Volume 9 Issue 1, January 2017

Michael Donnay and Michelle Francl want chemists to share the stories behind the work they do, and not be afraid to identify the heroines and heroes — and their epic adventures — that paved the way.

The design and prediction of network topology is challenging, even when the components' principle interactions are strong. Now, frameworks with relatively weak 'chiral recognition' between organic building blocks have been synthesized and rationalized in silico — an important development in the reticular synthesis of molecular crystals.

Nature oxidizes biosynthetic intermediates into structurally and functionally diverse peptides. An iron-catalysed C–H oxidation mimics this approach in the lab, enabling chemists to synthesize structural analogues with ease.

Although metal–organic frameworks are often seen as rigid crystalline structures, there is growing evidence that large-scale flexibility, the presence of defects, and long-range disorder are not the exception, but rather the norm. Here we propose that these concepts are inescapably intertwined, and the interfaces between them offer prospects for enhancement of materials' functionalities.

Porous molecular crystals have desirable properties, but are hard to form with the level of structural control seen for extended framework materials. Now, a ‘mix-and-match’ chiral recognition strategy has been used to form reticular porous supramolecular nanotubes and 3D networks, providing a blueprint for pore design in molecular crystals.

Transition-metal-catalysed direct C(sp³)−H functionalization of primary aliphatic amines is an attractive– but elusive – process that could provide efficient access to biologically and pharmaceutically important compounds. Now, a palladium-catalysed γ-arylation of primary alkylamines is achieved using an inexpensive, catalytic and transient directing group.

Lateral anchoring of heteromolecules to graphene paves the way for the creation of hybrid materials with tunable properties. Now, following a surface-assisted dehydrogenative coupling reaction, the edges of graphene on silver have been functionalized with porphines. This enables the assembly of well-defined multifunctional graphene-based nanostructures.

There is increasing evidence that highly dynamic, polydisperse peptide oligomers are the toxic species in amyloid-related diseases such as Alzheimer's and Parkinson's. Now, the secondary structure of individual amyloid oligomers has been analysed directly for the first time using a combination of ion-mobility spectrometry–mass spectrometry and gas-phase infrared spectroscopy.

The degree to which light-induced processes are sensitive to the shape of an incident electromagnetic wave remains a hotly debated topic. Experiments performed at very low levels of light agree with seminal theoretical predictions that tuning the phase of the light field does not affect photochemical reactivity at the single-photon level.

An artificial aldolase has been optimized using an ultrahigh-throughput microfluidic screening assay. The evolved enzyme exhibits excellent stereoselectivity and broad substrate scope. Structural studies suggest that a Lys-Tyr-Asn-Tyr catalytic tetrad, which emerged during directed evolution, is responsible for the >10⁹ rate enhancement achieved by this catalyst.

Metal surfaces have been believed to be catalytic, but the mechanism of catalysis is unknown. Now, graphene nanoribbons (GNRs) can be grown on Au(111) from a ‘Z-bar-linkage' precursor through a conformation-controlled mechanism. Chemical vapour deposition of precursors adopting a chiral conformation produced homochiral polymers, which are dehydrogenated to form GNRs.

The existence of linear scaling relations between the adsorption energies of reaction intermediates on transition-metal surfaces prevents their independent optimization and limits catalytic activity. It has now been shown that using a catalytic LiH site alongside a transition-metal catalyst can break these intrinsic scaling relations, leading to unprecedented lower-temperature ammonia-synthesis activity.

Control over the selectivity of chemical reactions and biological molecules requires an intimate understanding of how conformation impacts reactivity. It is now shown that the trans conformer of trifluoromethylhydroxycarbene preferentially rearranges through a quantum-mechanical hydrogen-tunnelling pathway, whereas its cis conformer is unreactive.

Crystals grow from nuclei. In systems where nuclei are nanometre-sized and form quickly, it is difficult to determine the mechanism of their formation. Now, through in situ TEM, the demixing of a supersaturated aqueous gold solution into metastable gold-poor and gold-rich liquid phases is observed, the latter yielding stable clusters that become nuclei for nanocrystal growth.

A family of fluorescent molecular rotors has been developed and their mechanism for emission understood. It has been observed that, although most fluorescent molecules emit from their lowest energy excited state, S₁ (in accordance with Kasha's rule), BODIHY dyes do not. Furthermore, their fluorescence is enhanced through restricted rotor rotation, which suppresses internal conversion to the dark S₁ state.

FeFe hydrogenases are highly efficient H₂ producing enzymes; however, they can be inactivated by O₂. Now, a mechanism for O₂ diffusion within FeFe hydrogenases and its reactions at the active site of the enzyme has been proposed. These findings could help with the design of hydrogenase mutants with increased resistance to oxidative damage.

Nadezda V. Tarakina and Bart Verberck explore the colourful history and assets of element 48.