Volume 8 Issue 1, January 2016

γ-Butyrolactone is a biomass-derived cyclic ester that is commonly thought to be non-polymerizable. Now, exploiting the thermodynamics of polymer formation and careful control of the reaction conditions has made this possible leading to high-molecular-weight products and control of polymer topology.

Fullerene-based dendritic structures coated with 120 sugars can be made in high yields in a relatively short sequence of reactions. The mannosylated compound is shown to inhibit Ebola infection in cells more efficiently than monofullerene-based glycoclusters.

Supramolecular processes are attractive for the generation of functional materials, but managing multiple, competing self-assembly pathways has remained challenging. Now, the self-assembly of a platinum compound into three different aggregates has been elucidated, visualized in real time, and controlled.

The catalytic activity of a rotaxane incorporating a gold(I) centre can be switched on by the addition of a guest ion that can bind inside the macrocyclic cavity of the system. The nature of the guest can also influence the selectivity of the catalyst, reminiscent of allosteric modulation in enzymes.

The self-assembly of building blocks is an enticing route towards functional materials, yet understanding and controlling the mechanisms at play has remained challenging. Now the different morphologies and emission colours of the aggregates of a platinum(II) compound has enabled its assembly pathways into different structures to be controlled and visualized in real time.

Singlet fission, a spin-allowed conversion of a spin-singlet state into a pair of spin-triplet excitons, may be useful for the development of next-generation photovoltaics. Ultrafast coherence measurements now show that vibrational motions play a critical role in fission as they facilitate the mixing of triplet-pair states with singlet excitons.

Synthetic anion transporters that replace the activity of defective anion channels have been proposed as treatments for cystic fibrosis; however, it remains uncertain whether such molecules are fundamentally toxic. A series of bis- and tris-(thio)ureas capable of transporting anions have now been tested in cells expressing halide-sensitive yellow fluorescent protein. One bis-urea compound proved especially effective while showing almost no toxicity.

Gels formed by metal–ligand coordination typically consist of single metal ions linked together by polymer chains. Now, metal–organic cages have been used as junctions instead. A gel was prepared that features a large number of polymer chains at each junction, including loops that further serve to functionalize the material.

Bio-derived γ-butyrolactone (γ-BL) is commonly referred to as ‘non-polymerizable’ due to its low strain energy. Now it has been shown that ring-opening polymerization of γ-BL can in fact proceed to high conversions under ambient pressure with a suitable catalyst, producing high-molecular-weight polymers with controlled topologies and complete recyclability.

Tridecafullerenes with 120 peripheral carbohydrate groups have been made in one step from hexakis-adducts of [60]fullerene by using azide–alkyne click chemistry. This synthetic approach offers control over the size and multivalency of these ‘sugar superballs', which are shown to be potent inhibitors of cell infection by an artificial Ebola virus, with IC₅₀ values in the sub-nanomolar range.

Although millions of zeolite structures have been predicted, only about 200 have been prepared over the past six decades. An assembly–disassembly–organization–reassembly process has now enabled the synthesis of two zeolites previously thought to be unfeasible, which have high framework energy and rare structural features such as odd-membered rings.

Pyrroles are a common substructure in pharmaceuticals, materials and natural products. Now a multicomponent, titanium-catalysed synthesis of polysubstituted pyrroles — a nitrenoid analogue of the Pauson–Khand reaction — is reported. Stoichiometric and kinetic studies suggest that the reaction proceeds through an unusual Ti^II/Ti^IV redox cycle.

A synthetic receptor has been designed to form pseudorotaxanes and polypseudorotaxanes with oligo/polysaccharides in water. Target substrates have all-equatorial substitution patterns, and include cellulose, cellodextrins and the cationic polysaccharide chitosan. The results suggest an approach to dissolving these polysaccharides under mild conditions and could prove useful for processing these abundant renewable resources.

Amides have historically been considered stable and unreactive functional groups because of resonance stabilization. Here, it is demonstrated that Boc-activated amides can be employed in Suzuki–Miyaura couplings using non-precious-metal catalysis. The overall reaction is complementary to the widely employed Weinreb ketone synthesis.

The structural order of supramolecular assemblies typically depends on the enantiomeric purity of their building blocks. Now, a perylene bisimide (PBI) derivative has been described that assembles into a single-handed supramolecular helix, which in turn packs into domains with an identical crystalline order irrespective of the PBI's chirality. A cogwheel mechanism is proposed.

Lars Öhrström relates the various roles played by rhodium in our daily lives, ranging from car components to drugs.