Chemical Science Blog

Physical organic chemistry, the study of the underlying principles and rationale of organic reactions which looks at the interrelationships between the structure and reactivity of organic molecules, now encompasses a wider range of contexts than ever before

Making use of tools such as chemical kinetics, quantum chemistry, thermochemistry, chemical equilibrium and computational chemistry, to name but a few, researchers are investigating topics such as:

• Supramolecular interactions, aggregation and reactivity
• The computation of transition states and mechanisms
• Molecular recognition, reactions and catalysis in biology
• Materials where molecular structure controls function
• Structure activity correlations
• Mechanisms in synthesis and catalysis

To highlight some of the cutting edge research that ChemComm, Chemical Science and Organic & Biomolecular Chemistry publish we have collected a selection of articles for you to enjoy. These will be free to access until 25^th September!

Click here for the full list of free articles

Boronic esters have been used by US scientists to transform the triphenylene core in discotic liquid crystals (DLCs) from electron-rich to electron-deficient.

DLCs are used in electronic devices such as light emitting diodes. They need an electron-rich donor and an electron-poor acceptor. Current electron-poor acceptors have shortcomings including the fact that they can’t form columnar mesophases.

The team incorporated a boronic ester into the triphenylene core, which makes it an electron-poor acceptor and they were able to achieve broad mesophase temperature ranges.

Boronic Esters: A Simple Route to Discotic Liquid Crystals that Are Electron Deficient
Benjamin King and Luke Andrew Tatum
DOI: 10.1039/C2SC20128C

Scientists in Canada have studied the synthetic scope of a new system of [2]rotaxane molecular shuttles based on a templating motif involving a benzimidazolium–crown ether recognition pair.

The template allows an array of molecular shuttles containing macrocyclic crown ethers of varying size and shape to be prepared.

The study also provides the beginnings of a property–structure relationship for molecular shuttling in this rigid, compact [2]rotaxane system. This could aid in the future design of [2]rotaxane molecular shuttles for incorporation into materials such as metal–organic frameworks.

Bis(benzimidazolium) axles and crown ether wheels: a versatile templating pair for the formation of [2]rotaxane molecular shuttles
Stephen J. Loeb, Kelong Zhu, V. Nicholas Vukotic and Nadim Noujeim
DOI: 10.1039/C2SC20986A

US scientists have come up with a general synthetic method to prepare macrocyclic tetracarbenes with first, second and third row transition metals from both sides of the periodic table, using a dimeric silver transmetallating reagent.

The facile synthesis of bidentate and tridentate N-heterocyclic carbenes (NHCs) coupled with their resistance to oxidation has made these chelating ligands an attractive alternative to phosphines for many applications. Despite numerous uses for these strong sigma-donor ligands, one class of chelating NHCs that has not been as thoroughly investigated is tetradentate carbenes.

Link to journal article
Exploiting a Dimeric Silver Transmetallating Reagent to Synthesize Macrocyclic Tetracarbene Complexes
Z Lu, S A Cramer and D M Jenkins
Chem. Sci., 2012, DOI: 10.1039/c2sc20628e

Highly active catalysts for manufacturing bulk and fine chemicals can be made by simply grinding metal acetate salts with pre-formed supports.

Heterogeneous catalysis is a key chemical manufacturing process and lies at the heart of green chemical processes. The use of catalysts can lead to greener reactions when compared to alternative routes. But many routes for making catalysts use halides as a starting point and the halides are difficult to remove from the final material.

UK scientists have prepared supported gold, palladium and gold-palladium catalysts by mixing the metal acetate precursors. The simple, reproducible and scalable preparation method ensures the catalysts prepared are halide free. They found that the removal of the halide from the preparation step and therefore from the final catalyst leads to a significant enhancement in performance compared to previously reported catalysts.

Link to journal article
Physical mixing of metal acetates: a simple, scalable method to produce active chloride-free bimetallic catalysts
S A Kondrat et al
Chem. Sci., 2012, DOI: 10.1039/c2sc20450a

A cylindrical supramolecular complex (yellow) interacting with the central target region of the amyloid beta protein (green, white and red ribbon). Image credit: Xiaogang Qu

Supramolecular chemistry could provide a new avenue in the treatment of Alzheimer’s disease, say scientists in China. The group demonstrates for the first time that supramolecular complexes can inhibit the aggregation of a peptide thought to cause Alzheimer’s disease.

Alzheimer’s disease (AD) is the most common cause of dementia among the elderly and is estimated to affect over 35 million people worldwide, a figure which is expected to triple by 2050. One of the pathological hallmarks of the disease is the polymerisation of amyloid β-peptides (Aβ) into insoluble fibrous protein aggregates known as plaques. Scientists have been trying to develop inhibitors of Aβ aggregation as a therapeutic and preventive strategy for AD treatment. Most reported Aβ inhibitors are small organic molecules or peptides, many of which act non-specifically.

Read the full article in Chemistry World

Link to journal article
Metallosupramolecular Complex Targeting a/ß Discordant Stretch of Amyloid ß Peptide
H Yu et al
Chem. Sci., 2012, DOI: 10.1039/c2sc20372c

The MOF incorporating carboxyl and pyridyl groups within its cavity selectively adsorbs CO2 over ethyne. Image credit: Martin Schröder

UK researchers have designed a metal–organic framework that, unusually, selectively adsorbs CO₂ over ethyne by a dynamic gate-opening mechanism and has potential applications in fuel gas separation.

Metal–organic frameworks, or MOFs, comprise metal clusters or ions complexed to organic ligands, forming an extended crystalline, often porous, structure. The pore sizes can be tuned by careful design, and as such, they are widely investigated for gas storage and separation technologies. However, most MOFs are usually selective to ethyne adsorption over CO₂, limiting their application, as the intermolecular interactions between ethyne and the MOF are stronger.

Now, Martin Schröder at the University of Nottingham, and colleagues, have synthesised a MOF that shows dynamic phase changing behaviour induced by CO₂, inverting the usual selectivity to ethyne.

Read the full article in Chemistry World

Link to journal article
Selective CO₂ uptake and inverse CO₂/C₂H₂ selectivity in a dynamic bifunctional metal–organic framework
W Yang et al
Chem. Sci., 2012, DOI: 10.1039/c2sc20443f