Volume 6 Issue 8, August 2014

Self-assembled amphiphiles are more common in the realm of aqueous systems than in organic solvents. Their scope has now been expanded with the advent of 'hydrophobic amphiphiles' of π-conjugated–alkyl systems, which show various self-assembled phases similar to classical amphiphiles.

A newly designed thiol catalyst for radical cyclization reactions is the result of a long and storied battle to control the reactivity of carbon-centred radicals.

Intramolecular aliphatic C–H amination reactions are greatly sought-after for the synthesis of N-containing heterocycles, but current methods require the use of highly activated nitrogen sources. Now, aziridination and lactamization have been achieved using fully aliphatic, unactivated, secondary amines.

For decades chemists have focused on increasing the brightness of fluorophores. In super-resolution microscopy, however, fluorophores that preferentially exist in a non-fluorescent state, but occasionally re-arrange into a fluorescent form, can give better results.

Biological systems have evolved sophisticated machinery to assemble polymeric receptors capable of molecular recognition. Although such precise levels of structural control are currently inaccessible to chemists, impressive progress has been made towards the realization of wholly synthetic analogues of antibodies and other proteins. Protein structure from H. Li et al. Biochemistry 33, 11734–11744 (1994); © American Chemical Society.

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.

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.

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.

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.

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.

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.

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.

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.

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 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.

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.

Anders Lennartson muses on molybdenum and its essential role in catalysing reactions from the bacterial to the industrial scale.