Articles in 2021

Dinitrogen conversion to ammonia is of great biological and industrial relevance, but modelling this process on a molecular level is challenging. Now, a biomimetic model offers new insights into the functionalization of a nitrido ligand to form NH₃ using either H₂ or H⁺/e^–.

Why do bulky anions solubilize macromolecules in water but precipitate out the corresponding monomers? The answer lies in the differences in local water structure. Polymers have now been shown to disrupt water structure more than their monomers, leading to an accumulation of anions near the polymers that increases their solubility.

Innovations in instrumentation together with new strategies of data collection and processing have been shown to solve the problem of data quality for time-resolved in situ X-ray diffraction studies on ball milling, opening new horizons in mechanochemistry.

Membraneless coacervate droplets have been widely investigated as potential candidates for early cells or protocells. Now, they are shown to grow, divide and differentiate into two populations in a rock pore model that mimics an early Earth environment.

Bilayer borophene, predicted to be stabilized by interlayer linkages, has now been grown by molecular beam epitaxy on copper and silver surfaces in two independent studies. The growth substrate and temperature are found to influence the lattice structures formed.

Multi-iron nitrides are implicated as potential key intermediates in biological nitrogen fixation and the industrial Haber–Bosch process, but well-described functional model systems are rare. Now, a well-defined thiolate-bridged Fe^IVFe^IV μ-nitrido complex has been found to show excellent reactivity toward hydrogenation with H₂ through a stepwise pathway to form ammonia in high yield.

Michelle Francl explores how chemists put line structures to work.

Aromatic systems that interact non-covalently are important in many settings, such as base-pair stacking and DNA–drug interactions; however, their excited-state molecular dynamics are not fully understood. Now, intermolecular Coulombic decay in benzene dimers has been observed. The process is initiated by electron-impact ionization and proceeds through ultrafast energy transfer between the benzene molecules.

The complex link between protein sequence and phase behaviour for a family of prion-like low-complexity domains (PLCDs) has now been revealed. The results have uncovered a set of rules—which are interpreted using a stickers-and-spacers model—that govern the sequence-encoded phase behaviour of such PLCDs and enable physicochemical rationalizations that are connected to the underlying sequence composition.

Threose nucleic acid (TNA) is a potential RNA evolutionary progenitor and a nuclease-resistant synthetic genetic polymer. Now, a TNA catalyst that cleaves RNA has been identified in vitro. The TNA catalyst shows strong sequence selectivity towards a mutant RNA substrate involved in drug resistance, resulting in selective gene silencing in eukaryotic cells.

Strategies for the selective modification of heteroatom-containing aromatic compounds are in high demand. Using a simple pyrylium reagent and a cheap chloride source, a method has now been developed that can selectively replace NH₂ groups attached to heteroaromatic rings with a chlorine atom to give heteroaryl chlorides.

Directed evolution of a primitive computationally designed enzyme has produced an efficient and enantioselective biocatalyst for the Morita–Baylis–Hillman reaction. The engineered enzyme uses a designed histidine nucleophile operating in synergy with a catalytic arginine that emerged during evolution and serves as a genetically encoded surrogate of privileged bidentate hydrogen-bonding catalysts.

A photoredox-mediated S_NAr reaction has now been developed for the direct radiofluorination of unactivated aryl halides. A series of arenes can be radiofluorinated in a site-selective manner from readily available aryl halide precursors under mild conditions. This strategy allows efficient ¹⁹F/¹⁸F isotopic exchange, enabling rapid PET probe diversification and clinical tracer preparation.

The efficacy of carbapenem antibiotics can be compromised by metallo-β-lactamases, but a high-throughput screen followed by optimization has now enabled the discovery of indole-2-carboxylates (InCs) as potent broad-spectrum metallo-β-lactamase inhibitors. The results highlight the potential of InC–carbapenem combinations for clinical use as well as mechanism-guided approaches to combatting globally disseminated antibiotic resistant mechanisms.

Without directing auxiliaries, the addition of carbogenic groups to unactivated alkenes is typically inefficient and suffers from poor regioselectivity. Now, a directing-group-free, nickel catalyst-controlled strategy has been developed, enabling the site-selective dicarbofunctionalization of a broad array of activated and unactivated alkenes.

Complex coacervate microdroplets have been proposed as primordial cells, but their ability to evolve by fusion, growth and fission has not yet been demonstrated. Now, it has been shown that gas bubbles inside heated rock pores can drive the growth, fusion, division and selection of coacervate microdroplets.

DNA-encoded libraries facilitate the discovery of ligands that interact with biomolecules but such technologies do not take full advantage of the principles of Darwinian selection. Now, libraries of conformationally constrained peptides (^Dsuprabodies) have been assembled using a strategy that allows for iterative cycles of selection, amplification and diversification. This method was validated with selections against streptavidin and PD-L1.

Synthetic approaches that can simultaneously control both polymer sequence and dispersity are difficult to achieve. Now, a switchable RAFT agent that regulates chain transfer activity during controlled radical polymerization has been shown to enable the one-pot synthesis of sequence-controlled multiblocks with on-demand control over dispersity while maintaining high livingness.

Water-walking insects harness capillary forces by changing body posture to climb or descend the meniscus between water and a solid object. Now, autonomous aqueous-based synthetic systems have been shown to overcome the meniscus barrier and shuttle cargo subsurface between a landing site and targeted drop-off sites.