Light can selectively drive and control the reversible reaction between a nitrogen nucleophile and a photoswitchable carbonyl electrophile by inducing wavelength-specific tautomerization cycles. This enables external and bidirectional regulation of closed dynamic covalent systems via C=N exchange, resembling a light-powered bidirectional molecular-scale Dean–Stark trap.

Catalyst-controlled site selectivity without relying on the influence of a directing group within the substrate is a major challenge in C–H functionalization. Now a catalyst is described that selectively functionalizes non-activated primary C–H bonds in the presence of a variety of other C–H bonds and functional groups.

Functional group interconversion typically requires reactive reagents to irreversibly generate a desired product in high yield and selectivity. Now, a CO-free catalytic functional-group-metathesis approach can be used to interconvert aroyl chlorides and aryl iodides—two important classes of electrophiles often employed in the preparation of pharmaceuticals and agrochemicals—with the help of metathesis-active phosphine ligands.

Triplet–triplet energy transfer activation of disulfides enables the chemoselective anti-Markovnikov hydroalkyl/aryl thiolation of alkenes and alkynes—and can also be used for the biologically important hydromethylthiolation reaction. This fast disulfide–ene reaction is biocompatible and is tolerant of a wide range of functional groups. The triplet–triplet energy transfer sensitization process was studied in detail with transient absorption spectroscopy.

Heteroatom doping is a widely used modification method for carbon-based catalysts. Now, chemically defined sp-hybridized nitrogen atoms have been selectively introduced to the acetylene groups in ultrathin graphdiynes, resulting in good catalytic activity for the oxygen reduction reaction in both alkaline and acidic media.

Although ubiquitous throughout chemistry and biology, the structure and transport mechanism of the aqueous proton in solution remain elusive. Through advances in ultrafast broadband 2D IR spectroscopy, the structure of the aqueous proton is revealed to have a charge-delocalized H₅O₂⁺ Zundel-like core arrangement with surprisingly persistent structural heterogeneity.

A simple amino acid can be recognized by a synthetic catalyst in a process that initiates the sequential reduction of cyclic dehydropeptides. An experimental and theoretical study provides evidence for a unique mechanism that involves unidirectional reduction to set four stereocentres around a macrocyclic ring.

Mechanistic studies of the hemilability of MIDA (N-methyliminodiacetic acid) boronates reveal the chameleonic behaviour of the BMIDA group. The superior migratory aptitude of BMIDA compared to hydride and the capacity to resemble a proton when nitrogen decoordinates from boron have now been exploited for the design of new boron transfer reactions.

CO₂ can be used as an activator for the direct transformation of abundant and unprotected primary aliphatic amines into valuable γ-lactams under photoredox and hydrogen-atom-transfer catalysis. Electrostatic interactions between the in situ generated alkylammonium carbamate and the positively charged quinuclidinium radical lead to regioselective hydrogen atom abstraction.

Natural product chemistry remains critical to the discovery of small molecules that possess unique bioactivities. A collaborative approach to studying the phomactin diterpenoid family that spans isolation, chemical synthesis and investigation of their bioactivity is now reported. The novel congeners that were isolated inspired a divergent strategy to achieve their practical preparation and their anti-tumour evaluation.

Strained organic compounds have long fascinated the chemistry community. Heterocyclic allenes are particularly interesting strained intermediates, but their use in synthetic chemistry is rather scarce. Now, an experimental and computational study of azacyclic allenes demonstrates that heteroatom-containing cyclic allenes can be harnessed for the construction of complex molecular scaffolds, including those that bear multiple stereogenic centres.

Membranes with high selectivity and high permeance that allows rapid passage of solvent molecules are desirable for efficient separation processes. Microporous conjugated-polymer membranes have now been fabricated through surface-initiated polymerization. These membranes are capable of ultrafast organic-solvent nanofiltration because of the high porosity and pore interconnectivity originating from the rigid skeleton.

Potassium channels rapidly move K⁺ ions across cell membranes while blocking Na⁺, but how these two effects are achieved simultaneously has remained unclear. Now, extensive molecular simulations show a single mechanism that features fully dehydrated ions can explain both rapid transport and impeccable selectivity.

Enzymes can perform various biological functions because of their delicately and precisely organized structures. Now, simple inorganic nanoparticles with a rationally designed recognition capability can mimic restriction enzymes and selectively cut specific DNA sequences.

Vikki Cantrill tells the story of element 88’s discovery and how its glowing reputation eventually faded.

Bruce C. Gibb takes us on a journey through the physical and chemical evolution of planet Earth and suggests that the reverse Hofmeister effect, the phenomenon whereby poorly solvated ions associate in water, could be a powerful driving force towards the first hint of life on the rock we call home.

A new pyrrolysyl-tRNA synthetase/^PyltRNA (PylRS/^PyltRNA) pair that is mutually orthogonal to existing PylRS/^PyltRNA pairs has now been discovered and optimized. This system could enable the site-specific incorporation of a greater number of distinct non-canonical amino acids into a protein.