Research articles

A practical and selective palladium-catalysed process for C(sp³)–H arylation of tertiary alkylamines is enabled by the use of a simple amino acid-derived ligand. The reaction combines a range of multifaceted tertiary alkylamines with readily available aryl-boronic acids to form γ-aryl tertiary alkylamines and can also be performed enantioselectively.

Screening commercial kinase inhibitors for antibacterial activity identified the anticancer drug sorafenib as a major hit. Subsequent structure–activity optimization created a new antibacterial analogue with high potency against methicillin-resistant Staphylococcus aureus, including challenging persisters and biofilms, as well as demonstrating efficacy in an in vivo mouse model. The mode of action involves stimulation of protein secretion and inhibition of menaquinone biosynthesis.

Gaining a better understanding of the complex electronic structure of single-molecule magnets is essential for their design and development. The 4f-electron density distribution of a dysprosium single-molecule magnet has now been experimentally determined using synchrotron diffraction data interpreted with a multipole model. The magnetic easy axes were recovered by analysis of the 4f-electron density shape, which is clearly oblate.

A disordered metal–organic framework converts into a more porous, crystalline phase within 40 s following solvent exchange and desolvation. The rapid domino rearrangement of the whole lattice, which involves carboxylate migration on coordinatively unsaturated metal sites, is accompanied by a substantial increase in surface area.

A stable zinc-based metal–organic framework known to retain its porosity and crystallinity after exposure to moisture has been shown to undergo structural changes at the molecular level on adsorbing water. This dynamic and reversible response to the presence of water, including the rearrangement of bonds, is suggested to be the reason for the hydrolytic stability of this particular metal–organic framework.

Quantum dots functionalized with energy-accepting dyes hold promise for converting low-energy photons into higher-energy visible light for bioimaging, catalysis and solar energy harvesting. Now, it has been shown that non-toxic silicon quantum dots can be used in these systems; the transfer of spin-triplet excitons to molecules at their surface has been observed.

Flavin-dependent ‘ene’-reductases have now been shown to catalyse redox-neutral radical cyclizations of α-haloamides to form enantioenriched oxindoles. Mechanistic studies indicate the reaction proceeds via the flavin semiquinone/quinone redox couple, where a ground state flavin semiquinone provides the electron for substrate reduction and flavin quinone oxidizes the radical formed after cyclization.

It is difficult to develop suitable fluorescent probes for live-cell nanoscopy, but a general strategy is now reported that can transform regular fluorophores into fluorogenic probes with excellent cell permeability and low unspecific background signals. Using this approach, probes in a variety of colours were developed for different cellular targets and used for wash-free, multicolour, live-cell confocal and STED microscopy.

Intermolecular coupling plays a critical role in singlet fission. Now, high-resolution 2D white-light spectroscopy has been used to map the presence of non-equilibrium molecular packing in single TIPS-pentacene microcrystals and characterize its effect on the dynamics of singlet fission.

Owing to the electropositive character of aluminium it is difficult to prepare Al anions; the few that exist are supported by nitrogen ligands. Now, a dialkyl-alumanyl anion has been synthesized that features a polar Al–K bond. This anion reacts as a very strong base that deprotonates benzene, and undergoes nucleophilic substitution reactions.

The broad infrared spectrum of water in the OH stretching region shows how significantly a water molecule is distorted when within a hydrogen-bonding network; it also raises the question of what the spectrum of a single OH oscillator would be. Now, the spectral signatures of isolated OH oscillators embedded in cold water cages have been measured using vibrational spectroscopy.

DNA is capable of self-assembling into a wide range of user-defined structures and so can be used as a scaffold to arrange binding motifs with nanometre precision. Now, DNA has been used to accurately display aptamers that fit the repeated epitope pattern of a dengue viral antigen to produce a nanostructure that can be a potent viral inhibitor or a fluorescent sensor.

Despite the potential of fluorinated compounds in pharmaceuticals and agrochemicals, the formation of C–F bonds remains challenging. It has now been shown that aryl sulfonium salts, which can be made by site-selective C–H functionalization, have advantageous photoredox reactivity compared to conventional (pseudo)halides and can be used for late-stage C–H fluorination.

High electrical conductivities in metal–organic frameworks—attractive for applications in sensing and energy storage—typically arise in layered MOFs from metal–ligand bonds with strong covalent character. Now, lanthanide-based MOFs have shown high out-of-plane conductivities originating instead from the π-stacking of organic ligands.

Gene-circuit-based sensors have, to date, largely relied on optical proteins (such as green fluorescent protein) to report the output, which limits the signalling bandwidth. Now, an electrochemical output has been developed and integrated with cell-free gene circuits. This approach enables multiplexing of sensors and introduces the possibility of electronic-based logic, memory and response elements to synthetic biology.

Singlet fission produces two low-energy triplet excitons that are difficult to dissociate into free charges. Now, separate optima in charge yield have been observed as a function of driving force for singlet and triplet excitons in pentacene. At optimal driving forces, the triplet-exciton dissociation rate is at least five orders of magnitude smaller than the singlet-exciton dissociation rate.

Nitrogen oxides are major air pollutants; capture and abatement technologies exist but they typically involve toxic species or precious-metal catalysts. Now, a metal–organic framework has been shown to store NO₂ dimers selectively, and to separate NO₂ from other gases under wet conditions. Treatment with water in air leads to conversion of NO₂ into HNO₃—an important feedstock for fertilizer production—with full recovery of the host.

All-carbon tetrasubstituted olefins are challenging to prepare in a regio- and stereocontrolled fashion. Now, using an amide-substituted norbornene as a co-catalyst, alkenyl halide- or triflate-mediated palladium/norbornene (Pd/NBE) catalysis has been demonstrated, providing an efficient strategy for modular and regioselective construction of all-carbon tetrasubstituted olefins.

Replacing rare elements in benchmark photosensitizers with iron would facilitate the large-scale implementation of solar energy conversion, but iron complexes generally do not exhibit sufficiently long-lived photoexcited states. Now, it has been shown that iron(ii) complexes with carefully designed ligands can absorb broadly across the visible light spectrum and have charge-transfer excited states with nanosecond lifetimes.

A solution-processing step has been used to prepare quantum-well structures that comprise a thin layer of perovskite sandwiched between two layers of conjugated oligothiophene derivatives. The band gap of the resulting 2D hybrid perovskites can be fine-tuned by functionalizing the organic component, which also improves the stability of the system.