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Preparation of monocyclic 1,2-azaborines, a unique class of benzene isosteres, has been challenging. Now, an efficient and modular method has been developed to access diverse multi-substituted 1,2-azaborines from readily available cyclopropyl imines/ketones and dibromoboranes. The reaction goes through an unusual ring-opening BN-isostere benzannulation mechanism.

Tetrafluorenofulvalene (TFF) defies conventional rules of bond strength in organic chemistry. In particular, the central alkene bond of TFF becomes stronger in the quintet state and in the tetraanion. These changes arise from the unusual interplay between the twist, aromaticity and spin pairing in the π-electron system of TFF.

Few explosives are better-known to non-chemists than trinitrotoluene (TNT). Thomas M. Klapötke reflects on the enduring appeal of TNT and whether its starring role as an explosive is nearing its end.

The factors that control the solubility of a salt are many and varied. Now a set of salts with closely related cations suggests that weak London dispersion-controlled CH···π interactions can dominate solubility, despite the presence of much stronger forces.

The intentional interweaving of two different metal–organic framework (MOF) lattices could offer a strategy for combining the disparate properties of the two frameworks within a single MOF material. Now, the rational construction of such hetero-interpenetrated MOFs has been demonstrated.

Light is a major driver of the chemistry of the atmosphere and usually involves the photolytic fragmentation of molecules into radicals before their reaction. New results show that formaldehyde, excited by low-energy light, can react with oxygen, opening up alternative atmospheric oxidation pathways.

Teaching the history of science along with the science itself can give students greater context about the topic they are learning and a wider perspective on how it has developed. Michelle Francl, who has wrestled with how much time to spend on teaching history in the chemistry classroom for years, considers how unconventional histories can shift the curriculum.

The reversible N–H activation and catalytic transformations of ammonia are a challenge. Now, a hidden frustrated Lewis pair is shown to activate non-aqueous ammonia thermoneutrally and split the N–H bond reversibly at ambient temperature. The N–H-activated ammonia was also utilized as an atom-economical nitrogen source for catalytic NH₃ transfer reactions.

Although amorphous calcium carbonate represents an important biomineralization precursor, its structure has been difficult to understand. Now, amorphous calcium carbonate’s structure is shown to arise from the different bridging modes available to the calcium ions. This effective multi-well potential that drives calcium arrangements creates a geometric incompatibility between preferred Ca–Ca distances and frustrates crystallization.

Understanding of the molecular mechanisms underlying the maturation of protein condensates into amyloid fibrils associated with neurodegenerative diseases has so far remained elusive. Now it has been shown that in condensates formed by the low-complexity domain of the amyotrophic lateral sclerosis-associated protein hnRNPA1, fibril formation is promoted at the interface, which provides a potential therapeutic target for counteracting aberrant protein aggregation.

An infrared laser-induced temperature jump provides a rapid and broadly applicable perturbation to protein dynamics. Temperature-jump crystallography was paired with time-resolved X-ray crystallography to study the dynamic enzyme lysozyme. Measurements with and without a functional inhibitor revealed different patterns in the propagation of motion throughout the enzyme.

While aromaticity is a useful concept for assessing the reactivity of organic compounds, the connection between aromaticity and on-surface chemistry remains largely unexplored. Now, scanning probe experiments on cyclization reactions of porphyrins on Au(111) show that the peripheral carbon atoms outside of the aromatic 18-π electron pathway exhibit a higher reactivity.

Covalent organic frameworks offer a highly tunable class of materials for a range of applications, although their dynamic structural transformations are challenging to analyse. Now single-crystal X-ray diffraction is shown to demonstrate single-crystal-to-single-crystal transformations of the imine linkages, showing a well-defined interpenetrating topology and affording structures that have high positive thermal expansion and anhydrous proton-conduction properties.

Shifts in temperature alter the structure and dynamics of macromolecules. Now, infra-red laser-induced temperature jump is combined with X-ray crystallography to observe protein structural dynamics in real time. Using this method, motions related to the catalytic cycle of lysozyme, a model enzyme, are visualized at atomic resolution and across broad timescales.

Experimental and computational studies establish the operation of Fe(iii)-based metalloradical catalysis for the asymmetric cyclopropanation of alkenes with different classes of diazo compounds. The reaction proceeds through a stepwise radical mechanism involving α-Fe(iv)-alkyl and γ-Fe(iv)-alkyl radical intermediates. This work provides a future direction for the development of metalloradical catalysis.

Deuterated compounds are used in many applications such as mass-spectrometry standards, drugs or in organic light-emitting diodes. Now, hydrogen-activated homogeneous pincer complex catalysts can be used to perform selective alkene deuteration with the cheapest available deuterium source, D₂O.

The discovery of biomarkers remains challenging owing to a lack of methods sensitive enough to identify such rare molecules. Now, by simultaneously exploiting the catalysis and affinity of a DNAzyme, candidate biomarkers with low abundance in cancers can be pulled down for identification and validation.

Biological membranes are asymmetric bilayers, but little is known about how this asymmetry modulates membrane protein folding or stability. Now, folding and stability assays with bacterial outer membrane proteins reveal an exquisite sensitivity to asymmetric membrane charge distribution and a required matching of protein charge for efficient folding.

Phase separation is being revealed as important in many biological processes. Most attempts to mimic and deconstruct this use engineered natural proteins. Now it is shown that de novo proteins can be designed from first principles to undergo liquid–liquid phase separation in cells, with the potential to organize multi-enzyme pathways.

Aryl ethers are useful intermediates in organic synthesis and are found in countless biologically active compounds. Now, through palladium/norbornene cooperative catalysis and incorporation of a polarity-reversed N–O reagent as the O-electrophile, an efficient arene methoxylation approach has been successfully developed.