Volume 4 Issue 4, April 2012

Thomas Hager, author of popular science books that revisit some of the most significant developments in chemistry over the past century, talks to Nature Chemistry about the challenges of writing for a general audience, and how his dislike of chemistry was turned around by a fellow Oregonian of considerable repute.

Two-dimensional polymers can serve to organize chemical functionality periodically over large areas, but their rational synthesis has remained limited. Now, a free-standing, single-layer polymer sheet has been prepared and isolated through a two-step procedure — a photochemical reaction within a layered organic crystal followed by exfoliation.

The splitting of water molecules into protons and hydroxide ions, and their recombination, occurs by proton transfer along hydrogen-bond wires. Now, first principle simulations of the recombination reaction reveal new atomic-scale details of the process showing that compression of the wire plays an important role.

Polymer vesicles have been constructed that entrap platinum nanoparticles in their outer surface. These serve to break down a fuel of hydrogen peroxide, generating water and oxygen and in turn inducing a propulsive effect.

Fluorescent labels can now be attached to a specific protein on the surface of live cells using a two-step method that reacts a norbornene — introduced using genetic encoding — with a variety of dyes.

The technological relevance of zeolites, the desire to improve their efficiency and the inexhaustible synthetic options to tailor their properties have triggered a permanent evolution of this superclass of materials. Two zeolite nanosystems prepared by distinct approaches reflect this and offer hope for new applications.

Transparent, metallic conducting thin films are key for applications such as flatpanel displays and solar cells, and heavily electron-doped ionic oxide materials have been intensively studied for this purpose. A class of conductors that are transparent in the near-infrared region has now been developed using a topological insulator.

A simple aldehyde has been shown to catalyse an intermolecular hydroamination, not by activating either reaction partner, but simply by bringing them into close proximity.

Redox sites can be incorporated within dendrimers — highly branched, well-defined macromolecules — at specific locations, such as their core, branching points, periphery or inner cavities. These dendrimers can serve to functionalize surfaces, and electron-transfer processes at their redox sites show promise for various applications ranging from metallo-protein modelling to sensing to catalysis.

A supramolecular system has been assembled that moves autonomously in the presence of a molecular fuel. Platinum nanoparticles entrapped in a polymer stomatocyte — a bowl-shaped polymer vesicle — catalyse the decomposition of the molecular fuel, hydrogen peroxide. The resulting generation of water and oxygen induces a directional movement of the stomatocyte.

An isolable diamidocarbene is shown to participate in reversible [2+1] cycloadditions with a variety of both electron-deficient and electron-rich olefins and aldehydes. Subsequent hydrolysis of a N,N′-diamidocyclopropane derived from styrene afforded the corresponding linear carboxylic acid, effectively establishing a metal- and carbon monoxide-free, anti-Markovnikov olefin hydrocarboxylation reaction.

Transparent conductive electrodes are widely used in modern optoelectronic devices, but they are rarely transparent in the near-infrared, limiting their use. Nanostructured bismuth selenide, a topological insulator, is now shown to be a flexible near-infrared transparent electrode.

A two-dimensional polymer with internal periodicity has now been constructed. The procedure involves the rational molecular design of monomers, which first crystallize into a laminar lattice. A photo-induced polymerization then occurs laterally within each layer, and the resulting polymer crystals are subsequently delaminated into individual, free-standing two-dimensional polymers.

The connection between protein dynamics and catalysis is an issue of vigorous debate in enzymology. Conformational motions are known to be important for the physical steps in the catalytic cycle of dihydrofolate reductase, however, it is now reported that there is no evidence of a correlation between such motions and the actual chemical step, hydride transfer.

The site-specific incorporation of a norbornene amino acid into proteins via genetic code expansion, together with the synthesis of a series of tetrazine-based probes that exhibit turn-on fluorescence on their fast cycloaddition with norbornene, enables rapid protein labelling on mammalian cells.

Graphene oxide produced via the standard Hummers method possesses a high degree of chemical inhomogeneity and limited reversibility. Now, it has been shown that an alternative ultra-high-vacuum approach for oxidizing epitaxial graphene yields uniform epoxy functionalization with thermal reversibility at temperatures as low as 260 °C.

Surfactant-capped nanoparticles of various sizes, shapes and compositions have been completely enshrouded within a metal–organic framework in a controlled, well-dispersed manner. The resulting hybrid materials exhibit active properties — catalytic, magnetic and optical — arising from the nanoparticles as well as sieving and orientation effects originating from the porous framework.

A functional active-site mimic of the oxy-tyrosinase enzyme forms through self-assembly of monodentate imidazole ligands, copper(I) and oxygen at −125 °C. The fidelity of this copper–dioxygen complex to the native enzyme, its inherent stability and hydroxylation reactivity suggest that an organizational role of the protein matrix suffices to realize function.

Proton transfer is usually considered in the context of hydrogen-bonding networks serving as proton-shuttling pathways. Now, an efficient ionization-induced proton transfer in the absence of hydrogen bonds has been observed in a model π-stacked system, the 1,3-dimethyluracil dimer.

A molecular ‘stellated polyhedron’ with concave faces — constructed by extending the faces of its counterpart polyhedron until they intersect — has now been synthesized. Ligands that constitute the square faces of a metal–organic cuboctahedral cage were decorated with pendant side chains, which reversibly coordinate to additional metal centres to give rise to the stellated cage.

Copper, routinely encountered in daily life, may at first glance seem a little unexciting. Tiberiu G. Moga relates how science, however, has not overlooked its promise.