Volume 1 Issue 2, May 2009

The Cambridge Pre-University Qualification (Pre-U) offers a fresh approach for the teaching of a number of subjects — including chemistry — to 16–18 year olds. Pre-U courses were first implemented in the UK in September 2008, and are expected to eventually become international qualifications.

There are many different versions of the periodic table, but one among them reigns supreme. Michelle Francl ponders on why chemists put elements in boxes.

Latent catalysts require activation, and this is often achieved with either heat, light or an additional chemical agent. By attaching polymer chains to known classes of metal–carbene complexes, it has now been shown that mechanical force can also be used to induce catalytic activity.

Reactants require a certain amount of energy to react — but what kind of energy? Chemical dynamics simulations predict that vibrationally exciting reactants can promote 1,3-dipolar cycloaddition reactions by bending them into the correct transition state shape.

Cooperative assembly between surfactants and inorganic species is a versatile synthetic route to materials with various nanostructures, and has now been extended to a structure composed of three continuous yet independent networks of mesoporous channels.

Some sequences of DNA conduct charge better than others. Replacing adenine with an analogue allows more sequences to transport charge effectively.

In a metal complex, a tin ion can be pushed and pulled through a flat macrocyclic ring with a scanning tunnelling microscope, allowing the molecule to act as a switch.

Chemists envy the ease with which some bacterial enzymes can break carbon–hydrogen bonds. They now imitate the enzyme active site in an oxo-bridged diiron compound that can cleave these strong bonds.

The total synthesis of a bisanthraquinone natural product provides the opportunity to investigate the medicinal properties of a new class of antibiotics.

Molecules with a Möbius geometry are not found in nature, and have thus been a target for synthetic chemists since the first prediction of its existence in 1964. This review summarizes recent successes in synthesizing these fascinating forms, with particular emphasis on expanded porphyrins.

Porous materials with very different pore sizes and structures are commonly used for various applications. But although bicontinuous pore networks — with two interwoven yet unconnected channels — have been reported, tricontinuous structures have so far only been predicted theoretically. Now, researchers have prepared a mesoporous silica with three identical, interpenetrating channels.

The enantioselective construction of quaternary stereocentres, particularly those with all-carbon substituents, is a challenging problem in asymmetric synthesis. It has now been shown that an alternative retrosynthesis of aldol products provides an opportunity to form such stereocentres with a reaction that creates three new carbon–carbon bonds in a single step.

Latent catalysts are usually activated by heating them or adding an external chemical agent, but now it has been shown that mechanical force is also an option in some instances. Ultrasound can be used to dissociate polymeric ligands from metal-containing complexes to reveal the innate catalytic ability of one of the two fragments.

The transport of bicarbonate anions across cell membranes by proteins is an important biological process, and if not regulated properly it can lead to cystic fibrosis and heart disease. Now, it has been shown that ‘small’ molecules can also promote efficient bicarbonate transport across lipid membranes and could be used to probe this process.

Carbon–hydrogen bonds are strong and stable, rarely succumbing to the activation attempts of chemists. Certain bacteria are able to metabolize methane using a diiron-centred enzyme, but synthetic analogues have had much less reactivity. Now, an oxo-bridged diiron complex has been shown to have extremely high activity towards C–H bonds.

Self-assembly of discrete and well-defined supramolecular structures often requires a delicate balance of non-covalent forces such as hydrogen bonding and metal–ligand interactions. Now, by studying the formation of G-quadruplexes, it has been shown that the Coulombic energy associated with the separation of ion pairs can also be used to precisely regulate self-assembly processes.

The presence of adenine–thymine base pairs in DNA duplexes significantly reduces their electrical conductivity. However, by replacing adenine with a closely related analogue that does not disturb the normal complementary base pairing, it is possible to make duplexes that can transfer charge efficiently without having to use only guanine–cytosine base pairs.

A metallo-organic hybrid material prepared by reduction of a palladium salt in the presence of cinchona alkaloids shows moderate enantioselectivity in organic transformations. The metal retains some chiral character after extraction of the dopant, selectively readsorbing the original alkaloid and showing different responses to clockwise and anticlockwise circularly polarized light.

Mietek Jaroniec reflects on how silicon, whether bonded with other elements in a variety of materials, in high purity for electronic devices, or in its newer 'black silicon' form, continues to be invaluable in many aspects of our lives.