Volume 12 Issue 7, July 2020

Michelle Francl worries about the long-term effects of playing by pandemic rules.

The potential applications of smart photoswitchable porous materials are currently limited by incomplete switching. Now, efficient bulk switching has been achieved by embedding a photoisomerizable overcrowded alkene in a highly porous aromatic framework, creating a material capable of photomodulated gas uptake.

It’s not known how life’s essential properties of replication, metabolism and compartmentalization were first integrated. Two recent articles now shed light on how metabolic characteristics may be incorporated into replicating systems, harnessing an external energy source to increase their rate of replication and acquiring catalytic activity.

Is a nanoscale hydrophobic bowl wet or dry when dissolved in water? It turns out that the answer depends on the architecture of its rim. A molecular host decorated with four methyl groups around its rim pointing inward, rather than up, has now been shown to expel water from the bowl, making it dry and sticky.

Water plays an active role in modulating guest recognition by both artificial and biological hosts, but how this role can be controlled is unclear. Now, the de-wetting of the non-polar pockets of cavitands is shown to be affected by the orientation of methyl groups encircling the portal, which moderate the enthalpic and entropic contributions driving recognition.

Despite numerous potential applications, the development of light-responsive solid materials based on molecular photoswitches is impeded by the low efficiency of photoisomerization in the solid environment. Now a robust, solid porous material made from tetraphenylmethane and a photoswitchable overcrowded alkene exhibits nearly quantitative photoisomerization in the bulk and in photomodulation of gas uptake.

The integration of replication with metabolism represents a key step in the transition of chemistry into biology. Now, it has been shown that a self-replicator can recruit and activate two different photocatalytic cofactors, which then catalyse the synthesis of the precursors for the replicator.

Compounds of main-group elements rarely undergo direct carbonylation reactions. Now, an electron-rich silylene intermediate has been shown to readily react with CO to form a silylene carbonyl complex that is stable at room temperature. This complex engages in CO substitution as well as oxidative addition reactions.

Despite five decades of research, the alkaloid (+)-brevianamide A has remained an elusive target for chemical synthesis. Now, it has been shown that the total synthesis of (+)-brevianamide A can be achieved in seven steps and 7.2% overall yield to give 750 mg of the target compound.

A naturally occurring stand-alone and intermolecular Diels–Alderase, MaDA, has been identified from Morus alba cell cultures. MaDA is a FAD-dependent enzyme, which catalyses the intermolecular [4+2] cycloaddition via a concerted but asynchronous pericyclic pathway between morachalcone A and a diene generated from moracin C. Characterization revealed that MaDA possesses good substrate promiscuity towards both dienes and dienophiles.

A ruthenium-catalysed multicomponent reaction provides rapid and tunable access to 1,3-dienyl-6-oxy polyketide motifs. An initial alkene–alkyne coupling produces unsymmetrical 3-boryl-1,4-dienes. Allylation of aldehydes and ketones with these products is highly diastereoselective and results in the formation of two carbon–carbon bonds, two stereodefined olefins and up to three contiguous sp³ stereocentres.

Oxygen is a potent inhibitor of radical polymerization reactions, but the facultative bacterium Shewanella oneidensis has now been shown to facilitate aerobic radical polymerizations by first consuming dissolved oxygen and then directing extracellular electron flux to a metal catalyst. Aerobic polymerization activity is dependent on the S. oneidensis genotype and can be initiated using lyophilized or spent cells.

In contrast to the variety of stable carbonyl complexes of group 7–12 metals, few are known for group 3–5 metals; among those, cations have only been identified in the gas phase or by matrix isolation. Now, several unusual niobium and tantalum carbonyl compounds have been prepared as bulk crystalline compounds, including heptacarbonyl salts and the neutral ditantalum dodecacarbonyl.

Metallacycles formed from two large, under-coordinated actinide M^IV cations and two rigid arene-bridged aryloxide ligands are capable of binding dinitrogen inside their cavity. These f-block complexes can catalyse the reduction and functionalization of dinitrogen as well as the catalytic conversion of molecular dinitrogen to a secondary silylamine.