Chemical Science Blog

Scientists in the US and Saudi Arabia have made a new family of conjugated polymers that change colour in response to changes in their redox state. The stimuli-responsive polymers are the first example where an azulene building block is incorporated into the polymer backbone through linkages in the 7-membered ring, rather than the more synthetically accessible 5-membered ring.

The polymers’ properties may be of great importance for developing new organic field-effect transistors, organic light-emitting diodes, and dye-sensitised organic solar cells.

Link to journal article
Azulene-Based Conjugated Polymers: Unique Seven-Membered Ring Connectivity Leading to Stimuli-Responsiveness
Masahito Murai , Elizabeth Amir , Roey J. Amir and Craig J. Hawker
Chem. Sci., 2012, DOI: 10.1039/c2sc20615c

While most people over a certain age are trying to slow down the ageing process, scientists from the UK and Canada are trying to speed it up to help them make new materials more cleanly.

‘Accelerated ageing’ could become a new paradigm for the clean, low energy and solvent-free synthesis of metal-organic materials, claim the researchers. They were inspired by the slow geological processes of mineral weathering, which convert metal oxides and sulfides to metal-organic materials by exposing them to small organic molecules. By accelerating this process, they claim materials can be made without the continuous input of mechanical energy, high temperatures or organic solvents. Their simple process involves exposing a mixture of a metal oxide and an organic ligand to catalytic amounts of an ammonium salt at mild temperature and high humidity.

Link to journal article
Accelerated aging: a low energy, solvent-free alternative to solvothermal and mechanochemical synthesis of metal-organic materials
Tomislav Friscic, Matthew J Cliffe, Cristina Mottillo, Robin S Stein and Dejan-Kresimir Bucar
Chem. Sci., 2012, DOI: 10.1039/c2sc20344h

UK scientists have isolated and identified the biosynthesis genes of the metabolite coelimycin P1 (a yellow pigment, unprecedented in nature to the team’s knowledge) by Streptomyces coelicolor M145, using a combination of genetic experiments, bioinformatic analyses and structural analyses.

Analysing the genome sequences of plants, bacteria and filamentous fungi, together with the screening of extracts of novel organisms isolated from underexplored habitats, revealed that many (perhaps most) structurally novel bioactive natural products remain to be discovered. Sequencing the complete or partial genomes of several Streptomyces species and related actinomycetes has shown that they invariably contain numerous cryptic gene clusters with the potential to direct the production of hitherto undiscovered bioactive natural products, say the researchers.

Link to journal article
Structure and biosynthesis of the unusual polyketide alkaloid coelimycin P1, a metabolic product of the cpk gene cluster of Streptomyces coelicolor M145
Juan-Pablo Gomez-Escribano, Lijang Song, David Fox, Valerie Yeo, Mervyn Bibb and Gregory L Challis
Chem. Sci., 2012, DOI: 10.1039/c2sc20410j

Certain transition metal ions, particularly Fe, Co and Ni, can significantly improve the catalytic activity of molybdenum sulfide hydrogen evolution catalysts, claim scientists in Switzerland.

Sunlight-driven water splitting is an attractive method for solar energy conversion and storage. Achieving efficient water splitting requires active hydrogen evolution catalysts. Recently, molybdenum sulfide materials have emerged as a class of promising hydrogen evolution catalysts because of their high abundance, low cost and high activity. Xile Hu, at the Federal Polytechnic School of Lausanne, and colleagues, incorporated metal ions into amorphous molybdenum sulfide and demonstrated up to a 12-fold increase in exchange current density and a 10-fold increase in the current density at a given overpotential at pH = 7.

Link to journal article
Fe, Co, and Ni Ions Promote the Catalytic Activity of Amorphous Molybdenum Sulfide Films for Hydrogen Evolution
Daniel Merki, heron vrubel, lorenzo rovelli, Stephan Fierro and Xile Hu
Chem. Sci., 2012, DOI: 10.1039/c2sc20539d

Eggs can often be safe to eat for at least a month after their use-by date

Scientists in the US have developed a cheap fluorescent sensor for food spoilage that could be as easy to use as litmus paper.

