Volume 2 Issue 3, March 2010

Traditional scientific conferences can be costly and time-consuming, and certainly aren't 'green', with participants travelling long distances to attend. Are there advantages to meetings held in the virtual world, and can they really offer equally satisfying — or even better — experiences compared with the real world?

A linear molecule containing three bipyridine ligands can be wrapped around a single metal-ion template to form an open-knot complex. The loose ends of the knot can be 'tied' together through esterification or olefin-metathesis reactions to form closed knots that do not unravel when the metal template is removed.

Monitoring the dynamics of a single molecule is impeded by their motion in solution, and immobilizing them without changing their properties is problematic. By using a trapping method that counteracts a molecule's Brownian motion, the complex dynamics of a fluorescent protein, allophycocyanin, have been investigated.

The long-awaited first total synthesis of the structurally intriguing natural product palau'amine has now been achieved. The synthesis features cascade reactions and an 'across ring' stitching of a 'macropalau'amine', and sets the bar for future efforts towards an enantioselective variant.

Public acceptance of the expansion of nuclear power may hinge on the safe disposal of nuclear waste. Ion exchangers that remove radioactive metals — such as caesium ions — from the waste could provide part of the answer, so a flexible-framework material that selectively grab them from solution is a step in the right direction.

Supramolecular gels, which rely on non-covalent interactions, are typically fragile. Now, hydrogels that possess remarkable mechanical strength combined with the ability to rapidly self-heal have been built through multiple non-covalent interactions.

Monomers that contain masked ketene groups provide new opportunities for facile crosslinking and post-synthetic modification of polymers in a wide variety of materials applications.

Electromerism is an unfamiliar concept to many chemists and refers to molecules that are not conventional isomers but instead differ in how the electrons are distributed across their structure. A novel example of such electromers has now been demonstrated.

The field of organocatalysis has grown rapidly in the past decade to become, along with metal catalysis and biocatalysis, a third pillar of asymmetric catalysis. Here, progress in the use of organocatalytic cascade reactions for total synthesis is reviewed. The elegance and efficiency of such cascades mean that they have emerged as a powerful tool in synthetic organic chemistry.

A method for observing the photodynamics of single molecules, without having to immobilize them to a surface or confine them within vesicles, has been used to study the important photosynthetic antenna protein, allophycocyanin. Light-induced conformational changes and a complex relationship between fluorescence intensity and lifetime have been observed.

A perforated framework material of gallium antimony sulfide is able to selectively extract caesium ions from solution. After this capture, the holes close and prevent the ions leaching back out. This dynamic response could be used to remove caesium from nuclear waste.

The selective construction of multiple adjacent stereocentres is an important challenge for synthetic organic methodology, and only a handful of catalytic methods exist that can forge adjacent quaternary and tertiary stereocentres. Here, a palladium-catalysed multiple-bond-forming cascade leads to the construction of such systems in high yield, diastereomeric ratio and enantiomeric excess.

Chlorine-activation reactions on polar stratospheric cloud (PSC) particles are crucial to ozone depletion in the winter/spring polar stratosphere and their rates depend on the phase state of the PSC particle surface. Now experiments show that, on particle formation, a phase separation into pure ice with a residual solution coating takes place.

A combined theoretical and experimental approach has been used to investigate the structure and bonding of an all-boron cluster (B₁₉⁻). Calculations suggest that the minimum energy structure is a near-planar one — in which a pentagonal B₆ unit is encircled by a larger B₁₃ ring — possessing two concentric aromatic π systems.

The ability to rapidly functionalize polymers is vital for application development. Here, a method for the introduction of masked ketenes into monomers for both ring-opening metathesis and radical-type polymerizations is described. These ketenes — a group previously underexploited in polymer chemistry — allow both crosslinking and post-polymerization functionalization of the polymers.

The movement of oxygen ions through materials is important in electrolytes and separation membranes, but is rare at lower temperatures. Two different low-temperature diffusion pathways are revealed during the reduction process of CaFeO_2.5 to CaFeO₂. The two pathways are significantly different, resulting in anisotropy.

The synthesis of interlocked compounds such as catenanes and rotaxanes has undergone much development in recent years, but molecular knots are still relatively hard to make. It has now been shown that a linear bipyridine oligomer can fold around a single zinc-ion template to form a complex that can be cyclized to give a molecular trefoil knot.

A methodology for describing local electronic transmission through bridging molecules between metallic electrodes is presented. Its application to simple alkane, phenyl and cross-conjugated systems highlights an unexpected number of cases whereby ‘through space’, rather than ‘through bond’ terms dominate and that interference effects coincide with the reversal of ring currents.

The incorporation of non-natural base pairs into double-stranded DNA, especially those mediated by metal–ligand interactions, offers new opportunities for synthetic DNA materials. The structural implications of such modifications will help guide developments in this area, and a solution structure of a B-type DNA duplex containing consecutive metal-mediated base pairs has now been elucidated.

The uptake of ammonia by a covalent–organic framework (COF) containing a high density of Lewis-acidic boron sites has been found to be significantly greater than that exhibited by other state-of-the-art porous materials. The ammonia can be removed by heating under vacuum and the structural integrity of the COF is maintained during adsorption/desorption cycles.

Herbert Roesky relates how the small, highly electronegative fluorine atom unveiled the chemical reactivity of noble gases and found many practical applications. but it can also render organic compounds highly toxic or pollutants.