Research articles

Two-dimensional synthetic polymers can be produced through solid-state topochemical polymerization, but achieving this through a single-crystal-to-single-crystal transformation has not yet been demonstrated. Now, a fluorinated Y-shaped monomer has been preorganized in a lamellar crystal, which goes through two successive single-crystal-to-single-crystal phototransformations to give a 2D polymer; single-crystal X-ray diffraction has been used to elucidate its structure.

Multi-electron redox chemistry is important in transition-metal-mediated processes, but is rarely observed with uranium due to its propensity to undergo single-electron reactions. Now, uranium can use its electrons, coupled with those stored in redox-active ligands, to perform multi electron reduction of organoazides and form uranium tris(imido) derivatives.

Several solutions to the ‘missing xenon’ problem have been proposed that involve the selective sorption of Xe in minerals found in the Earth. It is now shown that a zeolite, Ag-natrolite, absorbs and retains 28 wt% Xe at 1.7 GPa and 250 °C, conditions found in subsurface Earth, through expulsion of metallic Ag(0).

Directed evolution has emerged as a powerful tool for the identification of improved enzyme catalysts. Now, gel-shell beads are introduced as compartments that cage an enzyme with its encoding DNA, constituting a new genotype–phenotype linkage. Screening of 10⁷ gel-shell beads by flow cytometry leads to an improved phosphotriesterase bioremediation catalyst.

Conjugation of DNA to proteins often involves a choice between either expressing recombinant proteins with a specific handle, or labelling wild-type proteins with low site-selectivity. Now preorganization of a DNA–ligand complex to a metal-binding site enables site-selective conjugation of a DNA strand to lysine residues of wild-type proteins and antibodies.

A self-blinking fluorophore suitable for super-resolution imaging has been developed. The blinking arises from a reversible intramolecular spirocyclization in a rhodamine-based fluorophore that switches between a fluorescent open form and a non-fluorescent closed form. The advantages over existing methodologies are demonstrated using single-molecule localization microscopy imaging inside cells.

Amiloride is a widely used diuretic that blocks epithelial sodium channels (ENaCs); however, the functional role of the different ENaC isoforms is still poorly understood and no pharmacological tools exist to differentiate between them. Now, photoswitchable amilorides that enable the optical control of ENaCs, and can distinguish between different ENaC isoforms have been developed.

Shaping potential energy surfaces by tailored strong laser pulses has now been shown to be a powerful method for controlling product yields in an ultrafast polyatomic photodissociation reaction. Control over the velocity of the product fragments is also achieved through the generation of light-induced conical intersections and modulating the potentials around them.

The widespread use of fuel cells requires improved catalysts to reduce oxygen efficiently at the cathode. It is shown that model, well-characterized size-selected Pt_xY nanoparticles can be synthesized by the gas aggregation technique, and that they are highly active for this reaction.

Charge separation in oxygenic photosynthesis occurs with high quantum efficiency and is yet to be fully understood. Using two-dimensional electronic spectroscopy, coherent dynamics have now been observed in the photosystem II reaction centre, where charge separation occurs. Supporting simulations suggest that the coherences have mixed electronic–vibrational (vibronic) nature, and may enhance the rate of charge separation. Leaf image: © Michael Wesemann/Alamy.

Main-group analogues to fullerene-C₆₀ have been predicted theoretically many times. Now, B₄₀⁻ has been observed using photoelectron spectroscopy and, with its neutral analogue, B40, confirmed computationally. In contrast to fullerene-C₆₀, the all-boron fullerene (or borospherene) features triangles, hexagons and heptagons, bonded uniformly by delocalized σ and π bonds over the cage surface.

The ability of thiyl radicals to promote reactions has been known for decades although its extension to asymmetric catalysis has only rarely been explored. Now, an organic thiyl radical catalyst with a carefully structured chiral pocket has been designed as a means to achieve highly enantioselective radical cyclizations.

Strong mineral acids usually add to alkenes such that hydrogen is added to the least substituted carbon — a pattern known as Markovnikov addition. Now, using photoredox catalysis in conjunction with a redox-active hydrogen atom donor, it has been shown that this pattern can be reversed to produce otherwise difficult to access products.

Although widely used to form bridged ring systems, certain intramolecular Diels–Alder reactions are hampered by the strain inherent in forming an sp²-carbon at a bridgehead position. Now, an alternative strategy has been described to access these bridged ring systems through the C–C activation and coupling of cyclobutanones with olefins.

It is generally believed that, after being generated, an excess electron in water shrinks from a strongly delocalized to a localized state in about a picosecond. Now, these early stages in the behaviour of this electron have been observed using a combination of transient THz spectroscopy and ab initio molecular dynamics simulations.

It is often difficult to predict or control the topologies of metal–organic frameworks (MOFs) before synthesis. Now, the topology of a MOF has been used as an ideal blueprint for the deliberate design of a related MOF, by substitution of molecular building blocks with supermolecular building blocks. The two MOFs share the same underlying topology but have different chemical compositions.

Amphiphilic self-assembly usually involves molecules consisting of hydrophobic and hydrophilic segments. Now, this concept has been broadened to encompass the self-assembly of fully hydrophobic molecules that contain mutually immiscible alkyl and π-conjugated segments. Selective additives — n-alkanes or C₆₀ — direct their assembly into various ordered and optoelectronically functional structures.

A general and broad-ranging stereospecific coupling of secondary and tertiary boronic esters with electron-rich aromatics is reported. The reaction involves initial formation of a boronate complex followed by activation of the electron-rich aromatic moiety by an electrophile, which triggers a stereospecific 1,2-migration and subsequent elimination/re-aromatization.

Adjuvants are used to increase the immune response to molecular vaccines. A minimal synthetic variant of the saponin natural product QS-21 has been developed as a potent, non-toxic adjuvant, enabling dissection of structural requirements in the triterpene domain and in vivo biodistribution studies to probe mechanisms of action.

Proton-conducting materials have proved useful for renewable energy applications and bioelectronics technologies. The proton conductivity of thin films made from reflectin — a cephalopod structural protein — is now reported. Reflectin's electrical properties compare favourably to those of artificial materials, and have enabled the demonstration of protein-based protonic transistors.