‘Use-by’ dates on food products can give important guides as to whether the product is still safe to eat. However, they can be severely inaccurate. This leads to huge amounts of food waste, as supermarkets (and many consumers) dispose of anything that has exceeded this date, regardless of whether the food is actually spoiled.

Although accurate sensors for food spoilage are available – such as electronic noses and other fluorescent sensors – they often involve cumbersome or complicated procedures or lack generality, which makes them unsuitable for use in real-world applications.

Read the full article in Chemistry World

Link to journal article
Fluorescent DNAs printed on paper: sensing food spoilage and ripening in the vapor phase
Hyukin Kwon ,  Florent Samain and Eric T. Kool
Chem. Sci., 2012, Advance Article, DOI: 10.1039/C2SC20461D

Scientists in the US have reported a series of novel tris-diphosphane complexes that use a unique diphosphane constructed from elemental phosphorus. The synthesis combines a simple synthesis of the binucleating ligand together with the efficient self assembly of a novel class of elaborate dinuclear metal complexes. The cages that form are stable during ligand substitution at the axial positions so they could be used as components of coordination polymers and supramolecular structures.

Link to journal article
Bicyclic Dinuclear tris-(Ditopic Diphosphane) Complexes of Zerovalent Group 10 Metals
Daniel Tofan and C Cummins
Chem. Sci., 2012, Accepted Manuscript, DOI: 10.1039/C2SC20559A

A new way to make, move and immobilise complex functional microstructures using a combination of multiphoton polymerisation and optical trapping in water has been devised by researchers in the US.

The technique can create structures, for example microbraids, that are unattainable using conventional fabrication techniques. The team could create and manipulate microthreads from different materials that will enable a wide range of biophysical and biochemical studies on individual cells, they say.

Link to journal article
Simultaneous Microscale Optical Manipulation, Fabrication and Immobilisation in Aqueous Media
Farah Dawood, Sijia Qin, Linjie Li, Emily Y. Lin and John T Fourkas
Chem. Sci., 2012, Accepted Manuscript, DOI: 10.1039/C2SC20351K

The predicted structure of CuF

A project that ‘bubbled along in the background’ not only contradicts the inorganic textbooks, but also suggests a new material for photochemical applications. In fact, Aron Walsh from the University of Bath, UK, who worked on the calculations, describes cuprous fluoride as the ‘missing semi-conductor’ between zinc oxide and gallium nitride.

Open your inorganic text book and look up CuF – you’ll be told either it doesn’t exist, or that it was synthesised in 1933 and has a sphalerite structure. That’s what Walsh and his co-workers discovered when they were trying to do a systematic review of crystal types and what compounds form them. But modelling the compound in this structure showed that it wasn’t stable; they couldn’t explain why CuF would form the structure reported and so they did a little digging.

Read the full article in Chemistry World

Link to journal article
Prediction on the existence and chemical stability of cuprous fluoride
Aron Walsh, C. Richard A. Catlow, Raimondas Galvelis, David O. Scanlon, Florian Schiffmann, Alexey A. Sokol and Scott M. Woodley
Chem. Sci., 2012, Advance Article, DOI: 10.1039/C2SC20321A, Edge Article

Structure of the anionic host-guest complex

Scientists in the UK and China have encapsulated a bromine anion in a  supramolecular cavity to make a compound that could act as a model for metal-/anion-doped TiO₂.  The model could be used to find ways to improve current TiO₂-doped  photovoltaic, photocatalytic and sensing devices.

Dominic Wright from the University of Cambridge, UK, and colleagues, have incorporated a Br^– anion into a polyoxotitanate host, in which there is only very weak bonding between the bromine and the surrounding titanium oxide shell. ‘As well as providing a model for the way in which anions like Br^– are incorporated into TiO₂, purely inorganic host-guest arrangements like this are rare in their own right,’ says Wright.

Read the full article in Chemistry World

Link to journal article
Encapsulation of a ‘naked’ Br⁻ anion in a polyoxotitanate host
Yaokang Lv ,  Janina Willkomm ,  Alexander Steiner ,  Lihua Gan ,  Erwin Reisner and Dominic S. Wright
Chem. Sci., 2012, Advance Article, DOI: 10.1039/C2SC20193C