Volume 1 Issue 7, October 2009

The concept of the chemical bond has been around for quite some time and there are many models that try to explain what is going on in that hazy world of electron density that glues atoms together. But molecules that challenge our notion of just what a chemical bond is continue to be reported, often presenting us with more questions than answers.

Obtaining financial support for scientific research is generally more difficult for work that is fundamental in nature rather than applied. Bruce C. Gibb contemplates how topics such as complexity might get their share — and why it is vital that they do.

Improvements to the efficiency and lifetime of polymer electrolyte membrane fuel cells can be realized by finding more active and stable electrocatalytic cathode materials. A computational search has found two such alloys and confirmed their enhanced properties experimentally.

The highly selective oxidation of just one carbon–hydrogen bond out of almost 50 in a late-stage precursor can be used to construct the macrocyclic core on which the erythromycin antibiotics are based, and demonstrates the potential of such C–H activation approaches for natural product synthesis.

Dinitrogen ligands — key for understanding how atmospheric nitrogen can be reduced — almost exclusively have even-numbered oxidation states. Now, however, lanthanide complexes with [N₂]³⁻ ligands have been synthesized and investigated.

An amphiphilic molecule that contains a protein-specific ligand and an NMR-active tag forms the basis of a protein sensor. A measurable NMR signal results only in the presence of active protein that causes disassembly of clusters of the amphiphile.

In a Dutch city famous for the treaty that led to the creation of the European Union, delegates gathered at a conference to discuss recent advances in the chemistry of macrocyclic and supramolecular systems.

By studying non-covalent assemblies in the gas phase, it is possible to examine the mobility of the components within a single complex — rather than between different complexes — using hydrogen/deuterium exchange reactions.

Exponential signal amplification is achieved when a single molecule of analyte initiates a chain reaction in which a dendrimer releases a coloured 'reporter' molecule, and ultimately four further molecules of the analyte.

Transition metals can form extremely short bonds with very high bond orders. Bimetallic chromium complexes are the best-known examples, and quintuple bonds have been reported. This Review covers recent developments in the synthesis and theoretical description of quintuply bonded transition metal coordination compounds.

Ring-opening metathesis polymerization (ROMP) is a powerful and highly functional-group-tolerant technique for synthesizing polymers. However, this tolerance presents a great challenge for the selective introduction of functional end-groups. This Review discusses currently available end-functionalization strategies and also highlights factors to be considered when choosing the most appropriate approach.

A synthesis of 6-deoxyerythronolide B is reported that uses a late-stage C–H oxidative macrocyclization reaction to forge the key macrocyclic core found in the erythromycins. By installing oxygen at a late-stage, this strategy improves synthetic efficiency by minimizing the ‘oxygen load’, and provides stereochemical versatility at the site of oxidation.

Improvements in the activity and stability of catalysts for oxygen reduction reactions are needed to make low-temperature, polymer electrolyte membrane fuel-cells viable for mobile applications. Pt₃Sc and Pt₃Y are shown experimentally to have greater catalytic activity than pure Pt after being identified through computational investigation of Pt- and Pd-based alloys.

A ¹⁹F magnetic resonance imaging signal from a protein-specific binding agent can be used to detect the presence of the target protein in live cells. The signal is switched off in the absence of target protein due to aggregation of the probe into nanoclusters.

Industrial chemicals can pose serious health risks in the workplace, and monitoring them is of vital importance. Researchers now show that an optoelectronic nose based on a colorimetric sensor array of nanoporous pigments can rapidly identify a wide range of toxic gases at their IDLH (immediately dangerous to life or health) concentrations.

Compounds containing dioxygen bonded to metal atoms – such as metal-peroxo or -superoxo species – are models of enzymes that can activate oxygen. Now a mononuclear side-on nickel(III)-peroxo complex has been made, which is stabilized by a macrocyclic ligand. The complex can transfer the bound dioxygen to another metal, and conduct nucleophilic reactions.

H/D exchange reactions in the high vacuum of a mass spectrometer reveal how crown ethers move between ammonium ion binding sites of an oligolysine peptide. This study enables the dynamics of non-covalent interactions to be probed in a unique environment and could be applied to more complex artificial or natural systems.

The cycloaddition of N-metalated azomethine ylides to C₆₀ can result in the formation of a number of different stereoisomeric products. Now, it has been shown that the stereochemical outcome of this reaction can be controlled by carefully choosing the the correct combination of metal and ligand to form the complex that catalyses this process.

Catalysis using gold has fast become a major research field with great potential, and many new discoveries are being made. Graham Hutchings reflects on how this has come about.