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Polymers that exhibit a mechanical response to external stimuli are technologically important. Here, a polymer is described that shows a very large negative thermal expansion on heating or irradiation with near-infrared light. This property is stable over hundreds of cycles and is shown to be driven by a conformational change of an s-dibenzocyclooctadiene unit within the polymer structure.
A stable tetranuclear boron dication with a rhomboid B4 skeleton has been formed by B–B coupling between two diborane cations. In the course of this unusual reaction — which is not feasible for the isolobal ethyl cation analogues — two electron-precise B–B bonds are converted into two B–B–B three-centre bonds.
The coupling of carbon monoxide molecules is an attractive prospect for organic synthesis, but only a few metal complexes are known to do this. A compound containing a boron–boron triple bond has now been shown to induce the coupling of four CO molecules, through an intermediate with a single CO.
Vitamins are thought to be relics of a primordial RNA World. A demonstration that catalytic RNAs are capable of harnessing vitamin cofactors would support the likely role of vitamins in early metabolic processes. Here, a ribozyme that uses vitamin B1 to aid decarboxylation of a pyruvate-like substrate is reported.
Surfaces decorated with nanoparticles are typically prepared by depositing particles on the substrate. Instead, particles have now been grown in situ directly from perovskites, by exsolution through judicious tuning of the materials’ compositions, particularly their nonstoichiometry. This approach enables control over particle composition, size, surface coverage and anchorage.
Immobilized microfluidic water-in-oil droplets serve as templates for layer-by-layer deposition of lipid monolayers to create vesicles of programmable lamellarity and content. Arrays of vesicles allow reproducible assembly and multi-vesicle probing of complex membrane-associated parameters, such as permeability, asymmetry and membrane protein function.
A deficiency in our molecular-level understanding of the electronic structure of conjugated polymers hinders their potential use in electronic applications. Shape-persistent highly ordered ring structures have been used to mimic conjugated polymers and have now been studied using single-molecule spectroscopy. The fundamentally non-deterministic nature of excitation energy localisation in π-conjugated macromolecules has been demonstrated.
The programmable nature of chemical reactions enables the creation of complex networks; however, it can be difficult to redesign the underlying reactions. Here, systematic and quantitative control over the diffusivity and reactivity of DNA molecules yields highly programmable chemical reaction networks that execute macroscale pattern transformation algorithms, such as edge detection.
Caesium has so far not been found in oxidation states higher than +1, but quantum chemical calculations have now shown that, under high pressures, 5p inner shell electrons of caesium can participate in — and become the main components of — bonds. Caesium is predicted to form stable CsFn molecules that resemble isoelectronic XeFn.
Liquid water has the unique ability to mediate ultrafast energy transfer and relaxation in aqueous chemical reactions. Ultrafast broadband two-dimensional infrared spectroscopy that probes vibrations spanning the mid-infrared region with sub-70-femtosecond time resolution now provides evidence for highly intertwined intra- and intermolecular vibrations in water that act to efficiently dissipate vibrational energy.
Clamp proteins that encircle DNA and then recruit enzymes are one of nature's ways of making catalysis on DNA processive. Here, a clamp protein is equipped with a synthetic catalyst that sequence-specifically oxidizes DNA. The resulting biohybrid catalyst shows processive behaviour, which is visualized by atomic force microscopy.
Finding the right solvent can radically transform the rate of a reaction. Here, a systematic computational method for the identification of solvents that accelerate kinetics is described. Starting with a quantum mechanical computation of the reaction rate constant in a set of six solvents, a computer-aided approach identifies the best solvent among 1,341, with a 40% increase in reaction rate.
A base-stabilized silicon analogue of a reactive carbon species (vinyl carbene) is reported that features a silicon–silicon double bond and a silylene functionality, coordinated by an N-heterocyclic carbene. Ultraviolet–visible light and nuclear magnetic resonance spectroscopy in solution confirms that disilenyl silylene exists in equilibrium with the corresponding cyclotrisilene and free N-heterocyclic carbene.
Avoiding the development of microbial antibiotic resistance is a major challenge. Now the incorporation of a photoswitchable group into quinolones has been used to create ‘smart’ antibiotics that can be activated with light. The subsequent loss of activity (within hours) should prevent the build-up of active antibiotics in the environment.
An asymmetric pentalene-containing C1(51383)-C84 fullerene cage is found in two different metal carbide metallofullerenes. This particular cage can, in simple steps, rearrange into many well-known fullerene cages that are more stable and more symmetric, suggesting it is likely that metallofullerenes are generated by a ‘top-down’ formation mechanism.
Biological receptors communicate information through ligand-induced conformational changes. A synthetic receptor with a boron-containing binding site that can selectively and reversibly complex a ligand (such as a purine nucleoside) is shown to function in a similar fashion. The resulting conformational change is relayed through the receptor, communicating structural information about the ligand to a spectroscopic reporter more than 2 nm away.
Positron emission tomography imaging is an increasingly important technology in drug discovery and development, so there is an urgent need for logistically simple processes that allow access to [18F]CF3 (hetero)arenes. Here, a late-stage [18F]trifluoromethylation of (hetero)aryl iodides from [18F]fluoride and commercially available reagents is described, a process that relies on the in situ preparation of [18F]CuCF3.
The trioxacarcins are polyoxygenated natural products that potently inhibit the growth of cultured human cancer cells. Here, the syntheses of trioxacarcin A, DC-45-A1 and structural analogues are described — the majority of which were found to be active in antiproliferative assays. A convergent, component-based route comprising sequential stereoselective glycosylation reactions allows assembly of these analogues in 11 steps or fewer.
Although much is understood about the mechanical behaviour of macroscopic machinery, less is known about their molecular equivalents. It is now shown that for molecular machinery consisting of hydrogen-bonded components their relative motion is strongly accelerated by adding small amounts of ‘lubricating’ water, whereas other protic liquids have much weaker or opposite effects.
The site-specific incorporation of dendritic DNA amphiphiles into a DNA cage controls whether the resultant structures show intermolecular self-assembly or intramolecular assembly. Intramolecular assembly creates a hydrophobic core within the cage that is capable of encapsulating small molecules. These molecules can be released on addition of specific DNA strands.
