Research articles

Modular construction using connectable molecular subunits is a powerful strategy for making new carbon-based materials. So far, large crystals have been produced only from subunits linked by weak interactions. Covalently bonded analogues have now been prepared by reversible self-addition polymerization of suitable monomers and structurally characterized by single-crystal X-ray diffraction.

Diversity oriented synthesis (DOS) aims to build structurally diverse compound libraries — potentially useful in drug discovery — from a small number of starting materials. Here, the build/couple/pair algorithm — commonly used in DOS — is extended to incorporate variations in the coupling step as well as in the starting materials. This produces a compound library with exceptionally high diversity in fewer than five steps from a common precursor.

Structural analysis of the enzyme transketolase at sub-ångström resolution shows the existence of physically distorted covalent intermediates with elongated scissile substrate bonds. These observations highlight the ability of enzymes to enhance the reactivity of reaction intermediates leading to a more efficient process.

The manipulation of complex molecules offers an avenue for developing new therapeutics and biological probes. Here, a catalyst is described that forms a covalent bond to the substrate before selectively functionalizing a proximal functional group. Cis-1,2-diols are targeted allowing for the derivatization of the axial hydroxyls of monosaccharides in the presence of unprotected equatorial hydroxyls.

The combination of organocatalytic and photoredox cycles has attracted much attention for its ability to solve long-standing problems in asymmetric catalysis. Here, it is shown that easily available chiral organic catalysts can guide both the stereoselectivity-defining events and, through the transient formation of photon-absorbing chiral electron donor–acceptor complexes, the photoactivation of the substrates.

Materials typically break down in response to the repeated mechanical forces that they experience during use. Now, it has been shown that a mechanochemically active polymer can respond to shear forces by forming more bonds than are broken, leading to improved mechanical properties under conditions that would otherwise be destructive.

The catalytic activity of gold nanoparticles is known to be dependent on size, but less is known about the activity of even smaller gold clusters. It is now shown that clusters with 5 to 10 atoms supported on multiwalled carbon nanotubes are as active as enzymes for the oxidation of thiophenol to disulfide with O₂.

A counter-intuitive strategy that combines a chiral Lewis base catalyst with an achiral Lewis base co-catalyst results in an exceptionally large increase in the facility of catalytic enantioselective silylation of polyols. The catalytic ensemble drives such reactions to completion within a few hours, rather than the usual two–five days, without loss of enantioselectivity.

A molecular probe has been designed that distinguishes double-stranded DNA with single base-pair specificity. In this approach, two destabilizing bubbles, in which the base pairs are mismatched, are generated for each point mutation in the target DNA.

Hydrophobe/water interfaces are crucial for many chemical processes, but to be fully understood, a better appreciation of the behaviour of non-hydrogen-bonded OH groups of water is required. It is now shown that such ‘dangling’ OH structures are entropically stabilized and form cooperatively, that is, the probability of their formation depends nonlinearly on hydrophobic surface area.

The controlled functionalization of single-walled carbon nanotubes has been shown to brighten their photoluminescence up to 28 times, which challenges our current understanding of how chemical defects affect low-dimensional carbon materials. This significantly improved photon conversion efficiency promises to advance a broad range of optoelectronic and imaging applications based on carbon nanotubes.

Direct β-carbon activation of saturated carbonyl compounds represents a significant fundamental challenge in organic chemistry. Here, the catalytic activation of saturated ester β-sp³ carbon as nucleophile via N-heterocyclic carbene organocatalysis is reported. The catalytically generated nucleophilic β-carbon undergoes enantioselective reactions with various electrophiles.

Dysprosium alkoxides and dysprosium-doped yttrium alkoxides show very large energy barriers, greater than 800 K, to magnetic relaxation. These barriers arise from the presence of a strongly axial pseudo-octahedral crystal field, which switches off relaxation through the first excited state that typically occurs in single-molecule magnets, and favours a competitive pathway through higher-energy states.

A grossly warped nanographene, C₈₀H₃₀, that incorporates five 7-membered rings and one 5-membered ring embedded in a hexagonal lattice has been synthesized, isolated and fully characterized. Experiments revealing how the properties of such a large graphene subunit are affected by multiple odd-membered-ring defects are also reported.

Quinones are key electron acceptors in nature, however, the role of their excited states is not fully understood. Femtosecond spectroscopy and quantum calculations on the prototypical parabenzoquinone radical anion provide insight into quinones’ intrinsic electron-accepting ability, revealing how unbound electronically excited states relax to form the ground-state radical anion.

Frustrated Lewis pairs have been shown to be capable of heterolysis of strong covalent bonds such as those in molecular hydrogen, and have been used in the hydrogenation of polar multiple bonds. Here, a new type of ansa-aminohydroborane is shown to be active for the partial hydrogenation of alkynes under mild conditions.

In interstellar clouds, reactions that have an activation barrier have previously been considered too slow to be significant because of the low temperatures experienced. However, large enhancements in the rate coefficient for the reaction of OH with methanol have now been observed at temperatures below 100 K. A mechanism involving tunnelling has been proposed.

Daphenylline is an alkaloid containing a tetra-substituted arene within a sterically compact hexacyclic scaffold. Here, the first total synthesis of daphenylline is described. A gold-catalysed 6-exo-dig cyclization reaction was exploited to construct the bridged 6,6-bicycle at an early stage, the aromatic moiety was forged through a photoinduced olefin isomerization/6π electrocyclization cascade followed by oxidative aromatization.

Capsular polysaccharides (CPS) enclose many pathogenic strains of Escherichia coli, protecting the bacteria from the host. Here, an extracellular blocker of Wza, a pore-forming protein that transports CPS to the cell surface, has been discovered by single-channel electrical recording. Treatment with the blocker exposes the bacterial cell surface and thereby facilitates killing by the human immune system.

A far-red-fluorescent probe based on a ring-fused BODIPY core that is conjugated to a polyglycerol dendrimer is now reported. The most notable feature of this probe is its long-lasting fluorescence emission with a strikingly low level of blinking in single-molecule-imaging experiments, even in the absence of anti-fading agents such as Trolox.